400
FXUS63 KLSX 011138
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
538 AM CST Sun Nov 1 2026

.KEY MESSAGES...

- Beneficial rain and a few weak thunderstorms arrive with a
  strong system between late Monday and Wednesday. The threat
  for severe weather or flooding is low (less than 10%).

- Temperatures will cool closer to early November normals
  starting today.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 259 AM CST Sun Nov 1 2026

While not a completely dry Halloween, most locations saw little
to no impactful rain during peak trick-or-treating times before
a shortwave brought more substantial showers to the region.
This broad wave, embedded amidst deep southwest flow aloft in
advance of a more amplified trough out west, will gradually
meander east through the day. This feature will continue to
promote widespread cloud cover and showers through at least
midday today, the latter gradually ending from west to east.
The lower clouds and precipitation will greatly inhibit highs
today, with most locations struggling to warm to 70 degrees.

By about sunset, most of the precipitation will come to an end with
most guidance showing weak subsidence arriving for the overnight
hours. Despite the subsidence, abundant low cloud cover is forecast
to persist overnight with near-surface RH guidance remaining
saturated and a lack of dry air or stronger wind to scour out this
moisture. The lack of low-level lift evident in model soundings,
drizzle or light rain would be very hard to manifest. The only
impact from the cloud cover would be the warmer overnight lows. A
warm front is then forecast to lift north through the region on
Monday as the aforementioned highly-amplified trough advances east
and its surface cyclone deepens. Aside from a low (10-20%) chance
for weak showers Monday afternoon in the warm sector, primarily in
central Missouri, expect a dry start to the work week ahead of this
potent system.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 259 AM CST Sun Nov 1 2026

The timing of the upper-level wave and surface low/cold front
continues to gradually slow down among the available guidance
compared to recent runs, but confidence is increasing that rain
along and ahead of the cold front holds off until after midnight. At
that point, there is some potential for overnight showers as the low-
level jet intensifies across the Mid-Mississippi Valley. A closer
analysis of the ensemble guidance members suggests continued
variance in the trough`s structure, which will impact the track of
the surface low itself. That said, a majority of this guidance now
supports a few closed circulations embedded within the larger
trough: one originating from the polar jet and remaining to our
north and the other forming over the central Plains.

Both of these features and their surface reflections will work in
concert to bring rain along the cold front and gusty 15-30mph winds
through the day on Tuesday. The trough`s forward progress is still
expected to stall through the day, weakening any height falls across
our region. Precipitable water values near climatological maxima
will still be available to the front to promote precipitation along
the front. That said, the warm air aloft evident in model soundings
and meager mixed-layer CAPE (as much as 250 J/kg in the most bullish
guidance) won`t bode well for robust, deep convection. Even in this
worst-case scenario, it would be difficult for strong thunderstorms
to develop. One feature that may assist in large-scale ascent is the
presence of some favorable jet dynamics during the afternoon, but
instability is still quite meager overall. For the reasons outlined
above, we are choosing not to message the SPC Day 3 Marginal (Level
1) Risk for severe weather across southeast Missouri on Tuesday
afternoon. If instability increases and height falls become more
substantial among the guidance, the threat would certainly become
more probable.

Rain will continue in rounds along and ahead of the front through
late Wednesday, but the trough becomes more established across the
central CONUS and stalls. Several impulses will likely propagate
throughout the cyclonic flow aloft, each of which would threaten
additional showers through the rest of the work week. While our rain
chances in the forecast, which is largely based on the NBM, are
fairly low, that is more a function of where the rain falls, not if.
As such, I expect those values to climb a little bit as we approach
the end of the week. Still, we will begin to see more dry time once
the front passes to our east. We`ll also enjoy cooler and slightly-
drier conditions through the duration of the week.

&&

.AVIATION /12Z TAFS THROUGH 18Z MONDAY/...
Issued at 537 AM CST Sun Nov 1 2026

Flight conditions remain largely MVFR across the region, though
there are some intermittent breaks in the lower ceilings. These
conditions will likely not improve through the TAF period, and
in some places IFR conditions are forecast. While the
intermittent improved conditions will probably persist,
prevailing conditions will be at most MVFR through Monday
afternoon.

&&

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

&&

$$

SHORT TERM...MRB
LONG TERM...MRB
AVIATION...MRB