Thursday, November 30, 2006

Thursday Evening Forecast

Forecast issued by Michael Leach on 11/30/06 at 3:18:47 pm CST

Mobile, Alabama 5 Day Forecast
Tonight
Tomorrow
Saturday
Sunday
Monday
Rain and thunderstorms.
Isolated showers.
Partly cloudy.
Partly cloudy.
Partly cloudy.
54°F
58°F
59°F
54°F
43°F
32°F 35°F 32°F
S 10-20 mph
G 15-30 mph
NW 10-20 mph
N 4-8 mph
N 5-10 mph
N 4-8 mph
70%
20%
0%
0%
0%

Mobile, Alabama 5 Day Detailed Forecast
Tonight… Mostly cloudy with rain and thunderstorms. Low 43. Winds south 10-20 mph with gusts 15-30 mph, shifting to the northwest toward morning. Chance of rain is 70 percent.
Tomorrow... Partly cloudy with isolated showers in the morning. High 54. Winds northwest 10-20 mph. Chance of rain is 20 percent.
Friday Night... Mostly clear. Low 32. Wind chill values as low as 24 degrees are possible. Winds north 5-10 mph.
Saturday... Partly cloudy. High 58. Winds north 4-8 mph.
Saturday Night... Partly cloudy. Low 35. Wind chill values as low as 28 degrees are possible. Winds north 4-8 mph.
Sunday... Partly cloudy. High 59. Winds north 5-10 mph.
Sunday Night... Partly cloudy. Low 32. Wind chill values as low as 22 degrees are possible. Winds north 7-14 mph.
Monday... Partly cloudy. High 54. Winds north 4-8 mph.
Monday Night... Mostly clear. Low 30. Winds northeast light.
Technical Discussion
Forecast Discussion (Thursday through Monday):
The main concern for this forecast period is the potential of strong to severe storms tonight. A negatively-tilted shortwave trough will move from the Mid-South to the Ohio Valley tonight through Friday morning. At the surface, an area of low pressure is expected to move from near Memphis, TN, northeastward into the Ohio Valley. A cold front trailing from this low is expected to move across the region late tonight and early Friday morning.

A line of showers and thunderstorms is expected to move across the region in advance of the front. The better dynamics with this system should stay to our north and west, closer to the shortwave trough moving across the Mid-South. However, models do indicate a rather strong LLJ moving across the region late tonight. The 12z GFS indicates a LLJ around 40 kts., while the NAM indicates a LLJ around 50-55 kts. With strong wind fields in place in the upper levels of the atmosphere, some storms that form may be able to mix some of the high winds down to the surface. Therefore, the main severe weather risk will be damaging winds. Models soundings indicate some speed shear, and perhaps a little directional shear across the region late tonight. An isolated tornado cannot be ruled out as any showers or storms ahead of the line or embedded in the line may be able to rotate. The dynamics will be tempered by a lack of instability across the area. Model soundings indicate little CAPE across the region. Therefore, the severe threat should remain rather isolated.

Will hold on to a 20% PoP for Friday morning to account for any lingering showers. Temperatures will cool off sharply behind the front. Friday will be a chilly and raw day, with temperatures holding in the 50's, and a strong northwest wind making it feel ever colder. With skies clearing, lows Friday night will be near freezing. The weekend ahead looks to be nice. High pressure will remain across the region during the weekend, and CAA will continue. Cool temperatures can be expected throughout the weekend, with highs in the upper 50's to near 60, and lows in the 30's. A reinforcing shot of cold air will move into the area Sunday night and Monday. The coldest night of the period may be Monday night as the GFS indicates a center of high pressure moving close to the region, resulting in mostly clear skies and light winds.

Hazardous Weather
Hazardous Weather Outlook (Thursday through Monday):
A strong cold front will move across the region late tonight and Friday morning. Ahead of the front, showers and thunderstorms will become likely tonight. There may be a few isolated strong to severe storms across the region, with the main threat being damaging winds due to rather strong dynamics across the region. An isolated tornado cannot be ruled out. The severe threat should remain isolated in nature due to limited instability. After the cold front passes, the threat of storms will diminish by Friday morning. People are urged to keep track of this system through a reliable weather service and be ready to take action if a watch or warning is necessary.

No hazardous weather is expected throughout the remainder of the period.

Astronomical and Climatological Data
Moon Phase
Gibbous waxing moon.
Gibbous Waxing
Sunset 4:51 PM
Sunrise 6:31 AM
11/30/06
Normal
High
Record High
Normal
Low
Record Low
Temperature
66°F
80°F (1967)
45°F
24°F (1976)
November
Normal
Wettest
Driest
Precipitation
5.41 in.
13.65 in. (1948)
0.06 in. (1924)

11/30 in Mobile Area Weather History
In 1977 an early morning tornado struck northern Mobile in Mobile County, AL. The tornado destroyed a home, heavily damaged 5 other homes, and caused minor damage to 8 additional homes along with causing tree and power line damage.

(Data compiled from NWS Mobile, NWS Birmingham, newspaper articles, USA Archives, US Hurricanes and HurricaneCity.com)


Thursday Morning Forecast

Forecast issued by Justin Gibbs on 11/30/06 at 2:01:51 am CST

Mobile, Alabama 5 Day Forecast
Today
Friday
Saturday
Sunday
Monday
Rain and thunderstorms.
Isolated showers and thunderstorms.
Partly cloudy.
Mostly sunny.
Mostly sunny.
78°F
55°F
56°F
54°F
51°F
44°F 33°F 32°F 30°F
S 10-20 mph
NW 10-20 mph
NW 2-4 mph
N 2-4 mph
NE 2-4 mph
60%
20%
0%
0%
0%

Mobile, Alabama 5 Day Detailed Forecast
Today... Partly cloudy early with clouds increasing by mid afternoon. Showers and Thunderstorms likely, especially in the afternoon. High 78. Winds south 10-20 mph. Chance of rain is 60 percent.
Tonight... Cloudy with showers and thunderstoms likely. Low 44. Winds south 10-20 mph. Chance of rain is 70 percent.
Friday... Partly cloudy with a slight chance of showers. High 55. Winds northwest 10-20 mph. Chance of rain is 20 percent.
Friday Night... Partly cloudy. Low 33. Wind chill values as low as 25 degrees are possible. Winds north 5-10 mph.
Saturday... Partly cloudy. High 56. Winds northwest 2-4 mph.
Saturday Night... Partly cloudy. Low 32. Winds north light.
Sunday... Mostly sunny. High 54. Winds north 2-4 mph.
Sunday Night... Mostly clear. Low 30. Wind chill values as low as 19 degrees are possible. Winds north 7-14 mph.
Monday... Mostly sunny. High 51. Winds northeast 2-4 mph.
Technical Discussion
Synopsis:
Upper level low continues to dig eastward this morning. Ahead of it, a powerful surface cylcone and associated cold frontal boundary is providing a messy weather picture across the CNTRL CONUS. WV/RAOB indicates the main trof axis currently looks to be just west of the TX Panhandle with the building sfc low just NE of DFW with a strong cold frontal boundary stretched further north into NERN IL. 0z KLIX sounding shows airmass modification is underway ahead of this approaching storm system, as moisture advects in up to about the 700mb level. Strong subsidence inversion is still evident however in the 650mb area due to very dry air positioned from that level to the tropopause.

