Area Forecast Discussion
791
FXUS63 KLSX 242050
AFDLSX
Area Forecast Discussion
National Weather Service Saint Louis MO
250 PM CST Sat Jan 24 2026
.KEY MESSAGES...
- A major winter storm will continue to impact the region, with a
second wave of heavy snowfall passing through Sunday morning
and afternoon making travel nearly impossible for much of the
region.
- The combination of heavy snowfall and bitterly cold
temperatures will prove life-threatening for those with
prolonged exposure to the elements.
- A reinforcing shot of bitterly cold air and dangerous wind chills
will move into the area Sunday night and Monday morning. A Cold
Weather Advisory has been issued for this timeframe.
&&
.SHORT TERM... (Through Late Sunday Night)
Issued at 247 PM CST Sat Jan 24 2026
A deepening shortwave can be seen in water vapor imagery digging into
the Southwest as another spins over the California Baja. Broad
southwesterly flow ahead of these features is sending subtle
disturbances aloft over the Southern Plains, Mid South, and into the
Ohio Valley. Frontogenesis based at 850 mb stretches across the Mid
South and tilts northward over the Middle Mississippi Valley with
vertical extent, favoring our ongoing snowfall to continue as
moisture overrides the Arctic air mass. There have been efficient
pockets of snowfall rates with this first wave of snow, with
localized areas seeing rates of 0.5-1"/hr at times. This has led to
accumulating snowfall area wide, with the greatest amounts having
fallen along and south of I-70 thanks to greater moisture and
slightly better forcing.
This forcing will wane slightly this evening leading to lower rates
and more spotty snowfall. This is a slight change from prior
forecasts, when more of a pronounced lull was forecast. However,
this is not expected to have a significant impact on forecasted
snowfall amounts. However, what will has had a significant impact is
an increase of about 0.1" QPF among guidance consensus with the
second wave of snowfall that will being moving into the region later
this evening and continue through Sunday afternoon. This second wave
of snow will be forced by the aforementioned northern and southern
shortwaves phasing together over the Southern Plains, inducing
cyclogenesis over the Lower Mississippi Valley as they do so. The
result is that snow will once again ramp up in intensity across the
region, with the primary focus for snowfall being over the
southeastern 2/3rds of the CWA.
As this surface low gradually tracks northeastward tonight into
Sunday morning, robust dynamic lift via jet streak coupling in the
upper levels of the atmosphere will support a rapid deepening of the
low as it passes southeast of the CWA. The track of the 850mb low
through the Missouri Bootheel places much the southeastern 2/3rds
(roughly the Winter Storm Warning area) in favorable placement for
robust moisture transport via the TROWAL and then the later effects
of the deformation zone, climatologically favoring heavy snowfall.
Model soundings continue to show a deep isothermal layer within the
dendritic growth zone among robust lift through Sunday morning,
supporting snowfall rates at times reaching and exceeding 1"/hr
within the Warning area. This will cause conditions to rapidly
deteriorate and make travel difficult if not impossible. These more
intense rates will diminish during the late morning and afternoon,
with snow expected to depart the CWA to the east by late
afternoon/early evening.
After this event is all said and done, impressive snowfall totals
are forecast for locations within the Warning area. Generally along
the I-44 corridor in Missouri and the I-70 corridor in Illinois and
points south, confidence is high in an additional 6-10" of snowfall,
with confidence increasing in amounts reaching the higher end of
that range thanks to the increase in QPF. Given the QPF and
favorable thermodynamics and forcing, pockets of up to or greater
than 12" can not be ruled out. Further north-northeastward, but
still within the Winter Storm Warning, generally an additional 4-6
is expected, with amounts of 1-3" within the advisory area. In fact,
portions of the Advisory may only get snow with the ongoing round
today, but confidence in that is too low to make any headline
changes right now. Regardless of snowfall amounts, confidence in
widespread impacts is high, as snowfall will readily accumulate on
all surfaces and be difficult to remove and treat given the bitter
cold. Driving home this point, most locations as of this writing
have reported no more than 1" of snowfall with multiple accidents
having already occurred. Unless absolutely necessary, travel is not
advised through Sunday. The combination of treacherous travel and
bitter cold will make for life-threatening conditions for those
exposed to the elements.
As the low continues to depart the region Sunday night, deep
northwesterly flow will send a reinforcing shot of Arctic air into
much of the Midwest, with the tight pressure gradient from the
departing low serving to enhance northerly winds. This will drive
wind chill values late Sunday night into Monday morning to around -
15 degrees for the entire area. As such, a Cold Weather Advisory has
been issued for this portion of the period.
