Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

659
FXUS63 KLSX 041117
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
517 AM CST Wed Nov 4 2026

.KEY MESSAGES...

- Breezy westerly winds gusting 15-25mph and intermittent
  patches of light drizzle and passing showers are expected
  today.

- This weekend, low-lying areas have greater than a 50% chance
  for sub-freezing morning lows, though lingering cloud cover
  has the potential to limit just how cool some locations get.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 248 AM CST Wed Nov 4 2026

As of early this morning, around 09z, a vertically stacked mid-
latitude cyclone is lifting northeastward into the Upper
Midwest. There are two surface features that stretch to the
south of this occluded system that are both currently marching
eastward through the area. The first boundary is a pre-frontal
trough associated with the leading edge of the system dry slot
that has worked to push most showers east of the area with the
main swath of showers now across eastern IL. The second
boundary, a cold front, marks the western edge of the dry slot
and is apparent on the most recent surface analysis nearing
east-central and northeast MO. Along and behind this boundary,
weak low-level CAA is leading to higher relative moisture
content from the surface-850mb, which has resulted in areas of
drizzle/mist upstream across western/central MO. As this post-
frontal airmass filters into the region today, intermittent
pockets of drizzle/mist are expected. Forecast model soundings
for today reveal 0-1km lapse rates may be steep enough to get
weak and shallow instability, favoring the potential for some
quick hitting cumuliform type showers. In general, these pockets
of mist and drizzle/showers are expected to be fairly isolated,
but will be enough to make roadways wet where they move across.
In addition, westerly surface winds around 15-25 mph combined
with abundant cloud cover and temperatures mostly in the 50s
will make for a chilly day across the region.

A gradual clearing trend from south to north is forecast to happen
later this evening and into tonight. The reason for this being the
vertically stacked cyclone lifts a bit further to the north and so
does the best low-level moisture/synoptic lift. However, by Thursday
morning the northward progression of the retreating cloud cover may
come to a halt and move back south, as remnant lobes of mid-level
vorticity swing southward into the area. As a result, confidence in
clearing tonight is highest across southern MO/IL and decreases with
northward extent. Clearing trends will play a key role in
determining just how cool certain locations get tonight. Currently,
the best setup for radiational cooling looks to be across southern
MO/IL where light winds (<5kts) are expected along with a mostly
clear sky for a majority of the night. This is where valley
locations, particularly in the Ozarks in southeast MO, are expected
to fall into the 30s. Some of the more sheltered low-lying locations
that favor cold air drainage may approach the freezing mark by
Thursday morning. Across the rest of the area, morning lows are
forecast to reach the upper 30s with mid 40s favored where cloud
cover is more prevalent.

By Thursday, another mid-level shortwave moves into the Great
Plains, phasing with the current longwave trough that will still be
lingering across the Upper Midwest. A combination of a weak feature
aloft and limited moisture in the column results in a low chance 20%
chance for light showers across the area Thursday evening into the
night. The LREF indicates <10% chance of >0.1" of 24hr accumulated
precipitation, highlighting the light nature that is expected with
any associated showers. The most notable change will be increasing
cloud cover from the northwest Thursday afternoon into the night as
this feature traverses the region.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 248 AM CST Wed Nov 4 2026

More abundant cloud cover associated with this mid-level feature
Thursday night will lead to warmer lows than tonight with low/mid
40s expected across the area. As the shortwave aloft traverses to
the east, another surface cold front slides south across the region
Friday morning. Better low-level CAA will accompany this post-
frontal airmass, resulting in temperatures that are closer to
seasonable normals (highs in the 50s to near 60), or about 5-10
degrees cooler than highs on Thursday. Behind this front, a surface
high moves into the region from Canada, reinforcing northerly flow
across the region into the weekend. With lower humidity in place and
a nearby surface high leading to calmer winds at night, radiational
cooling will play an important role in how cool locations get this
weekend. Cloud cover is always a challenge to forecast, especially
3+ days in the future, leading to some variance in forecast lows.
Regardless, probabilities for lows <32F creep back into the area
beginning Friday night and stay around through early next week.
Currently, there is a good portion of the area that has >50% chance
for lows <32F sometime during this timeframe. The main takeaway is
locations that see sufficient clearing any nights this weekend will
fall into the 30s, potentially below the freezing mark. Like usual,
low-lying sheltered locations would be the favored cold spots having
the best chance of falling below freezing under mostly clear and
calm conditions.

By early next week, a signal for slight warming returns as mid-level
ridging works into the region. As a result, long range guidance
indicates 850m temperatures warm back into double digit territory
(near 10C) Monday into Tuesday. That would lead to highs back into
the mid 60s/low 70s given complete atmospheric mixing, which would
be seasonably warm once again. Recent LREF IQR spreads are <10
degrees early next week, indicating fairly good agreement among
guidance. Analysis of the 25th percentile for high temperatures also
highlights the potential for a warming trend with values that are
slightly above seasonal averages.

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 459 AM CST Wed Nov 4 2026

Widespread MVFR CIGs and areas of drizzle are resulting in
degraded flight conditions across the region, all forced by
strong cyclonic mid-level flow. Expect little improvement
through the day due, but gradually from west to east CIGs
should lift to VFR late this evening into tonight. The drizzle
will be intermittent, and may form into some showers given weak
instability evident, which would reduce visibility locally. The
TAFs currently don`t reflect this due to the low confidence in
when and where this drizzle/rain will exist, but expect brief
degradations today.

While VFR conditions resume tonight across much of the region, a
reinforcing shortwave in the cyclonic flow has potential to
bring another round of lower CIGs (and perhaps light rain) late
tonight into Thursday morning.

&&

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

&&

$$

SHORT TERM...Peine
LONG TERM...Peine
AVIATION...MRB