Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 231657
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
1157 AM CDT Wed Jul 23 2014

.UPDATE:
Issued at 1141 AM CDT Wed Jul 23 2014

Several bands of post frontal st/sc as been drifting across the
CWA during the morning...one w-e band from s MO into s IL which
appears to be just behind surface boundary, and a secondary nw-se
oriented cloud deck which formed in the resdiually high moisture
content air north of the cold front that has been working wsw from
southwest and central IL, with the leading edge of this cloudiness
now approaching mid MO/COU area.

Believe with strong July sunshine and drier air advecting into the
region these clouds will gradually break up during the afternoon,
but process could be somewhat slow. Because of this, have backed
off on max temps a couple of degrees most areas.

Other concern for afternoon is thunderstorm threat. Between
1615z-1645z "arc" of echo has appeared over southeast sections of
the CWA from south of Greenville to near Ste. Genevieve, and this
appears to be associated with outflow from morning complex that
worked across far s IL. Don`t think this boundary will get too
much further north due to impact of southward oozing cold front,
but will use this to mark the northern edge of PoPs for this
afternoon. Any surface based storms that do manage to form west
of the Mississippi River will pose some threat of severe weather,
primarily in the form of high winds. This threat should be
confined to our far southern counties where MLCAPES are currently
near 3000 j/kg, with only a limited window of opportunity...roughly
18-20z.

Truett

&&

.SHORT TERM:  (Through Late This Afternoon)
Issued at 330 AM CDT Wed Jul 23 2014

Cold front to continue tracking south through forecast area this
morning, before exiting region early this afternoon. Despite decent
cap over area, could still see some isolated/scattered storms
develop as front moves through. Highest pops will be this morning
for southern half of cwa, then taper off rather quickly after 18z.
As for highs today, will range from the low 80s far north to around
90 far south. Drier/cooler air is lagging behind boundary, so with
dewpts still in the 70s could see heat indicies approaching 95 early
this afternoon.

Byrd

.LONG TERM:  (Tonight through Tuesday)
Issued at 330 AM CDT Wed Jul 23 2014

By tonight, surface ridge begins to build in and bring in drier and
cooler weather for the last half of the work week. Lows tonight will
be in the mid 50s to near 60. Highs on Thursday will be in the upper
70s to low 80s.

Surface ridge to move off to the east by Friday with a warm front
developing across region with elevated convection possible for
northern portions of forecast area late Thursday night through
Friday night. Then as main cold front moves into region on Saturday,
will see additional rounds of storms through Sunday before system
exits region Sunday night. Temperatures to moderate through the
weekend once again. Models are indicating 850 temps between 24C and
26C on Saturday and if they mix down, could see highs in the upper
90s for portions of the area. For now raised highs a few degrees for
Saturday, into the upper 80s to mid 90s.

Beyond the weekend, surface ridge builds in once again for early
next week with highs cooling off into the upper 70s to mid 80s for
Monday and Tuesday.

Byrd

&&

.AVIATION:  (For the 12z TAFs through 12z Thursday Morning)
Issued at 620 AM CDT Wed Jul 23 2014

Cold front came through terminals overnight and skies are mostly
clear behind the front as of now. Should see at least scattered
diurnal cumulus develop as wind begins to increase from the north-
northeast. VFR conditions will prevail through tonight.

Specifics for KSTL:
VFR conditions with north-northeast wind today.

CVKING

&&

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

$$

WFO LSX





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