Area Forecast Discussion

498
FXUS63 KLSX 100010
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
610 PM CST Fri Jan 9 2026

.KEY MESSAGES...

- Light rain will likely (60-80%) transition to light snow across
  northeast Missouri and west central Illinois late tonight
  through tomorrow morning. While some light accumulations are
  possible on grassy or elevated surfaces, impacts to roads are
  not expected.

- A series of reinforcing cold fronts will bring cooler
  temperatures tomorrow and especially Sunday, along with some
  brisk west winds tomorrow and tomorrow night.

- A brief warmup is expected Monday and Tuesday, followed by
  another cooling trend. Other than occasional low (20% or less)
  precipitation chances, the next week looks mostly dry.


&&

.SHORT TERM...  (Through Late Saturday Night)
Issued at 213 PM CST Fri Jan 9 2026

Much quieter weather conditions are in place throughout the area on
the heels of yesterday`s rain and thunderstorms, thanks to a
transient area of surface high pressure. While some cloud cover
lingers along and just south of the I-70 corridor, coverage is
slowly decreasing, and most areas are getting a healthy dose of sun
as the afternoon progresses. Meanwhile, temperatures are running
anywhere from 5 to 15 degrees cooler than yesterday at the same
time, thanks to last night`s cold front, but are still climbing to a
relatively comfortable and above average upper 40s to near 60
degrees.

Overnight, attention turns to the approach of a southern-stream
shortwave emerging from the central/southern Rockies and central
Plains, which will begin to phase with a northern stream shortwave
digging in from the northwest. This feature remains very likely
(80%) to produce a brief round of light precipitation as it swings
through the area very late tonight through tomorrow morning,
particularly across the northern half of Missouri and central
Illinois. Overall amounts have trended slightly upwards in recent
forecasts, but not enough to result in noteworthy impact.

The biggest source of uncertainty with this wave, and also the only
real potential for any sort of impact, remains the possibility of a
brief burst of accumulating snow. A close examination of
deterministic profiles and cross sections reveals a relatively
concentrated band of mid-level frontogenesis developing, along with
a burst of omega (vertical motion) and a brief period of saturation
after fighting through some low-level dry air. While strongest lift
does not align perfectly with the dendritic growth zone, this does
support the potential for some mesoscale banding and narrow
corridors of slightly higher precipitation rates, at least for brief
periods.

Meanwhile, surface temperatures remain likely to stay near or
slightly above freezing through the night and into Saturday morning,
but this layer becomes very very shallow as precipitation reaches
it`s peak (1000 feet or less per most model soundings). As such, it
appears more likely than not (roughly 60-80%) that at least some
snow will reach the surface within any concentrated bands that form,
perhaps just enough for light accumulations on grassy/elevated
surfaces (90th percentile worst-case, up to 1 inch), and modest
visibility reductions. However, we still feel that the potential for
impactful accumulations on roadways (along with associated travel
impacts) is low (20% or less), given the brief duration and
previously mentioned warm surface temperatures. Any accumulations
will be most likely across northeast Missouri and west-central
Illinois.

During the day tomorrow, a reinforcing cold front will surge through
the area, bringing another round of brisk west-northwest winds and
cooler temperatures. While the coldest air won`t arrive until
tomorrow night, you can expect afternoon highs in the 40s, and
actually still a few degrees above seasonal averages.

In the evening and overnight, the last push of cold air will filter
into the area, perhaps also bringing a round of sprinkles and/or
snow flurries during the late afternoon and evening along the
leading edge of the reinforcing cold front. This is expected to be
brief, and noteworthy accumulations are not currently anticipated.

BRC

&&

.LONG TERM...  (Sunday through Next Friday)
Issued at 213 PM CST Fri Jan 9 2026

While there will be some non-trival temperature fluctuations and
low-end chances for light precipitation to discuss as we head into
next week, the upcoming pattern supports generally benign weather
conditions on the whole.

As has been the case, Sunday continues to look like the coldest day
of a brief cooldown, with morning low temperatures in the 20s and
afternoon highs in the mid 30s to low 40s. This is roughly 3 to 5
degrees below seasonal averages, but on-par with a "typical" winter
day in the mid-Mississippi river valley. Dry conditions are also
expected, and breezy morning winds will gradually subside through
the day as surface high pressure arrives from the west.

From Monday onward, a relatively persistent upper flow pattern is
expected to develop across the CONUS, with a longwave trough parked
across the eastern U.S. and northwest flow overhead. While this will
favor cooler temperatures in the long run, that won`t occur until
mid-week, and not before a brief warmup Monday and Tuesday. Driving
these warming temperatures will be the return of west-southwest low-
level flow, which is expected to persist both days and drive both
warm-air advection and warming downslope winds across the Ozarks. In
fact, by Monday we can expect temperatures to climb back to around
10 degrees above average, to roughly 15 degrees above average
Tuesday.

While this is still several days away, we will need to keep
an eye on the potential for locally elevated fire weather conditions
during this period, particularly Tuesday afternoon when breezy
southwest winds are most likely to peak, and afternoon humidity
forecasts are approaching 30% in the Ozarks. These conditions are
generally on the fringes of our "elevated" criteria and many fuels
may not adequately dry after recent rains to support a widespread
threat, but it wouldn`t be a stretch to see some pockets of elevated
conditions where fine-dead fuels are the primary fuel source.

Sometime late Tuesday or Wednesday, ensemble guidance continues to
support the arrival of another cold front thanks to a shortwave
pivoting around the eastern U.S. trough. The primary impact of this
is likely to be a reinforcing shot of colder air, and the return of
more seasonable temperatures for an extended period. Confidence in
forecast temperatures does drop considerably as we approach the end
of the week (as evidenced by growing ensemble spread), but again the
overall pattern of persistent northwest flow does support a cooling
trend. Meanwhile, models continue to hint at the potential for light
precipitation associated with the mid-week cold front and shortwave,
but ensemble probabilities remain low (20% or less) and amounts very
light. Otherwise, the long-term pattern appears to be quite dry,
with little evidence supporting any hydrologically significant
precipitation.

BRC

&&

.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 609 PM CST Fri Jan 9 2026

Currently, a broken MVFR stratus deck is slowly drifting from
Illinois westward toward the STL metro terminals and is expected to
move in within the next several hours. Our next weather system is
currently moving over the Central Plains and will begin to affect
KCOU, KJEF, and KUIN by late evening and the STL metro terminals
overnight as lower MVFR ceilings and visibilities move in from west
to east. Confidence in light stratiform rain is lowest (30%) at the
STL metro terminals with rain likely (70-90%) at the remaining
terminals. At KUIN, snow is expected to mix in with rain, resulting
in occasional IFR ceilings and visibilities. MVFR ceilings are
expected to scatter out by late morning. Winds will remain light and
variable this evening before prevailing west-northwesterly winds
pick up behind a cold front and begin to gust (20-25kts) by the late
morning on Saturday.

Peine/Carney

&&

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

$$

WFO LSX

NWS LSX Office Area Forecast Discussion