483
FXUS63 KLSX 281140
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
640 AM CDT Wed Oct 28 2026

.KEY MESSAGES...

- Warm and dry conditions are expected through Thursday.

- Chances of light rain showers increase this weekend, but
  better chances of a widespread beneficial rain event come
  early/mid next week.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 307 AM CDT Wed Oct 28 2026

Warmer temperatures are expected this afternoon due to
increasing low-level warm air advection along with more
plentiful sunshine. High temperatures in the mid to upper 70s
are expected, or about 15 degrees above normal for the date.

A weak midlevel shortwave is forecast to move across the Upper
Midwest overnight tonight, helping to increase mid/high level clouds
across northeast Missouri and west-central Illinois. At the surface,
a cold front is forecast to move southeast into northeast Missouri
and west-central Illinois Thursday morning. A few spot showers
cannot be ruled out, but the timing of the front is not favorable in
our region as the better mid/upper level forcing is to our north and
low-level moisture convergence decreases late tonight into Thursday
morning near the frontal boundary. Ahead of this front, highs are
expected to top out in the low 80s. Weak surface convergence along
the boundary along with a subtle midlevel impulse may yield a few
isolated rain showers, and possibly a rumble of thunder, during peak
heating.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 307 AM CDT Wed Oct 28 2026

(Thursday Night - Sunday)

The cold front is expected to stall by Thursday night across
southeast Missouri and southwest Illinois before pushing back
northward early Friday. Chances of rain showers increase
along/poleward of the retreating boundary as low-level moisture
convergence strengthens and a weak midlevel shortwave moves out of
the south-central Plains. The exact placement of the west-east
boundary varies slightly amongst deterministic guidance (~50 miles),
but the most likely location Friday afternoon is near the I-70
corridor. This means that the best chances (50-70%) of light rain
showers on Friday are across northeast Missouri and west-central
Illinois. The increased clouds/rain chances north of the front
should help create a north-south temperature gradient across the
region, with highs near 70 degrees across northeast Missouri and
west-central Illinois and closer to 80 degrees south of I-70.

Forecast uncertainty is higher for the weekend, as it now looks like
individual weak midlevel impulses will come across the Mississippi
Valley instead of one stronger shortwave trough. The track and
timing of each individual impulse is not certain, which is why there
is a fairly long duration of chance (30-50%) PoPs this weekend. Any
rain that does occur this weekend though does look light and
showery, with certainly more dry time than not this weekend.
Probabilities for both measurable (>=0.01") and 0.25"+ amounts on
the LREF have dropped about 10-15% compared to this time yesterday.
Cooler high temperatures are expected regardless due to thicker
cloud cover, with highs forecast to be in the upper 60s to low 70s.


(Sunday Night - Tuesday)

Ensemble guidance shows a deeper trough carving out across the
desert Sunday night into Monday. Cluster analyses of the 500-hPa
pattern diverge sharply by Tuesday with the track and timing of this
feature. Three of the four clusters show a closed, possibly cutoff,
mid/upper level low forming across the central Plains. These
clusters comprise 83% of the LREF membership, so the signal is
pretty strong. A closed mid/upper level low forming to our west
should lead to deep, anomalous southerly flow aloft. An increase in
deep-layer moisture along/ahead of a slow-moving frontal boundary is
a good recipe for a long-duration beneficial rain event across the
area. Probabilities through Tuesday of at least 0.50" of rain range
from 65-90% from southeast to northwest. Those numbers jump even
further if you go out through the middle of next week as the
potential for a deep, closed low could portend to it impacting the
region for at least a few days.

&&

.AVIATION /12Z TAFS THROUGH 18Z THURSDAY/...
Issued at 639 AM CDT Wed Oct 28 2026

Periodic fog may continue to impact KSUS over the next 1-2
hours. Otherwise, dry/VFR conditions are expected along with
predominantly light southerly winds.

&&

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

&&

$$

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