Forecast Discussion (Thursday through Monday):
Our relative humidity at 5-600mb doesn't look to make a tremendous change per NAM/GFS guidance as this system moves through. Downstream RAOBs would support this theory with most showing rather large 500mb dewpoint depressions. WV shows a ribbon of more moist air, but guidance picks up on this as well and keeps it held back until after the main energy works through. This drier air is projected to substantially decrease our ML Lapse rates making deeper convection rather unlikely throughout the day.

That being said guidance picks up as it has for the past few days on a rather concentrated low level instability. 0-3km CAPE values are running around 100 j/kg at peak heating, with 0-1km SRH around 130 m2/s2. Total SBCAPE is projected to peak out around 300-400 m2/s2. Deep layer shear looks to lag a bit behind the front but will be around 30-40kts at the time of FROPA. That would lead to the possibility of very low topped convection that might become capable of damaging wind bursts and isolated tornadoes. DCAPEs around 600-700 j/kg would be supportive of damaging downdrafts even in slightly less vigorous convection, especially given the marginally favorable deep layer shear. This seems to be what SPC is keying in on in SWODY2 regarding a previous damaging wind event they are drawing simililarities to.

It looks like Tuesday will play host to a bit of overrunning/WAA precip. Clouds will be off and on throughout the day, leaning more towards the "on" category by afternoon. Guidance has picked up speed on the front in the 0z data. 12/18z brought it through in the 12/14z Friday timeframe where the latest GFS run appears to pull it through around 4-8z. NAM is along the same lines but slightly quicker. Linear extrapolation assuming the 30-35mph speed the front appears to be moving at right now would lean towards the faster GFS solution. Deepening of the low level low that is expected to occur as the upper level trof deepens and digs eastward (and becomes slightly negatively tilted) will help keep this system on track so will tweak the going timing slightly, peaking our precip closer to the 0-1z timeframe and trimming 3rd period pops to 20% while splitting 60/70 likely category pops for the 1st 2nd period. MOS guidance suite shows a rather tremendous spread due to differences in timing of the front so will throw them all out and pretty much go right down the middle. Cooler NAM is too early with front, warmer GFS is too late with it and doesnt appear to factor in any clouds/showers that look rather possible in the prefrontal warm sector. Wide spread continues in MOS guidance on Friday. Like the NAMs handling of surging the cooler air in but prefer the GFSs better synoptic track record so will again split the difference and go with a blustery high of 55. Friday night a strong ridge builds in behind the sfc frontal boundary and guidance has really taken a nose dive on low temperatures. The breadth, intensity, and depth of this frontal boundary leads me to believe its time to bite on this trend. Will go ahead and put our overnight low at 33 degrees and if trends continue a night below freezing under calming winds near the ridge may be possible.

GFS/UKMET/ECMWF/NAM are all now rather bent on brining a very powerful ridge into the central CONUS that effectively takes over the weather pattern for the entire country, brining the first solid shot of winter to much of the mid-contient, and likely to some degree the Gulf Coast. MEX MOS puts our overnight lows near freezing through the duration of the forecast period. A weak trof builds in in the mid levels by Sunday and by Monday morning the gulf coasts 1000-500mb thickness is running between 552 and 546dm. Will be following the theme of MEX MOS into the "icebox" and likely lowering daytime highs by 2-3 degrees to respond better to the rather substantial decrease in our mean column thickness. A few ribbons of mid level moisture will flirt with the region through the weekend so will keep PC skies through the duration. Although it appears Saturday we may go slightly above that as a weak wave passes overhead. Zonal pattern sets up aloft under the powerful low level ridge so will make few day to day changes in the forecast through the early part of next week.

Hazardous Weather
"Hazardous Weather Outlook (Thursday through Monday):
A powerful surface low pressure system will move near the area Friday, bringing with it a strong cold front that is expected to spark showers and thunderstorms in the late afternoon and evening hours. Low level windfields, and relatively strong winds further aloft will lead to a slight chance of isolated severe weather. If severe weather occurs it is most likely to be in the form of isolated tornadoes and damaging winds. Behind the front lies a rather sharp change in our weather pattern as our temperatures are expected to drop and become much cooler for the next few days.

Astronomical and Climatological Data
Moon Phase
Gibbous waxing moon.
Gibbous Waxing
Sunrise 6:30 AM
Sunset 4:51 PM
11/30/06
Normal
High
Record High
Normal
Low
Record Low
Temperature
66°F
80°F (1967)
45°F
24°F (1976)
November
Normal
Wettest
Driest
Precipitation
5.41 in.
13.65 in. (1948)
0.06 in. (1924)

11/30 in Mobile Area Weather History
In 1977 an early morning tornado struck northern Mobile in Mobile County, AL. The tornado destroyed a home, heavily damaged 5 other homes, and caused minor damage to 8 additional homes along with causing tree and power line damage.

(Data compiled from NWS Mobile, NWS Birmingham, newspaper articles, USA Archives, US Hurricanes and HurricaneCity.com)


Tuesday, November 28, 2006

Tuesday Evening Forecast

Forecast issued by Michael Leach on 11/28/06 at 3:34:57 pm CST

Mobile, Alabama 5 Day Forecast
Tonight
Tomorrow
Thursday
Friday
Saturday
Fog.
Scattered showers.
Rain and thunderstorms.
Isolated showers and thunderstorms.
Partly cloudy.
75°F
77°F
60°F
61°F
60°F
62°F 58°F 39°F
SE 5-10 mph
SE 10-15 mph
SSE 10-15 mph
G 15-30 mph
NW 10-15 mph
N 4-8 mph
0%
30%
50%
30%
0%

Mobile, Alabama 5 Day Detailed Forecast
Tonight… Partly cloudy. Areas of fog developing. Fog may be dense at times. Low 60. Winds southeast 5-10 mph.
Tomorrow... Partly cloudy with scattered showers. High 75. Winds southeast 10-15 mph. Chance of rain is 30 percent.
Wednesday Night... Partly cloudy with scattered showers. Low 62. Winds southeast 7-14 mph. Chance of rain is 30 percent.
Thursday... Mostly cloudy with a chance of rain and thunderstorms. High 77. Winds south-southeast 10-15 mph with gusts 15-30 mph. Chance of rain is 50 percent.
Thursday Night... Mostly cloudy with rain and thunderstorms. Low 58. Winds south 10-15 mph. Chance of rain is 70 percent.
Friday... A chance of showers and thunderstorms in the morning. Then, decreasing clouds. High 60. Winds northwest 10-15 mph. Chance of rain is 30 percent.
Friday Night... Mostly clear. Low 39. Wind chill values as low as 32 degrees are possible. Winds north 5-10 mph.
Saturday... Partly cloudy. High 61. Winds north 4-8 mph.
Saturday Night... Partly cloudy. Low 43. Winds north-northeast 4-8 mph.
Technical Discussion
Forecast Discussion (Tuesday through Saturday):
The main concerns with this forecast are rain chances throughout the period and the risk of severe weather on Thursday and Thursday night. Also, the possibility of dense fog tonight and Wednesday morning is a concern.

