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
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 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)