443
FXUS63 KLSX 092331
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
631 PM CDT Thu Oct 9 2025

.KEY MESSAGES...

- There is a 20 - 40% chance of showers and thunderstorms in portions
  of central Missouri northeast into west-central Illinois
  tomorrow morning. Beneficial rain is not expected.

- A warming trend will kick off tomorrow and last through at least late
  next week.


&&

.SHORT TERM...  (Through Late Friday Night)
Issued at 140 PM CDT Thu Oct 9 2025

Mid to upper level ridging continues to build in the central CONUS
and now encapsulates the Mid-Mississippi Valley. In the low-levels,
weak cold air advection will give way to warm air advection
overnight. These two factors will kick off a warming trend that will
begin tomorrow and last through at least late next week. A cold
front or two may dent the warming trend in portions of the CWA north
of I-70 during the next 7 days. At least one will also bring rain
chances back into the area.

The first cold front will approach the area tonight. Ahead of the
front, aforementioned warm air advection will pair with modest
moisture return to increase instability and promote isolated to
scattered showers and thunderstorms. Despite the increasing heat of
the day, decreasing boundary layer moisture is expected to result in
less available instability during the day on Friday, leading to
convection waning with time and southeastward extent. Where
ensembles give northeast Missouri up to a 90% chance of seeing
measurable rain tomorrow, it gives St. Louis a 10 - 20% chance.

Jaja

&&

.LONG TERM...  (Saturday through Next Thursday)
Issued at 140 PM CDT Thu Oct 9 2025

Mid to upper level ridging will keep the region warm and dry this
weekend before deamplifying late Sunday. This will allow shortwaves
to ride into the Mid-Mississippi Valley, threatening additional rain
chances late Sunday into Monday. The synoptic setup looks very
similar to tomorrow`s rain chances with warm air advection showers
possible ahead of an approaching cold front. However, a lack of
sufficient moisture will likely keep showers limited if they can
develop at all.

The temperature forecast will remain fairly steady from this weekend
through the middle of next week south of I-70. There, highs in the
upper 70s to low 80s are forecast from Saturday on. To the north of
the interstate, daily high temperatures will fluctuate due to the
aforementioned cold fronts dipping into and then retreating back out
of the CWA. Generally, though, low to mid-70s are forecast through
the period.

Jaja

&&

.AVIATION...  (For the 00z TAFs through 00z Friday Evening)
Issued at 626 PM CDT Thu Oct 9 2025

Some patchy river valley fog may occur tonight, mainly in
southeast Missouri. Cannot rule out a brief period of fog at
KSUS/KCPS, but probability was too low to add to either TAF.
Chances of showers and a few thunderstorms increases for
KUIN/KCOU/KJEF Friday morning. The best chance of thunder is at
the central Missouri terminals where a PROB30 group remains.
Activity should weaken and largely dissipate further to the east
so kept metro terminals dry. Cannot rule out a light shower or
two, but visibilities should remain VFR even if there is -RA
observed.

Gosselin

&&

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

$$

WFO LSX