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Area forecast discussion...updated aviation 
National Weather Service St Louis MO 
626 am CDT Monday Mar 22 2010 


Discussion... 
/430 am CDT Monday Mar 22 2010/ 


Deformation rain on the backside of a very wound up storm system 
now approaching the southern Appalachians continues to push westward some 
towards the stl metropolitan area and persists over much of southern Illinois and 
southeastern MO as the outermost bands dissipate a bit further to the northwest. 
The 00z GFS is handling the northwestern edge of the deformation zone the 
best and used that as guidance...which will keep peristent light 
rain where it is at now through about middle morning before additional 
erosion or dissipation occurs. Strongly favor the higher MOS probability of precipitation 
for this morning...with perhaps just a few sprinkles lingering 
around the kslo area into early afternoon. Models doing a good job 
handling the northwestern edge of the clouds...which should see this edge 
get more diffuse with diurnal clouds later today with sun poking 
into the stl metropolitan area later in the afternoon. Areas further to the north 
and west will see abundant sunshine...while areas to the east of the stl 
metropolitan area will likely be in clouds for the vast majority of the 
day. This will create some challenges on temperatures...but should see 
widespread middle 50s in areas that see good sunshine. MOS has been 
too warm under the clouds the past couple of days with this 
system...and believe this will be no exception in the eastern forecast area where 
went at or below the coldest MOS temperatures...keeping upper 40s there. 


May see some fog develop later tonight as weak ridge settles in 
with clear(ing) skies. Areas S and east of stl metropolitan especially look 
favorable given they will be the last to clear of the clouds and 
they also received the most rainfall. Will let day shift make the 
final call here. 


Look for an excellent temperature recovery on Tuesday with west-southwest surface winds 
and sunny skies. Temperatures should rise into the 60s at all 
locations...with a few spots pushing 70f. 


The next chance for rain still on track for Wednesday night. 
Models have a few lead disturbances push through Wednesday but lower 
atmosphere appears too dry to support precipitation other than sprinkles. 
Maintained slight chance probability of precipitation for now over some areas...with 
chance category Wednesday night with the beginnings of the main 
system. Another rain maker appears on track for later in the 
weekend. 


Tes 


&& 


Aviation... 
/617 am CDT Monday Mar 22 2010/ 


Upper low continues to pull eastward out of the region this morning. 
Expect clear skies to continue through the next 24 hours at cou and 
uin. Ceilings will remain VFR at sus with the exception for an hour or 
two late this morning as diurnal cumulus is expected to develop on the 
back edge of this system. Skies will become clear this afternoon 
into evening at sus. Have kept fog out of sus for tonight as northerly winds 
may help advect in enough dry air to keep fog from forming. Believe 
fog will develop at uin/cou as winds will be light and back late 
tonight. With clear skies...will have a good radiational cooling 
setup. 


Specifics for kstl...VFR ceilings will continue this morning as upper 
low continues to pull eastward. Believe rain has ended...but a brief 
sprinkle may still be possible. Expect diurnal cumulus to develop late 
this morning with bases becoming broken briefly around 3 kft. Skies should 
clear out this afternoon into evening with winds becoming light and 
vrb. 


Tilly 


&& 


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


$$ 


Weather forecast office lsx