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fxus64 khun 231135 aaa 
afdhun 


Area forecast discussion...updated 
National Weather Service Huntsville Alabama 
534 am CST Monday Nov 23 2009 


Update... 
for 12z aviation. 


&& 


Aviation... 
extensive MVFR/IFR stratus cloud deck will be present throughout 
the taf period. Ceiling heights have gradually been falling this 
morning...and upstream observation show IFR conditions. So...expecting 
IFR ceilings at khsv/kmsl terminals by about 15-16z. Weak boundary layer 
mixing may help ceilings improve to MVFR again by about 18-20z. Patchy 
light fog possible tonight...but cloud cover may inhibit development 
of visible restrictions below 6sm. 


&& 


Discussion... /issued 212 am CST Monday Nov 23 2009/ 


Early morning surface analysis shows a ridge centered across New 
England with the ridge axis extending southwest along the 
Appalachians. Light easterly flow persists in wedge type 
pattern...and this has maintained low level moisture and cloud 
deck. Water vapor imagery and u/a analysis shows a complex upper 
pattern with multiple short wave troughs moving briskly eastward through a 
broad longwave trough over the lower 48. 


Expect low clouds to persist today with very little diurnal temperature 
range. Will mention patchy drizzle/fog through middle morning...though 
expect most areas should not have too much of an issue. Clouds 
should linger well into the night and most likely into 
Tuesday...though a brief clearing period is possible Tuesday afternoon. 
Will also continue with mention of patchy fog for tonight though 
fog should not be too extensive given anticipated cloud cover. 


An upper trough and weak surface reflection will swing across the 
region Tuesday night/early Wednesday. Some timing/sensible weather differences 
between the NAM/GFS persist with the NAM being more aggressive 
with the forcing/moisture convergence and subsequent precipitation. The 
srefs trend toward the drier GFS solution...and will continue to 
trend toward the lower range probability of precipitation for the moment. 


Latest GFS/European model (ecmwf) guidance both show a fairly deep upper trough 
digging across the Tennessee Valley on Thanksgiving. Although moisture 
will be quite limited with this system...expect a fair amount of 
cloud cover and a rather cool day across the region. Would also 
not be surprised to see patchy drizzle or sprinkles...but will 
hold off on mentioning that for now. The weekend is looking 
seasonably cool but dry with a potentially active start to the 
next work week. 


&& 


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


$$ 


Aviation...kdw 
discussion...15/cbd