Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 102339

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
539 PM CST Tue Dec 10 2019

.SHORT TERM... (Through Late Wednesday Afternoon)
Issued at 359 PM CST Tue Dec 10 2019

High pressure centered over eastern Nebraska will drift southeast
tonight and Wednesday.  Models show the high flattening out into an
elongated ridge stretching from east Texas northeast into Tennessee,
Kentucky, and West Virginia by early Wednesday morning.  A weak
short wave currently over northeast Nebraska will dig southeast into
Iowa tonight and will help to develop a weak warm front across Iowa
and northern Illinois.  Low level warm advection and moisture
convergence looks to produce a little light snow across Iowa and
northern Illinois and the southern edge of the forcing does scrape
far northeast Missouri and west central Illinois late tonight.
Current thinking is that any accumulating snow will stay north of
our forecast area...though a few flurries aren`t out of the
question.  Lows tonight should be similar to last night`s, although
we might see a little bump before sunrise as the wind turns to the
south with the high moving into the lower Mississippi River.  With
the southerly flow continuing on Wednesday highs are expected to be
5 to 10 degrees warmer than today`s in the mid 30s to mid 40s.


.LONG TERM...  (Wednesday Night through Next Tuesday)
Issued at 359 PM CST Tue Dec 10 2019

Southerly flow continues for Wednesday night through Friday.  This
will bring more mild temperatures back to the mid Mississippi Valley
with highs in the mid 40s to low 50s and lows mainly in the low to
mid 30s.  Medium range models are in pretty good agreement that the
next strong short wave to move through the Midwest Friday night into
Saturday will push a cold front through Missouri and Illinois.
Temperatures will fall sharply behind the front late Saturday and
Saturday night into the teens and 20s, and current indications are
that it will struggle to get above freezing on Sunday.  Mid and
upper level flow quickly becomes zonal after FROPA, so the front
should stall somewhere across the lower Mississippi Valley on
Sunday, then the next short wave digs into the Great Plains Sunday
night into Monday.  Guidance shows low level moisture convergence
along the baroclinic zone moving across Arkansas and southern
Missouri Monday morning, and the GFS pushes the moisture convergence
north all the way into Iowa.  The EC is more conservative, but both
models do print out precip across the majority of the forecast area.
GEFS plumes are almost all showing precip from late Sunday through
Monday, although there is quite a spread on how much.  Temperatures
should be cold enough for at least part of the time it`s
precipitating for some kind of wintry precip, though it`s very early
yet so have just kept a rain/snow mix going in the forecast at this



.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 530 PM CST Tue Dec 10 2019

VFR and dry conditions prevail across the area through the TAF
period. Lower clouds at UIN will shift east and dissipate as the
night goes on. Tomorrow winds will stay variable until becoming
predominantly southerly in the late evening, but remain light
until the end of the period.



Saint Louis     22  45  32  51 /   0   0   0   0
Quincy          18  36  28  49 /   5   5   0   0
Columbia        20  46  31  52 /   0   0   0   0
Jefferson City  20  48  31  54 /   0   0   0   0
Salem           21  41  28  47 /   0   0   0   0
Farmington      20  46  27  49 /   0   0   0   0




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