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000
FXUS63 KLSX 120544
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1144 PM CST Wed Dec 11 2013

.SHORT TERM:  (Through Late Tonight)
Issued at 322 PM CST Wed Dec 11 2013

Did not make much change to going dry and very cold forecast.
Surface high located over southeast Nebraska will continue to move
east, and cross the CWA late this evening and overnight.  This
should allow for strong radiational cooling with clear skies and
light winds.  The coldest temperatures will be over the snowpack
over southeast Missouri and southern Illinois which will be closest
to the center of the surface high at 12Z.

Britt

.LONG TERM:  (Thursday through Next Wednesday)
Issued at 322 PM CST Wed Dec 11 2013

Surface ridge to move off to the southeast on Thursday, so will see
temperatures moderate a bit with highs in the low 20s far east to
the upper 30s over central MO under mostly sunny skies.

Then Thursday night, temperatures to be about 15 to 20 degrees
warmer than tonight, in the upper teens to mid 20s.

All of this is ahead of next weather system that is still progged to
affect the area Friday and Friday night. Since the upper level
system is still off the southern CA coast, there are timing and
placement differences amongst the models, but are coming into better
agreement. Precipitation is still expected to spread northeastward
into the forecast area Friday morning as low level jet ramps up and
increases low level moisture along with waa.  Because the low levels
are initially fairly dry, there will be some evaporative cooling
which could cool down the column closer to zero, thus precipitation
will likely start out as a mix of sleet and freezing rain along
and south of Interstate 70. Temperatures are expected to warm up
above freezing during the afternoon hours, so could see a cold
rain situation setup for a large portion of the area with mainly
snow far north where the colder air is.

By Friday night, the precipitation will continue as inverted surface
trof slides east through region. Precipitation will eventually
change over to all snow by 06z Saturday as colder air filters in on
backside of system. Though could continue to see a mix of freezing
rain and sleet over southeast MO and southern IL with some icing
possible after 06z Saturday. As for snowfall amounts, there is the
potential for 3 to 5 inches of mainly snow across portions of
northeast MO and west central IL, with lesser amounts to the
south.

The precipitation to taper off by midday Saturday. Could see some
lingering freezing drizzle on Saturday as we lose ice crystals in
the column but low level moisture lingers overhead as a second upper
level shortwave slides through the region.

Beyond that a fairly quite weather period with some shortwaves
sliding through region, but more significant energy to remain north
of forecast area. Temperatures to moderate a bit by next Tuesday and
Wednesday with highs in the mid 30s to mid 40s.

Byrd

&&

.AVIATION:  (For the 06z TAFs through 06z Thursday Night)
Issued at 1145 PM CST Wed Dec 11 2013

VFR conditions with nearly cloudless skies expected into Thursday
evening as Arctic high works across the CWA during the remainder
of tonight, and into the lower Ohio and lower Mississippi Valleys
on Thursday. Winds will be quite light for the rest of tonight, with
return flow developing on the back side of the surface ridge
producing SW winds in the 8-12kt range by Thursday afternoon.

Specifics for KSTL: VFR conditions expected throughout the
forecast period, with little in the way of cloudiness. Light winds
tonight will become SW at around 10kts by midday Thursday.

Truett

&&

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

$$

WFO LSX