Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 170337
AFDLSX

Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
937 PM CST Tue Jan 16 2018

.UPDATE...
Issued at 929 PM CST Tue Jan 16 2018

Stratus located from southeast MO through east central MO into
southwest IL is clearing southward at around 15 kts. A few
flurries continue within the cloud deck. Based on extrapolation
the clouds should move south of the CWA probably by around 09z or
so. Temperatures are a bit tricky and they are definitely not
uniform within the clear skies across central and northeast MO due
to varying amounts of snow cover and wind speeds direction. The
surface high is currently centered in northeast OK and it will
ooze a bit southeast overnight with light and gradually backing
surface winds. The already clear skies and the eventually clear
skies in the wake of the clearing stratus, combined with the snow,
and light winds should allow for temps to fall below value
previously forecast. In general lowered mins 3-4 degrees, maybe a
bit more in spots. Even with the light winds, these lower temps
will push wind chills down to bitterly cold values - close to 14
to 15 below in isolated spots in from central MO into west central
IL.

Glass

&&

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 216 PM CST Tue Jan 16 2018

Upper level trough continues to move east out of the forecast area
this afternoon. In it`s wake we are left with scattered mid level
clouds and spotty snow showers in northeastern MO and west central
IL. Surface ridge will begin to build into the region this afternoon
and clouds will decrease and lift overnight.

The building of a surface ridge will begin to increase temps,
although not much warmer initially. Temps overnight will stay in the
single digits with CAA and some widespread snow cover in place but
no wind chill advisory will be needed as winds will remain light
overnight. Temps begin to moderate Wednesday as winds shift to the
southwest.

Walsh

.LONG TERM...  (Wednesday Night through Next Tuesday)
Issued at 216 PM CST Tue Jan 16 2018

The GFS and ECWMF continue to show mainly dry conditions through
Friday as moisture remains cut off from the Gulf of Mexico.  Both
models show that the surface high that is cutting off the moisture
flow will move southeast of the area by Wednesday evening.  This
will cause low level flow to turn out of the southwest which will
start the warm-up in earnest. 850mb temperatures will climb from
around -5C on Wednesday evening into the +5 to 10C range this
weekend.

It still looks like that chances for precipitation will increase
over the weekend as low level moisture transport in increase ahead
of deep trough that will approach the area from the west.  Will keep
a chance of showers going Saturday into Sunday. Still see enough
instability to keep slight chance of thunderstorms late Sunday
into Sunday evening over southeast Missouri into southwest
Illinois. Then the attendant cold front will move west to east
across the area on Sunday night into Monday morning. This is
still likely when there will be a transition from rain to snow.
Then the global models are showing that Monday and Tuesday will be
mainly dry in the wake of the weekend upper trough. Temperatures
early next week will be cooler behind the cold front, but still
above normal for mid-late January.


Britt

&&

.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 530 PM CST Tue Jan 16 2018

A good deal of low cloudiness persists across eastern MO and
southern/west central IL early this evening. The western-most edge
is impact KUIN and KCOU. There are also some breaks with the
larger region and CIGS heights are within the MVFR flight category
ranging from 1600-3000 feet. This cloudiness will move south this
evening exiting KCOU and KUIN, while impacting the St. Louis
region terminals. A few light flurries may occur as well. Present
indications are the stratus should move south of the terminals
between 04-05Z. The remainder of the night there could be some
patchy low clouds floating around but VFR flight conditions should
prevail through Wednesday.

SPECIFICS FOR KSTL:

Stratus/stratocu with cig heights in the MVFR flight category
ranging from 1800-2500 feet will impact the terminal this evening.
A few flurries will be possible as well. Present indications are
the stratus should move south of KSTL between 04-05Z. The
remainder of the night there could be some patchy low clouds
floating around but VFR flight conditions should prevail through
Wednesday.

Glass

&&

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

$$

WFO LSX



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