490
FXUS63 KLSX 052355
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
655 PM CDT Tue Aug 5 2025

.KEY MESSAGES...

- Dry conditions with warming temperatures will last from
  Wednesday through the end of the week.


&&

.SHORT TERM...  (Through Late Wednesday Night)
Issued at 143 PM CDT Tue Aug 5 2025

The Mid-Mississippi Valley is currently on the backside of a mid-
level shortwave trough. The best of the feature`s lift has exited
the region, but we still have a bit lingering behind the rest. This
weak lift in addition to increasing instability over southern and
central Illinois has resulted in isolated showers and
thunderstorms. These will remain sub-severe given the lack of
appreciable wind shear. Showers and thunderstorms will dissipate
this evening as daytime instability wanes.

Patchy fog is expected again tonight primarily in river valleys and
where radiational cooling conditions are present. Overnight lows
will fall into the 60s areawide.

Jaja

&&

.LONG TERM...  (Thursday through Next Tuesday)
Issued at 143 PM CDT Tue Aug 5 2025

A mid-level ridge currently centered over southern New Mexico will
expand into the central CONUS through the middle of this week. We`ll
see the influence of the subsequent height rises as early as
Wednesday in the form of dry conditions and warmer temperatures.
Where today widespread 80s are being observed this afternoon,
tomorrow low-90s will begin to creep into portions of central and
southeast Missouri. This trend will continue through the end of the
week with widespread highs in the low to mid-90s forecast by
Saturday. Dewpoints in the 70s will bring us back to the
uncomfortably humid side of summer, but heat index values as a
whole will remain below Heat Advisory criteria during the stretch.

The ridge will begin to erode late this week and give way to a
trough deepening over the northern CONUS. A cold front will
accompany the trough and will impact the CWA`s sensible weather, but
to what degree is still unclear. The trough`s speed and strength and
the number of any shortwaves along its southern periphery will
dictate the behavior of the cold front at the surface. That includes
if the cold front wavers about the region or if it pushes through
completely. As of now, ensemble guidance is very spread on when
exactly the front and rain chances will enter the CWA and how long
it`ll all last. For instance, 60%+ of ensemble members have at least
a trace of rain falling during all 6 hour periods between Sunday
night and Wednesday. This is obviously quite washed out and shows
that guidance has yet to really key in on any specific solution. The
NBM interquartile range reflects these uncertainties as well as it
spreads to 5+ degrees after Sunday.

Jaja

&&

.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 653 PM CDT Tue Aug 5 2025

VFR flight conditions are expected to prevail through Wednesday. A
few lingering showers will be strong enough to reduce the
visibility to 2SM or less early this evening across the eastern
Ozarks. Fog is possible before sunrise Wednesday, primarily in
river valleys and other sheltered spots.

Carney

&&

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

$$

WFO LSX