Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 080541
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1141 PM CST Wed Dec 7 2016

.UPDATE...
Issued at 928 PM CST Wed Dec 7 2016

Large and strong surface ridge building into MO from the northern
Plains tonight. Low-mid level cloudiness across southeast MO along
with flurries should shift south of the forecast area by midnight.
With a clearing sky along with continued low level cold air
advection and lowering surface dew points will lead to unseasonably
cold temperatures late tonight/Thursday morning. Lows tonight
will be close to 10 degrees below normal for early December. West-
northwest surface winds, gusty at times overnight will make it
feel colder.

GKS

&&

.SHORT TERM...  (Through Late Thursday Afternoon)
Issued at 239 PM CST Wed Dec 7 2016

Area of light snow across parts of central MO is expected to
continue to sink south this afternoon and evening. Did pull PoPs and
mention of flurries a little further west with very dry boundary
layer in place. Still appears the accumulating snow will remain just
west of the CWA.

PoPs drop quickly this evening as forcing pushes out of the region.
Expect clouds to clear out overnight. While the CWA should be
completely clear by sunrise Thurs morning, expect mixing to increase
overnight with gusts around 20 kts by 12z. Have overall trended twd
a compromise of guidance for temps tonight.

As for temps on Thurs, while the area will remain under CAA with the
sfc ridge building into the region, a clear sky shud help push temps
upward with mixing as deep as 925 mb. However, given the cold air
under the ridge currently upstream, have still trended twd the
coolest guidance for Thurs.

Tilly

.LONG TERM...  (Thursday Night through Next Wednesday)
Issued at 239 PM CST Wed Dec 7 2016

Main concerns during the long term are snow fall potential and
timing along with the cold weather. High pressure over the area will
slide into the Ohio valley by saturday morning. A progressive
shortwave will race over southern Iowa and into Indiana saturday
afternoon and evening. This will bring isolated chances of snow
showers to northeast Missouri into west central Illinois.

Attention then turns to the cold front which will provide better
chance for snow fall to areas north of I-70 with a rain/snow mix
more likely for areas south of I-70 Sunday. It is too early at this
point to speculate on accumulation amounts.  All precipitation
should end west to east with frontal passage late sunday night into
early monday morning. An even colder shot of air comes in behind the
front Tuesday into Wednesday.

Kelly

&&

.AVIATION...  (For the 06z TAFs through 06z Thursday Night)
Issued at 1130 PM CST Wed Dec 7 2016

Strong surface ridge over the northern Plains will build southeastward
into MO late tonight. West-northwest surface wind will strengthen
late tonight/early Thursday morning and become gusty. Some of the
2000-3000 foot cloudiness across IA may advect into UIN Thursday
morning, although it appears that most of the low level cloudiness
will remain north and east of the taf sites with mainly just some
high level clouds Thursday. The surface wind will weaken Thursday
night as the surface pressure gradient relaxes.

SPECIFICS FOR KSTL: Strong surface ridge over the northern Plains
will build southeastward into MO late tonight. West-northwest
surface wind will strengthen late tonight/early Thursday morning
and become gusty. Mainly just some high level clouds Thursday.
The surface wind will weaken Thursday night as the surface
pressure gradient relaxes.

GKS

&&

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

$$

WFO LSX



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