523
FXUS63 KLSX 011721
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1221 PM CDT Mon Sep 1 2025

.KEY MESSAGES...

- Largely dry and comfortable conditions continue through
  Wednesday morning before a strong cold front mid-week. Along
  with showers and a rumble of thunder, the front will usher in a
  notable cooldown through early next week.


&&

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 245 AM CDT Mon Sep 1 2025

Dry air is advecting west amidst weak but persistent easterly
near- surface flow as we enter climatological Fall. While mid-
level forcing continues to stimulate weak showers across western
Missouri, the dry air is inhibiting all but a few cells from
precipitating further east. While low (15-25%) rain chances
continue today in central Missouri, most of the region will enjoy
a dry Labor Day with very similar conditions to yesterday.
Temperatures will be further stunted in central Missouri where
cloud cover remains more abundant, but will be generally below-
normal areawide. The mid-level wave causing the showers is still
expected to slide south and east through the evening and settle
over the Ozarks on Tuesday. While temperatures will stay somewhat
suppressed (upper 70s to low 80s) during the day, rain chances
will be fairly low (20%) and confined to the Ozarks themselves.

MRB

&&

.LONG TERM...  (Tuesday Night through Sunday)
Issued at 245 AM CDT Mon Sep 1 2025

Most guidance is now suggesting a brief warmup on Wednesday ahead of
a strong cold front and impressive closed upper level low diving
south from central Canada. Warmer westerly winds and decreased cloud
cover will send temperatures back to near-normal ahead of the front,
roughly in the mid-80s for most of the area. Most solutions don`t
bring the front into the northern forecast area until around sunset.
Once here, confidence is increasing that showers will fill in along
the front and bring our best chance for more than a few hundredths
of an inch of rain in the next week. That said, convection will be
fairly weak, if it can occur at all with waining MUCAPE values in
most available guidance by the time the front arrives. NBM
probabilities of 0.50 inches of rain Wednesday night never tops more
than 15%, which doesn`t bode well for the gradually-worsening
drought.

While it`s not uncommon to see cold air lag behind the effective
cold front this time of year, that will certainly not be the case
Thursday morning. Much cooler and drier air will rush into the
region by Thursday, sending temperatures anywhere from 10-15 degrees
below Wednesday`s highs. The coolest conditions will be across
northern Missouri, where highs will struggle to warm to 70 degrees.
Elsewhere, upper 60s to low 70 are forecast and a stellar weekend is
on tap. The trend for a more persistent cooldown, at least through
the weekend, also continues with a reinforcing cold front diving
south Friday evening. This cooldown looks more likely to last
through the weekend, but those who are heralding this cooldown as
the "end of summer" may want to hold off on that rhetoric. The NBM
temperature envelope shows a persistent warming trend going into the
middle of next week, which matches the CPC Temperature Outlooks and
CIPS Extended Analog Guidance from Saint Louis University.

MRB

&&

.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1216 PM CDT Mon Sep 1 2025

VFR conditions are expected through the end of the TAF period as a
high pressure ridge maintains light easterly/variable surface
flow. An isolated showers is possible over central Missouri this
afternoon/evening, but dry air is favored to hold with any
precipitation being light and short-lived. Therefore, no
precipitation was included in the latest TAF update.

Maples

&&

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

$$

WFO LSX