933 
fxus63 kdvn 070822 
afddvn 


Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois 
320 am CDT Tuesday Oct 7 2008 


Synopsis... 
surface low centered over eastern Kansas this morning...with a 
stream of precipitation extending from Arkansas north up through 
Missouri and Iowa up into Minnesota. The cold front with this 
system extends from Oklahoma...north through the low...north into 
Iowa and Minnesota. At upper levels...the 500mb trough axis extends 
nearly north south over the Dakotas...Nebraska and Kansas down into 
Texas and Oklahoma. Main band of precipitation over Iowa is now 
pushing into the western portions of the forecast area...and has 
almost reached Cedar Rapids and Burlington. Deep 500mb trough is 
keeping the movement of this precipitation area to the east very 
slow...with individual feature movement almost directly north. 
.Le.. 


$$ 


Short term...today and tonight... 
precipitation to continue today as more moisture...warm air 
advection...and convergence continue over the forecast area through 
approximately 06z tonight. There may be some breaks in the 
precipitation waves as precipitation areas re-organize to our 
southwest...but it generally appears to be a rather rainy day as 
this upper level trough slowly translates across the forecast area. 
The 850mb low tracks northeast from eastern Kansas...across Missouri 
and then western and northwest Illinois...and moving into Wisconsin 
by Tuesday evening. Pattern recognition backs the forecast of 
periods of rain for today as that 850mb low tracks across the area. 
Temperatures today will be rather mild as we are starting out 
surprisingly warm this morning. As of 3 am...temperatures had only 
dropped into the upper 50s and low 60s...and do not expect much more 
drop with all the clouds and precipitation moving in. So...have 
gone with the warmer guidance which gives about a 5-10 degree 
diurnal range. We should get about that amount of heating...with 
enough breaks between rain bands and continuing warm air advection. 
Tonight min temperatures will be much cooler as cold air just begins to get 
into the western portions of the forecast area after the rain ends 
after midnight. ..le.. 




Long term...Wednesday through next Monday... 
latest suite of 00z run short range models generally agree on l/west 
trough migrating east of the area on Wednesday...with broad scale zonal 
flow pattern taking over much of the Continental U.S. In its wake through Thursday. 
Meanwhile on Wednesday...some signals of higher relative humidity/clouds getting trapped 
under 800 mb mb inversion for awhile before better low level northwesterly 
flow and subsidence translates from the middle levels and begins 
scouring out process from west to east Wednesday afternoon and evening. 
Some drizzle or light rain may even linger into Wednesday morning east 
of the MS river. If clouds persist long enough on Wednesday...temperatures may not 
get out of the lower 60s. But will bank on some middle afternoon clear 
out or breaks to get the high temperatures currently advertised. Will not 
introduce into the grids now...but clearing skies and light wind 
regime/surface decouple may Foster fog development later Wednesday night into 
Thursday morning...especially in areas that Don/T clear out until late Wednesday 
afternoon or evening. 


The New Run medium range models and ensembles are generally in 
decent agreement in suggesting Gulf of Alaska wave energy to eventually 
carve out a new l/west trough across much of the western intermountain 
region by weeks end. This will result in increasing southwesterly 
upper flow and wave eject process over tightening low level baroclinicity 
across much of the central to High Plains through Sat. While warm 
moist conveyor off the western Gulf lifts up over building inverted 
trough for more lift/organized precipitation developing processes to the west 
and northwest of the local forecast area into Sat night...the dvn County Warning Area 
may benefit from protective middle and upper level ridge and remain dry 
until the end of the long range/Monday when a substantial front may 
finally get shunted through the area. Before then...the latest 
run medium range models are again in good agreement of advertising 
enough of a lower level return flow/thermal moderation over the 
weekend for temperatures well above normal again...possibly pushing the 80 
degree mark in some locations by Sat or Sunday. ..12.. 


&& 


Aviation... 
cloud and visibility conditions to slowly deteriorate through the day 
today as the precipitation slowly moves in from the west. Beginning 
at VFR...expect a slow drop through MVFR and into widespread IFR 
conditions by 21z today. Expect that after 03z tonight...there may 
also be periods of LIFR conditions as lower visibilities and ceilings move in on 
the heels of this system. These LIFR and IFR conditions should 
linger through the end of the taf period...with clearing not expected 
until late Wednesday. ..le.. 


&& 


Dvn watches/warnings/advisories... 
Iowa...none. 
Illinois...none. 
MO...none. 


&& 


$$ 


Le/12