Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 300803
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
303 AM CDT Mon Mar 30 2015

.SHORT TERM: (Today through Tuesday night)
Issued at 259 AM CDT Mon Mar 30 2015

NW flow in place into Tue with upper lvl ridging beginning to
build in by Tuesday night. Weak short wave embedded in the NW flow
fcst to pass well NE of the FA Mon night into Tue. SFC ridge will
pass from the mid-MS vly into the TN vly today allowing winds to
become SW by this evng which will make a warmer night. An area of
low pressure assoc with the aforementioned short wave will drag a
weak cold front thru the CWA Tue. Should be an AM FROPA across the
nthrn CWA tempering the temp rise somewhat with NW winds and weak
CAA drng the aftn....though temps should still warm above avg with
highs near 70. South of I70...a good deal of sunshine and a longer
prd of SW winds should allow temps to rise well into the 70s.
Previous system from Sun has scoured out most of the available
moisture. Moisture return should be negligible due to limited
duration of return flow and sfc ridge across the Deep South
effectively closing the Gulf for business...so FROPA should be
dry. Removed slight chance PoPs across the far sthrn portion of
the CWA for Tue PM. Moisture appears to be limited and quite
shallow. Also...front settles along the AR/MO border which is
where there is marginally better moisture and hence any SHRA
activity should reside. SFC ridge builds into the Grt Lks Tue
night...sliding into the the OH vly by Wed.

2%

.LONG TERM: (Wednesday thru Sunday)
Issued at 259 AM CDT Mon Mar 30 2015

Upper lvl ridge axis passes Wed. A decent short wave tracks
across the nthrn CONUS Wed night/Thu with a general weakness in
the H500 heights extending SW into another short wave coming
onshore across CA Wed night. These two features will combine to
produce a prd of wet weather for the region.

Sfc ridge axis passes Wed mrng allowing return flow to begin by Wed
aftn. The first short wave will lift an area of low pressure from
the Dakotas into sthrn Canada Wed mrng into Wed evng. This will push
a cold front into the Midwest Wed aftn. Winds should strengthen and
become gusty by aftn as the pressure gradient increases in advance
of the cold front. The front will slowly slide SE Wed night and Thu.
The GFS is faster with the initial push of the bndry bringing it into
the nthrn FA Wed night while the ECMWF waits until Thu. This time
the Gulf will be open for business allowing sufficient moisture for
the system to work with with. Precip chances begin as early as Wed
aftn...mainly across MO with better chances across NE MO after
midnight Wed night. Precip chances increase from NW to SE on Thu as
the front sags south. The bndry is fcst to stall along or just north
of the AR/MO border Thu night as an area of low pressure dvlps
across the sthrn Pains Thu night in response to the second short
wave. The bndry is fcst to remain nearly stnry thru Fri until the
low passes Fri PM as it rides NE along the front into the OH vly by
Fri night keeping precip chances going for areas mainly along and
south of I70. Nthrn portions of the FA may only have one shot at
precip with FROPA with the main area of precip remaining along and
south of I70 Thu night thru Fri night. Stay tuned though as the
eventual position of where the bndry stalls will determine nthrn
extent of the precip.

Saturday through Sunday

High pressure builds into the cntrl CONUS for the wknd producing dry
conditions and seasonal temps.

2%

&&

.AVIATION:  (For the 00z TAFs through 00z Monday Evening)
Issued at 606 PM CDT Sun Mar 29 2015

Showers have pushed est of the area in advance of a cold front.
Pre-frontal trof has moved through producing a west wind with a
shift to the northwest coming this evening. Temp and dew point
spreads look to stay large enough to prevent fog, but will watch
closely given the light rain that fell at some locations. Some
mid clouds for a couple of hours then a clear sky. Wind shifts
back to the southwest Monday morning with continued VFR.

Specifics for KSTL: Gradual shift to a northwest wind, then
quickly back to southwest Monday morning. VFR through Monday.

JPK

&&

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

$$

WFO LSX





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