858
FXUS63 KLSX 112318
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
518 PM CST Tue Nov 11 2025

.KEY MESSAGES...

- Warm and dry weather is expected through Saturday. Each
  successive day will be a few degrees warmer until temperatures
  are as much as 20-25 degrees above normal by the end of the
  week.

- Although there is still a 20-30 percent chance for rain on
  Sunday, the next best chance for rain (30-50 percent) has been
  pushed back to Monday and Monday night.


&&

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 218 PM CST Tue Nov 11 2025

Warmer temperatures are expected tonight as southwest flow
ahead of a surface trough brings a milder airmass from the southern
Plains into the Mid Mississippi Valley.  Latest guidance shows lows
staying in the mid to near 40 across the area.  Any lingering mid
and upper level clouds should be gone by early evening, and given
the diminishing wind I wouldn`t be surprised if well sheltered
locations dropped to near freezing again, particularly across
central Missouri where the wind will be lightest.  Forecast
soundings are fairly dry through the depth of the troposphere on
Wednesday, indicating a clear sky and strong insolation.  The warmer
start to the day and full sunshine will lead to high temperatures
building a few degrees into the low to mid 60s.

Carney

&&

.LONG TERM...  (Wednesday Night through Next Tuesday)
Issued at 218 PM CST Tue Nov 11 2025

The long wave pattern remains fairly amplified headed into the long
term.  The GFS and ECMWF show a mid-upper level ridge drifting from
the western U.S. across the Rockies on Thursday and into the Midwest
on Friday.  Persistent south to southwest flow Thursday and Friday
along with the building upper ridge will produce unseasonably warm
temperatures for the latter half of the week with highs rising from
the low to mid 60s Thursday up to 75-80 by Saturday.  As the ridge
moves east, a long wave trough will dig into the West Coast behind
it and fracture on Friday, leaving a closed low off the coast of
southern California.  The northern stream trough continues east
across Canada and the northern U.S. The surface reflection of the
trough drives a cold front through the Upper Midwest on Saturday,
and into Missouri and Illinois by 00Z Sunday.  The LREF cluster
analysis is showing differences in timing and amplitude of the
pattern as the trough plows into the ridge late Friday into
Saturday, however the effects on sensible weather at the surface
here in the Mid Mississippi Valley appear to be minimal.  High
temperature IQRs are only 2-3 degrees through Saturday, so
confidence is high in the warm forecast.

Forecast confidence drops significantly for Sunday through Tuesday.
The cold front continues south on Saturday night into Sunday, but
guidance continues to show differences in how far south it
ultimately pushes.  The latest GFS stalls the front over northern
Arkansas on Sunday while the EC pushes the front into southern
Arkansas or northern Louisiana.  Meanwhile, the southern stream low
off the California coast moves ashore and across the Rockies into
the Plains.  There are some pretty major differences between how the
GFS and the EC handle this wave.  The GFS is about 12 hours faster
in moving it across the country, and the wave less amplified than
the EC solution.  Both models develop a surface low over the Plains,
link it up with the stalled front, and move it through the
Mississippi Valley.  However the position, timing, and strength of
the lows are very different resulting in different temperature and
precipitation forecasts for our area.

Unsurprisingly the LREF cluster analysis shows a great deal of
variability in the position and amplitude of both the northern and
southern stream troughs as they move across the country.  This
translates into temperature IQRs increasing to 10+ degrees for
Sunday through Tuesday. Additionally it calls precip chances into
question.  NBM PoPs have been steadily decreasing and moving to
later in the period with only a 20-30 percent chance on Sunday and a
30-40 percent chance on Monday, and I cannot disagree given the
variability shown by the LREF.

Carney

&&

.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 517 PM CST Tue Nov 11 2025

Surface winds continue to lighten under clearing skies tonight.
Light surface flow persists through the end of the period with
wind shifts accounting for prevailing groups in this evening`s
TAF. VFR conditions are expected through the period.

Maples

&&

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

$$

WFO LSX