Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 141141

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
541 AM CST Wed Nov 14 2018

.SHORT TERM... (Through Thursday)
Issued at 318 AM CST Wed Nov 14 2018

Main concern continues to be the winter storm that will affect
the area tonight into Thursday. Have upgraded the winter storm
watch to a warning for much of southwest Illinois and Ste
Genevieve County in MO. Also issued a winter weather advisory for
much of southeast and east central Missouri and a small part of
south central Illinois.

Water vapor is showing the upper low early this morning over the
Arklatex. Temperatures were quite cold across the area because of
the clear skies and the light winds associated with the surface
high moving across the area. Temperatures early this morning have
fallen into the teens across the entire CWA and today they will
only be able to recover into middle 30s.

The upper low is still expected to move northeast tonight across the
Bootheel into Ohio Valley on Thursday.  There is still some
disparity in the tracks, with the NAM taking the track of the 850mb
low farther east that the GFS or the ECMWF.  These two models have
been more consistent and still show a favorable path for
accumulating snow over the CWA this into Thursday morning. Still
expect the snow to be heavy at times over parts of southwest
Illinois as the deformation zone of upper low moves across the
area. Forecast soundings show a deep isothermal layer along with
favorable growth in the dendritic growth zone late tonight into
Thursday morning over southwest Illinois. Think this area could
see around 6 inches of snow before the deformation zone lifts out
on Thursday afternoon, with lesser amounts in the advisory area.
There could be significant travel impacts in the warning and
advisory areas because of the snow and the temperatures falling
into the mid to upper 20s overnight. The snow will end from west
to east as the upper low lifts out and shortwave ridge moves in
behind it.


.LONG TERM...  (Thursday Night through Tuesday)
Issued at 318 AM CST Wed Nov 14 2018

The next chance of precipitation will be over the weekend when a
cold front move south across MO/IL bringing a chance of rain and
snow. Dry weather will return early next week as high pressure
builds in behind the front. Temperatures will remain below normal
through the period, particularly over the weekend with the clouds
and precipitation.



.AVIATION...  (For the 12z TAFs through 12z Thursday Morning)
Issued at 520 AM CST Wed Nov 14 2018

Mainly dry and VFR conditions are expected through late this
evening. Then snow will spread northward with MVFR/IFR ceilings
and visibilities through southeast Missouri and southwest Illinois
by late afternoon. These conditions will reach the St. Louis area
terminals by late this evening and overnight. The snow will
accumulate overnight into Thursday morning. Light and variable
winds this morning will turn out of the north this morning.


Mainly dry and VFR conditions are expected through mid evening
before snow moves into the terminal from the south. The snow will
be steady overnight into Thursday morning with IFR ceilings and
visibilities expect after 06Z. Snow accumulations are expected to
be between 3-5 inches tonight and Thursday morning.



MO...Winter Weather Advisory from 6 PM this evening to 6 PM CST
     Thursday for Crawford MO-Franklin MO-Gasconade MO-Iron MO-
     Jefferson MO-Lincoln MO-Madison MO-Montgomery MO-Reynolds
     MO-Saint Charles MO-Saint Francois MO-Saint Louis City MO-
     Saint Louis MO-Warren MO-Washington MO.

     Winter Storm Warning from 6 PM this evening to 6 PM CST Thursday
     for Sainte Genevieve MO.

IL...Winter Weather Advisory from 6 PM this evening to 6 PM CST
     Thursday for Calhoun IL-Greene IL-Jersey IL-Macoupin IL-
     Montgomery IL.

     Winter Storm Warning from 6 PM this evening to 6 PM CST Thursday
     for Bond IL-Clinton IL-Fayette IL-Madison IL-Marion IL-
     Monroe IL-Randolph IL-Saint Clair IL-Washington IL.



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