Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 300451
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1151 PM CDT Mon Sep 29 2014

.UPDATE:
Issued at 915 PM CDT Mon Sep 29 2014

Despite a cold front dropping down and entering the far northern
portions of the forecast area (northeast MO and west- central IL)
late tonight, it should move thru dry. However, area of low
stratus has developed behind the front in northern IL and based on
relationship to front, is expected to affect some portions of the
far northern forecast area towards daybreak and shortly after
sunrise. Things a bit muddier after that, but should see the
southward stratus advance slow and halt during the morning with
the stratus probably scattering during the day. Have adjusted
cloud forecast accordingly, with areas to the south of the front,
including areas near the I-70 corridor and to the south of there
remaining clear.

Otherwise, remainder of the forecast on track with no adjustments
needed to temps or rain chances.

TES

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 315 PM CDT Mon Sep 29 2014

Another tranquil dry night on tap for the area. Weather features
we have been discussing the last few days remain the same. The
east-west cold front currently stretching across southern Wisconsin
into South Dakota will drop into northern MO and central IL
overnight in response to the digging trof moving into the Great
Lakes and downstream amplification. This front should reach near a
Columbia-St. Louis-Effingham line by 12z. Weak high pressure and
light winds will continue ahead of the front for a good part of
the night resulting in another round of overnight lows primarily
in the 50s.

Glass

.LONG TERM:  (Tuesday through Next Monday)
Issued at 315 PM CDT Mon Sep 29 2014

Not many changes needed to the previous forecast as it continues
to blend well with the latest thoughts and NWP guidance. Still
looking at a tranquil dry period Tuesday and Tuesday night. The
cold front will sag southward across eastern MO through the Ohio
Valley Tuesday as high pressure builds through the Great Lakes,
while retreating northward across the Plains region in response to
the migratory surface low. No sensible weather with the front
other than suppressing the temperatures a few degrees.

Active weather remains centered on the Wednesday night-Thursday night
period as the deep western upper trof progresses into the Nations
midsection. There are some questions initially Wednesday into
Wednesday night on the rate of eastward spread of precipitation as
the NAM and local WRF are quite a bit slower than the other operational
models. At this time I am favoring the more agressive GFS/ECMWF. An
intensifying and veering southwesterly LLJ and associated the pre-
frontal warm advection regime, along with weak impulses moving
across the region within the southwest flow aloft, would suggest
more progressive nature to the convection/MCS on Wednesday night.
Thunderstorms will remain likely Thursday/Thursday night as the
main short wave trof and attendant cold move across the region. Much
cooler weather remains on track in the wake of the cold front Friday
into Saturday with gusty northwest winds on Friday. Temperatures
return to seasonable normals on Sunday.

Glass

&&

.AVIATION:  (For the 06z TAFs through 06z Tuesday Night)
Issued at 1151 PM CDT Mon Sep 29 2014

Weak cold front to continue sliding south towards forecast area
early this morning. Some low stratus has developed behind this
boundary. Short range models want to bring stratus into KUIN
towards daybreak, then slowly break it up. For now will just add
scattered/broken mention to KUIN by 11z Tuesday, then scatter out by
16z Tuesday. As for rest of taf sites, just light and variable winds
becoming easterly as boundary slides through.

Specifics for KSTL:
Weak cold front to continue sliding south towards forecast area
early this morning. Some low stratus has developed behind this
boundary. Short range models want to bring stratus near metro area
then break it up. For now will leave out mention. Just have light
and variable winds becoming easterly as boundary slides through by
midday today.

Byrd
&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$
WFO LSX




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