351
FXUS63 KLSX 301910
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
210 PM CDT Sat Aug 30 2025

.KEY MESSAGES...

- Mostly dry conditions will prevail through the week. Cooler
  temperatures are in store through the rest of the weekend, and a
  stark cooldown is expected Thursday with the arrival of an
  unseasonably potent cold front.

&&

.SHORT TERM...  (Through Late Sunday Night)
Issued at 209 PM CDT Sat Aug 30 2025

A mid-level shortwave trough is currently meandering through the
central Plains, with vorticity maxima ejecting southeast from it.
These vorticity lobes are causing increased cloud cover in much of
Missouri, which will continue to be the case through early next week
as the shortwave draws closer to the Mid-Mississippi Valley. The
cloud cover and possible rain will act to dampen temperatures during
this period, with mid-70s to low 80s forecast each day from Sunday
through Tuesday. Monday will likely be the coolest day of this
stretch for most, as it`ll be the second day of increased clouds and
potential rain. Temperatures rebound slightly on Tuesday as cloud
cover begins to break and the sun is allowed to provide warmth.

The shortwave will bring the potential for rain as it nears the
forecast area, but actual rain chances and amounts remain slim.
Moisture associated with the shortwave`s surface reflection will not
be abundant, and most of it will stay closely tied to the center of
the surface low. As such, rain chances on Sunday and Monday will be
the highest along the low`s track as it treks through western
Missouri, with portions of central Missouri having a slight chance
(15 - 25%) of seeing remnant showers from out west. Rain chances
peak in southern Missouri on Tuesday as the shortwave pivots through
the Ozarks and strengthens. Even then, LREF probabilities of
measurable rainfall over a 24 hour period ending Wednesday morning
only peak at 60% in our southernmost tier of counties, and these
drop to 25 - 30% when the threshold is increased to 0.1" over 24
hours. In short, rainfall is not promised at any given location, and
amounts will not be high enough to be beneficial to ongoing drought
conditions.

Jaja

&&

.LONG TERM...  (Monday through Next Saturday)
Issued at 209 PM CDT Sat Aug 30 2025

An anomalously strong longwave trough for early September will dig
into the Great Lakes region and push a cold front through the region
on Wednesday. There is a chance of showers and thunderstorms along
the front as it passes, but dry air ahead of it will limit the
strength and coverage of any activity. The larger impact will be the
very strong and cool airmass that will move in behind the front. 850
mb temperatures will drop into the single digits by Thursday, within
the 0.5th percentile for September 4th. These values will translate
to surface highs in the upper 60s to low-70s for Thursday afternoon
which are 10 to 15 degrees below normal. Lows on Thursday and Friday
morning will be equally as anomalous with widespread mid to upper
40s in the forecast. Temperatures will moderate through next
weekend under the influence of weak warm air advection and
sunshine. In addition, dry conditions will follow the cold front
and persist through the weekend.

Jaja

&&

.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1156 AM CDT Sat Aug 30 2025

VFR and mostly dry conditions with generally light winds will
prevail through the TAF period. Isolated showers will continue in
west-central/south-central IL and eastern MO through this
afternoon, but confidence in direct impacts at KUIN/KSTL/KSUS/KCPS
is too low to mention in the TAFs at this time. Will continue
monitoring and will make any changes as needed.

Jaja

&&

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

$$

WFO LSX