Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

291
FXUS63 KLSX 080922
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
322 AM CST Sun Nov 8 2026

.KEY MESSAGES...

- The potential for light rain continues to increase over parts
  of the area late Wednesday, followed by much cooler air later
  in the week.

- The area will remain free of hazardous weather through at
  least late next week.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 322 AM CST Sun Nov 8 2026

Chilly morning temperatures and river valley steam fog will yield to
sunshine and rising temperatures today. Mild and dry conditions
continue into Monday.

A weak cold front extends south of a low pressure system that is
positioned southwest of the Hudson Bay early this morning. IR
satellite shows predominately high clouds stretching southward
through the Great Lakes, bending westward through Nebraska. There
may be enough cloud cover to inhibit temperatures from falling
much further than latest surface obs (mid-30s) over NE Missouri
and WC Illinois. Despite that the surface high has shifted
southward near the Missouri/Arkansas border, it maintains clear
skies and light winds south of I-70, where temperatures have
already fallen into the upper 20s to low-30s. This is the
southward shift in cooler, sub-freezing air that was advertised
in prior AFDs in recent days.

60s return today through Monday as milder air advects into the
region. The milder airmass actually originates from the central and
northern Plains and advects east-southeast around mid-level
ridging centered over Texas. Initially, the aforementioned
trough acts to stunt the eastward progression of the milder
air, keeping temperatures in the low to mid-60s north of I-70.
Tonight into Monday, 850MB temperatures rise approximately 2-4C
along and west of the Mississippi River. In conjunction with the
surface high to the south, mid-level warming will push
temperatures a little higher to start the work week. Southeast
Missouri and southwest Illinois locations are in better position
to reach the lower 70s Monday afternoon.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 322 AM CST Sun Nov 8 2026

Guidance remains tightly clustered through the early half of the
week with only a slight increase in spread by Wednesday. There is
high confidence in mild conditions through at least Tuesday with
widespread 60s for most areas, and low-70s across SE Missouri and SW
Illinois. Mild conditions continue into Wednesday for much of
the area, though an approaching cold front and arrival of a
surface low will determine how quickly cooler air arrives
through the later half of the day.

A surface low begins to develop over Kansas early Wednesday morning
as an upper level shortwave moves southeast out of the northern
Plains. The surface low tracks eastward through Missouri and
Illinois, eventually deepening as the northern and southern jets
begin to phase over the eastern U.S. around Thursday. This
evolution becomes a key player later in rain potential and cold
air advection. First, however, a more vigorous, amplifying
upper level trough digs southward out of Canada, eventually
consolidating with the shortwave from the northern Plains.
Consequently, this is where guidance begins to diverge with
timing and placement of these features.

Deterministic GFS guidance is notably more bullish late
Wednesday with deep saturation along and east of the Mississippi
River while the ECMWF phases later and strengthens the surface
low slightly further east. The difference between the two is
lighter rain showers in the ECMWF solution with GFS showing
better potential for a light rain, but enough to soak the
surface. That being said, NBM probabilistic data only shows
40-50% probabilities for measurable rainfall across the
southeastern CWA, while many of the wetter GFS ensemble members
land at or below 0.40 of an inch. The lower quartiles across
majority ensembles range from zero to a few hundredths of an
inch across southeastern sections of the CWA. Therefore, while
rain chances have crept up, there remains a considerable amount
of uncertainty in rainfall amounts with higher confidence that
the northwestern sections of the CWA miss out on measurable
rainfall.

By Thursday, much colder air arrives behind the surface low as
it departs to the east. Rainfall potential looks to be low
through the remainder of the period. However, confidence is
increasing that the region remains under the western edge of the
longwave upper trough. The anti-cyclonic side of these systems
can often lead to diurnal clouds that sometimes produce drizzle
or a few sprinkles. This is rarely picked up by lower spatial
and temporal resolution of long range guidance with better
insight as it is captured by medium and short range models. The
general theme will be a trend toward below normal temperatures
with the fall chill extending into next weekend. Some ensemble
members include highs in the 40s over parts of the region
Thursday and Friday. Temperatures eventually moderate at the
tail end of the period, though ensemble spread increases and
provides less confidence on the timing and magnitude of warmth.

&&

.AVIATION /00Z TAFS THROUGH 06Z MONDAY/...
Issued at 1038 PM CST Sat Nov 7 2026

Nighttime microphysics satellite imagery is already showing
steam fog on the mainstem rivers this evening. This fog will
persist through sunrise Sunday morning, with visibilities
likely below 1SM. Patchy and shallow 2-5 mile radiation fog
remains possible in other low lying and sheltered spots through
sunrise as well. Elsewhere and otherwise, VFR flight conditions
are expected to prevail through Sunday.

&&

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

&&

$$

SHORT TERM...Maples
LONG TERM...Maples
AVIATION...Carney