462
FXUS63 KLSX 291025
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
525 AM CDT Thu Oct 29 2026

.KEY MESSAGES...

- Unseasonably warm temperatures are expected to continue, but a
  change is coming this weekend.

- On and off rain chances begin Friday and last through next
  week. A more widespread, beneficial rainfall is likely
  early/mid next week.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 254 AM CDT Thu Oct 29 2026

A surface cold front currently extends from northeast Kansas
into central Wisconsin. This boundary is forecast to continue to
push southeast today, and should nearly bisect the CWA just
after midday. Weak surface convergence and some building
instability (SBCAPE >750 J/kg) could be just enough to produce
some isolated showers, and possibly a rumble or two of thunder,
along the boundary this afternoon. Given the expected location
of the boundary nearing the I- 70 corridor mid-late afternoon,
this is where the slight chance (~20%) PoPs are located later
today. Higher coverage of rain showers are not expected due to
rising mid/upper level heights (subsidence aloft). As the
already limited instability wanes nocturnally, a period of dry
weather areawide is forecast across the region as any lingering
shower activity dissipates by early this evening.

After midnight, low-level moisture convergence strengthens north of
the surface boundary, with a weak midlevel impulse also approaching
from the west. Scattered showers and a few thunderstorms are
expected across northeast Missouri and west-central Illinois into
Friday morning. There may be a "lull" later on in the morning hours
as the axis of low-level moisture convergence pushes off to the
northeast. Additional development of scattered light rain showers
are expected near the surface front as it retreats back northward as
a warm front.

Temperature wise, look for a north to south gradient both this
afternoon and on Friday due to the location of the frontal boundary.
Most of the area today should top out in the upper 70s to low 80s,
with exception of portions of northeast Missouri and west-central
Illinois. There is more uncertainty on Friday as there is some
spread (~50 miles) on how far north the boundary retreats during the
day. The most likely location of the front Friday afternoon is
somewhere near I-70, so the coolest (upper 60s) highs are expected
to be across northeast Missouri and west-central Illinois, with
upper 70s to near the 80 degree mark to the south in southeast
Missouri and southwest Illinois.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 254 AM CDT Thu Oct 29 2026

(Friday Night - Saturday)

The vast majority of the region should stay dry Friday night through
the day on Saturday, though a few spot showers are possible mainly
across northeast Missouri and west-central Illinois. This is where
the residual surface boundary may be located with a weak midlevel
shortwave trough also moving across Missouri early Saturday morning.
A mostly cloudy sky is favored otherwise, with very mild lows (mid
50s to near 60 degrees) and highs near 70 degrees.


(Saturday Night - Sunday)

Deterministic guidance shows better agreement with the timing/track
of another midlevel shortwave trough moving out of the south-central
Plains across southeast Missouri and southwest Illinois late
Saturday night into Sunday morning. At least scattered light rain
showers are expected ahead of this feature. The key word is "light"
though. While LREF 24-hour probabilities for measurable rainfall are
pretty high (60-75%) in southeast Missouri and southwest Illinois,
chances for at least 0.25" drop to 25-35%.


(Sunday Night - Wednesday)

Ensemble guidance remains in good agreement that a deep mid/upper
level trough will move out of the intermountain west Sunday night
into Monday. Cluster analyses of the 500-hPa pattern generally show
a closed, possibly cutoff, mid/upper level low across the central
Plains on Tuesday, with deep south/southwest flow aloft across the
mid-Mississippi Valley. Ahead of the closed mid/upper level low, a
surface low is expected to slowly move into the Upper Midwest, with
a cold front draped to its south. This boundary is expected to
gradually move eastward in time, but exactly when is not certain.
Regardless, the pattern still appears favorable for a long duration,
significant (>1") rain event across the CWA through the middle of
next week. LREF probabilities for at least 1" through Wednesday
afternoon are 60-90% from southeast to northwest, and 20-50% for
2+". While this event is largely 4-6+ days out and things can
certainly change, there does appear to be increasing potential for
substantial drought improvements across the region.

&&

.AVIATION /12Z TAFS THROUGH 18Z FRIDAY/...
Issued at 522 AM CDT Thu Oct 29 2026

A weak cold front will move through KUIN later this morning
before stalling out near or just south of the central Missouri
and metro St. Louis terminals this afternoon. There may be a few
spotty showers and even a rumble of thunder associated with the
front later today, but the coverage looked too low to include
anything in the TAFs. Light south/southwest winds are forecast
ahead of the front, with the wind direction becoming variable in
the vicinity of the front. For KUIN, winds are expected to veer
behind the front to the northwest, and then eventually
east/northeast overnight tonight.

&&

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

&&

$$

SHORT TERM...Gosselin
LONG TERM...Gosselin
AVIATION...Gosselin