396 
fxus63 kdvn 150831 
afddvn 


Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois 
331 am CDT Monday Mar 15 2010 


Synopsis... 
cyclonic flow persists across the County Warning Area with drier air advecting in 
the low levels from the northeast. Widespread stratus and fog 
remains to the west of our County Warning Area...while only spotty aviation fog is 
apparent on the 8z observation. Our next potential weather maker is a 
short wave trough apparent in the water vapor imagery over 
Saskatchewan...but it is associated with little clouds and no 
weather at this time. 


&& 


Short term...today and tonight 
as the persistent upper level and surface low continue to move 
east...high pressure will build into the area during the next 24 
hours. Models agree in a fair amount of sunshine today which 
should allow some locations to hit the 60 degree mark as occurred 
yesterday. Nigh time mins will continue on the mild side as middle- 
high clouds begin to move into the area later tonight. Went at or 
above guidance temperatures. Wolf 




Long term...Tuesday through Sunday... 
forecast focus on above normal temperatures for the remainder of the 
work week then much colder this upcoming weekend. By the way...rain 
and snow potential in the transition period. 


Trough/weak upper low drops out of Canada Tuesday and Tuesday night 
but will be moisture starved. Will maintain slight chance probability of precipitation for 
light rain showers or sprinkles. Ecm/GFS/Gem paint some light quantitative precipitation forecast 
west of the dvn County Warning Area with the UKMET the only one showing this in the 
dvn County Warning Area. The NAM on the other hand is completely dry. Either way not 
much to get excited about with this system. The trough does maintain 
the northwest flow aloft and some clouds so maximum temperatures to be mainly 
in the 50s to near 60. 


However the excitement begins to build for later in the week. 
Ecm/GFS/Gem all similar in turning the upper flow to more zonal and 
then southwest...ahead of upper trough that dives into the upper 
Midwest and deepens. Thursday appears to be the warmest day this 
week with plenty of sunshine and a dry southwest surface wind. Maximum 
temperatures should soar into the middle 60s in many locations. Considering 
some sites shot up to 60 yesterday with a north wind and cooler 850 
mb temperatures...raising temperatures on Thursday seems justified. At least 
modified Gulf air will be transported into the region on southwest 
to south winds ahead of strong cold front on Friday. Will have 
chance probability of precipitation for Friday but will probably need to be raised much 
further as we get closer to the event. Maximum temperatures should not be as 
warm due to more cloud cover and increasing rain. 


The ecm is progressive with this system moving the front through 
already by early Saturday morning...ending the precipitation. 
However the GFS wants to try to phase the system and deepen a 
surface low on Saturday which develops a band of heavier 
accumulating snow across portions of the dvn County Warning Area. This solution is 
much more ominous compared to the ecm. But even the ecm would 
suggest rain mixing with or changing to snow but the wintry precipitation 
would be brief. Hopefully this discrepancy will be resolved over the 
next couple of days. 


Later this weekend...much colder air arrives as strong clipper drops 
out of Canada and into the Great Lakes. Models plunge 850 mb temperatures 
to -14c over portions of the County Warning Area with the ecm somewhat faster in 
bringing this Arctic air into the region. This blast of cold air 
looks to be brief though as we get into the typical middle to late 
March roller coaster ride pattern. 


.Haase.. 


&& 


Aviation... 
VFR conditions forecast through the taf period after MVFR fog 
Burns off at Cid this morning. Only concern is that LIFR stratus 
over central Iowa remains to the west of our taf sites. Low level 
flow based on Blue River WI profiler and kdvn vwp suggests this 
will be the case. Otherwise clouds will be limited to diurnal cumulus 
today then middle-high clouds moving into the area later tonight. 


Wolf 


&& 


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


$$ 


Wolf/haase