544
FXUS63 KLSX 022327
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
627 PM CDT Thu Oct 2 2025

.KEY MESSAGES...

- Unseasonably warm temperatures are expected to continue through
  early next week.

- A cold front is forecast to move through the region between
  Tuesday and Tuesday night. This front will bring a chance
  (30-40%) of showers and thunderstorms along with much cooler
  temperatures by Wednesday.


&&

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 229 PM CDT Thu Oct 2 2025

Isolated showers and a few rumbles of thunder will remain
possible into this evening before dissipating with loss of daytime
instability. A stray shower or two cannot be completely ruled out
overnight with broad, weak low-level moisture convergence. By and
large however, look for a dry overnight with scattered midlevel
clouds and light/variable winds. A mild night is expected in terms
of temperatures with lows in the low to mid 60s. A few spots may
get below the 60 degree mark if less cloud cover is observed than
forecast in favored river valleys in east central and southeast
Missouri.

Persistence is the word for Friday with another day of unseasonable
warmth. Highs are forecast to reach into the mid to upper 80s.
Mid/upper level ridging is slightly stronger on Friday with less
daytime instability. Will therefore keep the forecast dry, but a
stray shower or two may occur in northeast Missouri/west central
Illinois during the afternoon hours.


Gosselin

&&

.LONG TERM...  (Friday Night through Next Thursday)
Issued at 229 PM CDT Thu Oct 2 2025

(Friday Night - Monday Night)

There is very little change anticipated in the synoptic pattern this
weekend into early next week with strong mid/upper level ridging
anchored across the southeastern CONUS. Dry weather with well-above
normal temperatures are expected through the period.

There may be one fly in the ointment regarding the dry forecast
however. There are some hints that a midlevel disturbance may
migrate northward from the Gulf coast toward the mid-Mississippi
Valley on Monday. This signal is fairly weak however, with only
about 30% of LREF members showing measurable rainfall.


(Tuesday - Next Thursday)

There are increasing signs of a real cold frontal passage sometime
Tuesday/Tuesday night ushering in a significant air mass change.
Both of the EPS/GEFS have trended cooler over the past 24-36 hours,
now depicting 850-hPa anomalies of -1 to -3C by Wednesday. The NAEFS
is showing a 1026+ hPa surface high moving into the Upper
Midwest/Great Lakes behind the cold front as well. This area of
surface high pressure would be >90th percentile of climatology.
There however is still some uncertainty, both with respect to the
timing of the front, as well as the strength of the air mass behind
the boundary. One of the four clusters (~26% of members) of the 500-
hPa height pattern shows a much weaker trough moving across the
Great Lakes and would not bring much cooler temperatures into the
area. The other three clusters all show a strong mid/upper level
trough moving across the Great Lakes, though with one cluster about
12 hours faster than the other two. The most likely scenario is for
temperatures to get back closer to normal starting Wednesday. The
spread however is pretty high, with the spread between the 25th/75th
percentiles 8-12 degrees. That is the difference between
temperatures about 5 degrees below normal to 5 degrees above normal.
This break in the anomalously warm pattern may be short-lived
however as ensemble guidance shows rising mid/upper level heights
and increasing low-level warm air advection commencing again heading
into the following weekend.

The best chance of widespread rainfall in almost 2 weeks should come
with the frontal passage itself. Currently, PoPs are only in the 30-
40% range Tuesday/Tuesday night. However, the expectation is for
them to come up as timing differences with respect to the cold front
decrease. For reference, the LREF has about 70% of members with
measurable rainfall across the CWA in the 24-hour period ending late
Tuesday night. The bad news? At this early juncture at least,
widespread significant rainfall appears unlikely with only about 10%
of members showing at least a half inch of rain.


Gosselin

&&

.AVIATION...  (For the 00z TAFs through 00z Friday Evening)
Issued at 624 PM CDT Thu Oct 2 2025

VFR conditions are likely to prevail throughout the 00Z TAF
period. Much like last night, there is a limited potential for a
brief period of fog at SUS near sunrise, but this is not expected
to be particularly impactful. Otherwise, there is another 10-15%
chance of a stray shower or thunderstorm at most terminals,
particularly UIN, but probabilities remain too low to include in
the TAF at this time.

BRC

&&

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

$$

WFO LSX