Tonight, warm temperatures are expected as overnight lows will only fall to around 60 degrees. MAV, MET, and FWC guidance all indicate dewpoint depressions around 0 beginning late this evening and during the overnight hours. MOS members also indicate very low visibilities across the areas (all MOS guidance indicates visibility in the lowest category). This points to the potential for dense fog across the area tonight. Will indicate areas of fog, some of which may be dense, in the forecast. Will not include any PoP's for tonight. KMOB WSR-88D does indicate a few isolated showers offshore currently. While some areas may see an isolated shower during the late afternoon or evening hours, do not believe it is a high enough chance to include in the forecast.

For Wednesday, will continue the mention of scattered showers in the forecast. WAA looks to become a little stronger at 850 mb during this time frame, leading to a little more lifting across the area. Some isentropic lifting may also occur across the area. With this said, will go above guidance for PoP's in the Wednesday and Wednesday night time frame, and keep PoP's around 30% for these periods.

Thursday, rain chances will increase as the cold front and associated upper level dynamics move closer to the region. 12z GFS and NAM models have trended a little farther south with the 500 mb negatively-tilted shortwave trough. The models show the axis of the trough across the Mid-South. Models indicate a ~40 kt. LLJ across the area Thursday and Thursday night. The dynamics with this system don't look quite as impressive as with the last system, as the better dynamics look to stay to our north and west. However, with strong wind fields in place, a few isolated strong to severe storms look to be possible (especially if models trend farther south with the trough). CAPE looks to be marginal with this event. Models indicate the highest MUCAPE of only around 500-750 J/kg. NAM indicates 0-3 km SRH values of 150-200 m2/s2 Thursday evening. A GFS model sounding for Thursday evening only indicates CAPE of around 300 J/kg, but most of this is confined to the 850 to 600 mb layer. The sounding indicates helicity of 174 ms/s2, with good speed shear but not much directional shear. With all of this said, some isolated strong to severe storms are possible. At this time, will not mention strong or severe wording in the forecast, but continue to monitor model trends and let future forecasters fine tune the forecast.

Will hold on to 30% PoP for Friday morning to account for a possible slower fropa. Decreasing clouds and CAA should commence on Friday afternoon after fropa, with cooler temperatures moving into the region behind the front. For Saturday, continue northerly flow and slight CAA should continue. With this, expect partly cloudy skies and dry weather on Saturday, with temperatures remaining rather pleasant.

Hazardous Weather
Hazardous Weather Outlook (Tuesday through Saturday):
Areas of fog are expected to develop across the area tonight. Some of the fog may be dense at times. Those planning travel across the region tonight should be aware of the potential for dense fog, and take extra caution in areas of fog.

On Thursday, a cold front is expected to move near the area. Along and ahead of the front, showers and thunderstorms will become likely by Thursday afternoon and evening. A few isolated strong to severe storms are possible. People should keep up to date on the latest forecasts concerning this weather system.

Astronomical and Climatological Data
Moon Phase
First.
First
Sunset 4:51 PM
Sunrise 6:30 AM
11/28/06
Normal
High
Record High
Normal
Low
Record Low
Temperature
67°F
80°F (2005)
45°F
25°F (1938)
November
Normal
Wettest
Driest
Precipitation
5.41 in.
13.65 in. (1948)
0.06 in. (1924)

Tuesday Morning Forecast

Forecast issued by Justin Gibbs on 11/28/06 at 1:39:49 am CST

Mobile, Alabama 5 Day Forecast
Today
Wednesday
Thursday
Friday
Saturday
Partly cloudy.
Scattered showers.
Rain and thunderstorms.
Isolated showers and thunderstorms.
Partly cloudy.
76°F
75°F
78°F
62°F
61°F
59°F 63°F 60°F 40°F
SE 5-10 mph
SE 10-15 mph
SE 10-20 mph
NW 10-15 mph
W 4-8 mph
0%
30%
50%
0%
0%

Mobile, Alabama 5 Day Detailed Forecast
Today... Partly cloudy. High 76. Winds southeast 5-10 mph.
Tonight... Partly cloudy with fog forming in the evening hours. Dense Fog possible in some areas. Low 59. Winds southeast 7-14 mph.
Wednesday... Partly cloudy with scattered showers. High 75. Winds southeast 10-15 mph. Chance of rain is 30 percent.
Wednesday Night... Partly cloudy with scattered showers and thunderstorms. Low 63. Winds southeast 10-15 mph. Chance of rain is 40 percent.
Thursday... Mostly cloudy with scattered showers and thunderstorms. High 78. Winds southeast 10-20 mph. Chance of rain is 50 percent.
Thursday Night... Cloudy with showers and thunderstorms likely. Low 60. Winds south 10-20 mph. Chance of rain is 60 percent.
Friday... Variable clouds with partial clearing in the afternoon. Isolated showers and storms in the morning. High 62. Winds northwest 10-15 mph.
Friday Night... Partly cloudy. Low 40. Wind chill values as low as 34 degrees are possible. Winds northwest 5-10 mph.
Saturday... Partly cloudy. High 61. Winds west 4-8 mph.
Technical Discussion
Synopsis:
Rather active pattern exists over the CONUS this morning with the main theme being ridge east..trough west. Mean deep layer ridge axis looks to be continuing to shift to the east; currently looking to be over GA/NC/WRN VA with the sfc ridge axis in the vcnty of a New Orleans to Atlanta line. However, this ridge is beginning to loosen its grip on our weather as the winds begin to pick up and the main ridge shifts ewd (currently centered over ERN Canada with the trof axis running along the eastern seaboard. Further upstream a once closed upper level low has again reopened as forecast and continues to dig east/southeastward. 0z Data puts the 500mb trof axis along a Sacremento, CA/Portland, OR line as it shifts eastward. This rather robust upper level low has led to surface cyclogenesis which remains underway on the lee side of the rockies. 0z KLIX sounding continues to reveal a very dry airmass with PWATs around 0.67 with strong indications of subsidence in the form of an inversion around 800mb.

Forecast Discussion (Tuesday through Saturday):
Short Term...

