Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

875
FXUS63 KLSX 221115
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
615 AM CDT Thu Oct 22 2026

.KEY MESSAGES...

- Warm and dry weather will extend through this weekend.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 300 AM CDT Thu Oct 22 2026

A mid-level longwave trough is currently swirling off the coast of
Southern California as seen in water vapor imagery. The trough will
make landfall today, and a shortwave on its poleward side will begin
to phase into the northern stream. What does that mean for us? For
now, nothing notable. Ridging in the mid and low levels will still
dominate our sensible weather despite being pushed eastward by the
western trough, and our copy-and-paste regime will continue.
Insolation will again push high temperatures a few degrees warmer
today than yesterday with most locations expected to peak in the
upper 70s this afternoon. Tomorrow, low-level winds will shift to
southeasterly as the ridge slides east, and weak cold air advection
will be introduced to the region. The effects of this will be
stronger with eastern extent. Mid-Missouri will likely experience a
very similar day to today, whereas south-central Illinois is
forecast to be a few degrees cooler. Expect morning lows to fall
into the 40s and low 50s in the interim.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 300 AM CDT Thu Oct 22 2026

A cold front will drape across the Upper Midwest this weekend in
response to the aforementioned northern stream shortwave trough
zipping into south-central Canada. It and all of its associated cold
air and rain are forecast to stay north of the Mid-Mississippi
Valley, so our warm streak will continue through the weekend. High
clouds blowing off from showers to our north and west may stunt
warming Saturday and Sunday afternoons, but highs are still expected
to climb well into the 70s each day.

The mid-level ridge centered over the eastern 2/3rds of the CONUS
will deamplify early next week as a longwave trough over the Desert
Southwest finally pushes into the Plains and weakens into a
shortwave. Its progression is expected to shove the cold front into
the Mid-Mississippi Valley sometime around Tuesday, but the
variability in guidance is too high to pinpoint an exact time. This
stems from differences in the phasing, amplitude, track, and timing
of the shortwave. For instance, the ENS shows a stronger shortwave
that swings more poleward than the other ensembles. As a result, the
front barely clears Chicago, and the majority of our CWA has a 40-
80% chance of reaching 70 degrees by 1pm Tuesday. The GEPS, on the
other hand, shows a very weak and much more southerly shortwave. In
this solution, the front clears St. Louis and the CWA has a 20-50%
chance of reaching 70 degrees by 1pm Tuesday. Then there is the
question of whether the front actually passes and we cool down, or
if it lifts northward as a warm front and the unseasonable warmth
continues further. This is a question that can`t be answered right
now given the reliability of the data, but it is what we`ll be
watching for the next several days.

&&

.AVIATION /12Z TAFS THROUGH 18Z FRIDAY/...
Issued at 614 AM CDT Thu Oct 22 2026

Any lingering fog in the region will dissipate shortly after
sunrise. Dry and VFR conditions with very light winds will
prevail thereafter.

&&

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

&&

$$

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