Affton, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

081
FXUS63 KLSX 281727
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1227 PM CDT Mon Jul 28 2025

.KEY MESSAGES...

- The dangerous heat will worsen today into Tuesday and likely
  linger for those along and south of I-70 through Wednesday.
  Those in the St. Louis metropolitan area and areas southeast,
  within the Extreme Heat Warning, will see the worst impacts.

- Long-awaited relief from the heat begins Wednesday with a cold
  front and increased rain chances. While some won`t feel the relief
  immediately, an areawide cooldown is likely (70% chance) by
  Thursday.


&&

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 314 AM CDT Mon Jul 28 2025

Fairly tranquil conditions exist across the region at this hour
under a strong upper-level ridge, though just to our north a
decaying MCS is dropping south across Iowa. The convection is
fairly robust and oscillating at near-severe levels, but as it
moves south along the MLCAPE gradient it will continue become more
disorganized with time. The outflow from this system, or the
system itself, may force some scattered showers and thunderstorms
later this morning across northeast Missouri and west-central
Illinois. However, by mid- morning any convection will likely
(80-90%) end, paving the way for dangerous heat across the region
today. Despite some fairly low (15- 20%) chances for airmass
thunderstorms south of I-44/I-55 this afternoon, little will
impede the impactful heat again today. As the case has been for
the last few days, the worst impacts will be felt in highly-
urbanized areas. After another very warm night under the ridge
aloft, complete with a similar-looking MCS ejecting from the
northern Plains and tracking into Illinois, another dangerously
hot and humid day (perhaps the worst of the stretch) is on tap
Tuesday. That said, a welcomed pattern change begins late Tuesday
across the northern CONUS that will gradually end this prolonged
heatwave.

MRB

&&

.LONG TERM...  (Tuesday Night through Sunday)
Issued at 314 AM CDT Mon Jul 28 2025

A longwave trough oozing south out of Canada into the Great Lakes
region late Tuesday into Wednesday will usher in the long-awaited
relief from the heat wave. However, the cooler air won`t come to the
entire region at once. Overnight Tuesday, a stronger shortwave that
is evident in most medium-range guidance on the southern fringe of
the longwave will push a cold front south through the Upper
Mississippi Valley. That feature doesn`t make much southward
progress, however, and while it may spark another MCS through
Wednesday morning north of the region to push the front further
south still, the southern half of the forecast area (generally
along/south of I-70) will still be under the influence of the upper
ridge. There is little spread in maximum temperatures evident in the
temperature/dew point output from the NBM or global ensembles across
this area, unfortunately lending credence to one more hot day for
some. As such, part of the Heat Advisory and the entire Extreme Heat
Warning was extended until 7 PM Wednesday. It`s worth noting that
there is some potential for part (if not all) of the Extreme Heat
Warning to be downgraded by that point if the coolest guidance
prevails, but that will need to be handled closer to Wednesday. As
for thunderstorm threats, convection should be progressive enough
to preclude a flash flood threat and outside of a marginally-
severe wind threat there isn`t much to support an organized
severer weather potential.

Convection on Wednesday and a reinforcing shortwave Wednesday
evening will push the front through the bi-state region, closing the
book on the heat wave and establishing much more comfortable
conditions Thursday into the weekend. Words to describe the weekend
include, but are not limited to, "refreshing," "picturesque," and
"wow it`s nice out" as a much cooler airmass settles in and rain
chances fall to near-zero. Some guidance even suggests high
probabilities (70-90%) of reaching the 10th climatological
percentile for high temperatures Saturday and Sunday, particularly
in northern Missouri. Regardless, there`s little doubt in an
unseasonable break from the summer doldrums to start August. The
depictions of the upper-level pattern diverge to start the next
week, with some keeping the cool air in place and others bringing
more seasonable warmth back. This forecast leans on the NBM
solution at this lead time, which supports a very gradual warmup
into Monday.

MRB

&&

.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1223 PM CDT Mon Jul 28 2025

Dry and VFR flight conditions will continue through the end of the
TAF period under variable winds largely less than 10 kts. Winds
are largely southwesterly now but will veer to the north this
afternoon before becoming light and variable overnight.

The one caveat is the potential for scattered showers and
thunderstorms early Tuesday morning across west-central Illinois,
though confidence in this occurring is very low. There will likely
be showers and thunderstorms across Iowa and northern/central
Illinois Tuesday morning, but how far southwest they extend into
the KUIN airspace.

Delia

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Heat Advisory until 7 PM CDT Tuesday for Audrain MO-Boone MO-
     Callaway MO-Knox MO-Lewis MO-Lincoln MO-Marion MO-Monroe MO-
     Montgomery MO-Pike MO-Ralls MO-Shelby MO-Warren MO.

     Extreme Heat Warning until 7 PM CDT Wednesday for Franklin MO-
     Jefferson MO-Saint Charles MO-Saint Louis City MO-Saint
     Louis MO-Sainte Genevieve MO.

     Heat Advisory from 7 PM Tuesday to 7 PM CDT Wednesday for Cole
     MO-Crawford MO-Gasconade MO-Iron MO-Madison MO-Moniteau MO-
     Osage MO-Reynolds MO-Saint Francois MO-Washington MO.

IL...Heat Advisory until 7 PM CDT Tuesday for Adams IL-Brown IL-
     Calhoun IL-Fayette IL-Greene IL-Jersey IL-Macoupin IL-
     Montgomery IL-Pike IL.

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

&&

$$

WFO LSX