859 
fxus64 khun 062049 
afdhun 


Area forecast discussion 
National Weather Service Huntsville Alabama 
349 PM CDT Monday Oct 6 2008 


Discussion... 
a deep trough currently stretching southward through the plains will be 
the main player in our weather over the next few days...finally bringing 
the best chances for beneficial rains in over two weeks to the 
Tennessee Valley. Timing issues associated with the effects of the 
trough remain to be resolved however. Beyond the trough and 
associated vorticity maximum...a fairly benign pattern is shaping up for the 
weekend...as a very deep trough digs in to the western Continental U.S.. and now 
for the details... 


Short term (tonight through wednesday)... 
analysis this afternoon shows a trough stretching from the High Plains 
southward through Texas. A vorticity maximum embedded within the long wave trough was 
moving through Kansas...and was showing signs of weakening. However...a 
secondary vorticity maximum evident in the northern High Plains will dig southward and 
reinforce the vorticity maximum/positive vorticity advection over the plains/miss valley later 
tomorrow. Ahead of the trough...srly/serly winds will allow for 
low/middle level Theta-E advection and moisture transport into the Tennessee 
Valley. Expect straocu/altocu to be on the increase later tonight 
especially in western areas where isentopic lift will be maximized. As 
model soundings have become increasingly moist/windy for the 
overnight period...have decided to increase temperatures a little...and 
will now show around 60f in most areas. 


Lift/moisture should be sufficient by ~18z in western areas to allow for 
sctrd rain showers potential...and in all areas between 18z and 00z. Have 
thus...increased probability of precipitation for tomorrow to reflect latest trends in 
dynamical as well as statistical guidance. Confidence has increased 
enough with timing/placement of precipitation to go with categorical all 
areas over Tuesday night. Although low-level shear will be fairly robust 
with ~20-30kts in the 0-1km layer...lapse rates are weak with 
soundings showing near moist adiabatic profiles. MUCAPES/MLCAPES are 
generally <500 j/kg and are primarily confined to areas to our S and 
west where better low-level moisture will exist. Thus...a MDT shear/Low 
Cape environ and I have reduced mention of thunder to isolated in 
grids/zones. 


Model guidance is fairly consistent in suggesting that the vorticity maximum 
will become cut off from the wrlies as it moves through the Tennessee Valley 
on Wednesday...and will slowly meander towards the east. There is 
disagreement amongst guidance as to the subsequent speed of movement 
as might be expected with a cutoff low. I have taken the middle Road 
for now...with precipitation gradually winding down late Wednesday. 
Overall...precipitation amounts through the period are expected to be ~1.5 
inches. 


Long term (thursday through monday)... 
the upper low will continue to move ewrd into the Carolinas by late 
Thursday. Residual cloud cover/cool advection on the backside of the 
low should help keep highs suppressed a little on Thursday...keeping 
afternoon readings in the middle/upper 70s. 


A large trough will begin to dig into the western Continental U.S. By late in the 
week as a strong vorticity maximum currently moving through the Gulf of Alaska 
moves sewrd. This will set up a period of generally benign dry/warm 
weather as deep southwesterly flow sets up across much of the southeastern Continental U.S.. daytime 
highs will be in the low 80s with overnight lows mostly in the 
middle/upper 50s...a few degrees above normal for this time of year. The 
latest guidance has trended slower with the evolution of the 
trough...and forces much of the associated lift/dynamics further 
north. Thus...I have scaled back pop/weather mention for sun...but left 
in grids/zones for Monday. 


&& 


Preliminary point temps/pops... 
Huntsville 61 80 64 72 57 / 10 50 80 80 20 
Shoals 61 77 64 72 56 / 10 60 80 70 20 
Cullman 60 79 64 73 56 / 10 50 80 70 20 
Fayetteville 58 78 62 71 55 / 10 40 80 80 20 
Albertville 59 80 63 73 58 / 10 30 80 80 20 
Fort Payne 56 78 60 71 53 / 10 20 80 80 30 


&& 


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


$$ 


Kdw.03