Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 170536

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1136 PM CST Tue Jan 16 2018

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



.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


.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

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.



.AVIATION...  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1132 PM CST Tue Jan 16 2018

MVFR stratus across southeast and extreme east central MO into
southwest IL continues to move southward, and this trend will
continue overnight. The entire St. Louis region and terminals
should clear in the 06-08Z time frame. Otherwise VFR flight
conditions are expected through the forecast period. Light surface
winds tonight will gradually back to southwesterly on Wednesday
morning, increasing from 8-11 kts by midday.


MVFR stratus continues to push south and should exit the terminal
by 07Z. Thereafter VFR flight conditions will prevail.





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