886
FXUS63 KLSX 231039
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
539 AM CDT Thu Jul 23 2026

.KEY MESSAGES...

- Cooler temperatures will continue through tomorrow before the heat
  and humidity returns by late this weekend.

- There is a chance (40-70%) for showers and scattered
  thunderstorms from late tonight through Saturday with locally
  rainfall possible.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 259 AM CDT Thu Jul 23 2026

Another dry and relatively cool July day is expected as low level
easterly flow continues to advect dry air into the area.  Highs this
afternoon will range from the upper 70s over the eastern CWA to the
mid 80s over parts of central and southeast Missouri.

The chance for showers and scattered thunderstorms will return after
midnight tonight over our Missouri counties as there will be
convergence on the nose of a broad low level jet.  This will spread
across the CWA on Friday and Friday night as there will be increased
lift associated with a shortwave trough moving southeast across the
area in the northwest flow aloft.  There remains some timing
differences with how quickly the rain will move out of the area,
with some models dry on Saturday with others showing showers and
thunderstorms lingering through the day.  The LREF is showing PWATS
around 2" Friday into Saturday (>90th percentile) at the same time
that the RAP is showing warm cloud depths above 10k feet which
favors locally heavy rainfall.

The clouds and showers will help keep highs down in the 70s and 80s
again on Friday.  Low level warm air advection is expected to help
boost highs on Saturday back into the 80s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 259 AM CDT Thu Jul 23 2026

The LREF is continuing to show a large ridge building over the
central CONUS over the weekend with northwest flow setting up over
Missouri and Illinois.  Less than 15-20% of NBM/LREF members are
producing any rain over the area from Saturday night through next
Thursday favoring mainly a dry forecast.  It does look to be hot and
humid as 850mb temperatures increase into the 22-26C range (>95th
percentile) supporting highs in the 90s.  The warmest day at this
point looks to be Monday as the NBM IQR at St. Louis is only 3
degrees with highs in the mid to upper 90s.  With dewpoints forecast
to be in the 60s and 70s, afternoon heat indexes on Sunday into
Tuesday will likely climb above 100 degrees in most areas with some
areas reaching above 105.   There is some indication as the pattern
continues to amplify by the middle of next week, a weak front will
move in from the east which will cause a slight drop in temperatures
providing some relief.

&&

.AVIATION /06Z TAFS THROUGH 12Z FRIDAY/...
Issued at 529 AM CDT Thu Jul 23 2026

Mainly dry and VFR conditions are expected this period. There
are low chances (<30%) for showers with VFR conditions moving
into UIN/COU/JEF between 06-12Z, with a better chance (>30%) for
these conditions moving into the St. Louis airports between
12-18Z. Have only added PROB30 only to STL after 12Z where I
have the most confidence in the timing. Otherwise winds will
continue to be east to northeast and light through the period.

&&

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

&&

$$

SHORT TERM...Britt
LONG TERM...Britt
AVIATION...Kimble