Area Forecast Discussion

725
FXUS63 KLSX 171152
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
552 AM CST Sat Jan 17 2026

.KEY MESSAGES...

- Light snow showers or flurries will be possible across the area
  today. The most likely areas to see light snow will be south of
  the Missouri River this morning, and then across northeast
  Missouri and west central Illinois this afternoon. Widespread
  accumulations of more than a dusting are not expected although a
  few spots could receive one or two tenths of an inch.

- Temperatures will be very cold today and tonight with wind chill
  values near zero to 5 below zero Sunday morning. After a brief
  warm up Sunday, another Arctic front will move through the area
  Sunday night which will drop wind chill readings to zero to
  around 10 below zero Monday morning. After another cold night
  Monday night, temperatures will begin to moderate on Tuesday.


&&

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 342 AM CST Sat Jan 17 2026

A deep upper level long wave trough over the Central U.S. will drag
a 1040mb Arctic high from South Central Canada into the Central
Plains today.  Northwest flow on the eastern side of this high is
bringing very cold air into the Mid Mississippi Valley.  The RAP is
showing 925-850mb frontogenesis over central Missouri which
corresponds to an area of light to moderate snow.  This f-gen
spreads east-southeast through the morning into east central
Missouri and southwest Illinois. The low levels are quite dry though
with dew point depressions om excess of 15 degrees F.  NWS Doppler
RADAR in Weldon Spring is showing light returns spreading east,
nearly encircling the RADAR at this time indicating snow aloft not
reaching the ground.  If snow does make it to the ground, it looks
most likely south of the St. Louis Metro Area this morning where dew
point temperatures are a little higher so have increased Pops to
around 40 percent through 12-15Z when the f-gen weakens.

Guidance suggests there will be scattered to broken stratocumulus
today, which will limit isolation.  Between the clouds and
continuing cold advection, temperatures will only rebound 4-6
degrees from this morning`s lows yielding highs ranging from around
20 in northeast Missouri to the upper 20s and low 30s across the
eastern Ozarks. Forecast soundings are showing steep low level
lapse rates today with a bit of CAPE, so scattered flurries and/or
light snow showers will be possible again today.  SLRs are 18-21:1
so any snow that falls will be light and fluffy, and capable of
producing a quick dusting. Should see the stratocu mostly dissipate
during the late evening/overnight hours.  Winds will briefly become
light and variable producing excellent radiational cooling
conditions.  The deterministic NBM looked a little warm when
compared to traditional NAM/MAV guidance.  Given the upstream
temperatures across the Upper Midwest this morning, I stuck closer
to the 25th percentile NBM yielding lows mainly in the single digits
to low teens.

Deterministic guidance shows a short wave moving from the Northern
Plains southeast into the Mississippi Valley Sunday into Sunday
evening. Guidance is indicating strong low level warm advection
ahead of the wave Sunday afternoon. Previous runs have kept the
passage of this wave dry, however the latest ECMWF and GFS are now
squeezing out a hundredth or two of liquid equivalent. CAMs are also
showing light precip moving across the area Sunday afternoon. Given
the strength of the warm advection and support from the CAMs, have
increased PoPs Sunday afternoon across northeast Missouri and west
central Illinois.  Surface temperatures should warm up into the
upper 20s to mid 30s Sunday afternoon due to the warm advection
ahead of the wave, but temperatures aloft remain cold enough for
snow, so have kept snow as the dominant precip type.  Any
accumulations should be light and confined to northeast
Missouri/west central Illinois where temperatures are unlikely to
rise above freezing.

Carney

&&

.LONG TERM...  (Sunday Night through Friday)
Issued at 342 AM CST Sat Jan 17 2026

Sunday`s short wave drags a reinforcing shot of Arctic air down into
the Mississippi Valley for Monday which will produce sub-zero wind
chill readings across most of the area Monday morning and highs only
reaching the teens to mid 20s Monday afternoon.  The long wave
pattern attenuates toward the middle of the week which allows
temperatures to moderate.  The LREF cluster analysis continues to
show a good deal of uncertainty with how much attenuation occurs
though, which produces a wide range of possible temperatures.
While it does look likely that temperatures will move closer to
seasonal normals, high temperature IQRs increase from 6-8 degrees to
15 degrees by Friday. Guidance is showing zonal flow over the area
by that time with a cold front drifting slowly south through the
area.  With this in mind, confidence in the forecast for the latter
half of the week remains low.

Carney

&&

.AVIATION...  (For the 12z TAFs through 12z Sunday Morning)
Issued at 538 AM CST Sat Jan 17 2026

VFR flight conditions with ceilings around 4000 ft are expected
to prevail this morning. An area of very light snow or flurries
may occasionally produce an intermittent drop in visibility to
3SM or less, but these lower visibilites are not expected to last
very long at any given location. The area of snow will clear from
west to east through 15-16Z this morning. Another area of light
snow may develop over northeast Missouri and west central Illinois
this afternoon. Ceilings MVFR ceilings and visibilities are
possible with this precipitation into early evening. Should see
ceilings scatter out during the late evening into early Sunday
morning.

Carney

&&

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

$$

WFO LSX

NWS LSX Office Area Forecast Discussion