Pressure gradient will tighten as the afforementioned low pushes eastward through the first few periods. Going wind forecast looks to be in good shape with SE winds at 5-10mph. NAM/GFS projections show little change in the overall airmass/column thickness for the first period from what we saw today...so feel comfortable with the MOS consensus of 76 which is 1 degree warmer than what we saw today. As the winds move to the southwest, guidance is in solid agreement with a slow modification of our airmass, especially in the lower levels. This slow increase in moisture provides confidence in continuing the going Partly Cloudy forecast in the first period. We will likely see a cloud or two more into the overnight hours as the slow modification continues. 700/850mb/sfc NAM/GFS windfields also continue to support the eeking upward of the wind speeds to the 7-14mph range as the upper level and surface low continue to approach from the west. Main question regarding 2nd period lows revolves around the amount of moisture advection we will see during the day today. Guidance looks to bring dewpoints of 58/60 in by late evening. That lines up well with what we are seeing tonight (looking downstream) so will lean on the more mixed side of things and go with 59 for the second period low. Will also include fog, as an event slightly more substantial than tonights looks to be in the cards as the dewpoint depression looks to drop to 0 at several regional stations by 3-4z. Agreement amongst guidance and MOS and low visibility signals amongst the MOS suite, will go ahead and mention dense fog in some areas and patchy fog metro area wide. Later shifts will likely need to reevaluate this and make mention of what may become a more significant fog event in the overnight hours Tuesday.

Wednesday it appears we will begin to be within flirting range of the warmfront ahead of the surface low. Nevertheless, a slight amount of overrunning looks to be possible during the day Wednesday. Also will bump windfields up a half category to 10-15mph to come into better agreement with the latest GFS guidance which looks good in response to the deepening trof through the column and the subsequent behavior of the sfc storm system. With the tightening windfield and associated overrunning will go with a slight step in the wetter direction with a 30% pop in the afternoon and maintain the going 40% pop in the overnight hours. Will also handle the thunder/no thunder similarly adding the chance of a rumble in the post 0z hours once a bit of elevated instability builds in closer to the warmfrontal boundary. Will remain on the Mostly Cloudy boat through the passage of the storm system due to the substantial column moisture expected to be in place invof the low.

Overall, prefer the slightly slower and HPC endorsed GFS on timing, this brings the main frontal boundary through in the 10z time frame. Will slow this down a few hours to allow for slowdown during a very complex evolution of this storm system. Will go with a mostly cloudy and breezy solution for the Wednesday/Wednesday night period as the warm front passes early in the day and we remain in the warm sector. Mid-level moisture will be somewhat lacking subsequently mid level lapse rates follow suit with nothing greater than 5 c/km indicated in any going guidance. Forecast soundings and MUCAPE plan view fields reveal about 500-1000 j/kg CAPE at peak instability from surface based lifted parcels (elevated instability earlier in the event looks to be in the sub 500 j/kg range.) Best dyanmical support may be just behind the event as during frontal passage we look to be in the 20-40kt range in the 0-6km range. Additionally the best low level jet (>50kts) looks to build in over the lower Ohio Valley as opposed to this region. Backed sfc winds in the warm sector to yield 0-1km SRH values in the 150-200 m2/s2 levels which would help support rotating updrafts in the event of convection in this area.

That being said there are a lot of questions regarding how all of this will come together but it appears we run a relatively conditional threat for severe weather, with it being too early to get detailed as to the main threats. The rain and thunderstorm threats though are pretty cut and dried, so will bump to likely pops for the Wednesday night period and hold the going 50% for the Thursday day period, mainly becuase of questions regarding timing. Will carry the going blustery wind forecast into into the Thursday evening period as well.

Long Term...

Friday the front looks to push through by noon at the very latest, will introduce a 20% pop to ease the possibility of a slowed FROPA into the forecast. Will include morning wording on this however and paint a cooler and breezy forecast picture. Like the going 'variable cloudiness' as the best 4th and 10 scenario for the time being, but additionally believe with the ribbons of moisture behind the front that likely will be the best depiction of sensible wx for the day.

Friday evening looks to be a cool and mostly clear night. MOS consensus is around 42 but will tweak that a touch downward as it appears the cloud cover is a bit too high considering the column moisture that will be present (not to say there won't be any clouds--but there probably won't be quite as many as the GFS is currently forecasting) so will go with a 40 for Friday evening.

Will paint a partly cloudy and 61 degree day for Saturday as a ridge builds to our west.

Hazardous Weather
Hazardous Weather Outlook (Tuesday through Saturday):
Fog will become possible in the evening and overnight hours Tuesday across the Mobile area. Current indications are the fog may be rather widespread and likely will be dense in some areas. Motorists with travel plans for Tuesday night should be prepared for the possibilty of rapidly reduced visibilities in areas of heavy fog. Areas such as the Mobile Bayway and Causeway and areas over and near bodies of water will be most susceptible to dense fog. By midweek organized showers and thunderstorms are expected, there is a slight chance a few of these storms may be severe, mainly on Thursday evening and early Friday morning. It is too early to provide details on the type of severe weather that may occur or exact timing of this system. Residents of the Mobile area should monitor updated forecasts throughout the week as the event nears and more details become available.

Astronomical and Climatological Data
Moon Phase
First.
First
Sunrise 6:29 AM
Sunset 4:51 PM
11/28/06
Normal
High
Record High
Normal
Low
Record Low
Temperature
67°F
80°F (2005)
45°F
25°F (1938)
November
Normal
Wettest
Driest
Precipitation
5.41 in.
13.65 in. (1948)
0.06 in. (1924)

Tuesday, November 14, 2006

Tuesday Evening Forecast

Forecast issued by Michael Leach on 11/14/06 at 2:35:20 pm CST

Mobile, Alabama 5 Day Forecast
Tonight
Tomorrow
Thursday
Friday
Saturday
Rain and thunderstorms.  Some storms may be severe.
Rain and thunderstorms.  Some storms may be severe.
Decreasing clouds.
Mostly sunny.
Sunny.
74°F
61°F
66°F
67°F
63°F
47°F 40°F 43°F
S 10-20 mph
G 15-30 mph
SW 10-20 mph
G 15-30 mph
NW 7-14 mph
G 10-20 mph
N 5-10 mph
N 5-10 mph
70%
90%
0%
0%
0%

Mobile, Alabama 5 Day Detailed Forecast
Tonight… Mostly cloudy with showers and thunderstorms becoming likely. Some storms may be severe late. Low around 45. Winds south 10-20 mph with gusts 15-30 mph. Chance of rain is 70 percent.
Tomorrow... Rain and thunderstorms. Some storms may be severe. High near 71. Winds southwest 10-20 mph with gusts 15-30 mph. Chance of rain is 90 percent.
Wednesday Night... Mostly cloudy with isolated showers, mainly early in the evening. Low around 60. Winds west-northwest 10-15 mph with gusts 15-30 mph. Chance of rain is 20 percent.
Thursday... Decreasing clouds. High near 73. Winds northwest 7-14 mph with gusts 10-20 mph.
Thursday Night... Mostly clear. Low around 47. Wind chill values as low as 34 degrees are possible. Winds northwest 5-10 mph.
Friday... Mostly sunny. High near 63. Winds north 5-10 mph.
Friday Night... Clear. Low around 42. Winds north 4-8 mph.
Saturday... Sunny. High near 67. Winds north 5-10 mph.
Saturday Night... Mostly clear. Low around 40. Winds northeast 5-10 mph.
Technical Discussion
"Short Term (Tuesday through Wednesday evening):
The main focus on this forecast will be the potential of severe thunderstorms tonight and Wednesday. Also, strong gradient winds will also be a concern.

