Hidden Valley

000
FXUS63 KLSX 312356
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
656 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 /00Z TAFS THROUGH 06Z MONDAY/...
Issued at 656 PM CDT Sat Oct 31 2026

VFR conditions are expected to remain into the early morning at all 
terminals. As showers move into the area during the early morning 
hours, ceilings will lower to MVFR. Showers will tapper off in the 
early morning causing ceilings to lift slightly but remain MVFR. 
Tomorrow evening ceilings are expected to lower once again, but 
potentially accompanied with light drizzle or fog lowering 
visibility. These impacts will be monitored for future TAF
issuances.

&&

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

&&

$$

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