Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 222049
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
249 PM CST Mon Jan 22 2018

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 249 PM CST Mon Jan 22 2018

The sfc occluded front continues to move east thru the CWA this
afternoon. Ahead of this front, temps have climbed into the upper
50s and 60s with clouds behind the front. The cold front is
currently just beginning to enter the wrn portions of MO. The sfc
low is expected to pull newd out of the region tonight into Tues
morning. As it does, areas of precip will also move NE thru the
region.

This precip will be the focus for tonight. There is a fair amount of
uncertainty regarding precip coverage and intensity thru tonight. At
least some of the precip across central and wrn portions of MO is
convectively driven and is expected to diminish somewhat with
sunset. While the going forecast mentions showers, it is possible at
least a portion of this will be more drizzle than showers. Precip
will begin as rain as it enters the CWA this afternoon. As the cold
air filters into the region, this rain shud gradually mix with, then
change to snow. Have kept out mention of FZRA/FZDZ as currently
expect precip to end as ice crystals are lost and due to forecast
soundings that are cold enuf to support cloud ice, albeit on the
warm side of that threshold. Still not expecting much in the way of
accumulation with light precip expected. What does accumulate shud
remain a half inch or less.

Clouds are expected to linger thru much of the day Tues due to
cyclonic curvature across the region. These clouds are also expected
to be somewhat low, around 2000 ft or so. While some breaks are
possible, with CAA across the region, have trended twd the cooler
guidance.


Tilly

.LONG TERM...  (Tuesday Night through Next Monday)
Issued at 249 PM CST Mon Jan 22 2018

A northwest flow shortwave will move through our area late Tuesday
night and Wednesday morning.  Ahead of this feature there will be
mid level cloudiness, but it appears that low level moisture will be
too limited for any precipitation.  Could not rule out a few
flurries, but will leave the forecast dry for now as the models have
none or very little spotty QPF.  Temperatures Tuesday night through
Wednesday night will be close to seasonal normals for late January
with a surface ridge moving from the Plains southeastward into the
Gulf Coast states.  Warmer temperatures can be expected on Thursday
as an upper level ridge moves eastward into the central US, and
surface winds become southerly as the surface ridge shifts well
southeast of our region.  Highs on Thursday should be around 15 to
20 degrees above normal.  The chance of rain will return Friday
afternoon and night as an upper level trough and associated cold
front approaches, while low-mid level moisture increases over our
area. There were significant differences between the operational GFS
and ECMWF model for Friday night through the weekend.  The ECMWF
model phases both the northern and southern stream, developing a
deep slow moving upper level trough, and keeping the chance of
precipitation going for parts of our forecast area until late
Saturday night.  The GFS does not phase the northern and southern
stream energy, and hence is much weaker and more progressive with
the northern stream upper level trough, and weaker with the surface
reflection.  For now will lean more toward the stronger and slower
solution of the ECMWF model, and keep the chance of precipitation
going until late Saturday night.  It appears that the precipitation
type should be all liquid rain, with a small chance the rain could
change over to light snow just before ending Saturday night if the
precipitation duration lasts this long. Colder temperatures can be
expected Saturday night and Sunday after passage of the cold front,
albeit still a little above seasonal normals.

GKS

&&

.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1212 PM CST Mon Jan 22 2018

Area of clouds across wrn MO will continue to slowly move east
thru the afternoon. The area of light rain and/or snow will also
move east thru tonight. At this point, still expect any precip to
be light with little if any snow accumulation. Otherwise, winds
will continue to be strong and gusty thru the period, although
winds shud diminish slightly this evening. Clouds are expected to
linger thru Tues as the system slowly pulls out of the region.

SPECIFICS FOR KSTL: Area of clouds across central and wrn MO will
continue to move east. Showers are possible thru this evening, but
are expected to be scattered and have kept only a mention of VCSH.
Can not completely rule out precip changing over to snow, but
precip may come to an end before changing to snow. Otherwise,
expect clouds to linger thru Tues, but may clear late Tues
afternoon before clouds return ahead of the next approaching
system.

Tilly

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     33  39  27  44 /  60  10   5   5
Quincy          29  36  24  40 /  60  10  10   5
Columbia        29  37  25  44 /  60  10   5   5
Jefferson City  31  39  25  45 /  60  10   5   5
Salem           34  38  26  41 /  20  10   5   5
Farmington      32  40  26  46 /  20   5   5   5

&&

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

$$

WFO LSX


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