12z NAM and GFS guidance in basic agreement with a strong low pressure system moving across the mid-South through Wednesday. The NAM is slightly farther south than the GFS, but not so much so as to really affect any sensible weather. As the low pressure system develops to our northwest, a strong pressure gradient is expected to develop across our area, leading to gusty winds. Basically kept the wind forecast from the previous forecaster, and indicated gusts to 30 mph possible beginning tonight and continuing through Wednesday.

WAA/LLJ should rapidly strengthen across the area tonight. Lifting associated with the WAA should lead to showers and thunderstorms developing across the area tonight (already, radars are showing showers and thunderstorms developing over Louisiana and southern Mississippi). By late tonight and early Wednesday morning, strong convection is expected to develop across the region as the LLJ strengthens more and centers itself close to our area. A warm front moving off the Gulf will also enhance the convection. GFS and NAM forecast soundings indicate CAPE values possibly over 1000 J/kg, with rather substantial positive areas on the sounding. 0-3 km SRH values look to possibly be over 400 m2/s2, with EHI values approaching 3 (per GFS sounding for 18z Wednesday). The LLJ at this time looks to be around 60 kts. Looks like the greatest severe threat will be damaging straight line winds due to the very strong wind fields expected. Directional shear does not look too impressive according to model soundings (although the latest GFS soundings do indicate a touch more directional shear than previous model runs). With this said, believe that we do have an isolated tornado threat. Tornadoes will be most likely in any supercells able to form out ahead of the main squall line, and also in individual cells embedded within the squall line. The NAM appears to be a little slower with fropa than GFS. I believe the front should cross the area by 00z Thursday (6 pm Wednesday), with the squall line preceding the front.

Left in slight chance PoP's for Wednesday night to account for any lingering showers along and just behind the front. Did not clear skies out on Wednesday night as MAV and MET guidance did to account for the possibility of low clouds behind the front.

Long Term (Thursday through Saturday):
On Thursday, indicated decreasing clouds as the low clouds should move off to the east. Drier and cooler weather should be on tap for the end of the week, with mostly sunny skies on Friday and highs in the 60's. High pressure is expected to continue across the area through Saturday, providing us with a northerly wind. CAA and subsidence will dominate this period. "

Hazardous Weather
Hazardous Weather Outlook (Tuesday through Saturday):
An intense storm system that is expected to stengthen over the plains later today and move toward the area. As it does, warm moist air will surge nortward ahead of the system and set the stage for a potential severe weather event. Strong low-level wind fields will support storms to become organized pose a threat of wind damage. Although damaging winds is expected to be the primary threat, large hail and isolated tornadoes will be possible. Thunderstorms should increase in coverage tonight and be scattered across the area into the morning hours on Wednesday. As the system passes later during the afternoon on Wednesday, a line of thunderstorms will likely sweep across the area bringing the highest threat for severe weather. The most likely time for this line to impact the area will be from early to mid afternoon. Residence should review severe weather safety information and be prepared to take action should severe weather threaten. Now is a good time to develop a plan of action if you do not already have one. Monitor a reliable weather source, such as NOAA Weather Radio, for the latest on the dangerous weather situation.

Astronomical and Climatological Data
Moon Phase
Last.
Last
Sunset 4:55 PM
Sunrise 6:18 AM
11/14/06
Normal
High
Record High
Normal
Low
Record Low
Temperature
70°F
82°F (1955)
48°F
32°F (1986)
November
Normal
Wettest
Driest
Precipitation
5.41 in.
13.65 in. (1948)
0.06 in. (1924)

11/14 in Mobile Area Weather History
In 1983 an early evening storm dropped an F0 tornado near Fulton in Clarke County, AL where a roof of a home was damaged and several trees were downed.

(Data compiled from NWS Mobile, NWS Birmingham, newspaper articles, USA Archives, US Hurricanes and HurricaneCity.com)


Tuesday Morning Forecast - UPDATE

Forecast issued by Randy Bowers on 11/14/06 at 11:36:39 am CST

Mobile, Alabama 5 Day Forecast
Today
Wednesday
Thursday
Friday
Saturday
Scattered showers and thunderstorms.
Rain and thunderstorms.  Some storms may be severe.
Decreasing clouds.
Mostly sunny.
Mostly sunny.
70°F
74°F
62°F
68°F
73°F
65°F 48°F 39°F 40°F
SE 10-15 mph
SW 10-20 mph
NW 10-20 mph
W 2-4 mph
W 2-4 mph
60%
90%
0%
0%
0%

