Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

109
FXUS63 KLSX 232304
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
604 PM CDT Wed Sep 23 2026

.KEY MESSAGES...

- Normal to below normal temperatures will remain in place
  through the weekend.

- The next chance for widespread rain arrive next week.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 134 PM CDT Wed Sep 23 2026

There is a weak upper level low/shortwave over the Midwest situated
to the south of a anomalously strong ridge over eastern Canada.
That ridge is reflected in the surface pattern by a 1040 mb high
centered over SE Canada and New England, resulting in persistent,
cool northeasterly flow over the Mid-Mississippi Valley. The NE
flow, coupled with ample low level moisture associated with the
weak upper low mentioned above, has been advecting stratus westward
across the forecast area, keeping temperatures below normal,
especially over our eastern counties. The stratus will continue to
mix somewhat this afternoon, but should be reinforced by continued
moisture advection through tomorrow morning. This will push low
stratus back to west,reaching somewhere near the Mississippi River.
The precise location of those clouds will dictate temperatures
tonight, with mostly clear areas dropping into the low 50s or maybe
even upper 40s in sheltered locations.

The above pattern will slowly drift east over the next few days,
with the upper low giving way to ridging across the central CONUS.
Tomorrow morning`s stratus will again mix out through the day,
perhaps a bit quicker than today given that the upper low will be
further from the area. Should that occur, temperatures tomorrow are
expected to be a few degrees warmer than what we`re experiencing
today. Temperatures should further moderate on Friday beneath the
upper level ridge, pushing back toward normal area-wide.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 134 PM CDT Wed Sep 23 2026

On Friday night and Saturday, a broad shortwave will briefly impinge
on the ridge, driving very modest cyclogenesis over the Northern
Plains. As a result, much of the deterministic guidance depicts a
weak warm front extending to the southeast of the shortwave and into
the Mid-Mississippi Valley. This will support widespread cloud
coverage on Saturday and perhaps some light precipitation closer
to the shortwave. In fact, LREF probabilities of at least 0.01"
of QPF exceed 50% in northeastern MO and west-central IL on
Saturday afternoon. Given the weak forcing, I do not expect any
of this precipitation to be impactful, but it should help pull
temperatures back down a bit.

Ridging will take hold again on Sunday and into Monday ahead of a
sharp shortwave that`s expected to move through the central CONUS
sometime on Tuesday or Wednesday. This will be our next chance for
widespread precipitation across the region, with LREF 24 hour
probabilities of > 0.01" around 100% and > 0.25" over 50%.

&&

.AVIATION /00Z TAFS THROUGH 06Z FRIDAY/...
Issued at 604 PM CDT Wed Sep 23 2026

The primary concern during the 18Z TAF period will be the
potential for lowering ceilings late this evening through
tomorrow morning. While stratus already blankets much of the
area at the start of the period, ceilings are largely still VFR
as of 23Z. However, ceilings are expected to lower later this
evening, likely to at least MVFR levels. There is some potential
to drop to IFR levels at times, but probabilities are too low to
include IFR ceilings in the TAF at this time. MVFR ceilings will
likely persist through mid morning tomorrow and gradually lift
to VFR late in the morning. Confidence in the exact timing of
the lowering/raising of cloud bases is relatively low, but we do
expect several hours of at least MVFR ceilings, mainly at
UIN/STL/SUS/CPS.

&&

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

&&

$$

SHORT TERM...BSH
LONG TERM...BSH
AVIATION...19