Weather

487 
fxus64 kbmx 131125 
afdbmx 


Area forecast discussion 
National Weather Service Birmingham Alabama 
625 am CDT Monday Oct 13 2008 


Update...aviation discussion. 


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Short term...today and tonight. 


Short term guidance in reasonable agreement this morning. Deep 
easterly flow dominates conditions across central Alabama courtesy 
of a large ridge developing from the southern Appalachians to the 
Great Lakes. Middle to upper level low that brought US our last good 
rain chance has retrograded westward and weakened considerably... 
with only a weak trough evident from the north central Gulf into 
North Florida. Mean moisture values rather limited through tonight 
but quantitative values of precipitation water at 1.50 inches or so are 
plenty for rain showers. The main missing ingredient appears to be 
lift. Differential heating will be limited due to the cloud cover 
expected during the period. Some isentropic lift is present at 
differing elevations across central Alabama. Wind direction will lend 
itself to some orographic lift north and east. Will keep mention of 
slight chance all locations with mainly drizzle or sprinkles early 
this morning. 1000-850mb thicknesses increase some today and along 
with the 850 mb temperatures. Cloud cover will hold temperatures down but will have 
to watch for those breaks. Generally went fro the low side of MOS and 
close to previous forecast for highs 75 to 80. Significant deep layer 
drying will begin scouring out the clouds east to west overnight. 
Kept lows close to guidance consensus. 


75/linhares 


Long term...Tuesday through Monday. 


Unseasonably strong upper ridge settles over the region Tuesday and 
Wednesday. Additionally...the atmosphere will be very dry. 
Therefore...a wide diurnal swing is anticipated with highs above 
normal in the middle 80s. Lows will exhibit local variations with some 
below normal and others just above normal in the 40s and 50s. 


GFS and European model (ecmwf) displaying fair agreement in the more extended time 
frame. Best rain chances come Thursday and Friday as a cold front 
will slowly traverse the area. Dry airmass ahead of the front and 
dry airmass behind the front will make the moisture available only 
in a narrow band at the frontal zone. No huge influx of Gulf 
moisture apparent here. Previous runs have hinted at a stalling 
front while the last few model outputs have a slightly more 
progressive front. Started to transition to the bit more progressive 
approach...believe we will see an airmass change by late Friday 
followed by another drier surge Saturday. Mentioned 20-30 probability of precipitation 
along Thursday through Friday. 


75/linhares 


&& 


Aviation...12z taf discussion. 


MVFR ceilings should persist through around 20z before lifting to 
VFR conditions. A few sprinkles are also possible at all sites but 
should not diminish visibility to less than MVFR conditions. 
Clouds will continue to dissipate during the evening...with sky clear 
conditions expected by midnight area wide. 


12/sirmon 


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Bmx watches/warnings/advisories...none. 


&& 


$$ 


75/75/16