Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 140002

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
602 PM CST Wed Dec 13 2017

.SHORT TERM...  (Through Late Thursday Afternoon)
Issued at 247 PM CST Wed Dec 13 2017

Main impact for tonight will be gusty winds over the area through
the evening. There have already been observed gusts over 45 mph in
central Missouri and western Illinois this afternoon. A Wind
Advisory has been posted through part of the evening for parts of
northeast Missouri and western Illinois. A cold front located just
north of the Interstate 70 corridor will continue to push southeast
and clear the region by the middle of this evening.  The gusty winds
will continue overnight behind the cold front then decrease around
sunrise over the entire area as the trough moves away from the area
and a ridge of high pressure moves over the region. Temperatures
will be slightly below normal in the upper 30s on Thursday.


.LONG TERM...  (Thursday Night through Next Wednesday)
Issued at 247 PM CST Wed Dec 13 2017

A decent shortwave/cold front to slide southeast through region late
Thursday night/Friday morning. Little in the way of moisture
associated with it, but could see some flurries after midnight
Thursday night for portions of northeast MO and west central IL.
Otherwise, another cold night with lows in the low to mid 20s.

By Friday, despite passage of cold front, not a lot of CAA
associated with it and winds will back to the west to southwest as
weak surface ridge builds in. So will see partly sunny skies and
highs in the upper 30s to mid 40s.

Upper ridge to build in Friday night/Saturday, allowing southwest
winds to bring in decent WAA for first half of weekend. Lows
Friday night will be in the mid 20s to low 30s, while highs on
Saturday will be in the upper 40s to upper 50s.

Extended models having major differences on timing and strength of
next system that will affect area beginning late Saturday night
through Sunday. ECMWF remains a bit faster with system than GFS.
Kept initial blend, which backed off on pops after 06z Saturday, but
ramped them up Sunday morning, before tapering off Sunday afternoon.
As for precipitation type, should be mostly rain, though would not
be surprised to see a few flakes mixed in around sunrise on Sunday.

Beyond the weekend, the extended models really diverge in their
solutions for first part of work week. So for now went with the
warmer solution with highs about 10 degrees above normal for this
time of year. Could see another system move through on Tuesday, but
for now kept slight chance pop mention for portions of area.



.AVIATION...  (For the 00z TAFs through 00z Thursday Evening)
Issued at 523 PM CST Wed Dec 13 2017

Gusty northwest winds will gradually diminish during the first
0-9 hours of the TAF period. An area of MVFR cigs was located
north of the terminals at TAF issuance, and this cloud deck is
expected to rotate into the region overnight. Increasingly dry
air at low levels should help to erode cloud bases overnight and
should lead to improvement back to VFR around daybreak. Winds will
further diminish after 12z after the pressure gradient relaxes.



MO...Wind Advisory until 9 PM CST this evening for Knox MO-Lewis MO.

IL...Wind Advisory until 9 PM CST this evening for Adams IL-Bond IL-
     Brown IL-Clinton IL-Fayette IL-Greene IL-Macoupin IL-Marion
     IL-Montgomery IL-Pike IL-Washington IL.



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