Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 291151

651 AM CDT Sun Mar 29 2015

.SHORT TERM:  (Through Late This Afternoon)
Issued at 324 AM CDT Sun Mar 29 2015

Main forecast issues today are the chance of rain and the amount
of temperature moderation. Mid level based showers have been slowly
increasing in coverage from western Iowa into eastern Nebraska in
association with strong warm advection and large scale ascent in
advance of a digging trof. Virtually all the guidance has this
trend continuing this morning as showers spread into northeast MO
and west central IL and then gradually backbuild some into central
MO this afternoon. Temperatures today should be a good deal warmer
than yesterday thanks to gusty southerly winds and warm advection
ahead of the encroaching cold front, but will still be a bit below
average for late March.


.LONG TERM:  (Tonight through Saturday)
Issued at 324 AM CDT Sun Mar 29 2015

A few lingering showers may affect parts of southeast MO and
southwest IL early this evening. Otherwise the cold front will be
entering the St. Louis area early tonight and settle into the
lower MS and TN Valley region by Monday morning as weak high
pressure builds into the area. The center of the high will settle
south and southeastward on Monday with surface winds backing to
southwesterly and the development of decent WAA from late morning
into the afternoon. Temperatures should respond favorably warming
to seasonable levels. Surface winds remain southwesterly Monday
night into early Tuesday and the GFS at least thinks this may push
some stratus into the area. The flow however quickly veers above
the surface to westerly and northwesterly and this is not a
typical scenario for seeing stratus and low level moisture return
as aggressively as the GFS thinks. Another weak cold front moves
into the area on Tuesday and moisture ahead of it remains poor in
quality and shallow. This front settles southward into the lower
MS and TV Valley are Tuesday night as high pressure builds
southeastward through the Great Lakes into the OH Valley. Low
level moisture return and quality should improve Wednesday into
Wednesday night however it will be a slow process as the moisture
initially remains quite shallow.

The threat of showers and thunderstorms in the Wednesday night
through Friday period still looks on track although there remains
uncertainty with the progress and position of the associated cold
front and potential development of a migrating frontal low
pressure wave Thursday night into Friday. These variances in the
deterministic models are at least partially due to the differences
in the models with disturbances in the west-southwest flow aloft.



.AVIATION:  (For the 12z TAFs through 12z Monday Morning)
Issued at 633 AM CDT Sun Mar 29 2015

Fcst focus is on rain chances today. Strong upper lvl disturbance
currently over the ern Dakotas will track ESE today. A cold front
assoc with the upper lvl energy will slide SE thru the terminals
this aftn. A band of showers has dvlpd ahead of the front across
cntrl/ern IA arcing back into n cntrl/NW MO. This activity should
continue to push ESE thru the mrng. Radar looks worse than reality
as much of what is showing up is virga. The precip is originating
from an 8-12kft CIG so conditions should remain VFR with any rain
that does reach the ground. KUIN should have a several hour window
this mrng for sctrd -SHRAs. Guidance indicates the precip will dry
up as it attempts to reach the I70 corridor late this mrng with
another batch dvlpng later this aftn. very near I70. The threat of
precip should exit SE by 00Z with clearing skies this evng. The
pressure gradient is expected to strengthen today in advance of
the cold front which will cause srly winds to gust 20-25 kts.

Specifics for KSTL:

VFR fcst thru the prd. A cold front will combine with a strong
upper lvl disturbance to produce sctrd VFR -SHRAs this aftn. It`s
not out of the question that VSBYs may drop into MVFR range if a
heavier SHRA impacts the terminal. Srly winds will gust near 25
kts today diminishing this evng.




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