Weather

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fxus64 khun 071122 
afdhun 


Area forecast discussion...updated 
National Weather Service Huntsville Alabama 
620 am CDT sun Sep 7 2008 


Update...for 12z aviation discussion 
&& 


Aviation... 
dense fog continues at both sites and will linger until around 14z 
before dissipating with conditions improving to VFR by middle morning. 
Expect fluctuating visible/ceilings until then...sliding between LIFR/IFR 
and eventually MVFR. VFR conditions expected for the remainer of the 
period...aside from patchy fog overnight Sunday. 
&& 


Discussion... 
widespread dense fog is coating many of the central and western 
valleys of north Alabama/southern Tennessee. GOES fog product and NASA/sport fog depth 
product indicate deepening fog depths especially along lake 
Guntersville and the Tennessee River...and along the Paint Rock and Elk 
valleys. The fog appears shallower in the Shoals region. In either 
case...will maintain a dense fog advisory through 14z. 


Expect fog/St to "burn off" today...unlike on Saturday given a 
shallower depth. 800 mb temperatures of near 17c should equate to highs in 
the u80s/n90 in the valleys...l-m80s higher elevations. Ample 
heating and dry advection today should lessen the threat of dense 
fog tonight...so have excluded for now. 


Not much change in the bigger picture with a broadscale upper trough 
encompassing nearly all of the northern Continental U.S.....Drawing Hanna 
through New England...while shortwaves drops into the Central Plains 
and upper Midwest. A shear zone and weak surface trough extends from the 
western Carolinas into the deep south....while another shear zone 
sits across the far desert SW. Convection developed across southeast Alabama 
into central and southern Georgia on Sat afternoon...and expect the same later 
today...but well to our southeast. This zone shifts back to nwwd into 
the Tennessee Valley late Monday as southeast-southerly low-middle level flow 
develops...somewhat influenced by "ike" tracking S of the Florida Keys. 
Isentropic surfaces and forecast soundings show a definitive moisture 
increase on Monday. The increase in moisture and 
instability...accompanied by convergence along the inverted surface 
trough...lead to at least widely scattered afternoon/evening thunderstorms and rain as the models 
suggest. The deeper layer shear will remain displaced to our 
north however...soundings forecast ml-convective available potential energy near 1k j/kg...mdpi just 
under 1.0 and windex in the u60s indicating some threat of brief 
downbursts. The models spread convective activity northward Monday 
evening...but will keep in local forecast overnight just in case. A 
better chance of more organized thunderstorms and rain activity sets up on Tuesday as 
a cool front drops rapidly southeast into the region. This as shortwave 
energy zooms eastward through the upper Midwest and Great 
Lakes...drawing the shear zone/vorticity maxima in the desert SW into 
the MS valley. This in combination with precipitable waters of 1.8-1.9 inches 
equate to a decent shot of thunderstorms and rain increasing through the day...and 
not entirely along the cold front. Have increased probability of precipitation to 40 
percent...but certainly could go higher in later packages. 


Uncertainty has not changed in the extended with respect to Hurricane Ike. 
Confidence is much higher that it will move into the Gulf of 
Mexico early this week...so an eventual landfall somewhere on the 
Gulf Coast appears more likely...but where is still up in the air. 
Will keep a status quo in the forecast until we gain more 
confidence on an eventual track. 


&& 


Hun watches/warnings/advisories... 
Alabama...dense fog advisory until 9 am CDT this morning for the 
following zones: Colbert...Cullman...De Kalb...Franklin 
Alabama... 
Jackson...Lauderdale...Lawrence...Limestone...Madison... 
Marshall...Morgan. 


Tennessee...dense fog advisory until 9 am CDT this morning for the 
following zones: Franklin Tennessee...Lincoln...Moore. 


&& 


$$ 


Aviation...jll 
discussion...Kula