Elmore
&&
.LONG TERM... (Monday through Next Saturday)
Issued at 247 PM CST Sat Jan 24 2026
At the start of the extended period, an Arctic high will likely be
situated to the southwest of the region leading to weak
northwesterly surface flow to start the day on Monday. Given the
forecasted placement of this high and the expected snowpack over the
area, most, if not all locations will start the day with temperature
readings below zero. These bitterly cold temperatures coupled with
the light northerly winds will lead to morning wind chill values
ranging from -10 to -20 across the area, which is when a Cold
Weather Advisory will be in effect for the entire area until noon on
Monday. The Arctic high will be slow to move, and as a result, all
locations will struggle to reach the mid teens on Monday with the
continuation of northerly flow and fresh snowpack, despite what is
expected to be a mostly sunny day. The Arctic high will slowly push
southeast, eventually making it to the lower Mississippi River
Valley Monday night, when southerly return flow at the surface will
commence, helping to keep temperatures slightly above zero.
For the remainder of the extended, there will be several mid/upper-
level shortwave disturbances that traverse around the base of a
persistent upper-level trough over southern Canada. The first
shortwave will be dropping southward across the Upper Midwest Monday
night along with the weak and dry attendant low-level cold front.
This front is currently anticipated to drop through Iowa on Tuesday,
placing our region under increased southerly flow during the day
when solar insolation is also aiding the warmup. With the setup
described above, high temperatures on Tuesday could reach the upper
20s with even some low/mid 30s south of I-70. However with the
widespread snowpack, which could potentially be significant in some
areas, the result would be a colder solution with highs staying in
the 20s areawide. The passage of the mid/upper-level shortwave and
its attendant cold front Tuesday night will result in a slightly
colder day on Wednesday with highs expected to be in the 20s
areawide. A secondary mid/upper-level shortwave disturbance will
drop in from the north right behind the first one, with the
attendant low-level cold front reaching the area Wednesday night
bringing another reinforcing shot of Arctic air. The strength of
this Arctic airmass is still uncertain this far out, but current
indications are that the remainder of the week and into the weekend
will be well-below climatology with highs in the teens/20s and lows
around zero/single digits.
Precipitation chances next week are limited with the next chance
centered around Wednesday evening, when the LREF has a 20-30% for
QPF >0.01". Our current forecast, which is the latest deterministic
NBM, only includes slight chances across west-central Illinois with
the rest of the area remaining dry. Given how far out this is and
that the LREF is only slightly higher, this was left unchanged for
this forecast package. However, it is valuable to note, anything
that may fall Wedneday into Wednesday night would be frozen given
temperatures will be well-below freezing, so any trends in model
guidance will continue to be monitored into the week.
Peine/Elmore
&&
.AVIATION... (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1131 AM CST Sat Jan 24 2026
Confidence is high in impacts continuing at all local terminals
through the period as a winter storm slides through the region.
Relatively lighter storm, as a part of the first wave of snow
with this system, is bringing reductions in visibility to all
local terminals. This first wave is more intermittent, so
visibility may bounce around more than what is indicated in the
current TAFs. A brief lull in the greater snowfall rates is
expected this evening before a second wave moves through the
region. This wave will bring heavier snowfall than the first,
mainly to KSUS, KSTL, and KCPS for a period of time early tomorrow
morning. Similar conditions can`t be ruled out at KCOU, KJEF, and
KUIN, but confidence is low in this occurring right now. This
snowfall will readily accumulate on all surfaces, with KSUS, KSTL,
and KCPS seeing the greatest snowfall totals by the time snowfall
begins to wind down tomorrow afternoon.
Elmore
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Winter Storm Warning until 6 PM CST Sunday for Audrain MO-Boone
MO-Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
Iron MO-Jefferson MO-Lincoln MO-Madison MO-Moniteau 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-Warren MO-Washington MO.
Cold Weather Advisory from midnight Sunday night to noon CST
Monday 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.
Winter Weather Advisory until 6 PM CST Sunday for Knox MO-Lewis
MO-Marion MO-Monroe MO-Shelby MO.
IL...Winter Storm Warning until 6 PM CST Sunday for Bond 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.
Cold Weather Advisory from midnight Sunday night to noon CST
Monday 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.
Winter Weather Advisory until 6 PM CST Sunday for Adams IL-Brown
IL.
&&
$$
WFO LSX
NWS LSX Office Area Forecast Discussion
