258
FXUS63 KLSX 301926
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
226 PM CDT Wed Jul 30 2025

.KEY MESSAGES...

- Scattered thunderstorms with gusty winds are expected through
  this evening, mainly in southeast Missouri and southwest
  Illinois.

- Much cooler weather will move into the area tonight and last
  through this weekend.


&&

.SHORT TERM...  (Through Late Thursday Afternoon)
Issued at 223 PM CDT Wed Jul 30 2025

A MCS very gradually weakened all morning, allowing a composite
outflow boundary to progress southeast of the I-44/I-70 corridors
in Missouri and Illinois respectively. Along/southeast of this
boundary will be the focus through early this evening for the
redevelopment of showers and thunderstorms. Some of the stronger
cores may be able to produce wind gusts up to 60 mph in
microbursts across parts of southeast Missouri and southwest
Illinois through about 9 PM this evening.

For the remainder of the night, the synoptic cold front continues to
make gradual progress southward, ushering in much cooler
temperatures to the region. Isolated to widely scattered showers are
possible overnight tonight into Thursday morning, with the best
chances centered in/near the 850-hPa cold front. Behind this
feature, dry weather is expected.

Behind the surface cold front, look for northerly winds to increase
to around 10-15 mph, with widespread low stratus enveloping the
area. Temperatures will struggle to rise much during the day with
increasing low-level cold air advection and the aforementioned
stratus. High temperatures ranging from the mid 70s to low 80s are
forecast from north to south. These temperatures would be nearly 10
degrees below normal and the first time most locations would be
below normal at all in almost 2 weeks.


Gosselin

&&

.LONG TERM...  (Thursday Night through Next Wednesday)
Issued at 223 PM CDT Wed Jul 30 2025

(Thursday Night - Sunday)

A sprawling 1028+ hPa surface high will completely control our
sensible weather through the weekend, providing cool, dry
northeasterly surface flow. Dry weather is favored through the
period along with well-below normal temperatures and low humidity.
What a change compared to the heat and humidity of the past week and
a half. High temperatures are forecast to be in the mid 70s to near
80 degrees with lows in the mid 50s to low 60s. These temperatures
would be about 10 degrees below normal as we cross over from the
month of July to August, and more typical of those of the third week
of September.


(Sunday Night - Next Wednesday)

The mid/upper level pattern begins to change as we head into next
week. Flow aloft turns from northwesterly to more zonal, with a
mid/upper level ridge trying to push out of the intermountain west
into the south-central Plains. This means moderating temperatures,
likely inching closer to normal. In addition, it portends the
return of chances for showers and thunderstorms as a midlevel
shortwave trough moves southeast into the Mississippi Valley
sometime Sunday night through Monday night. There is quite a bit
of spread with the strength and timing of this feature, so PoPs
are not too high quite yet. They generally are in the 20-30%
range, or near normal for early August.


Gosselin

&&

.AVIATION...  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1159 AM CDT Wed Jul 30 2025

A composite outflow boundary along with some scattered showers and
storms continues to move east and should be through metro
terminals. This should be completely through by 1900 UTC. There
may be some redevelopment, but the best chances should tend to
focus across southeast Missouri and southwest Illinois. Scattered
showers and possibly a few thunderstorms are expected overnight
tonight into Thursday morning, but there is not much confidence in
where and when the best chances are. Therefore, left TAFs dry for
now. The synoptic cold front will be moving through tonight.
Behind the front, look for a wind shift to the north and lowering
ceilings. MVFR ceilings with bases between 1000 and 2000 feet AGL
are mostly expected then through Thursday morning. There also will
be some IFR ceilings at least for a period of time the further
northwest you go, with KUIN and KCOU having the best chances.

Gosselin

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Extreme Heat Warning until 7 PM CDT this evening for Franklin MO-
     Jefferson MO-Saint Charles MO-Saint Louis City MO-Saint
     Louis MO-Sainte Genevieve MO.

     Heat Advisory until 7 PM CDT this evening for Boone MO-Callaway
     MO-Cole MO-Crawford MO-Gasconade MO-Iron MO-Madison MO-
     Moniteau MO-Montgomery MO-Osage MO-Reynolds MO-Saint
     Francois MO-Warren MO-Washington MO.

IL...Extreme Heat Warning until 7 PM CDT this evening for Bond IL-
     Clinton IL-Madison IL-Marion IL-Monroe IL-Randolph IL-Saint
     Clair IL-Washington IL.

     Heat Advisory until 7 PM CDT this evening for Fayette IL.

&&

$$

WFO LSX