308
FXUS63 KLSX 281927
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
227 PM CDT Wed Oct 28 2026

.KEY MESSAGES...

- Warmth persists through Friday with temperatures well into the
  70s to near 80 degrees over much of the area.

- Variable precipitation chances extend from late Thursday
  through the weekend, but there will be plenty of dry time
  between showers. Better chances of rain arrive early next
  week.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 222 PM CDT Wed Oct 28 2026

High pressure encompasses the eastern U.S. coastline and extends
westward through the southern half of the Mississippi Valley
this afternoon. Mid to high clouds, originally accompanied by a
few light showers over central Missouri this morning, have all
but dissipated as they approach the Mississippi River this
afternoon. Mostly sunny skies have dominated much of the region
with light southerly flow and temperatures rising through the
70s. Highs are expected to top out in the upper 70s to near 80
degrees.

A weak cold front, which trails southwest of a Canadian low pressure
system, will slowly sag southward into northern Missouri tonight
into Thursday. Tonight`s lows are dependent on increasing cloud
cover, mainly impacting the northern sections of the CWA. HREF data
shows the best probability (30-60%) for scattered/broken ceilings
extending from Moberly, MO to Quincy, IL and northward with dry air
winning out to the south. This will keep Thursday morning lows
a little milder (mid/upper 50s) and cooler air to the south
(upper 40s/ mid-50s).

The main items to focus through Thursday are the stalling cold
front, increasing clouds, and late evening rain showers. RAP
guidance shows dewpoints near 60 degrees pooling along the front
from Kansas City, MO through Quincy, IL. Higher RH is gradually pull
northeastward around the eastern ridge with HREF indicating clouds
may increase quick enough to impact high temperatures along and west
of the Mississippi River. NBM has been bullish with highs in the low-
80s and while this may be plausible with clear skies, moisture
trends and HREF temperature data would counter this with upper 70s.
Highs were reduced by just a couple of degrees to account for these
trends. Precipitation chances are limited (<20%) to the frontal
boundary until Thursday in the late evening. The stalled from drifts
as far south as the I-70 corridor, but then lifts northward under
the western influence of the mid-level ridge. Fragments of mid/upper
vorticity lift over the front and induce scattered showers late
Thursday night. While NBM probabilities 60-65%, saturation is
limited to around 850-900MB, indicating a high prob/low QPF
potential heading into early Friday morning with just a few
hundredths of rainfall over northeast Missouri and west-central
Illinois.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 222 PM CDT Wed Oct 28 2026

Temperatures remain quite warm at the start of the period, then
trend cooler beyond Friday. Despite rain chances being dispersed
through each day of the period, there will be plenty of dry time
between showers over the upcoming weekend.

Surface high pressure builds southeastward from southern Canada into
the Great Lakes Region through the day Friday. A mid-level ridge
compliments the surface feature with easterly surface flow
undercutting westerly flow aloft. High clouds will be on the
increase as southwest/westerly flow aloft draw moisture in around
the western side of the mid-level ridge. Though a stray shower
cannot be entirely ruled out north of I-70 Friday, limited support
and drier air below 850MB should stave off measurable precipitation.

A shortwave that resides at the base of the western trough tracks
northeastward into the central CONUS Saturday. Ascent is broadly
spread from the Dakotas southeastward through the Lower Mississippi
Valley, which encounter east/southeastly flow as a consequence of
the southeastern shift in the Great Lakes surface ridge. This will
initially impede moisture from reaching the surface until late
Saturday. At that time, dry air below 700MB begins to give way to
increasing moisture as the surface high moves over the New England
Region. The system is not well organized and produces broadly
scattered showers late in the evening into Saturday night with LREF
75th percentile data ranging from 0.15-0.25" from north to south.
The lower end of the IQR zeroes out and probabilities for measurable
rainfall center on the 6pm-6am period Saturday night into Sunday
morning and peak at 30-50%. This suggests that while the area will
see rainfall to some degree, it will largely be light.

Attention turns to two upper level waves within the amplified
western trough. Long range, global guidance diverges between a
cutoff, slow-moving closed low (GFS) and a more progressive
amplified trough (ECM) heading into next week. While this brings the
best potential for widespread rainfall, the evolution deserves
attention to provide better confidence in rainfall amounts. The
split flow pattern can often provide early signals for precipitation
that, at times, become less promising as the days progress. What is
more certain is the lean toward cool temperatures, though they
remain seasonably mild. Highs through the period are generally
in the low to mid-70s with lows in the 50s.

&&

.AVIATION /18Z TAFS THROUGH 00Z FRIDAY/...
Issued at 1220 PM CDT Wed Oct 28 2026

A few mid/high clouds continue to erode as they approach the
Mississippi River and encounter dry air. Light southerly flow is
expected with VFR conditions persisting through the end of the
period.

&&

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

&&

$$

SHORT TERM...Maples
LONG TERM...Maples
AVIATION...Maples