Des Peres Missouri Weather Forecast Discussion

222
FXUS63 KLSX 100326
AFDLSX
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1026 PM CDT Thu Oct 9 2025
.KEY MESSAGES...
- There is a 20 - 40% chance of showers and thunderstorms in portions
  of central Missouri northeast into west-central Illinois
  tomorrow morning. Beneficial rain is not expected.
- A warming trend will kick off tomorrow and last through at least late
  next week.
&&
.SHORT TERM...  (Through Late Friday Night)
Issued at 140 PM CDT Thu Oct 9 2025
Mid to upper level ridging continues to build in the central CONUS
and now encapsulates the Mid-Mississippi Valley. In the low-levels,
weak cold air advection will give way to warm air advection
overnight. These two factors will kick off a warming trend that will
begin tomorrow and last through at least late next week. A cold
front or two may dent the warming trend in portions of the CWA north
of I-70 during the next 7 days. At least one will also bring rain
chances back into the area.
The first cold front will approach the area tonight. Ahead of the
front, aforementioned warm air advection will pair with modest
moisture return to increase instability and promote isolated to
scattered showers and thunderstorms. Despite the increasing heat of
the day, decreasing boundary layer moisture is expected to result in
less available instability during the day on Friday, leading to
convection waning with time and southeastward extent. Where
ensembles give northeast Missouri up to a 90% chance of seeing
measurable rain tomorrow, it gives St. Louis a 10 - 20% chance.
Jaja
&&
.LONG TERM...  (Saturday through Next Thursday)
Issued at 140 PM CDT Thu Oct 9 2025
Mid to upper level ridging will keep the region warm and dry this
weekend before deamplifying late Sunday. This will allow shortwaves
to ride into the Mid-Mississippi Valley, threatening additional rain
chances late Sunday into Monday. The synoptic setup looks very
similar to tomorrow`s rain chances with warm air advection showers
possible ahead of an approaching cold front. However, a lack of
sufficient moisture will likely keep showers limited if they can
develop at all.
The temperature forecast will remain fairly steady from this weekend
through the middle of next week south of I-70. There, highs in the
upper 70s to low 80s are forecast from Saturday on. To the north of
the interstate, daily high temperatures will fluctuate due to the
aforementioned cold fronts dipping into and then retreating back out
of the CWA. Generally, though, low to mid-70s are forecast through
the period.
Jaja
&&
.AVIATION...  (For the 06z TAFs through 06z Friday Night)
Issued at 1017 PM CDT Thu Oct 9 2025
Some river valley fog is expected overnight into early Friday
morning, mainly in southeast Missouri. A brief period of fog is
likely to impact KSUS, so did add a TEMPO for MVFR visibilities in
fog.
The threat for showers and thunderstorms increases Friday morning,
mainly in central/northeast Missouri. Coverage still looks mostly
scattered, so maintained PROB30 groups for MVFR visibilities in
thunderstorms for both KCOU/KJEF. The threat for thunder is less
further east, so just have PROB30 for showers. Activity should
weaken and largely dissipate by evening, so kept metro sites dry.
Cannot rule out a brief shower or sprinkle, but any visibility
restrictions are unlikely.
Gosselin
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX

NWS LSX Office Area Forecast Discussion