519
FXUS63 KLSX 221926
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
226 PM CDT Thu Oct 22 2026

.KEY MESSAGES...

- Dry and seasonably warm conditions will persist through the
weekend.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 219 PM CDT Thu Oct 22 2026

A slow-moving upper-level ridge will dominate the Mid-Mississippi
River Valley through the weekend with dry conditions continuing and
only slight variations in above average temperatures. With a
gradual exit of the surface high pressure center extending into
the CWA this afternoon, the balance of airmass modification and
subtle southeasterly low-level CAA through Friday followed by
waves of upper-level clouds on Saturday and Sunday combined with weak
southerly WAA will contribute to only slight fluctuations of
high temperatures within the 70s F. Each night, the most
favorable radiational cooling and coolest low temperatures in
the 40s F will also become more and more confined to river
valleys and southeastern MO/southwestern IL, closest to the
high pressure and where clouds will be less prevalent and/or
thinner. Patchy river valley fog is expected again Friday
morning and potentially Saturday morning but coverage should be
less.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Issued at 219 PM CDT Thu Oct 22 2026

Global model guidance diverges considerably early to mid-next week
in the evolution of an upper-level trough that propagates into the
central CONUS Monday into Tuesday as the Omega Block breaks down.
The track, amplitude, and tilt of this trough vary across guidance
including whether an associated cold front passes through the CWA
Tuesday or early Wednesday, enters and then stalls in the CWA, or
stalls before reaching the CWA altogether. Accordingly, the NBM
interquartile range increases to between 7 and 15 F Tuesday onward,
with the 75th percentile remaining steady and the 25th percentile
cooling closer to average. If the front reaches the CWA, showers
will also become possible, with greatest probabilities of measurable
rainfall in global ensemble models across central/northeastern MO
and west-central IL at 30 to 50 percent. However, a widespread,
substantial rainfall appears unlikely in the ranges of current
scenarios. The aforementioned uncertainties persist through the end
of the forecast period, late next week.

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 1211 PM CDT Thu Oct 22 2026

Dry and VFR flight conditions will persist through the TAF period
with the exception of river valley fog again Friday morning. KSUS
and KCPS are most favored for a short period of impacts from fog
around sunrise Friday. Winds will remain light and eventually become
more southeasterly to southerly on Friday.

&&

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

&&

$$

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