982
FXUS63 KLSX 241056
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
556 AM 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 405 AM CDT Mon Aug 24 2026

A high amplitude upper pattern remains in place over the CONUS with
a ridge centered over the Southwest U.S. extending north through the
Plains, and a trough over the Great Lakes Lakes extending through
the Southeast. The trough drifts east a bit today, which also causes
the surface high currently over the Midwest to drift east into the
Great Lakes Region and Ohio Valley. This will result in little
change to the sensible weather at the surface, other than the winds
turning to a more east or southeast direction.  There are some
isolated showers over western Missouri that are likely being forced
by low level moisture convergence on the eastern periphery of a low
level jet originating over the southeast Plains, however it`s
unlikely this precip will get too far east this morning before the
low level jet weakens.  Highs today should be very similar to
yesterday`s in the low to mid 80s under a partly to mostly sunny
sky.  Temperatures tonight look to be a bit warmer than this morning
due to the continuing east-southeast flow with lows bottoming out in
the low to mid 60s in most locations.

&&

.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

River fog will locally reduce the visibility to 1SM or less
through 13Z this morning. There are also isolated light showers
over parts of central Missouri which will likely persist through
13Z-14Z, although it`s unlikely the rain will be heavy enough to
reduce the visibility. Otherwise, VFR flight conditions and
light east to southeast winds will prevail through the period.
There may be river fog again tonight, though current indications
are that conditions will be less favorable than this morning.

&&

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

&&

$$

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