Mobile, Alabama 5 Day Detailed Forecast
This Afternoon...Cloudy showers and thunderstorms becoming likely. High 70. Winds southeast 10-15 mph with gusts to 25 mph late. Chance of rain is 70 percent.
Tonight... Cloudy with showers and thunderstorms. Some storms may be severe with damaging winds. Low 65. Winds south 15-25 mph with higher gusts possible, especially toward daybreak. Chance of rain is 90 percent.
Wednesday... Cloudy with rain and thunderstorms. Some storms may be severe with damaging winds. High 74. Winds southwest 15-25 mph with higher gusts. Chance of rain is 90 percent.
Wednesday Night... Mostly cloudy with a slight chance of showers. Low 48. Winds northwest 10-20 mph. Chance of rain is 20 percent.
Thursday... Mostly cloudy with decreasing clouds late. High 62. Winds northwest 10-20 mph.
Thursday Night... Mostly clear. Low 39. Winds west 2-4 mph.
Friday... Mostly sunny. High 68. Winds west 2-4 mph.
Friday Night... Mostly clear. Low 40. Winds west 2-4 mph.
Saturday... Mostly sunny. High 73. Winds west 2-4 mph.
Technical Discussion
"Forecast Discussion (Tuesday through Saturday):
Quick update to adjust timing. Have introduced likely PoP for later today based on latest RUC/short term analysis and radar trends. Quciker WAA onset than models had previously shown. Also, adjusted winds for first period. Went with categorical PoPs overnight as well. -Prvious AFD sent 3:00 am CST- Main focus for this forecast will be potent mid/upper trough that is to impact the area starting tonight. Several concerns with this system from strong gradient winds, to potential for severe tstms and heavy rainfall. Sfc ridge axis located over the area early this morning with calm winds at KMOB last hr. Td/T depressions narrowing and a few areas of fog has formed per area ASOS network. Fog that does form later this morning should mix out quickly with diurnal heating. Meanwhile, Srly flow should increase dramatically throughout the day in response to lee sfc cyclogenesis evolving as a result of digging/amplifying mid/upper trough. Per previous AFDs and HPC PMDHMD, NAM has trended deeper/further south and slightly slower over the past few runs. This results in more intense sfc cyclone over the Mid-South with a slightly further south track than previously expected. Strength and position of surface low raises concern for strong gradient winds. In fact, 00z guidance consensus is for slightly stronger winds than going forecast has. Have raised pre-frontal sfc winds in public forecast in Tue night-Wed timeframe. Post-frontal winds were also on the low side and chose to increase as well. LLJ/WAA expected to strengthen dramatically late Tue/Tue night w/ potential for WAA SHRA/TSRA as soon as Tuesday evening. Have thus reintroduced PoP for Tue night period and have chosen to go likely. Toward daybreak Wed, position of 850 mb LLJ and warm front/best low-level moisture favors increased potential for deep convection. GFS and NAM forecast soundings both indicating rather substantial positive area w/ column CAPE AOA 1800 J/KG. Much of this is located in the lower portion of the column where best lapse rates reside. Significant 0-3 km CAPE and strong shear yielding EHI values approaching 3. NAM is overall weak with mid-level lapse rates, while GFS is slightly steeper but shows a rather substantial inversion between 500 mb and 700 mb. Feel that given this, best chance for deep convection would be in the form of a squall line during the afternoon where forcing/convergence along sfc boundary should be sufficient. Convection along the warm front or discrete cells in the warm sector likely to remain rather shallow. Despite this, low-level speed shear will be significant. 0-1 km shear AOA 35 kts or greater will be present. Given this, damaging winds would be a concern in even shallow convection. Undoubtedly, damaging winds will be the primary severe wx concern given intense wind fields. Directional shear in the lowest 3 km not overly impressive and substantial tornado threat is therefore not expected. Still, sufficient directional shear combined with intense speed shear will be enough for the threat of isolated tornadoes, particularly in discrete cells or embedded supercells within the line. Current thinking is that convection will increase in coverage/intensity overnight Tue night with pcpn coverage probably attaining likely criteria by or just before daybreak as warm front passes. Scattered to numerous convection likely to persist in warm sector before fropa/squall line passage early/mid-afternoon. Post-frontal lingering moisture should result in overcast through at least early-afternoon Thur, and possibly the entire day. Have worded the public forecast accordingly. A quick peak at the 06z NAM shows a slightly slower/less intense system overall w/ 500 mb hieght falls not quite as strong as previous run. Also, fropa is delayed slighty to about 22z. This should not require much in the way of changes in the 00z-based forecast package and will leave all the same for now. Later shifts will want to consider timing trends if nothing else. "
Hazardous Weather
Hazardous Weather Outlook (Tuesday through Saturday):
An intense storm system that is expected to stengthen over the plains later today and move toward the area. As it does, warm moist air will surge nortward ahead of the system and set the stage for a potential severe weather event. Strong low-level wind fields will support storms to become organized pose a threat of wind damage. Although damaging winds is expected to be the primary threat, large hail and isolated tornadoes will be possible. Thunderstorms should increase in coverage tonight and be scattered across the area into the morning hours on Wednesday. As the system passes later during the afternoon on Wednesday, a line of thunderstorms will likely sweep across the area bringing the highest threat for severe weather. The most likely time for this line to impact the area will be from early to mid afternoon. Residence should review severe weather safety information and be prepared to take action should severe weather threaten. Now is a good time to develop a plan of action if you do not already have one. Monitor a reliable weather source, such as NOAA Weather Radio, for the latest on the dangerous weather situation.

Astronomical and Climatological Data
Moon Phase
Last.
Last
Sunrise 6:17 AM
Sunset 4:55 PM
11/14/06
Normal
High
Record High
Normal
Low
Record Low
Temperature
70°F
82°F (1955)
48°F
32°F (1986)
November
Normal
Wettest
Driest
Precipitation
5.41 in.
13.65 in. (1948)
0.06 in. (1924)

11/14 in Mobile Area Weather History
In 1983 an early evening storm dropped an F0 tornado near Fulton in Clarke County, AL where a roof of a home was damaged and several trees were downed.

(Data compiled from NWS Mobile, NWS Birmingham, newspaper articles, USA Archives, US Hurricanes and HurricaneCity.com)


Tuesday Morning Forecast

Forecast issued by Randy Bowers on 11/14/06 at 3:05:12 am CST

Mobile, Alabama 5 Day Forecast
Today
Wednesday
Thursday
Friday
Saturday
Increasing clouds.
Rain and thunderstorms.  Some storms may be severe.
Decreasing clouds.
Mostly sunny.
Mostly sunny.
71°F
74°F
62°F
68°F
73°F
63°F 48°F 39°F 40°F
S 10-20 mph
SW 10-20 mph
NW 10-20 mph
W 2-4 mph
W 2-4 mph
10%
90%
0%
0%
0%

Mobile, Alabama 5 Day Detailed Forecast
Today... Areas of fog this morning giving way to mostly sunny skies. Becoming partly cloudy during the afternoon. High 71. Light south wind increasing to 10 to 20 mph late.
Tonight... Mostly cloudy with showers and thunderstorms becoming likely. Low 63. Winds south at 15 to 25 mph with gusts around 30 mph. Chance of rain is 60 percent.
Wednesday... Mostly cloudy with thunderstorms. Some storms may be severe with damaging winds. High 74. Winds southwest 15 to 25 mph with gusts to around 30 mph. Chance of rain is 90 percent.
Wednesday Night... Mostly cloudy with a slight chance of showers. Low 48. Winds northwest 10 to 20 mph. Chance of rain is 20 percent.
Thursday... Mostly cloudy. High 62. Winds northwest 10 to 20 mph.
Thursday Night... Mostly clear. Low 39. Winds west 4 to 8 mph.
Friday... Mostly sunny. High 68. Winds west 2 to 4 mph.
Friday Night... Mostly clear. Low 40. Winds west 2 to 4 mph.
Saturday... Mostly sunny. High 73. Winds west 2 to 4 mph.
Technical Discussion
Main focus for this forecast will be potent mid/upper trough that is to impact the area starting tonight. Several concerns with this system from strong gradient winds, to potential for severe tstms and heavy rainfall.

