449
FXUS63 KLSX 021909
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
209 PM CDT Fri Oct 2 2026

.KEY MESSAGES...

- Dry and generally warming conditions will continue through at least
  late next week.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 208 PM CDT Fri Oct 2 2026

Rain has completely exited the forecast region and only low stratus
remains in its wake. This, too, is forecast to pass early tonight
and the weather will be fairly uneventful thereafter. Of most
importance between now and Saturday night will be the potential for
fog each night. By 12z tomorrow, surface high pressure will be
centered over Michigan`s Lower Peninsula. The Mid-Mississippi Valley
will be in its southwest quadrant, a climatologically favorable
location for radiation fog development. We`ll also have plenty of
ground moisture leftover from the rain and mostly clear skies in
place. If these variables were in a vacuum, fog would be a certainty
tonight...but they`re not. Dry air advection would make fog
persistence difficult, as it would dissipate with vertical extent.
High resolution models also almost universally show a 60-100% chance
of wind speeds >5 kts, which is too high to support fog. Despite
this, in low-lying and sheltered areas-where winds will be generally
lighter-there is reason to believe shallow, patchy fog will develop
tonight. Tomorrow night winds will slacken to near calm. However,
mid-level cloud cover is forecast to build into the area from the
southwest, and dry air will be coming in from the northwest. These
factors aren`t favorable for fog sustenance, but it`s possible
patchy fog is able to develop where the least overlap between clouds
and dry air occurs.

Otherwise, we`ll experience a brief warming trend this weekend with
temperatures reaching near 80 degrees for highs on Sunday. Each
night, lows are forecast to dip into the 40s and 50s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 208 PM CDT Fri Oct 2 2026

A dry cold front is expected to pass on Sunday. Its passage will
only serve to briefly stunt the warming trend on Monday, keeping
highs in the upper 60s to mid-70s as opposed to the 80s we`d likely
see without its influence. Temperatures will rebound quickly, though
due to the increasing influence of mid-level ridging and daily
insolation. Confidence is high that we`ll see widespread highs in
the 80s again by Wednesday. LREF probabilities of >79 degrees at 1pm
Wednesday are 50-70% south of I-70, and this isn`t even capturing
peak heating. The same NBM probabilities at 4pm call for a 50-90%
chance south of US 36/I-72, and its IQR spread through Wednesday is
only 3-5 degrees. This new regime will keep the forecast dry through
the period as well. Ensemble guidance between now and late next week
show peak PoPs of 20%, and those are from the most excited models.
Overall, expect dry and warming conditions until further notice.

&&

.AVIATION /18Z TAFS THROUGH 00Z SUNDAY/...
Issued at 1231 PM CDT Fri Oct 2 2026

Dry and VFR conditions will persist through the TAF period.
Shallow fog is possible in low-lying and sheltered areas
tonight, but elsewhere, easterly winds around 5+ kts will keep
it at bay. The easterlies should also keep any steam fog away
from KJEF, KSUS, and KCPS if it were to develop.

&&

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

&&

$$

SHORT TERM...Jaja
LONG TERM...Jaja
AVIATION...Jaja