Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 241006
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
406 AM CST Fri Nov 24 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 404 AM CST Fri Nov 24 2017

The upper air pattern will be progressive but will undergo a good
deal of amplification over the next 30 hours. The short wave trof
currently exiting the Northern Rockies will amplify as it moves east
and into the MS Valley be early this evening. Accompanying this
short wave will be a cold front which should extend from eastern IA
through NW MO into SE KS at 00Z tonight. Mild temperatures and
breezy conditions will be the story for today. A batch of high
clouds will slide southeast across the area this morning, while the
surface pressure gradient and low level height gradient tighten.
This will result in increasing and gusty south-southwest winds from
mid-late morning into the afternoon and prominent low level WAA.
Highs today will be quite mild ranging from 15-20 degrees above
normal.

The short wave trof will continue to move east tonight and into the
OH/TN Valleys sending the cold front through the area. There is some
weak large scale forcing accompanying the upper trof and cold
front, as well a band of mid level moisture. Interestingly, a few
of the CAMS also have a little light precipitation. We previously
had some sprinkles in the forecast and the new forecast expands
the coverage in a swath that migrates southeast tonight coincident
with the weak forcing and moisture. Even though we will see a
cold fropa tonight, the air is not particularly cold, and mins
will be above normal.

Glass

.LONG TERM...  (Saturday through Thursday)
Issued at 404 AM CST Fri Nov 24 2017

Main focus thru the forecast period will be temps with low chances
of precip thru the period.

Forecast period begins with a cdfnt pushing thru the area Fri night.
Not much moisture is available for this front, however, with a sharp
upper trof associated with it and a sfc trof just ahead of the
front, some sprinkles are possible ahead of the front as it passes
thru the CWA.

Mdls are in good agreement through about Mon. A large sfc ridge
builds into the area behind the front and have trended twd the
cooler guidance for Sat with nly flow and cool 925mb temps, despite
ample insolation. Temps rebound quickly for Sun as sfc winds become
sly to swly and the thermal ridge builds into the region. Sun and
Mon shud see temps some 10+ degrees above seasonal average.

Mdls differences appear by Mon and result in a low confidence
forecast for the remainder of the forecast period. Important
differences actually show up by Sun which may result in Sun being
slightly cooler and Mon/Tues warmer than currently forecast. Trends
will need to continued to be monitored. Regardless, have trended
slightly cooler for Tues with an approaching cdfnt. With changes to
timing of the front on Tues and into Wed once again, have continued
low PoPs. If the ECMWF verifies, can not rule out a low chance of
frozen precip, but this seems unlikely.

With such large differences among the explicit models as well as the
GEFS, have kept PoPs low and trended temps twd a compromise for now.

Carney

&&

.AVIATION...  (For the 06z TAFs through 06z Friday Night)
Issued at 1145 PM CST Thu Nov 23 2017

VFR conditions to prevail through the period. High clouds over
northwest MO will continue to stream southeast overnight and into
the day on Friday. Southwesterly winds will increase late Friday
morning into Friday afternoon, with gusts of 20-25 knots likely
ahead of a cold front. This cold front will push through all sites
Friday evening, bringing a wind shift to the northwest along with
some enhanced mid/high cloudiness.

SPECIFICS FOR KSTL:
Main TAF concern will be crosswind potential on the parallel
runways Friday afternoon. Southwest winds will increase by late
Friday morning, with gusts of 20-25 knots possible Friday
afternoon. Otherwise, a cold front will bring a wind shift to the
WNW Friday evening with some increase in mid/high cloudiness.

KD

&&

.CLIMATE...
Issued at 404 AM CST Fri Nov 24 2017

Record High Temperatures for Nov 24

STL...74 1966
COU...70 1966
UIN...69 1931

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     71  46  57  36 /   0  10   0   0
Quincy          68  40  55  33 /   5  10   0   0
Columbia        70  41  58  34 /   5  10   0   0
Jefferson City  72  42  59  34 /   0  10   0   0
Salem           61  43  56  34 /   0  10   0   0
Farmington      66  44  59  34 /   0  10   0   0

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX



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