Sfc ridge axis located over the area early this morning with calm winds at KMOB last hr. Td/T depressions narrowing and a few areas of fog has formed per area ASOS network. Fog that does form later this morning should mix out quickly with diurnal heating. Meanwhile, Srly flow should increase dramatically throughout the day in response to lee sfc cyclogenesis evolving as a result of digging/amplifying mid/upper trough. Per previous AFDs and HPC PMDHMD, NAM has trended deeper/further south and slightly slower over the past few runs. This results in more intense sfc cyclone over the Mid-South with a slightly further south track than previously expected. Strength and position of surface low raises concern for strong gradient winds. In fact, 00z guidance consensus is for slightly stronger winds than going forecast has. Have raised pre-frontal sfc winds in public forecast in Tue night-Wed timeframe. Post-frontal winds were also on the low side and chose to increase as well.

LLJ/WAA expected to strengthen dramatically late Tue/Tue night w/ potential for WAA SHRA/TSRA as soon as Tuesday evening. Have thus reintroduced PoP for Tue night period and have chosen to go likely. Toward daybreak Wed, position of 850 mb LLJ and warm front/best low-level moisture favors increased potential for deep convection. GFS and NAM forecast soundings both indicating rather substantial positive area w/ column CAPE AOA 1800 J/KG. Much of this is located in the lower portion of the column where best lapse rates reside. Significant 0-3 km CAPE and strong shear yielding EHI values approaching 3. NAM is overall weak with mid-level lapse rates, while GFS is slightly steeper but shows a rather substantial inversion between 500 mb and 700 mb. Feel that given this, best chance for deep convection would be in the form of a squall line during the afternoon where forcing/convergence along sfc boundary should be sufficient. Convection along the warm front or discrete cells in the warm sector likely to remain rather shallow. Despite this, low-level speed shear will be significant. 0-1 km shear AOA 35 kts or greater will be present. Given this, damaging winds would be a concern in even shallow convection. Undoubtedly, damaging winds will be the primary severe wx concern given intense wind fields. Directional shear in the lowest 3 km not overly impressive and substantial tornado threat is therefore not expected. Still, sufficient directional shear combined with intense speed shear will be enough for the threat of isolated tornadoes, particularly in discrete cells or embedded supercells within the line.

Current thinking is that convection will increase in coverage/intensity overnight Tue night with pcpn coverage probably attaining likely criteria by or just before daybreak as warm front passes. Scattered to numerous convection likely to persist in warm sector before fropa/squall line passage early/mid-afternoon.

Post-frontal lingering moisture should result in overcast through at least early-afternoon Thur, and possibly the entire day. Have worded the public forecast accordingly.

A quick peak at the 06z NAM shows a slightly slower/less intense system overall w/ 500 mb hieght falls not quite as strong as previous run. Also, fropa is delayed slighty to about 22z. This should not require much in the way of changes in the 00z-based forecast package and will leave all the same for now. Later shifts will want to consider timing trends if nothing else.

Hazardous Weather
Hazardous Weather Outlook (Tuesday through Saturday):
An intense storm system that is expected to stengthen over the plains later today and move toward the area. As it does, warm moist air will surge nortward ahead of the system and set the stage for a potential severe weather event. Strong low-level wind fields will support storms to become organized pose a threat of wind damage. Although damaging winds is expected to be the primary threat, large hail and isolated tornadoes will be possible. Thunderstorms should increase in coverage tonight and be scattered across the area into the morning hours on Wednesday. As the system passes later during the afternoon on Wednesday, a line of thunderstorms will likely sweep across the area bringing the highest threat for severe weather. The most likely time for this line to impact the area will be from early to mid afternoon. Residence should review severe weather safety information and be prepared to take action should severe weather threaten. Now is a good time to develop a plan of action if you do not already have one. Monitor a reliable weather source, such as NOAA Weather Radio, for the latest on the dangerous weather situation.

Astronomical and Climatological Data
Moon Phase
Last.
Last
Sunrise 6:17 AM
Sunset 4:55 PM
11/14/06
Normal
High
Record High
Normal
Low
Record Low
Temperature
70°F
82°F (1955)
48°F
32°F (1986)
November
Normal
Wettest
Driest
Precipitation
5.41 in.
13.65 in. (1948)
0.06 in. (1924)

11/14 in Mobile Area Weather History
In 1983 an early evening storm dropped an F0 tornado near Fulton in Clarke County, AL where a roof of a home was damaged and several trees were downed.

(Data compiled from NWS Mobile, NWS Birmingham, newspaper articles, USA Archives, US Hurricanes and HurricaneCity.com)


Monday, November 13, 2006

Monday Morning Forecast

Forecast issued by Justin Gibbs on 11/13/06 at 4:31:26 am CST

Mobile, Alabama 5 Day Forecast
Today
Tuesday
Wednesday
Thursday
Friday
Mostly sunny.
Variable clouds.
Rain and thunderstorms.
Mostly sunny.
Mostly sunny.
68°F
70°F
73°F
64°F
67°F
46°F 59°F 57°F 43°F
Calm
NW 5-10 mph
SW 15-30 mph
NW 7-14 mph
W 4-8 mph
0%
10%
70%
0%
0%

Mobile, Alabama 5 Day Detailed Forecast
Today... Mostly sunny. High 68. Winds calm.
Tonight... Partly cloudy. Low 46. Winds north light.
Tuesday... Variable cloudiness. High 70. Winds southwest 5-10 mph.
Tuesday Night... Mostly cloudy with scattered showers and thunderstorms. Low 59. Winds south 10-20 mph. Chance of rain is 50 percent.
Wednesday... Mostly cloudy with showers and thunderstorms likely. High 73. Winds southwest 15-30 mph. Chance of rain is 70 percent.
Wednesday Night... Variable cloudiness with scattered showers and thunderstorms. Low 57. Winds west 15-30 mph. Chance of rain is 30 percent.
Thursday... Mostly sunny. High 64. Winds northwest 7-14 mph.
Thursday Night... Mostly clear. Low 43. Winds northwest 7-14 mph.
Friday... Mostly sunny. High 67. Winds west 4-8 mph.
Technical Discussion
Synopsis:
Several major players are affecting our weather this morning as a complex forecast scenario unfolds.

Upper level analysis reveals zonal flow in the upper levels over the northcentral Gulf coast as a jet max associated with the subtropical jet slides just to our south this morning. Further north, weak ridging exists as the flow splits either side of a vertically stacked closed low located just off the eastern VA/NC coast. As you approach the surface, ridging becomes evident in the 700/850mb level. This picture is reflected well in WV imagery this morning which also gives away a larger upper level disturbance pushing eastward across the central CONUS. A rather weak sfc low and associated frontal boundaries can also be found with the warm front/associated upper level divergence responsible for a trail of showers and storms across CNTRL MO/AR. Closer to home a bone dry airmass is in place with 0z LIX sounding showing a PWAT value of 0.29in. and a noticable subsidence inversion.

