545
FXUS63 KLSX 292358
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
558 PM CST Thu Jan 29 2026

.KEY MESSAGES...

- Snow remains likely across parts of east central Missouri into
  southwest and south central Illinois this evening. Little or no
  accumulation is expected in most locations, however a narrow
  band of 0.5 to 1 inch is possible.

- Another round of very cold weather is expected this weekend.
  Wind chill values of -10 to -15 degrees are possible Saturday
  morning.

- There will be a chance for snow on Sunday. Accumulations, if
  any, are expected to be light. Another round of precipitation is
  possible Tuesday and Wednesday.



&&

.SHORT TERM...  (Through Late Friday Night)
Issued at 258 PM CST Thu Jan 29 2026

The primary concern in the short term remains accumulating snow this
afternoon and tonight.  A band of precipitation is drifting across
northeast Missouri and west central and south central Illinois at
this time.  The vast majority of this precipitation is not reaching
the ground at this time, although a webcam in La Plata showed a few
flurries, and there was one mPING report of snow from western Ralls
county. ACARS soundings from KSTL are showing a dry layer from the
surface to around 7000 feet which is evaporating the snow before it
can reach the ground, and the layer is represented pretty well in
model soundings this afternoon.  While the dry layer is being
reinforced through a northeast wind, model soundings show it
gradually moistening late this afternoon into the evening, primarily
along and south of I-70 in east central and southeast Missouri into
southwest and south central Illinois.  Still seeing a good deal of
mid-level frontogenesis in the models from 850-700mb this evening to
keep generating precip, so have kept likely PoPs in the forecast
this evening in the aforementioned areas of Missouri and Illinois.
There is less QPF in the guidance than there was yesterday, most
likely due to more evaporation in the dry low levels, so have
lowered snow amounts marginally.  The overarching message remains,
most areas will see little or no accumulation, but localized
accumulations of 0.5 to an inch will be possible. Any snow that
falls should be largely out of the area before 09Z.

A strong short wave will move through the Midwest on Friday and
Friday night.  Strong PVA ahead of the wave will produce a great
deal of synoptic scale lift, model soundings show steep low level
lapse rates and a saturated layer around 3000 feet.  This looks like
a classic cold advection stratocumulus set up for Friday afternoon.
Clouds linger into the evening and deterministic guidance spits out
spotty QPF as the wave passes...mainly outside of our forecast area.
Could see spotty snow showers or flurries.  However ensemble
guidance snows basically 0 chance for snowfall >0.1 inch so will
keep mention of snow out of Saturday/Saturday night`s forecast for
now.

Lastly, the short wave will be dragging another strong Arctic high
pressure system behind it through the Midwest and Great Plains. This
will bring us another round of bitterly cold air.  Friday`s highs
will only be in the mid teens to low 20s and Saturday morning`s lows
are still looking like 0 to 5 above with wind chill values between 5
and 15 below zero.


Carney

&&

.LONG TERM...  (Saturday through Next Thursday)
Issued at 258 PM CST Thu Jan 29 2026

Little change to the forecast for Saturday night into next week.
The Arctic high moves southeast of the area Sunday allowing some
milder air to return to the Mid Mississippi Valley with highs
approaching freezing. There`s still a chance for some light snow on
Sunday, mainly across northern Missouri into central Illinois as
another wave passes over the region. The GFS and ECMWF are dry, and
have very light QPF respectively.  LREF probabilities for measurable
snow are 20-40 percent, so the NBM`s 20-30% look reasonable.  Monday
through next Thursday`s temperatures continue to warm up, although
another cold high pressure system will be lurking over southern
Canada and the Upper Midwest.  This will try to continually funnel
colder air south into the Mid Mississippi Valley.  Temperature IQRs
next week are as wide as 15 degrees in some locations due to
uncertainty in the position of the high. Another short wave will roll
through the Midwest Tuesday into Wednesday with another chance for
precipitation.  The GFS and ECMWF vary widely on how much QPF they
produce, and the LREF 24 hour QPF ranges from 0 to nearly 0.3 inches
at the 25th and 75th percentiles.  The wide variance in solutions
obviously lends little confidence in the forecast into midweek.


Carney

&&

.AVIATION...  (For the 00z TAFs through 00z Friday Evening)
Issued at 558 PM CST Thu Jan 29 2026

A 4-7kft stratus deck is currently draped west to east just to the
north of the St. Louis metro with an embedded band of light
precipitation being picked up on doppler radar. There have been a
few reports of light snow reaching the ground under this band as it
slowly drifts to the southeast. This cloud deck and scattered snow
showers will threaten the St. Louis metro terminals over the next
several hours and is expected to exit southeast of the area by 06z.
Within this band, only very isolated pockets of relatively heavier
(but still light) snow appear to have any potential of causing
visibility reductions.

Otherwise, light northeasterly surface flow will persist this
evening with river valley terminals expected to go calm and variable
overnight. Surface winds back slightly from the north by tomorrow
with MVFR ceilings forecasted to move in from the north by tomorrow
afternoon. There is another chance of light snow by late tomorrow,
but given the time range and low confidence (20%) in this occurring,
any mention of it has been left out of this TAF package.

Peine/Elmore

&&

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

$$

WFO LSX