Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 160959
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
359 AM CST Tue Jan 16 2018

.SHORT TERM...  (Through Late Tonight)
Issued at 321 AM CST Tue Jan 16 2018

Clouds continue to develop within convective rolls behind the front
early this morning. Sub-cloud air appears to be dry enuf to prevent
flurries from reaching the ground, but can not be completely ruled
out. However, the clouds behind the sfc trof currently across nrn
IL/IA and into NEB, will swing south across the region today as the
low pulls eastward. Expect at least some flurries with these clouds
thru the morning hours as they drop south. However, with some
warming today, expect low levels dewpoint depressions to widen enuf
that flurries shud struggle this afternoon.

As the upper trof continues to move SE thru the region, warmer air
will slowly filter in. Granted, not much warmer. Expect to see
mixing to around 925mb and have based temps today off of the 925mb
temps of -14C to -16C. However, these temps wud suggest some warmer
temps in some areas, but have trended temps today twd a compromise.

The sfc ridge will build swd today and tonight across NEB and KS
leaving the CWA under CAA. Surface winds do become wly across nrn
portions of the CWA late tonight which shud help slow the cooling
overnight. As mentioned above, with the upper trof pulling away,
still expect slightly warmer temps tonight compared to early this
morning. Still, with the light winds and snow cover, have trended
aob the cooler guidance.

Tilly

.LONG TERM...  (Wednesday through Monday)
Issued at 359 AM CST Tue Jan 16 2018

A gradual warming trend will begin on Wednesday as upper level
heights begin to rise as the upper level trough shifts east of the
region, and the surface wind becomes southwesterly as the surface
ridge shifts south of the area.  The models were forecasting the 850
mb temperatures to slowly rise from northwest to southeast.  Any low
level cloudiness should advect east-southeast of our forecast area
Wednesday morning with little if any cloud cover expected from then
through Friday.  This will allow plenty of daytime solar insolation
Wednesday through Friday.  By Thursday high temperatures will be
slightly above normal, with highs by Friday about 10 degrees above
normal.  Temperatures will continue to rise to well above normal on
Saturday, but low-mid level warm air advection along with increasing
low level moisture will lead to increasing cloud cover by Saturday.
It appears that there will also be some patchy drizzle Saturday and
Saturday night due to weak upward lift and shallow low level
moisture.  A developing upper level low and associated deepening
surface low and trailing cold front will impact our area Sunday and
Sunday night.  The operational GFS is a little quicker and further
south with the track of the surface low compared to the ECMWF model,
but with either solution it appears that most of our forecast area
will be in the warm sector of the storm system with showers and
possibly a few thunderstorms along and just ahead of the cold front
Sunday afternoon and evening. Colder air will move into our area
Sunday night after passage of the surface low and trailing cold
front with the possibility of rain changing to snow before ending,
mainly across northeast MO and west central IL. The precipitation
should shift east of our area by Monday with colder temperatures,
although still at or slightly above normal.

GKS

&&

.AVIATION...  (For the 06z TAFs through 06z Tuesday Night)
Issued at 1117 PM CST Mon Jan 15 2018

Cloud trends this evening have been rather odd. Narrow streaks of
stratocu have been appearing within the low level cyclonic flow.
Some that develop earlier have since dissipated, but there has
been an increase in them across eastern MO and extreme western IL
within the last hour. I have added some scattered stratocu to all
TAFS but KCOU overnight, with a TEMPO initially to account for
brief periods of broken CIGS. The height of the cloud bases has
been between 2000-3000 ft. I am not sure of the longevity of
these, they could come and go all night. A better increase in
stratocu should occur during the predawn hours across northern MO
into west central IL with clouds spreading/developing southward
Tuesday morning. MVFR flight conditions should occur with this
stratocu and there could be a few flurries as well. CIG heights
should improve to VFR as the afternoon progresses, and think much
of the cloudiness will diminish near/after sunset. Modest
northwest winds will continue overnight and into Tuesday.

SPECIFICS FOR KSTL:

Narrow streaks of stratocu have developed across the St. Louis
region within the last hour. I have added some scattered stratocu
to KSTL and a TEMPO to account for potentially brief periods of
broken CIGS. The height of the cloud bases has been between
2000-3000 ft. I am not sure of the longevity of these, they could
come and go all night. A better increase in stratocu is expected on
Tuesday morning as clouds spread/develop into the area from the
north. MVFR flight conditions should occur with this stratocu and
there could be a few flurries as well. CIG heights should improve
to VFR as the afternoon progresses, and I think much of the
cloudiness will diminish near/after sunset. Modest northwest winds
will continue overnight and into Tuesday.

Glass

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     15   7  26  18 /  10   0   0   0
Quincy          11   2  23  15 /  10   0   0   0
Columbia        10   2  25  15 /   5   0   0   0
Jefferson City  11   3  26  16 /   0   0   0   0
Salem           14   6  23  14 /   5   0   0   0
Farmington      14   5  26  15 /   0   0   0   0

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Wind Chill Advisory until noon CST today for Audrain MO-Boone MO-
     Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
     Iron MO-Jefferson MO-Knox MO-Lewis MO-Lincoln MO-Madison MO-
     Marion MO-Moniteau MO-Monroe MO-Montgomery MO-Osage MO-Pike
     MO-Ralls MO-Reynolds MO-Saint Charles MO-Saint Francois MO-
     Saint Louis City MO-Saint Louis MO-Sainte Genevieve MO-
     Shelby MO-Warren MO-Washington MO.

IL...Wind Chill Advisory until noon CST today for Adams IL-Bond IL-
     Brown IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL-Jersey
     IL-Macoupin IL-Madison IL-Marion IL-Monroe IL-Montgomery IL-
     Pike IL-Randolph IL-Saint Clair IL-Washington IL.

&&

$$

WFO LSX



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