" "Forecast Discussion (Monday through Friday):
First and second periods will be most affected by the afforementioned upper level wave. Trof axis is forecast by both WRF/GFS to push through around 0z Tuesday. Fcst soundings indicate some disagreement between those two models with GFS being much more aggressive with column moisture. Both models appear to have initialized reasonably well, but NAM has performed better through the first 12 hours of the model run, so will go with the slightly drier NAM and keep all pcpn out of the forecast tonight. This is supported with a lack of overall divergence aloft, and associated low level vertical motion, and an overall lack of a substantial isentropic upglide signal in guidance. Will increase cloud cover slightly to announce the shortwaves presence. For first period high will go with majority MOS which seems to handle the less CAA oriented airmass but slightly lower overall column height well, and go with a high of 68. Will go 1 degree above MOS majority at 46 for second period low.

Tuesday business begins to pick up as by midday a substantial airmass modification is forecast to be underway. We will likely start the day relatively cool and dry but the column is forecast to rapidly moisten ahead of an approaching upper level wave. Main fcst challenge this period is timing of warmfrontal boundary and type/amount of convection/precip that will be associated with it. For now will handle the forecast by increasing cloud cover to Partly Sunny for the Wednesday period and allowing a fairly large wind spread from 5-15 mph from the south as we will start off fairly weak and pick up by late afternoon. GFS/NAM forecast soundings reveal a rather dry airmass aloft with a very thin low level moisture level until later in the evening; so most cloud cover is expected to be in the thin low level strat deck variety. Will go with a high of 69 on Tuesday as WAA should overcome some of the lack of insolation expected from the cloud cover.

Tuesday night is when the forecast becomes the most tricky. Main dynamics move into place as the sfc warmfrontal boundary surges northward as the main upper level trough rapidly and dramatically amplifies. Sfc low responds in kind as do our low level windfields, as well as our deeper layer windfields. Will increase winds to 15-25 mph and introduce a 50% pop with increasing clouds. Severe weather also appears to become possible in the overnight hours Wednesday as instability increases with moisture/warm air advection and speed and directional shear improve dramatically. The best directional shear appears as one would expect to occur while we remain in the vicinity of the warm front in the overnight hours Tuesday. 0-3km SRH values per NAM are at 498 m2/s2 while GFS is somewhat lower at 317 m2/s2. This directional shear however becomes much more unidirectional as the main upper level wave approaches and the flow on the whole becomes stronger, which is after the warm front moves well to the north. That will present the question as to whether or not we will become unstable enough and have sufficient shear in place for much in the way of convection/severe weather and subsequently, isolated tornadoes that would be associated with such a scenario. At this point it does not appear that scenario is particuarly likely but later shifts will need to keep a very close eye on this possibility.

At 12z Wednesday GFS projects a very dynamically impressive scenario with the WRF not lagging far behind. GFS paints 20-25kt sfc winds at a 50-60kt LLJ with 700-500mb winds in the 80-100kt category. With this type of windfield substantial moisture advection will be underway and our column is forecast to become rather saturated, which is expected to lead to rather substantial cloud cover which is projected to limit instability somewhat. With GFS/NAM overall picture painting CAPE values around 600-1000 j/kg with LIs in the -2/-3 range at the peak. FROPA timing is the main challenge this morning as ever so slightly slower guidance continues to trickle in, with the best guess now at a 20-21z FROPA Wednesday, but the trend indicates a slightly slower scenario. Agree very much with SPCs thinking on this event which involves the possibility of a few isolated storms/supercells out ahead of the main front in the warm sector due to the more than substantial deep layer shear, with a strongly forced squall line/MCS racing eastward ahead of the front. Timing of this feature is obviously virtually impossible at the moment and that feature will have a major impact on the type of weather we see. If the system is somewhat slower to initiate and doesn't push through til 2-3pm Wednesday we obviously would have a little better instability in place. Using the trof axis to time where the strongest upper level forcing will be in place it appears this is a plausible scenario. For now will go with a 70% pop but hold off on ""severe"" wording in the actual forecast product. In the worst case scenario it appears we could see a rather serious squall line/MCS event with damaging winds possibly large hail in the strongest cells and embedded tornadoes. With the main limiting factor being a bit of a lack in instability, which likely would be overcome by the tremendous dynamics in place. However, it is still too early to pin down the likelihood of such a scenario occuring.

Wednesday evening is only made challenging by the GFS appearing to flatten the front out along the coast and leave us with the possibility of a post 0z FROPA. Given the tremendous dynamics pushing this frontal boundary and the fact it is nearly perpendicular throughout the event to the mean flow have discounted this solution and gone with the more progressive NAM. However, have left a 30% pop in to allow for any lingering postfrontal moisture as both models indicate at the possibility of a little wraparound moisture behind this very powerful deep layer low that may work its way in to our airmass and fall as anafrontal precip. This also allows us to gently slow FROPA if that becomes prudent.

Thursday things calm substantially under strong northwesterly flow at the sfc and aloft. Will keep winds fairly brisk in the 5-15 mph range through Thursday and Thursday Night. Will go slightly below MOS due to the depth and bredth of this apparent plunge of cool air. Friday also looks cool and mostly clear with Friday night being the coolest night of the period as a sfc ridge axis moves across the region and our winds calm.

Hazardous Weather
Hazardous Weather Outlook (Monday through Friday):
A powerful storm system will affect the region Tuesday and Wednesday. A warm front is currently forecast to move northward through the area late Tuesday into early Wednesday, organized thunderstorms may develop along and just south of this boundary. There is a slight chance of isolated tornadoes and damaging winds during this timeframe.

Thunderstorms will remain possible throughout the day Wednesday and the threat for organized thunderstorm activity will reach a peak as a powerful upper level storm system and associated cold front push through during the day Wednesday. There is a better chance of damaging winds, and possibly isolated tornadoes and small hail, during this time period. The most likely scenario will involve a line of thunderstorms in the afternoon hours Wednesday.

There are several questions that remain with this system and residents of the Mobile area should monitor for updated forecasts regarding the possibility of severe weather.

Astronomical and Climatological Data
Moon Phase
Last.
Last
Sunrise 6:16 AM
Sunset 4:56 PM
11/13/06
Normal
High
Record High
Normal
Low
Record Low
Temperature
71°F
83°F (2005)
48°F
31°F (1911)
November
Normal
Wettest
Driest
Precipitation
5.41 in.
13.65 in. (1948)
0.06 in. (1924)

11/13 in Mobile Area Weather History
In 1972 an afternoon storm produced an F2 tornado in Rosinton in Baldwin County, AL that destroyed a barn, damaged the Rosinton school, unroofed the Rosinton school gym, and damaged several other buildings.

(Data compiled from NWS Mobile, NWS Birmingham, newspaper articles, USA Archives, US Hurricanes and HurricaneCity.com)