911
FXUS63 KLSX 202253
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
453 PM CST Tue Jan 20 2026

.KEY MESSAGES...

- Confidence is high in bitter cold from late Friday through at
  least early Sunday.

- The chance for snowfall is increasing on Saturday (now 50-60%),
  especially across southeastern Missouri, though confidence
  remains low in amounts.


&&

.SHORT TERM...  (Through Late Wednesday Night)
Issued at 250 PM CST Tue Jan 20 2026

Southerly surface winds have aided in a nice warmup today, despite
some pesky low to mid-level clouds this morning. Areawide
temperatures are now in the low 30s to the northeast with low 40s
being observed across the Ozarks. Throughout the short term period,
a persistent and broadened upper-level trough will remain to the
north over Canada with a large upper-level ridge to the west off the
Pacific coast, placing us under northwesterly flow aloft. Within
this broadened upper-level trough a shortwave is currently swinging
to the southeast across the Northern Plains.

For most of the area, this shortwave will bring only an increase in
mid-level cloud cover from the northwest, which is already moving
into northern Missouri and west-central Illinois. Increased low-
level southerly flow ahead of this system`s attendant surface front
will lead to moisture advection, particularly across southeastern
Missouri, where the front will be slower to reach. Therefore, the
best precipitation chances with this system look to be limited to
the far southern CWA across Reynolds, Iron, and Madison counties.
Model guidance forecasted soundings for this area indicate a mostly
saturated column from the sfc-15kft by early Wednesday morning,
along with a sufficient amount of lift present. Temperatures
throughout the saturated layer will be near the freezing mark
resulting in snow, freezing rain, and rain all being possible for a
brief period from 08-14z on Wednesday. With the brief duration and
weaker intensity forecasted, any precipitation that does fall is not
anticipated to accumulate.

After the FROPA Wednesday morning, winds will switch from southerly
to westerly. Despite the shift in wind direction, Wednesday will be
the warmest day of the week since this post-frontal airmass lacks
access to any cold air. As a result, afternoon highs are forecasted
to reach the upper 30s to the north with mid to upper 40s to the
south. Another, weaker, shortwave disturbance swings by the area to
the north Wednesday night bringing another trailing cold front with
it. The biggest thing to note here is this FROPA will switch winds
from the north, opening up access to the much colder air that will
be displaced to the north. The result will be Wednesday night lows
in the low 20s to the south with mid teens sneaking back in for the
northern areas.

Peine/Elmore

&&

.LONG TERM...  (Thursday through Next Tuesday)
Issued at 250 PM CST Tue Jan 20 2026

Guidance consensus is that broad upper-level troughing will still be
present over much of the CONUS at the start of the extended forecast
period; its axis over the Ohio Valley toward the Northeast. This
will have the CWA beneath quasi-zonal to slightly northwesterly flow
in the upper-levels, though low to mid-level flow will become
increasingly northwesterly through the day, pushing Wednesday
night`s cold front southward away from the CWA. This will mark the
entrance of a potent Arctic air mass that will slowly ooze into the
region through the day Thursday. Areas north of I-70 will feel the
initial brunt as they struggle to crack freezing, though the cold
will be realized area-wide as ensemble means tank into the low teens
to single digits for most locations.

Over the last 24-36 hours, guidance has been trending colder with
Friday`s temperatures, with them now rivaling what has been
previously forecasted on Saturday. Ensemble means both days favor
the teens to single digits for highs both days, with the exception
being far southeastern Missouri. There, Friday currently has
temperatures warming into the upper teens to low 20s, with mid-teens
favored on Saturday due to the delay in the cold air advection.
However, with guidance trending colder on Friday over the last
several initializations, these temperatures may be too warm. The
cold may reach dangerous thresholds Friday and Saturday nights as
lows approach 0 degrees and winds stay up out of the north. There`s
still enough spread among guidance with exact temperatures and wind
speeds that confidence is low in whether or not portions of the area
reach criteria for a Cold Weather Advisory. Ensemble IQRs support
temperatures moderating Sunday into early next week as the core of
the air mass shifts eastward with the trough weakening, though
spread within the IQR of 10-15 degrees leads to low confidence in by
how much. Additionally, any accumulating snowfall will aid in
nudging temperatures downward for as long as it remains on the
ground, and the occurrence of snowfall remains the more
challenging aspect of this forecast.

Great attention has been given to the potential for snow this
weekend accompanying the cold, but confidence in specific remains
low and hinges on the phasing of a northern and southern stream
shortwave. The phasing of these features varies drastically among
deterministic guidance, with ensemble systems falling into similar
camps to that of their deterministic parent models. The GFS/GEFS is
slower and weaker with both waves and more aggressive with the Arctic
air mass, keeping precipitation chances south of the CWA and the
area dry Friday through Sunday. The EURO/ENS and Canadian/GEPS is
faster and stronger with the waves, pulling more moisture northward
over the air mass, leading to precipitation across the CWA focused
mainly on Saturday. These latter two model suites would favor
snowfall given the sub-freezing lower atmosphere and dendritic growth
zone, with the greatest accumulations expected across southeastern
Missouri and southwestern Illinois - as much as 4"+ with amounts
tapering off northward toward the I-70 corridor. This is the worst-
case scenario, and confidence in either solution remains low at this
point given the spread in guidance and initialization variability.

Elmore

&&

.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 447 PM CST Tue Jan 20 2026

VFR conditions are expected throughout the 00Z TAF period, with
only a few low probability exceptions. Wind and low level wind
shear are the primary concerns, as a strong low level jet will
bring very strong winds just above the surface overnight through
early tomorrow morning. While there is minimal directional shear
expected, the speed shear alone may result in marginal low level
wind shear being observed at all terminals. This will diminish by
mid morning when a cold front moves through, which will also veer
winds from southwest to westerly and maintain modest wind gusts
through the day. Winds are likely to weaken again near the end of
the period, but another cold front will bring more gusty winds
between 00Z and 06Z tomorrow, which only impacts the end of the
30 hour STL TAF at this time.

Otherwise, some mid-level cloud cover is likely to move through
all terminals overnight, with a limited potential for snow
flurries as well. The probability of this producing accumulations
or visibility reductions is very low (20% or less).

BRC

&&

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

$$

WFO LSX