737
FXUS63 KLSX 061951
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
251 PM CDT Mon Oct 6 2025

.KEY MESSAGES...

- There is a 20-60% chance of showers and isolated thunderstorms
  this afternoon through Tuesday morning. Widespread, beneficial
  rainfall is not expected.

- Cooler, near normal temperatures are forecast Tuesday through
  Friday before warming above normal next weekend.

&&

.SHORT TERM...  (Through Late Tuesday Night)
Issued at 247 PM CDT Mon Oct 6 2025

A couple of features embedded in the regional synoptic pattern
will bring chances of rain and isolated thunderstorms today and
Tuesday. Unfortunately, trends continue to indicate a lack of
widespread, beneficial rainfall.

The two items to watch today will a surface low moving through the
Missouri Bootheel and the cold front that extends from the northern
Great Lakes into the central Plains. As the system passes to our
south, the northward push ahead of the system will gradually draw
additional moisture into southeast Missouri and southern Illinois.
RAP guidance shows some locations may even flirt with dewpoints near
70 degrees this evening, which is notable considering the recent
dryness that helped make anomalous warmth more bearable.
Satellite imagery shows cloud cover more prevalent around the
system to the south and the cold front to north, while diurnal
cloud development begins to impede the clearing in between as
moisture increases from the south.

Rain chances (30-50%) will initially be highest around the system
to the south this afternoon through early evening. The northward
extent will be limited to areas along and south of I-44/I-64,
becoming more isolated between the system and the approaching cold
front. Much of what develops during the daylight hours will be
driven by modest mid-level lift in a region of southerly flow
that runs over top marginal surface instability. SPC mesoanalysis
show SBCAPE nearing 1000 J/kg early this afternoon with 20-25
knots of 0-6km shear over much of the region, closing in on 30
knots near the front to the north. Mid- level lapse rates tuck
under 6C with model soundings showing narrow CAPE profiles. This
isn`t much of an argument for more than showers and occasional
thunder through diurnal peak with weakening trends thereafter.
While severe weather is not expected, PWAT values around 1.6"
indicate that where isolated thunderstorms develop, brief,
localized episodes of heavy rainfall are possible. Even that will
be hard to come by with the lack of stronger forcing and scattered
nature of precipitation. PMM 6-hourly QPF shows isolated
0.25-0.50" values through 00z, mainly south of St. Louis, further
highlighting the lack of widespread beneficial rainfall.

Showers and thunderstorms develop along the cold front
(Iowa/Illinois) to the north this afternoon, as well. However, the
slow progression of the front brings it into northeast Missouri and
west-central Illinois as instability wanes this evening. Initial
development is expected in the warm sector, but gradually becomes
post-frontal tonight. Thunderstorms along the front weaken to
scattered showers overnight and trends toward less coverage
through early Tuesday morning. Meanwhile, additional precipitation
develops along and south of the front Tuesday afternoon. With the
departure of the southern system, the the front is pulled
southward and brings it into the southern sections of the CWA
Tuesday late morning. Additional precipitation develops along the
front Tuesday afternoon, but should be far enough south that
rainfall gradually shift south of the CWA. The bigger story will
be the cooler temperatures that work into the region as surface
ridging builds in from the north. Cloud cover holds through much
of the day, making it feel and look more like fall with steady or
slowly falling temperatures.


Maples

&&

.LONG TERM...  (Wednesday through Next Monday)
Issued at 247 PM CDT Mon Oct 6 2025

The long range pattern holds little promise for beneficial rainfall
with the lack of any organized systems in the Midwest.

Surface high pressure builds east-southeastward from the northern
Plains Tuesday night into Wednesday as mean upper level flow briefly
turns quasi-zonal through the midweek period. A bulk of the colder
air remains over the Great Lakes Region and northward. However, some
of the cooler air is pulled southward on north-northeasterly flow
around the eastern side of the ridge with 850mb temperatures running
between 3-5C. Despite ample sunshine under mostly clear skies,
temperatures will be more representative of typical fall weather for
October. This is especially true for Wednesday night into Thursday
morning as the surface ridge centers overhead. Clear skies and
calm/light surface winds result in efficient radiational cooling
with lows dipping into the 40s areawide. There is a slight chance
(10-20%) that a couple of outlying rural locations touch the upper
30s Thursday morning. After a cool start in the morning,
temperatures rise back into the 70s Thursday.

NBM data remains fairly well-clustered through the end of the period
with a gradual moderating trend in temperatures late this week into
the weekend. The midweek surface high moves into the Great
Lakes/northeastern U.S. through the day Thursday with surface flow
turning southerly late Thursday. Mid-level temperatures climb by 10-
15C from west to east Friday as a cold front begins to wash out to
our north. The front would have been the only shot at rainfall, as
small as it may have been. Trends no long favor this either, as
upper level ridging amplifies over the southern and central Plains
and surface ridging maintains dry conditions. Both long range
ensemble solutions (GFS/ECM) look rather concerning with the highest
outliers indicating less than 1.75" of QPF through the next 7-10
days. The end of the period is favored to end dry and warmer than
normal with temperatures returning to the 80s.


Maples

&&

.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1248 PM CDT Mon Oct 6 2025

There will be two features driving precipitation chances in the
period. The first is a system moving through southeast Missouri
tonight, which is expected to give rise to scattered showers and
isolated thunderstorms over central Missouri eastward into the
metro terminals during the day today. The limited coverage and
support for activity to become organized or sustained will be
better handled through amendments, as most areas remain dry.

A cold front then pushes southward through the region this evening
through early Tuesday. The bulk of the impacts will come along and
behind the front as weakening thunderstorms trend toward scattered
showers and lowering ceilings behind the front. Guidance is
bullish on IFR ceilings, but much of the upstream observations
show MVFR more widespread with isolated IFR. Therefore, the SCT
IFR deck was maintained late tonight through early Tuesday. These
may be better handled with TEMPO groups, if trends show conditions
favoring IFR Tuesday. Surface winds turn out of the north behind
the front with a gradual improvement to VFR late Tuesday morning
into the early afternoon.

Maples

&&

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

$$

WFO LSX