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afdhun 


Area forecast discussion...updated 
National Weather Service Huntsville Alabama 
540 am CST sun Nov 23 2008 


Update...12z aviation. 
&& 


Aviation... 
expansive area of stratus looks to work its way back into northern Alabama 
this morning...as soon as 12-13z at mean sea level...an hour or so later at 
hsv. Initially expect ceilings to be VFR...but cloud bases will 
lower to the edge of VFR/MVFR by afternoon. Rain and lower ceilings are 
expected to hold off until very late in the taf period...and confidence 
remains too low to pinpoint tempo/prob30 groups at this time. South winds 
may begin to gust overnight...and low-level wind shear may also become 
a concern towards daybreak with winds potentially increasing to 
35-40kt at the top of the 2000ft above ground level layer. 
&& 


Discussion...issued 344 am CST sun Nov 23 2008... 
trough #1 which brought the cloud cover late Saturday afternoon/evening 
across our County Warning Area...is now moving into the Middle Atlantic States. Weak 
upper ridge following behind trough #1 was dissipating the cloud cover 
over most of the Tennessee Valley at this time. However...trough #2 now over western 
Texas...was beginning to pull Pacific moisture into the Southern Plains on a 
fairly strong low level 800 mb jet. Thus expect more cloud cover 
today...especially this afternoon. This will no doubt play havoc with 
afternoon highs. For now will go with increasing clouds for today. As for 
temperatures...will go with lower 50s in northwestern zones and middle 50s in Tennessee 
zones/northestern zones...to account for increasing clouds from SW to NE. 


Tonight...atmosphere should be dry enough this evening to keep probability of precipitation 
out of forecast. But trough #3 now over the northern rockies will quickly move 
southeast and merge with trough #2 after midnight...increasing the chance of 
precipitation. Thus will keep current probability of precipitation for 2nd period as is...after 
midnight. This whole mess will drag a cold front through the County Warning Area by Monday 
afternoon...and all models show that precipitation will be over by Monday 
evening...due to the quick movement of trough #3. 


Rest of forecast...kept Tuesday through Thanksgiving dry due to ridging. 
However...confidence in the forecast from Thanksgiving Onward drops. 
European model (ecmwf) shows a dry Thanksgiving but GFS hints at a little light rain. 
As for Friday/Saturday...both European model (ecmwf)/GFS shows that this will be the 
best chance of precipitation...thus will keep low probability of precipitation for this timeframe. Any 
severe weather looks very iffy at this time. 
&& 


Hun watches/warnings/advisories... 
Alabama...none. 
Tennessee...none. 
&& 
$$ 


Aviation...bcc 
discussion...07