553
FXUS63 KLSX 012351
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
551 PM CST Sun Nov 1 2026

.KEY MESSAGES...

- A strong storm system will bring rain and a few thunderstorms
  to the area Monday night through Wednesday. Flooding and/or
  severe thunderstorms are not expected with this system.

- Cooler temperatures near seasonal normals are expected in the
  wake of the storm system for Thursday into the weekend.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 236 PM CST Sun Nov 1 2026

An upper level ridge is building across the Midwest this afternoon.
Soundings show a shallow layer of moisture just off the surface
that`s trapped under the subsidence inversion caused by the upper
ridge. Forecast soundings show this layer of moisture will remain in
place through Monday resulting in persistent low clouds and the
occasional sprinkle or patch of drizzle.  The spotty precip will be
the exception though as broad-scale subsidence under the upper ridge
and some weak dry-air advection from a surface ridge to our east
should suppress most precip.  Low temperatures will remain mild in
the mid to upper 50s tonight due to the cloud cover and persistent
southeast flow. Surface winds turn more to the south on Monday ahead
of the next upstream wave which produces stronger warm advection.
This will bump temperatures up into the upper 60s to low 70s in most
locations on Monday afternoon despite the clouds.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Issued at 236 PM CST Sun Nov 1 2026

The primary concern beyond the next 24 hours continues to be a
highly amplified and progressive long wave trough that will move
across the CONUS this week. The 12Z deterministic GFS and ECMWF look
to be in near lock-step with the synoptic pattern this week. The
trough will move across the Rockies tonight and into the Great
Plains on Monday.  The surface reflection of the trough develops
overnight tonight and then tracks into the Upper Midwest by 06-12Z
Tuesday.  The trough then slows and closes off Tuesday, and then
opens back up and continues to the east-northeast across the Great
Lakes into New England by next Sunday.  Models show the cold front
associated with this system entering northwest Missouri Monday night
and continuing slowly to the east to near the Mississippi River by
around 06Z Wednesday.

Models continue to show strong low level moisture convergence ahead
of the front with anomalously high precipitable water values in the
1.5 to 2 inch range.  Would normally be concerned for potential
flooding in this situation with the slow movement of the front and
high p-wats, but antecedent dryness and low flow on most area streams
and rivers largely mitigates the flooding risk.  Additionally,
guidance suggests there will be very little instability for
convection to tap into.  What little there is will probably produce
some thunderstorms, but BUFKIT soundings indicate the storms will be
moving quickly enough that long-durration heavy rain is not likely,
and CAMs that go out that far agree.  While some locations could get
more than one or two rounds of moderate to heavy rain, flooding does
not look likely due to the aforementioned conditions.  Severe
thunderstorms also look unlikely due to the lack of instability
despite deep-layer shear between 45-65kts.  However the threat for
severe storms should be monitored closely as breaks in the overcast
on Tuesday would allow for more heating than is presently forecast
and therefore greater instability.

Rain chances end from west to east on Wednesday as the surface front
clears the area and drier air moves into the Mid Mississippi Valley.
 The airmass behind the front will be drier and noticeably cooler,
but temperatures are forecast to remain near to a degree or two
above normal through the end of the forecast period.  The next
chance for accumulating rainfall is Saturday night into Sunday as
another strong trough moves into the Midwest.  While this system is
still far out in the future, initial indications are that it will
not produce hazardous weather.

&&

.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 540 PM CST Sun Nov 1 2026

Ceilings will lower making IFR conditions more common through the
night and into early Monday morning. Light drizzle or fog impacting
the St. Louis metro terminals can not be ruled out, but confidence
is low of it impacting the terminals. By noon on Monday the winds
are expected to pick up allowing for deeper boundary layer mixing,
which will allow ceilings to lift back to MVFR in the afternoon.
However, it is uncertain how quickly ceilings will lift.

&&

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

&&

$$

SHORT TERM...Carney
LONG TERM...Carney
AVIATION...Asel/Pfahler