128
FXUS63 KLSX 020501
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1101 PM CST Sun Feb 1 2026

.KEY MESSAGES...

- Flurries and light snow may produce a dusting to perhaps a 0.1"
  of snow in places east of the Mississippi River. Light snow
  tapers off this evening.

- Temperatures waver between seasonable warmth and a seasonable
  chill. Chances of precipitation are limited to Tuesday (20-30%)
  and look to remain light (<0.05").


&&

.SHORT TERM...  (Through Late Monday Night)
Issued at 236 PM CST Sun Feb 1 2026

Water vapor imagery shows a shortwave dropping through eastern Iowa
and into Illinois this afternoon. Radar mosaics have shown light
precipitation following this feature since early this morning.
However, local radar is reflecting mid-level moisture with
soundings indicating it is falling into very dry surface to mid-
level air. Surface precipitation has been largely absent, aside from
a few isolated reports of flurries and light snow. What is falling
is overrepresented by current radar sensitivity (VCP 35). Only the
strongest reflectivity (>25 dBz) have yielded any real ground truth
so far, coinciding with earlier surface observations of reduced
visibility (1.52 miles) over south-central and southeast Iowa. This
area has reached northeast Missouri and west-central Illinois, with
light snow or flurries reported around KUIN and Pittsfield prior to
20z. Given the scattered nature of this activity, accumulations are
expected to be limited to a dusting or a tenth of an inch.

The system is accompanied by a reinforcing cold front, though its
impact over central and southeast Missouri will be short-lived. A
slow eastward shift in the upper ridge and a 10C increase in 850mb
temperatures will push in from the southwest late tonight into
Monday. Warm advection stalls, creating a disparity between
seasonally mild air over southeast Missouri and seasonally cold
temperatures north and east of the Ozarks. After falling into the
teens tonight, highs Monday rise into the 40s from central to
southeast Missouri and mid to upper 30s elsewhere. Another northwest
flow shortwave will approach late Monday with a stronger push of
cold air, though sensible changes are expected to hold off until
Tuesday.


Maples

&&

.LONG TERM...  (Tuesday through Next Sunday)
Issued at 236 PM CST Sun Feb 1 2026

Mean 500mb heights on Tuesday show an amplified ridge over the
western U.S. and an expansive longwave trough covering the remainder
of the CONUS east of the Rockies. Persistent northwesterly upper
flow will track a shortwave into the central Plains and Midwest.
Simultaneously, another shortwave stemming from a cut-off low west
of the Baja Peninsula will move east across the Gulf Region.
Moisture is drawn northward ahead of the southern stream wave and
around the western side of a mid-level gulf ridge. Moisture return
stalls at the hands of a reinforcing cold front associated with the
northern shortwave. This is expected to keep precipitation
chances primarily south of I-44 (MO) and I-70 (IL).

This system will likely bring a quick round of light snow, with
southern portions of the CWA seeing a brief rain/snow mix before the
system exits Tuesday afternoon/evening. ECM/GFS QPF plumes are
largely clustered at or below 0.05, and LREF guidance shows low
probabilities for measurable snowfall. While a dusting to a few
tenths of an inch of snow are possible, the warming trend and
progressive nature of the system should limit overall impacts.

The system moves out quickly Tuesday evening, followed by cold air
advection bringing a reinforcing shot of seasonably cool air through
Wednesday. From mid to late week, the eastern trough/western ridge
patterns begin to deamplify. A moisture-starved shortwave rounds the
western ridge, arriving from the northwest on Thursday. This brings
high clouds and a brief reinforcement of cool air that ultimately
gives way to warm air advection late Thursday.

As the ridge and trough shift eastward, warmer air will move into
the region late Thursday into Friday. While the pattern favors
milder temperatures toward the end of the week, the magnitude of the
warmth remains uncertain as NBM data spreads, and the
timing and placement of small scale features is less clear.


Maples

&&

.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1100 PM CST Sun Feb 1 2026

A large stratus field that extends north into the Upper Midwest
continues to push southward into the region. The leading southern
edge, which has impacted the central Missouri and St. Louis metro
terminals for the past few hours, largely consists of VFR ceilings
around 4-5kft. Further north into the stratus over far northern
Missouri and southern Iowa, including KUIN, ceilings are mostly MVFR
ranging from 2-3kft. Model guidance continues to struggle with the
southern progression of this stratus field and any MVFR ceilings,
resulting in low confidence regarding the southern extent of these
impactful ceilings. There is a low chance of MVFR ceilings impacting
the St. Louis metro terminals. Our current expectation is conditions
generally won`t improve until sunrise tomorrow when solar insolation
can start to elevate ceilings or help erode any lingering stratus.
Surface winds remain very light for the entire TAF with
southwesterly winds briefly veering to the northwest overnight
before going light and variable tomorrow afternoon with light
easterly winds returning by tomorrow night.

Peine/Elmore

&&

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

$$

WFO LSX