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FXUS63 KLSX 031121
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
521 AM CST Mon Nov 3 2025

.KEY MESSAGES...

- Mild temperatures return this week with highs mainly in the 60s
  to near 70. A sharper cool down comes this weekend.

- The next chance of rain comes with a cold front Thursday night.


&&

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 206 AM CST Mon Nov 3 2025

Broad surface high pressure over the Lower Mississippi Valley and
the Central Plains exists beneath northwesterly flow on the
downstream side of a ridge axis over the Rocky Mountains. The
combination is bringing subsident flow to our region leading to a
clear sky. As the ridge nudges east today we`ll see the temperature
rebound into the 60s area wide, some 10 to 12 degrees warmer than
yesterday.

The ridge flattens out into more of a zonal flow across the central
US on Tuesday, with an embedded shortwave trough entering the
Northern Plains and sending a cold front southeast toward our
region. Ahead of that front, we do get a fairly brisk return
southwesterly flow as the surface high shifts east and the pressure
gradient increases. The temperature warms several more degrees on
Tuesday with more areas reaching the 70s. Modest moisture recovery
with dewpoints rising into the mid 40s will help limit the fire
danger threat on Tuesday`s southwesterly flow.

Kimble

&&

.LONG TERM...  (Tuesday Night through Sunday)
Issued at 206 AM CST Mon Nov 3 2025

A series of cold fronts move through the region later this week with
the mid level flow gradually transitioning from zonal to more
troughing over the central to eastern US by this weekend. Although
the daytime temperature forecast remains fairly stable in the 60s to
low 70s each day this week, the various air mass changes are more
noticeable in nighttime low forecasts. During periods of return
flow, higher dewpoints will lead to warmer nights in the 50s, while
during periods of drier air behind cold fronts will see lows in the
30s and 40s. The best combination of moisture and lift with each of
these frontal waves remains to our north, limiting precipitation
chances in our region. The one exception is Thursday night into
Friday when a deeper wave stands a better chance of spreading at
least some light rain across the northern half of our forecast area.
Among the long range guidance, up to 70 percent of ensemble members
produce measurable rain up near the Quincy area in the 24 hours
ending Friday morning. However, less than 30 percent of members
produce 0.1 inch of rain, indicating a high likelihood that this
will be a light rain.

Just as Thursday night`s wave is a bit deeper than the previous
ones, the next one taking aim at our area late Saturday is even
deeper, helping to establish broader troughing over the central US
for at least a few days this weekend into early next week. Rain
chances with this wave are fairly low at the moment as most guidance
keeps the better synoptic lift with this trough to our north across
Iowa into the southern Great Lakes while better moisture return (for
warm sector thunderstorms) doesn`t meet up with the surface front
until it gets southeast of our area. But this front will be stronger
and much more noticeable than the previous several. Long range
guidance continues to trend colder with the air mass behind this
front. Both the ECMWF and GFS operational runs indicate 850MB
temperatures falling 10C below normal or more Sunday into Monday
giving us higher confidence that even daytime highs in this air mass
will be significantly colder than the rest of this week. Dewpoints
falling into the teens indicate a very low floor for nighttime lows
as well if we manage to get a clear, calm night. Latest NBM guidance
now indicates widespread freezing temperatures Sunday night, even
more widespread than were observed yesterday morning. While there
remains variability in the long range guidance on the trajectory of
the cold air push and the timing of its arrival and exit, there is
high confidence in a substantial cool down late this weekend into
early next week that will last a couple of days. Ridging returns
shortly thereafter which limits the duration of this winter-like air
mass.

Kimble

&&

.AVIATION...  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 519 AM CST Mon Nov 3 2025

Although we expect a clear sky and VFR conditions, we do expect a
wind shift as a cold front moves into the region from the
northwest today. This will shift winds to the northwest but only
briefly. They`ll return out of the south again tomorrow.

Kimble

&&

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

$$

WFO LSX