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FXUS63 KLSX 100330 CCA
AFDLSX

Area Forecast Discussion...CORRECTED
National Weather Service St Louis MO
1030 PM CDT Fri Oct 9 2026

.KEY MESSAGES...

- Slightly "cooler" weather is forecast this weekend before a
  return to near-record warmth on Monday.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 247 PM CDT Fri Oct 9 2026

A mostly clear sky is expected this evening along with
slackening southerly winds. An increase in high-level clouds is
forecast from southeast to northwest late tonight into the day
on Saturday along the northwestern periphery of the remnants of
Hurricane Isaias. The clouds will be the main impact across the
region. Temperatures late tonight should level off in parts of
southeast Missouri and southwest Illinois in the mid to upper
50s. More persistent southerly winds should prevent much in the
way of radiational cooling across parts of central and northeast
Missouri as well as west-central Illinois. Lows in the upper
50s to low 60s are expected in these locations.

The track of the remnants of Hurricane Isaias have continued to
trend eastward over the past 24 hours, with the most likely track
courtesy of the National Hurricane Center through central Tennessee
into the Upper Ohio Valley this weekend. Chances of light rain have
also shifted east as a result. Nearly the entire area should stay
completely dry, with some light rain just skimming parts of
southeast Missouri and adjacent southwest/south central Illinois
late Saturday afternoon through the evening hours. Any rain that
does occur in these locations would be light, with both HREF and
LREF probabilities for >0.10" below 30%. The increase in mid/high
level clouds will however help keep temperatures a bit "cooler" on
Saturday, with highs ranging from the upper 70s to mid 80s from
southeast to northwest. Lows Saturday night will also be milder due
to these same clouds, only dropping back into the mid to upper 50s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 247 PM CDT Fri Oct 9 2026

(Sunday - Monday Night)

Decreasing clouds are forecast from west to east on Sunday as the
remnants of Hurricane Isaias moves toward the mid Atlantic.
Temperatures will begin to rebound with widespread 80s areawide. A
few locations in central Missouri may top out at the 90 degree mark.
The warmest day of the next week is still likely to be on Monday.
This is when mid/upper level ridging is centered across the
Mississippi Valley, with 850-hPa temperatures nearing +20C (near-
record for the date). Winds also veer more to the southwest, which
downslope off of the Ozark Plateau. There also isn`t much of a
signal for any cloud cover. In other words, the ingredients are all
there for a day of record-breaking warmth. Most locations are
forecast to reach the low 90s, with a few spots potentially in the
mid 90s in central/east central Missouri due to the downsloping. All
three daily record highs from St. Louis (90F/1924), Columbia
(94F/1899), and Quincy (88F/1975) are in jeopardy. For St. Louis,
the all-time record warmest October temperature (94F on 10/11/1963)
may also be threatened.

(Tuesday - Next Friday)

A midlevel shortwave trough is expected to transverse the Great
Lakes early next week, with a surface low downstream across the
northeast. A cold front will be draped to its southwest and move
toward the mid-Mississippi Valley late Monday night into Tuesday
before stalling. The timing and evolution of this front remains
highly uncertain, with large run-to-run variability on deterministic
guidance. Overall, we should see at least a slight "cooling" trend
for midweek, as at the minimum, a substantial increase in clouds are
expected in the vicinity of the boundary. Chances of showers and
thunderstorms will also increase, which would also limit the diurnal
rise in temperatures. Speaking of which, it does look like a wet
period of time regionally, with multiple rounds of showers and
thunderstorms focused mainly along/north of the quasi-stationary
front. Rainfall anomalies over the 5-day period ending next Friday
on both the GEFS and EPS show surpluses of 0.25-0.75" from southeast
to northwest across our region.

Clusters of the 500-hPa height pattern show a stronger trough
digging into the Great Lakes. There is however a considerable amount
of spread, both in terms of timing but also the strength of the air
mass advecting southward out of Canada. Two of the four clusters
(~47% of LREF members) have a very strong trough, which would bring
in the coolest air so far this Fall by a considerable margin (think
highs in 50s, lows in 30s potentially). On the other side of the
spectrum, the other two clusters show a much more modest trough
swinging through the Great Lakes. There is still a clear cold
frontal passage between Thursday and next Friday, but temperatures
only drop back closer to, or slightly above, normal.

&&

.AVIATION /06Z TAFS THROUGH 12Z SUNDAY/...
Issued at 1027 PM CDT Fri Oct 9 2026

VFR conditions are expected at all terminals throughout the 06Z
TAF period. Mostly light southeast winds will persist, with
increasing high level cloud cover throughout the day. Some
patchy fog is possible at SUS overnight tonight, but confidence
remains low that winds will become calm enough for widespread
fog formation. Rain is expected to remain southeast of local
terminals.

&&

.CLIMATE...
Issued at 247 PM CDT Fri Oct 9 2026

Record high temperatures are possible between Friday 10/9 and Monday
10/12. Here are current records at each of our 3 official climate
stations:

                    KSTL            KCOU            KUIN
Friday 10/9       89/1938         91/1893         89/1938
Saturday 10/10    92/1963         92/1963         89/1963
Sunday 10/11      94/1963         89/1962         88/1962
Monday 10/12      90/2024         94/1899         88/1975
Tuesday 10/13     90/1899         95/1899         87/1975

&&

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

&&

$$

SHORT TERM...Gosselin
LONG TERM...Gosselin
AVIATION...BRC
CLIMATE...Gosselin