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FXUS63 KLSX 122314
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
514 PM CST Wed Nov 12 2025

.KEY MESSAGES...

- Unseasonably warm conditions are expected Friday-Saturday. Highs
  on Saturday could approach daily records.


&&

.SHORT TERM...  (Through Late Thursday Afternoon)
Issued at 144 PM CST Wed Nov 12 2025

A ridge of surface high pressure will push eastward across the
Mississippi River into Illinois overnight tonight. Aloft,
northwest flow is expected to bring increasing cirrus, which will
help limit the cooling tonight. Lows in the upper 30s are expected
where thicker clouds are anticipated (northeast Missouri/western
Illinois) with mid 30s mostly elsewhere. Favored river valleys in
east central and southeast Missouri may flirt with the freezing
mark.

Increasing low-level warm air advection is expected on Thursday as
winds turn out of the south behind the departing surface ridge axis.
The increasing mid/high level cloudiness may put a slight damper on
the warmup, but still believe highs should be on average 2-3 degrees
warmer than this afternoon. Look for highs to range from the low 60s
(south-central Illinois) to the upper 60s (central Missouri).


Gosselin

&&

.LONG TERM...  (Thursday Night through Next Wednesday)
Issued at 144 PM CST Wed Nov 12 2025

(Thursday Night - Saturday)

There remains very high confidence in unseasonably warm temperatures
(day and night) late this work week through Saturday. The mid/upper
level ridge is expected to push eastward into the mid-Missouri
Valley with 850-hPa temperatures on the latest NAEFS soaring above
+15C Saturday afternoon. Those values are >99th percentile of
climatology and near daily records. Speaking of daily records,
Saturday may see temperatures approach record highs. The setup is
quite favorable with the aforementioned 850-hPa temperatures in
place and surface winds veering to the west/southwest ahead of the
approaching cold front. This wind direction is ideal for parts of
central/east central Missouri as it downslope off of the Ozark
Plateau. There are two limiting factors however: 1) mid/high level
clouds should limit warming at least slightly and 2) mixing is more
limited on Saturday compared to Friday (to near 875 hPa). For record
highs, you usually need everything to go "right" or work in concert.
At this time, this doesn`t appear to be the case given the limiting
factors detailed above. Therefore, highs are expected to be in the
mid to upper 70s. These values would fall about 3-4 degrees short of
record highs for 11/15 (KSTL: 81F, KCOU: 78F, KUIN: 75F).


(Saturday Night - Sunday Night)

A cold front will move through the area by late Saturday evening.
The air mass behind this feature is not particularly strong. This
looks like another Pacific front where the cooling is more modest.
Highs in the upper 50s to mid 60s are expected moving from north to
south. Low temperatures are expected to drop back into the 30s/40s.


(Monday - Next Wednesday)

Forecast uncertainty drastically increases as we head into early
next week. Ensemble guidance (as it has the past several days) is
really struggling with how to handle the west coast trough and its
evolution. WPC clusters of the 500-hPa height pattern show two main
camps, with one having southwest flow aloft vs. another with quasi-
zonal to northwest flow aloft across the mid-Mississippi Valley.
There is a break between the GEFS/EPS, with the GEFS mostly in the
zonal/northwest flow aloft camp due to the closed low hanging out in
the desert southwest. There is a bit more spread on the EPS, but
most members show southwest flow aloft with a stronger lead
disturbance ejecting out of the four corners region. It is difficult
to say which scenario is more likely to be correct. On one hand, the
EPS has been handling the west coast trough a bit more
consistently/better than the GEFS. On the other hand, closed lows
in/near the desert southwest are typically very slow to move
eastward. Sensible weather wise, the differences are pretty stark
though. The southwest flow scenario would lead to warmer
temperatures (especially Tuesday) with increasing chances of showers
(and possibly some thunderstorms). The more zonal/northwest flow
aloft scenario would be much cooler with a surface low passing well
to our south (and maybe some light rain). The spread on the NBM is
about as high as you see for maximum temperatures on Tuesday. The
difference between the 25th/75th for highs is 20-25+ degrees and
closer to 30-35+ degrees! The deterministic NBM was a blend of these
two camps and settled about ~5 degrees above climatology. This seems
like a good compromise for now, but there very well may be
significant changes to the forecast for early/mid next week,
especially with regards to temperatures.


Gosselin

&&

.AVIATION...  (For the 00z TAFs through 00z Thursday Evening)
Issued at 510 PM CST Wed Nov 12 2025

Dry and VFR conditions are expected through the period. Winds will
be light and variable tonight before turn out of the south to
southeast on Thursday morning at 5-7 knots.

Britt

&&

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

$$

WFO LSX