Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 270912
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
312 AM CST Fri Feb 27 2015

.SHORT TERM:  (Through Late This Afternoon)
Issued at 311 AM CST Fri Feb 27 2015

Primary concern for the short-range today is wind chill values up
across northeast Missouri and west central Illinois.  Quincy has
been reporting wind chill readings at or below -15 for the past
couple of hours.  Temperatures will continue to drop a few degrees
as well, so even with the wind falling off to around 5 mph we should
continue to see wind chill readings between -15 and -20 through
13-14Z.  Have therefore gone ahead and fired off a quick advisory
for this morning.

After the extremely cold start to the day, we`ll have trouble
rebounding much higher than the mid teens to low 20s.  Forecast
soundings show decent low level lapserates, reaching near saturation
around 2000 FT.  This would indicate scattered to perhaps broken
cumulus.  Wouldn`t be surprised to see a few flurries, though
various hi-res models show no indications of precip, so did not
mention in the forecast for today.

Carney

.LONG TERM:  (Friday through Next Thursday)
Issued at 327 PM CST Thu Feb 26 2015

With the cold air solidly in place over the are it will set the
stage for a winter system to affect a large portion of the
forecast area for the weekend and again early next week. Broad
troughing over the northern part of the CONUS will bring mostly
zonal mid level flow over the forecast area. As a more potent area
of low pressure energy digs into the west coast a low level trough will
take form over the interior mountain west and start a flow of warm
air advection into the area. With the warm/moist air
isentropically lifting over the cooler air in place it will
gradually re saturate the atmospheric column and start to
precipitate Saturday afternoon to evening across central Missouri
and probably Saturday night for eastern Missouri and western
Illinois. Since the thermal profile will be very cold, expect this
activity to be all in the form of snow. At least for now it does
not appear that P-type will be in much question, especially for
the Saturday night period. At this time it does not appear that
there will be much in the way of heavy snow, but the prolonged
nature of the warm air advection, as the low stays anchored over
the west coast will provide at least 24, and perhaps 36 hours of
very light snow, which will likely accumulate several inches
through the weekend. Right now the models still favor a track of
the higher snow amounts to be generally along and north of
Interstate 70, and this makes sense since this corridor will have
the better chance to maintain a cool enough thermal profile to
keep everything snow. Farther south, in southern MO and IL there
is a chance that some warmer low level temps could creep into the
thermal profile, which would maybe cause some mixed precip types
on Sunday. Given some lingering model discrepancy the confidence
on specific amounts in a given location are still somewhat low to
medium, however it does appear that areas along and north of I-70
will see several inches of accumulating snow, perhaps getting up
to 4 to 6 inches. As stated above, standard uncertainty caveats
apply, so amounts and locations will likely shift as we approach
the event.

The focus then shifts to early next week as another wave of energy
ejects out of the desert southwest and into the forecast area.
This trough will be a bit more potent than the weekend system, and
will likely draw in more low level warm air and more moisture. At
this point both EC and GFS would hint toward a large portion of
the forecast area, especially areas south of I-70 getting mostly
rain, with a few hours on either side of the rainy period of
wintry mix as the thermal column warms up. Confidence is rising
that there will be at least a decent amount of precipitation over
a widespread area through the early to mid week period, but again,
thermal column uncertainty will preclude any hard amounts and
locations for any specific precip type. By late next week another
strong cold front will sweep through and scour out the moisture,
effectively ending chance for PoPs and ushering another cool down
for the end of next week.

&&

.AVIATION:  (For the 06z TAFs through 06z Friday Night)
Issued at 1121 PM CST Thu Feb 26 2015

For COU/UIN...Sfc ridge builds into the region overnight and
Friday. Nly winds will persist thru the TAF period and become
light and vrb Fri afternoon. Expect CU to develop late
morning/around Noon and become bkn persisting into the afternoon.
CU dissipates in eve leaving ovc cloud deck with bases around 9
kft.

Specifics for STL/SUS/CPS: Sfc ridge builds into the region
overnight and Friday. Nly winds will persist thru the TAF period
and become light and vrb Fri eve. Expect CU to develop late
morning/around Noon, but do not anticipate bkn cigs. CU dissipates in
eve leaving ovc cloud deck with bases around 9 kft.

Tilly

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     17  11  30  27 /   0   5  30  80
Quincy          14   4  24  21 /   0   0  40  80
Columbia        19  11  30  26 /   0   5  60  80
Jefferson City  20  12  31  27 /   0   5  60  80
Salem           17  10  29  27 /   0   5  10  80
Farmington      20  11  32  27 /   0  10  20  60

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...WIND CHILL ADVISORY until 9 AM CST this morning FOR Knox MO-
     Lewis MO-Marion MO-Shelby MO.

IL...WIND CHILL ADVISORY until 9 AM CST this morning FOR Adams IL-
     Brown IL-Pike IL.

&&

$$

WFO LSX






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