Thursday Evening Forecast

Forecast issued by Michael Leach on 09/21/06 at 2:16:14 pm CDT

Mobile, Alabama 5 Day Forecast
Tonight	Tomorrow	Saturday	Sunday	Monday
	86°F	87°F	85°F	85°F
70°F		74°F	74°F	70°F
SE 5-10 mph	S 7-14 mph	S 7-14 mph	SW 7-14 mph	N 5-10 mph
20%	40%	30%	50%	10%

Mobile, Alabama 5 Day Detailed Forecast

Tonight… Partly cloudy with isolated showers, mainly after midnight. Low 70. Winds southeast 5-10 mph. Chance of rain is 20 percent. Tomorrow... Partly cloudy with scattered showers and thunderstorms. High 86. Winds south 7-14 mph. Chance of rain is 40 percent. Friday Night... Partly cloudy with isolated showers and thunderstorms. Low 74. Winds south 5-10 mph. Chance of rain is 20 percent. Saturday... Partly cloudy with scattered showers and thunderstorms. High 87. Winds south 7-14 mph. Chance of rain is 30 percent. Saturday Night... Partly cloudy with isolated showers and thunderstorms. Low 74. Winds south 5-10 mph. Chance of rain is 20 percent. Sunday... Partly cloudy with scattered showers and thunderstorms. High 85. Winds southwest 7-14 mph. Chance of rain is 50 percent. Sunday Night... Partly cloudy with scattered showers and thunderstorms. Low 70. Winds west 5-10 mph. Chance of rain is 40 percent. Monday... Partly cloudy. High 85. Winds north 5-10 mph. Monday Night... Mostly clear. Low 64. Winds north 4-8 mph.

Technical Discussion

Synopsis: Today has been another very pleasant day across the Mobile area. Dewpoints remain rather low (60 at KMOB at 12z), but are gradually rising as surface winds have shifted to the southeast. Also, a few clouds have begun to develop over the air as the air moistens. 17z RUC shows that WAA has started over the area at 850 mb. 12z regional soundings indicated signinifant subsidence starting around 900 mb, with PWAT values of under 1" (significantly below normal). With the WAA pattern and Gulf moisture returning, expect PWAT's to be significantly higher in future soundings. Short Term (Tonight through Saturday): Precip chances are the main challenge in the short term. WAA pattern will conitnue across the area tonight. With rising dewpoints and more cloud cover, overnight lows tonight will be much higher than last night. Models have dewpoints climbing into the upper 60's to lower 70's overnight. With some isentropic lift occurring across the area, expect a few showers to develop over the area toinght. Slight chance PoP's seem to cover this well. Models indicate development tonight initially over Gulf waters, with some activity spreading inland overnight. Friday, GFS and NAM both really increase precip chances with MOS guidance indicating PoP's of around 80%. I believe that the models are overdoing the precip chances for tomorrow. Looking at the upper levels of the atmosphere, I see no real indications of any significant lifting that would support PoP's that high. Both GFS and NAM show some very weak pertubations in the 500 mb flow which may be enough to lead to some lifting across the area on Friday. But any PVA looks to be weak. WAA advection looks to continue at 850 mb, with a LLJ between 20-30 kts. indicated on models. With all that said, going 40 PoP for Friday looks reasonable, and mainly for the afternoon hours with diurnal heating. Saturday, with deep moisture remaining over the area, and with diurnal heating, expect scattered SHRA/TSRA to affect the area. Prefer the NAM on Saturday as it seems to have a better handle on QPF fields. Will keep 30 PoP for Saturday. Long Term (Sunday through Monday): Rain chances were increased to 50% for Sunday with the approach of an upper level trough and associated cold front. The NAM indicates more lifting than the GFS in association with the trough, and has higher QPF values across the area. In fact, with -15 omega values approaching the area Sunday afternoon on the NAM, the model is indicating a rather robust line of convection approaching the area. The GFS 500 mb pattern is not as amplified as the NAM, with much less lifting indicated. The GFS is also quicker with fropa than the NAM. If the GFS were to verify, the main chance of rain would be Sunday afternoon. If the NAM were to verify, the rain could hold off until Sunday evening. At this time, will indicate 50% PoP's for Sunday during the day, tapering off to 40% Sunday night. Future forecasters can fine-tune the PoP forecast. As far as any severe weather goes, the main risk of severe weather will likely be well to our north. However, if the NAM verifies, with a sharper trough moving through the region, would not be surprised to see a few strong thunderstorms. Will not mention this in the hazardous weather section at this time, but will continue to monitor. Monday, if the models are correct the front should have cleared the region. However, I am more inclined to go with a slower fropa than models at this time as models often slow down the progression of fronts as the timeframe gets closer. I did not decrease clouds as quickly as the GFS indicates, and left a silent 10% PoP in the forecast for Monday, just in case the front moves through later than what models indicate at this time. By Monday night, expect mostly clear skies, with cooler overnight temperatures returning. ML

Hazardous Weather

Hazardous Weather Outlook (Thursday through Monday): No hazardous weather is expected through the forecast period.

Astronomical and Climatological Data
Moon Phase New Moon Sunset 6:50 PM Sunrise 6:40 AM	09/21/06 Normal High Record High Normal Low Record Low Temperature 86°F 99°F (1925) 67°F 51°F (1918) September Normal Wettest Driest Precipitation 6.01 in. 24.12 in. (1998) 0.47 in. (1923)

09/21 in Mobile Area Weather History

In 1926 a hurricane approached from the southeast and gradually weakened. However, newspaper reports indicate that the offshore winds were able to push the water out of Mobile Bay. While the storm had a history of producing winds over 100 mph offshore, the Mobile area experienced 60 mph winds as the storm moved northwest. The storm paralleled the Alabama coast before making landfall over the west Mississippi coastline. (Data compiled from NWS Mobile, NWS Birmingham, newspaper articles, USA Archives and HurricaneCity.com)