053
FXUS63 KLSX 241724
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
1224 PM CDT Mon Aug 24 2026

.KEY MESSAGES...

- Seasonably warm temperatures in the 80s will continue this
  week. There is a chance for thunderstorms Tuesday night and
  Wednesday ahead of a weak cold front.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 915 AM CDT Mon Aug 24 2026

Today: Surface high pressure was centered over western
Illinois early this morning with convection currently ongoing
over Nebraska/ Iowa. These showers and thunderstorms are
expected to quickly weaken as they progress southeast. The only
thing that will remain from the showers and thunderstorms will
be mid and high clouds across Missouri/ western Illinois. No
precipitation is expected. Even with the approaching cloud
cover, expecting highs in the lower 80s as the sun will not be
completely obscured.

Tonight: Expect lows 10 to 15 degrees warmer tonight compared to
this morning (Monday) as surface high pressure moves east.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 405 AM CDT Mon Aug 24 2026

The latest guidance continues to show a highly amplified long wave
pattern over the CONUS at least through Friday. The upper trough
continues drifting east through midweek which allows temperatures
to continue to warm back into the mid and upper 80s by Wednesday.  A
short wave moves through the Midwest into the Great Lakes and Ohio
Valley by late Wednesday afternoon/evening.  This reorients the long
wave trough back to the west and pushes a cold front south through
the Mississippi Valley.  Models print out light QPF ahead of the
front Tuesday night and Wednesday, however the forcing isn`t
particularly strong Tuesday night, and elevated instability is
limited.  While CAPE increases to 2000+ J/Kg ahead of the front on
Wednesday, there`s enough CINH ahead of the front to make precip
chances questionable.  The going 20-30 PoPs look reasonable given
the cap and relatively weak forcing, but if the cap breaks there
could certainly be more widespread thunderstorms.  Deep-layer wind
shear will be around 30kts, so any storms that do form could be
strong to severe.

The airmass behind the cold front isn`t that much cooler, so highs
Thursday and Friday will likely only be 2-3 degrees cooler than
Wedneday`s.  However it does look drier, so lows drop as much as 5-7
degrees back into the upper 50s and low 60s across much of the area
by Friday morning.  The long wave pattern begins to attenuate
Friday, and by Saturday the flow aloft is quasi-zonal. Deterministic
guidance is pretty insistent that temperatures will rise back into
the upper 80s and low 90s Saturday and some locations will see mid
90s by Sunday afternoon.  The LREF agrees, and even the lower
quartile high temperatures are in the low to mid 90s Sunday
afternoon.  That being said, the IQR is fairly wide at 6-8 degrees.
With that in mind confidence in the temperature forecast for
Saturday and Sunday isn`t particularly high.

&&

.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 553 AM CDT Mon Aug 24 2026

All TAF sites are currently VFR this afternoon with weakening
showers currently over northeastern Missouri. Latest observed
ACARs soundings shows substantial dry air in the 800 to 900 mb
layer, and with a rapidly weakening low level jet further
weakening is expected. The main impact will be a SCT to BKN 7 -
8kft deck.

Tonight, surface high pressure will center near the Ohio/
Indiana border with light to variable southeast winds across the
terminals. Cloud cover from this afternoon is forecast to mostly
remain in place which makes the chance of morning fog less
likely.

&&

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

&&

$$

SHORT TERM...BAH
LONG TERM...Carney
AVIATION...BAH