504
FXUS63 KLSX 232308
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
508 PM CST Sun Nov 23 2025

.KEY MESSAGES...

-Widespread light rain will move over the area Monday afternoon and
overnight.

-Dry weather and below normal temperatures will enter Wednesday
 and persist through Friday.


&&

.SHORT TERM...  (Through Late Monday Night)
Issued at 225 PM CST Sun Nov 23 2025

This morning`s stratus continues to linger across central and east-
central Missouri and into southern Illinois this afternoon. As low-
level warm air advection along southerly flow continues into this
evening and overnight, stratus will spread back out into areas that
have cleared today. Combined with incoming high clouds from an
approaching system, low temperatures tonight will remain elevated,
in the 40s, and several degrees warmer than last night.

Meanwhile, a strengthening mid-level trough is currently over the
Four Corners region, it`s associated surface low sitting over the
Texas panhandle. The mid-level trough will swing into the region
Monday, pushing the surface low through the mid-Mississippi Valley.
Warm air advection and low-level moisture convergence will produce
widespread rain during the afternoon and evening Monday, extending
overnight as the surface low moves east over the area. Everywhere
will see at least some rain, and about 70% of the area will see at
least 0.25" of rain. A few isolated areas may see up to 1.25" of
rain, but this depends on the heaviest rain moving over the same
area throughout the day.

Delia

&&

.LONG TERM...  (Tuesday through Next Sunday)
Issued at 225 PM CST Sun Nov 23 2025

While the first surface low will push east out of the region
Tuesday, another surface low will move through the upper Mississippi
Valley ahead of another mid-level trough moving from the Dakotas
into the Great Lakes region Tuesday. This second low will swing a
cold front through the forecast area Tuesday afternoon. While the
mid-levels will be dry along the western side of the first low,
lingering low-level moisture has a 20-30% chance of producing light
rain/drizzle across the area along the front. The surface pressure
gradient will tighten with the exit of this system, resulting in
elevated northwesterly winds Tuesday evening and overnight. The 850
mb front will slide through the forecast area overnight, and cold
Canadian air will surge into the region. After a mild day Tuesday
with highs in the 50s, the advancing of this cold air mass will
cause lows Tuesday night into Wednesday morning to drop into the 30s.

Ensemble guidances shows a clear cooling trend with this air mass,
resulting in highs in the 40s for the second half of the week,
including the Thanksgiving holiday. Under deep northwesterly flow,
the region will remain dry during this period.

Weak mid-level ridging returns to the area Friday into Saturday,
while another trough begins to dig into the West Coast. Flow quickly
becomes southwesterly over the weekend as the trough deepens into
the Four Corners region. At the same time, a surface low will
develop over the south-central US, with southwesterly flow and warm
air advection kicking off Saturday across our forecast area. Current
guidance shows warm air advection precipitation, potentially
interacting with a surface warm front, widespread across the region.
While some guidance sources are indicating that at least some of
this precipitation will fall as snow across the northern portions of
our forecast area, confidence in this occurring is very low. The
warm air advection nature of the precipitation, potentially falling
during the day, doesn`t provide a lot of confidence for snow to
maintain to the surface. Therefore we are continuing to forecast
mostly rain during this period. Even so, a number of details remain
in question at this point, including the timing and strength of the
surface low and upper level support, the strength of the warm air
advection, and timing of precipitation. All of this will determine
precipitation type with this system.

Delia

&&

.AVIATION...  (For the 00z TAFs through 00z Monday Evening)
Issued at 504 PM CST Sun Nov 23 2025

It will not be a great night for air travel as IFR/LIFR is
expected at all terminals. IFR stratus is expected to expand and
continue to build down to the surface, resulting in lowered cigs
and eventually vsbys at all sites tonight. The worst conditions
are expected at COU/UIN, where vsbys less than a half mile are
likely at times overnight. The forecast is a little more uncertain
in metro St. Louis as the edge of the stratus is currently near
CPS/STL. Even if they briefly go VFR, expect the stratus to fill
back in overnight with reductions in vsbys as well at all St.
Louis TAF sites.

Cigs will rise slightly through the day on Monday, but as that
occurs showers are expected to move through all terminals Monday
afternoon into Monday evening.

Deitsch

&&

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

$$

WFO LSX