Area Forecast Discussion

237
FXUS63 KLSX 022321
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
521 PM CST Fri Jan 2 2026

.KEY MESSAGES...

- Temperatures will remain near normal for early January this
  weekend. A significant warm up is expected next week with
  temperatures 20-25 degrees above normal.

- The next chance (40-50%) for significant rainfall begins next
  Wednesday night and continues through Thursday. Lower rain
  chances linger into Friday.


&&

.SHORT TERM...  (Through Late Saturday Night)
Issued at 221 PM CST Fri Jan 2 2026

A ridge of high pressure currently centered over the Upper Midwest
and Northern Plains will build slowly south through Saturday night.
Drier air associated with the high will filter into Missouri and
Illinois tonight and this should bring the recent string of days
with low clouds and fog to an end.  However, some mid and high
clouds will likely linger as the next upstream short wave moves from
the Great Plains into the Mississippi Valley. The clouds will
provide some insulation so lows tonight in the mid 20s to near 30
won`t be as cool as they otherwise might be.  Forecast soundings
suggest the clouds shouldn`t be too thick or persistent on Saturday
afternoon resulting in decent insolation which will bring
temperatures up into the mid 30s to low 40s. Clouds should largely
clear out Saturday night and winds become light and variable
producing good radiational cooling conditions. Sunday morning lows
will therefore be a little cooler in the low to mid 20s.

Carney

&&

.LONG TERM...  (Sunday through Next Friday)
Issued at 221 PM CST Fri Jan 2 2026

Models continue to advertise a pattern shift early next week showing
good run-to-run consistency as well as good agreement between
different models.  The upper ridge which is currently over the
western U.S. will shift east Sunday, and become less amplified as it
moves into the Plains.  This pushes the cold surface ridge out of
the Mississippi Valley by Sunday night.  Sunday`s highs will be
similar to Saturday`s, in the upper 30s to low 40s due to the chilly
start.  However, persistent southerly flow on the western periphery
of the high will cause a significant warm up Monday and Tuesday.
Ensemble guidance is showing less variability with temperatures both
days with 55-60 degrees Monday, and then upper 50s to mid 60s
Tuesday. Temperature IQRs have fallen to 3-4 degrees in most
locations, so confidence in this forecast is much better than
earlier this week.  Confidence in the forecast falls Wednesday
through Friday as first a weak cold front moves through Tuesday
night, and then the pattern begins to re-amplifiy Thursday as a long
wave trough digs into the western U.S.  The deterministic GFS and
ECMWF are in pretty good agreement shifting the trough east over the
Rockies and northern Plains by Friday, however the LREF cluster
analysis shows a great deal of variance in the ensemble.  500mb EOF
patterns indicate large differences between ensemble members in both
the position and amplitude of the trough as it moves east.  The NBM
continues to show warm temperatures in the upper 50s and 60s with an
increasing chance for rain Wednesday night and Thursday.  However
high temperature IQRs jump to 15+ degrees in some locations by
Friday.  As such, confidence in the forecast is significantly lower
toward the end of the week.

Carney

&&

.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 517 PM CST Fri Jan 2 2026

Stratus continues to gradually advect to the west/southwest, and
we expect this trend to continue over the next several hours. This
should mean a return to VFR flight conditions for all of the TAF
sites by midnight, with KCOU/KJEF improving last. Thereafter,
generally light winds are expected with a surface ridge of high
pressure nearby.

Gosselin

&&

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

$$

WFO LSX

NWS LSX Office Area Forecast Discussion