179
FXUS63 KLSX 311955
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
255 PM CDT Sat Oct 31 2026

.KEY MESSAGES...
- Intermittent sprinkles/light rain showers are expected this
  evening with temperatures in the 60s.

- Another system will affect the region Monday night through
  Wednesday with intermittent rain and a few thunderstorms.
  Widespread beneficial rainfall is expected with this system.
  Hazardous weather is not expected at this time.

- Temperatures cool gradually through the end of the week,
  though highs are expected to remain near to above normal for
  early November.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 247 PM CDT Sat Oct 31 2026

A negatively tilted short wave moving though the eastern Plains and
lower Mississippi Valley is producing clouds an occasional sprinkles
this afternoon across our forecast area.  The wave will continue to
move northeast through the Mississippi Valley tonight into Sunday
morning, and is forecast to be over the Ohio Valley by Sunday
afternoon/evening.  Low level moisture convergence along and
ahead of the 850mb reflection of the wave will continue to produce
intermittent light rain and sprinkles tonight into Sunday morning,
and then short wave ridging will build across Missouri and Illinois
late in the morning into the afternoon which will bring the rain to
an end.  The remainder of the short-range looks dry as the short
wave ridge drifts east through Sunday night.  Temperatures through
the period remain mild under expansive cloud cover and light east to
southeast flow with lows main in the mid to upper 50s tonight and
Sunday night and highs around 65 to 70 Sunday afternoon.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 247 PM CDT Sat Oct 31 2026

The progressive, high amplitude pattern continues into next week as
another trough moves across the Rockies Sunday night and into the
Great Plains Monday.  Lee-side cyclogenesis forced by the trough
produces a strong low level low over the Great Plains Monday, and
the system moves slowly into the Midwest by Tuesday morning.
Deterministic guidance shows some differences in the speed and
amplitude of the trough as it drifts northeast through midweek, but
those differences do not look to affect the sensible weather at the
surface across Missouri and Illinois too much.  Showers and a few
thunderstorms develop ahead of the cold front associated with this
system on Monday over the eastern Plains and move east along with
the cold front as it drifts through the Midwest.  Current thinking
is that rain will hold off in our area until Monday night, and then
will move slowly east across our area from after 06Z Tuesday through
early Wednesday morning.  While deep-layer shear ahead of the front
is forecast to be in the 45-60kt range, persistent clouds and
showers will put the damper on heating and instability.  While there
will likely be occasional rumbles of thunder Monday night through
Tuesday night the lack of instability should minimize the severe
threat.  Additionally, a persistent blocking surface ridge along the
Gulf Coast will keep the richest Gulf moisture from moving up into
the Mid Mississippi Valley ahead of the cold front.  While P-wats
are relatively high for early November in the 1.5 to 1.8 range ahead
of the front, the lack of instability should also reduce the threat
for heavy rainfall as it does with severe storms.  This period of
rainfall through Tuesday night/early Wednesday should therefore be
beneficial with little if any threat for flooding.

The details in the model guidance diverge further after the front
finally moves through on Wednesday, but the generally unsettled
pattern looks to continue.  Another wave moves across the Plains and
Midwest later in the week, though there may not be much moisture in
the wake of Wednesday`s FROPA for this next system to tap into.  The
short wave does look like it will amplify the long wave pattern
over the eastern 1/2 to 2/3s of the United States for Friday and
Saturday.  This allows cooler air to filter into the CONUS east of
the Rockies bringing highs down from the low and mid 70s during the
first 1/2 of the week to the mid 60s for the latter half.  In fact,
NBM max temps are likely being affected by warm bias-corrected
guidance it incorporates, so highs later in the week may end up
cooler than currently forecast.

&&

.AVIATION /18Z TAFS THROUGH 00Z MONDAY/...
Issued at 1240 PM CDT Sat Oct 31 2026

VFR flight conditions with occasional sprinkles or even a few
areas of light rain will prevail this afternoon into the
evening. Rain is expected to become more persistent and
widespread this evening, and ceilings/visibilities will fall to
MVFR from south to north tonight. Areas of IFR look likely by
early Sunday morning across the eastern Ozarks, and possibly as
far north as the I-70 corridor, however confidence is not high
enough to include IFR in STL Metro or central Missouri TAFs at
this time.

&&

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

&&

$$

SHORT TERM...Carney
LONG TERM...Carney
AVIATION...Carney