939
FXUS63 KLSX 241900
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
200 PM CDT Sat Oct 24 2026

.KEY MESSAGES...

- Seasonably warm and predominantly dry conditions will persist
  through next week.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 159 PM CDT Sat Oct 24 2026

An upper-level ridge will remain over the Mid-Mississippi River
Valley, locked in place by an Omega Block spanning much of the
CONUS. With very little change at the surface and low levels
including a lack of substantial advection, temperatures will remain
steady in the 70s to near 80 for highs and in the mid-40 to low-50s
F for lows. The only thing of note otherwise is increasing, thicker
upper-level clouds overspreading the region Sunday and Monday.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Issued at 159 PM CDT Sat Oct 24 2026

Global model guidance is coming into a better agreement that the
Omega Block will only ebb and flow in strength next week, keeping
the Mid-Mississippi River Valley in southwesterly to broadly
anticyclonic flow near the ridge as it shifts slightly eastward. The
main impact of multiple upper-level troughs rounding the ridge will
be waves of upper/mid-level clouds, but ensemble model probabilities
of measurable rainfall are 20 to 40 percent in northeastern/central
MO and west-central IL late Tuesday onward where forcing/moisture
and wavering front clipping the area could be sufficient for a few
brief periods of light showers. However, the consensus is that
predominantly dry conditions and continued seasonably warm
temperatures will persist through at least Friday with the NBM
interquartile range of temperatures contracting at the expense of a
warming trend in the 25th percentile.

The big question is:  when does the Omega Block break down? There
are some signals that at least increasing moisture return and
continued passages of upper-level troughs in the southwesterly flow
will be enough for increasing probabilities of measurable rainfall
next weekend of 60 to 80+ percent. However, confidence is much lower
that the pattern undergoes a significant change, with the breakdown
of the Omega Block being delayed further and further into the future
with successive model iterations.

&&

.AVIATION /12Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1156 AM CDT Sat Oct 24 2026

Dry and VFR flight conditions will persist along with light, mainly
southeasterly winds. Patchy river valley fog is possible again
Sunday morning, but confidence is low in any TAF sites being
impacted.

&&

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

&&

$$

SHORT TERM...Pfahler
LONG TERM...Pfahler
AVIATION...Pfahler