241
FXUS63 KLSX 212250
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
550 PM CDT Wed Oct 21 2026

.KEY MESSAGES...

- Dry and seasonably warm conditions will persist through the
  weekend.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 207 PM CDT Wed Oct 21 2026

Wednesday: Surface high pressure is currently centered across
eastern OH and western PA with weak mid-level vorticity over
central MO. This mid-level vorticity is rounding the top of a
ridge axis which has resulted in mid to high clouds across the
area. Given that, there is not much moisture in the mid-levels
and cloud cover has been slowly dissipating through the day.
There is a weak cold front across KS/ NE that is expected to
washout as the primary mid-level wave moves east over Ontario
and Quebec. The primary impact for us will be the surface ridge
over southern Ontario. This surface high will start to merge
with the high over PA/ OH. This will allow a subtle backing of
surface winds across central MO and IL. Given this weak CAA, the
thinking is that lows will again be in the lower 40s (for
normal cold spots) with mid to upper 40s elsewhere.

Thursday: Surface high pressure will center over Ontario/ Quebec
allowing for another day of high temperatures in the mid to
upper 70s (around 10 degrees above normal for this time of
year). No precipitation is forecast.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
Issued at 207 PM CDT Wed Oct 21 2026

Overall, confidence in the forecast remains relatively high
through Monday, with confidence rapidly decreasing Tuesday and
Wednesday. This means above normal temperatures and below normal
precipitation are forecast through the weekend.

On Friday, a closed low over southern California will be quasi-
stationary with a mid-level ridge over the central United
States. Sunday into Monday, a potent mid-level wave will move
east across British Columbia. The latest run of the WPC ESA
webpage shows this to be the source of the uncertainty Tuesday
and Wednesday. Two clusters show a stronger wave that wave
breaks (forming a closed off low), while other guidance has a
more progressive wave. The wave breaking scenario is favored by
the CMC (GEPS), while the ECMWF (EPS) and GFS (GEFS) show a
colder solution. When looking at box and whisker plots, the
LREF and NBM have a 10 to 20 degree spread for Tuesday and
Wednesday. The sensitivity analysis also shows that model
guidance will likely not find agreement until Sunday. Either
solution set shows the area dry through Tuesday, the main
difference being temperatures. As of current, it appears ~50%
split between warmer and cooler solutions. Through Monday,
expect highs in the upper 70s, with lows around 50 degrees.

&&

.AVIATION /18Z TAFS THROUGH 00Z FRIDAY/...
Issued at 547 PM CDT Wed Oct 21 2026

Dry and mainly VFR conditions are expected through the period.
There will be some fog late tonight into early Thursday in low
lying areas with MVFR and occasional IFR visibilities including
at JEF, SUS, CPS. Otherwise winds are expected to remain light.

&&

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

&&

$$

SHORT TERM...BAH
LONG TERM...BAH
AVIATION...Britt