069 
fxus63 klsx 072112 
afdlsx 


Area forecast discussion 
National Weather Service St Louis MO 
312 PM CST Wednesday Jan 7 2009 


Discussion... 
/302 PM CST Wednesday Jan 7 2009/ 
active northwest flow across the center of the nation continues with 
next shortwave and sharp baroclinic zone dropping south out of Iowa 
late this afternoon. Model guidance still underestimating quantitative precipitation forecast with 
this feature as light snow has already developed across Iowa. Have 
increased probability of precipitation to likely and will let evening shift Nowcast the 
event as the band of snow enters Missouri. Do expect snowfall 
amounts to remain under one inch as this system is a quick 
mover...with skies becoming partly cloudy or clear behind it. Have 
sided with cooler FWC guidance and even undercut it a few degrees up 
north as airmass behind this clipper is quite chilly. 


High pressure will move across the County Warning Area on Thursday and therefore 
have continued to side with coolest guidance. Early evening low 
temperatures on Thursday night will give way to a warming trend 
into Friday as a southwest low level jet and strong surface winds 
send temperatures above normal. Another cold front will move 
across the area Friday evening with rain changing to a wintry mix 
and eventually snow before ending. Do not anticipate significant 
winter accumulation at this time. 


Cold and blustery day expected Saturday behind the front...with 
temperatures 20 to 25 degrees colder than on Friday. 


The extended features a series of cold fronts that will send 
reinforcing Arctic highs southward into the Midwest. Have trended 
temperatures below guidance and kept the extended dry. There is 
little skill in forecasting light precipitation events from clipper 
type systems more than a few days in the future. 


Cvking 


&& 


Aviation... 
/1120 am CST Wednesday Jan 7 2009/ 
for the 18z tafs... 
first area of low clouds over Illinois/eastern MO with ceilings ovc024-032 will 
move out of the taf sites 18-20z...but then ovc025 ceilings will move 
back into KUIN from Iowa around 21z. Farther south...ceilings ovc080 
will move in 19-21z followed by ceilings ovc025 in the early evening 
00-02z. Prob30/tempo 4sm -sn ovc015 groups at kcou/kstl/ksus this 
evening still look good...but have moved the timing up by a couple 
of hours. Some minor snow accumulation will be possible early this 
evening in the band of snow...1/4 inch or less. Then low clouds 
should clear out 04-07z leaving scattered middle-high clouds. 


Britt 


&& 


Lsx watches/warnings/advisories... 
MO...none. 
Illinois...none. 
&& 


$$ 


Weather forecast office lsx