694 
fxus63 kilx 231157 
afdilx 


Area forecast discussion 
National Weather Service Lincoln Illinois 
557 am CST sun Nov 23 2008 


Discussion... 
issued 150 am CST sun Nov 23 2008 


Latest surface analysis had a large area of high pressure... 
centered east of the Appalachian Mountains...exerting its 
influence over much of the eastern United States. Meanwhile...low 
pressure and an associated frontal system was beginning to come 
together over the High Plains. A broad area of southerly flow was 
evident between these two pressure areas. Aloft...a vigorous short 
wave was pulling away from the forecast area over the Ohio Valley... 
with short wave ridging building across the Midwest in its wake. 
Not too many forecast concerns the next several days as local 
weather pattern will generally be quiet but cool. However...the 
complex approaching High Plains frontal system...and the driving 
upper waves...have the potential to bring precipitation to the 
region later tonight into Monday. 


00z models in reasonable agreement the next few days with respect 
to features expected to impact forecast area. Despite the general 
agreement in the overall pattern...there is spread evident in the 
guidance temperatures. For the most part...have followed a blend 
of model solutions. 


Short term...today through Tuesday...strengthening southerly flow 
is expected across the region today into tonight with the approach 
the plains frontal system...as well as the passage of short wave 
ridge aloft. As these upstream features move closer by later 
tonight...a quick shot of relatively strong warm air advection/isentropic lift 
will likely produce some light rains. However...model soundings 
suggest moisture depth will be lacking...mainly below 800 mb...so 
expect precipitation totals to be minimal. 


Cold front and driving upper wave will cross the region early 
Monday...quickly bringing the measurable precipitation threat to 
an end. Sounding profiles dry out quickly behind the front...so do 
not really expect any Post frontal precipitation Monday. However... 
if any does occur...it should fall as flurries. 


Another upper wave...and reinforcing shot of cold air...will cross 
the region late Monday night/early Tuesday. Not much moisture is 
expected with this impulse...but would not be surprised to see a 
few flurries as the associated thermal trough swings through. 


Long term...Tuesday night through Saturday...quiet/cool conditions 
appear likely through the period...though model/ensemble spread 
suggests this is far from a forgone conclusion. Some degree of 
troffing is expected to remain across eastern Canada/northeast United 
States...with the persistent northwest flow aloft helping to 
provide chilly air. A southern stream wave...arriving anywhere 
from Thursday into Saturday...may phase with the eastern trough or 
lift across region if troffing ends up like one of the weaker 
model solutions. The lack of confidence in the ultimate 
timing/track of the southern stream wave precludes a mention of 
precipitation in the forecast at this time. 


Bak 


&& 


Aviation... 
issued 557 am CST sun Nov 23 2008...for the 12z tafs 


High clouds are already streaming in well ahead of the next cold 
front. Southerly winds will increase today as the low level flow 
responds to the intensifying middle level jet. The models and 
forecast soundings point toward a disjointed moisture profile. 
There will be plenty of moisture below 850 mb...but relatively dry 
air above that. The isentropic lift ahead of the front appears 
strong enough to generate showers...but precipitation amounts will be 
light due to a limited amount of moisture with the fast moving 
system. 


Ceilings are expected to drop rapidly as the front approaches later 
this evening. Ceilings of around 1500 feet will develop toward 
06z...with ceilings down to 700 feet expected by 09z. Rain will be quite 
light...so I only went with vcsh and no prevailing rain just yet. 
Winds will shift to the west as the front passes...and eventually 
northwest by 12z Monday. 


Shimon 
&& 


Ilx watches/warnings/advisories... 
none. 
&& 


$$