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fxus63 kdvn 210832 
afddvn 


Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois 
330 am CDT sun Mar 21 2010 


Discussion... 
in the near term for today and tonight...will let ongoing winter weather 
headlines ride again until 6 am CDT in the far southeast...although 
the western portion of it just light snow with minimal impact. 
East-southeast elevated warm flow across Illinois producing more of an 
impact in the far southeastern County Warning Area where the headlines are still 
warranted with the precipitation arriving at the surface in the form of freezing 
rain and sleet along and east of a line from Carthage Illinois...to south 
of Princeton Illinois. Hope to not have to extend the headlines for such a 
limited area but will watch precipitation trends through sunrise and 
may handle any lingering trouble with a Special Weather Statement if 
needed. Will also keep mix wording going through at least 15z this 
morning in these west central Illinois to Princeton Illinois areas before 
elevated convergent forcing weakens or shifts eastward and the precipitation 
starts to wane. Diurnally recovering surface and boundary layers may also 
just change what ever precipitation lingers in these areas to rain or a 
rain-snow mix with little consequence. 


Synoptical trends suggest that the large southeastern plains cut-off 
upper low will steam roll eastward toward the eastern Tennessee Valley and 
middle Gulf Coast states by late tonight. This would suggest a good 
bout of drying and subsidence whirling into the region initially 
from the northeast...and then from the north late tonight. An upper 
ridge axis also will look to unfold across the area by late tonight in 
wake of the cyclone well off to the southeast by then. Thus after 
walking the lingering precipitation out of the area this morning...the rest 
of the dvn County Warning Area to experience drying and clearing as the day 
progresses. With the southeast the last to clear...temperatures will 
warm/recover more sufficiently back into the middle or even upper 40s in 
the west and north this afternoon. A temperature contrast of the mildest 
temperatures in the west and northwest...with the coolest readings taking 
place in the southeast forecast area/west central Illinois. 


Clearing skies and decoupling winds away from lingering surface cyclonic 
flow under building h9-800 mb mb inversion may Foster some fog 
development. Areas most favorable for this look to be generally across 
the northwest half of the dvn County Warning Area and previous shift already 
introduced patchy fog wording. For now will keep going or even 
expand coverage some. Seasonably cool temperatures still look to be on tap 
with the expected clearing...continued drying dewpoints from the north 
and surface wind decouple especially over any lingering snow cover that 
manages to survive the afternoon insolation. ..12.. 




Long term...Monday through next Saturday... 
..quiet and dry late March weather with overall near seasonable 
temperatures with modest day to day variances... 


Overview...initialization and verification average. Quiet regime 
supports a 50/50 blend of GFS and hi-res European model (ecmwf). No major energy 
pulses to impact area until next weekend at the earliest. 


Monday and Tuesday...little changes made. Fair and dry with mainly 
near to above normal temperatures and light winds with weak high pressure 
nearby to overhead. Slightly larger diurnal range may occur due to 
copious late March sunshine with highs possibly a degree or two 
warmer and mins a degree or two colder due to radiational cooling. 
Highs Tuesday with approaching cool front may be at least 3 degrees 
warmer from SW winds and pre-compressional heating. 


Wednesday and Thursday...went dry with weak front to slide into 
region but Gulf closed for limited moisture. Temperatures have trimmed 
a few degrees with north sections possible still a bit too mild. 
Modest frontal thermal gradient to result in light to moderate northwest 
winds under a fair sky with near normal temperatures. 


Friday...Saturday...no changes made...moderate strength system on 
track to impact region by late Saturday supportive of needing probability of precipitation 
with a mix of rain/snow north and rain south. ..Nichols.. 


&& 


Aviation... 
drying northeast flow will continue to lead to higher based MVFR or 
VFR conditions at the dbq...Cid and mli terminals for this taf forecast 
cycle. The brl terminal to still get clipped by snow or a mixed 
bag of sleet...rain and snow. Freezing rain threat should remain to 
the eat of brl through 15z. Brl may improve to MVFR or even VFR by 
17z today still. Watching the mli terminal and banking on drying 
northeast fetch to keep any precipitation reaching the surface at Bay to the 
south and east...but snow aloft will be in the vicinity through 15z. 
.12.. 


&& 


Dvn watches/warnings/advisories... 
Iowa...Winter Weather Advisory until 6 am CDT early this morning 
for Des Moines-Lee. 


Illinois...Winter Weather Advisory until 6 am CDT early this morning for 
Hancock-Henderson-McDonough-Warren. 


MO...Winter Weather Advisory until 6 am CDT early this morning for 
Clark-Scotland. 


&& 


$$ 


12/Nichols