Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 140920

Area Forecast Discussion
National Weather Service Saint Louis MO
320 AM CST Thu Dec 14 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 319 AM CST Thu Dec 14 2017

Main focus thru tonight will be cloud cover, which will dictate

Low clouds currently covering the CWA are expected to push south and
west thru the morning. As they do, a thick layer of mid and high
clouds are expected to spread over the area. With ample cloud cover
expected thru peak heating and CAA continuing thru the day, have
trended temps today twd the cooler guidance. With cloud cover
anticipated to persist thru tonight, have trended twd the warmer

However, a fair amount of uncertainty exists regarding cloud cover
thru tonight. Expect breaks in the low clouds to develop today.
While fewer breaks in the high clouds are expected, thinner spots
are very possible, allowing more heating than currently expected.
This uncertainty continues into tonight, however, this is more
uncertainty due to differences in mdl guidance. Have trended twd a
more cloudy forecast and kept mention of flurries across nrn
portions of the CWA.

Had considered removing flurries given the 00z guidance, but 06z
NAM just arriving wud suggest a chance of flurries still being
possible. Uncertainty remains how far south flurries is possible,
but kept confined to nrn counties. Otherwise, no precip is


.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 06z TAFs through 06z Thursday Night)
Issued at 1132 PM CST Wed Dec 13 2017

An area of MVFR to VFR stratus was rotating through the region at
TAF issuance, and clouds are expected to persist for the next
several hours before increasingly dry air at low levels leads to
rising cloud bases. Gusty northwest winds have persisted longer
than previously expected however the sustained winds and gusts
have both been gradually diminishing with time. This trend will
continue overnight and wind speeds will be much lower after
12-15z. Winds will begin to back after 18z and should become
westerly by the end of the valid TAF period.



Saint Louis     36  28  45  33 /   0   0   5   0
Quincy          32  24  40  30 /   0  10   5   0
Columbia        36  27  44  33 /   0   5   0   0
Jefferson City  37  27  45  32 /   0   5   0   0
Salem           36  24  41  30 /   0   0   0   0
Farmington      37  27  44  30 /   0   0   0   0




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