Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 241731
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1131 AM CST Tue Feb 24 2015

.UPDATE:
Issued at 1021 AM CST Tue Feb 24 2015

Favorable wind direction (W/WSW), full insolation, good mixing, and
a relatively dry air mass all support raising high temps by a few
degrees over a corridor from central MO through east central MO
where snow cover is limited. Updated grids and products have been
sent.

Kanofsky

&&

.SHORT TERM:  (Through Late This Afternoon)
Issued at 334 AM CST Tue Feb 24 2015

SFC ridge has settled just south of the area early this mrng with
sthrly winds at almost all stations within the CWA with a few
exceptions across the ern zones. Temp trends across the area
overnight have been a challenge to say the least with various
combinations of bare ground vs. snow cover...clouds vs. no clouds
and sthrly winds vs. calm winds. Deck of mid clouds across southern
IL/MO will continue to push east and out of the area drng the
mrng. This will set the stage for a nice warm up...esp for areas
lacking significant snow cover. Full sunshine and a favorable wind
direction from the W/WSW in advance of the next bndry means temps
should rise into the 40s along the I70 corridor where snow cover
is nonexistent west of the STL metro area. Going fcst may very
well not be warm enough in those locations. Think there will be
pretty decent temp gradients on either side of this area though
due to significant snow cover. The next cold front begins pushing
into the nthrn portions of the FA late this aftn with some
attendant mid/high clouds...but due to their late arrival they
should not significantly affect temp trends.

2%

.LONG TERM:  (Tonight through Monday)
Issued at 334 AM CST Tue Feb 24 2015

Weak frontal boundary to slide south through forecast area
tonight with just an increase in cloud cover initially. Lows will
be in the mid teens to low 20s.

Then northern stream clipper system to slide into region Wednesday
morning. Decent energy with this shortwave with plenty of WAA and
enough moisture to see snow accumulations up to 3 inches, with
highest amounts over northeast Missouri. The system is a bit slower
exiting region, so raised pops a bit on Thursday before coming to an
end. Will see highs in the upper 20s to upper 30s on Wednesday
before dropping off into the teens and 20s Thursday and Friday as
colder air filters in. Wind chill indicies will be between zero and
10 below Thursday night...but above wind chill advisory criteria for
now.

Beyond that, the forecast for the weekend and into early next week
remains rather messy with extended models showing a prolonged period
of precipitation across the region. The temperature profiles still
show a mixed bag of precipitation types, so just made minor
adjustments to the forecast. Will see a wintry mix at onset Saturday
through early Sunday before warmer temps move in giving portions of
the area a cold rain before transitioning back to snow Sunday night
and beyond. Will need to keep an eye on this system with subsequent
model runs as exact track of this system is crucial to what kind of
precipitation we get.

Byrd

&&

.AVIATION:  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1124 AM CST Tue Feb 24 2015

VFR through the period. Gusty WSW winds will diminish after sunset,
then veer and become northwesterly with the passage of a cold
front tonight. A band of VFR clouds will likely accompany the
front.

Specifics for KSTL: VFR for at least the first 0-6 hours and
probably much longer. Gusty WSW winds will diminish after sunset,
then veer and become northwesterly with the passage of a cold
front tonight. A band of VFR clouds will likely accompany the
front. The greatest uncertainty at KSTL is during the last 3
hours of the 30hr TAF period when a clipper system will be
approaching from the northwest.

Kanofsky

&&

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

$$

WFO LSX





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