Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 140322

1022 PM CDT Sat Sep 13 2014

Issued at 1001 PM CDT Sat Sep 13 2014

Latest trends on water vapor imagery shows scattered mid to high
layer clouds moving from eastern Kansas - eastern and central
Oklahoma across the southern two thirds of Missouri at this time.
Looks like this is due to a weak distrubance in the upper levels.
low temperatures will fall into the upper 30s to lower 40s over
the region. Additional patchy mid to upper level clouds will be
moving across Missouri on Sunday as moisture from the tropics
moves over the region. Will continue with mostly sunny conditions
for much of Missouri on Sunday with some patchy mid to upper
clouds during the day. Clouds will be increasing from the
southwest as tropical wave from the southwest and shortwave
impulse from the northern plains aligns and brings a threat of
showers and thunderstorms over the area early Monday morning
through Monday.



.SHORT TERM:  (Through Late Tonight)
Issued at 307 PM CDT Sat Sep 13 2014

Center of the large surface high responsible for the area`s
unseasonably cool weather will shift into central Illinois
tonight. This feature will keep skies clear through early morning
while favorable conditions for radiational cooling once again
bring temperatures down into near-record territory with lows in
the upper 30s and lower 40s. Forecast lows for STL and UIN are
both within a degree or two of record (see climate section below)
while increasing southerly flow across Mid-MO should keep COU a
few degrees above record. Could once again see areas of fog toward
sunrise though not as widespread as it was this morning. Most
favorable areas for fog will be across west central Illinois as well
as some eastern Missouri river valleys.


.LONG TERM:  (Sunday through Next Saturday)
Issued at 307 PM CDT Sat Sep 13 2014

Weak southerly winds on Sunday and mostly clear skies will allow
temperatures to rise a few degrees with highs in the upper 60s and
lower 70s. While warmer than the past couple of days, this is
still 10 to 12 degrees below average and more representative of
mid-October than mid-September.

Warm air advection will get underway Sunday night into Monday
while a broad upper-level wave digs into the Upper Midwest.
Interaction of the two along with some increasing moisture will
allow for numerous to widespread showers and a few storms
spreading into northeast Missouri and west central Illinois Monday
morning. Best chances for rain will be along and northwest of I-44
in MO and I-55 in IL where lift will be maximized closer to the
upper wave. These areas could see up to a half inch of rainfall,
especially given a rapid increase in moisture Monday morning with
precipitable water values up to 1.5". Forcing shouldn`t be strong
or organized enough for amounts much higher than this so this
shouldn`t have much of an impact on any ongoing flooding.

Another cold front will spread across the area Monday evening and
could bring scattered showers and perhaps a thunderstorm or two as
far southeast as the Farmington and Centralia areas. With quasi-
zonal flow developing into early next week, the airmass behind
Monday night`s front won`t be nearly as chilly as what is in place
this weekend though still several degrees below normal. Highs on
Tuesday will be in the upper 60s and lower 70s...gradually rising
into the middle to upper 70s by Friday. Lows will generally be in
the 50s. GFS brings a weak wave and resulting light precipitation
to central and eastern Missouri on Wednesday, though this seems
too aggressive given the dry airmass in place. Opted to stay
closer to the ECMWF with dry weather for the Tuesday through
Saturday period.



.AVIATION:  (For the 00z TAFs through 00z Sunday Evening)
Issued at 720 PM CDT Sat Sep 13 2014

High pressure centered over northern Illinois will continue to
slowly move eastward during the next 24 hours. Surface winnds will
be light easterly winds over east central Missouri and southeast
winds over central and northeast Missouri. Warm advection over
central plains is producing mid level clouds over central plains
will move easterly and spread into parts of central and southern
Missouri early Sunday morning before daybreak. Surface winds will
remain southeasterly over central and northeast Missouri on


Specifics for KSTL:

Clear skies and light easterly winds will continue over STL
through early Sunday morning. High pressure will remain anchored
over Illinois and Indiana on Sunday. Warm advection will result in
some mid to high level cloudiness before daybreak. Winds will
remain light easterly on Sunday.



Issued at 236 PM CDT Fri Sep 12 2014

Record Lows This Weekend:

       STL        COU        UIN
13   43(1975)   33(1902)   33(1902)
14   46(1996)   40(1892)   38(1996)




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