Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

996
FXUS63 KLSX 231116
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
516 AM CST Mon Feb 23 2026

.KEY MESSAGES...

- After one more chilly day today, a drastic warmup will pull
  temperatures up across the region by 15-30 degrees for Tuesday.

- Southwesterly winds up to 25mph will develop Tuesday ahead of a
  cold front, bringing warmer, dry air from the Ozarks and
  resulting in a 60% chance for an areawide elevated fire danger.

- After a quick-moving system brings rain to much of the region
  late Wednesday into Thursday morning, warm, dry weather stays in
  place through the end of the month.

&&

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 245 AM CST Mon Feb 23 2026

The impressive nor`easter ongoing off the the Mid-Atlantic coast
continues to force a stronger pressure gradient as far west as the
Mid-Mississippi Valley, keeping a stout northerly wind ongoing at
this hour for most of us. That said, the system is making
agonizingly-slow progress eastward and a strong (97th-99th
climatological percentile) surface ridge over the northern Plains is
inching closer to the forecast area. This cold airmass will promote
one last chilly day across the region today, with winds thankfully
slackening from west to east through the day to keep wind chills
somewhat in check. That said, there will still be enough of wind
across Illinois to make being outside a bit uncomfortable today.

Winds become light and variable this evening as the surface ridge
axis arrives in the region, but nearly all guidance quickly advances
the high to our east. Weak southerly return flow looks to be in
place by the early hours Tuesday morning, which will promote one
last night of radiational cooling and cooler lows (albeit a few
degrees warmer than last night). Meanwhile, a shortwave amidst
northwesterly flow aloft will force a clipper in the northern
Plains. While the clipper itself will stay to our north, its cold
front will be drawn southeast into the Mid-Mississippi Valley and
tighten the surface pressure gradient yet again. The resultant
strong southwesterly winds with gusts up to 35mph, evident in nearly
all guidance, will lead to a quick and dramatic warmup across the
region on Tuesday in spite of dense cirrus streaming north limiting
insolation. The warmest temperatures are likely just north of the
Ozark Plateau, where low 60s are currently forecast, but a 15-30
degree jump in highs compared to Monday`s temperatures is expected
areawide.

While there is guidance that quickly builds surface moisture back
into the region amidst the return flow, this seems unrealistic given
past events and local climatology. As a result, a combination of
warm, dry air, gusty winds, and dry vegetation will promote an
elevated fire danger areawide (more details can be found in the Fire
Weather Forecast). Some uncertainty exists regarding exactly how dry
any one location will be with the high clouds stunting deeper
mixing, though the strong winds will likely (60-70% chance)
compensate for the marginal humidity and result in this threat.
Those with plans to burn vegetation or handle flames outdoors should
exercise caution on Tuesday.

MRB

&&

.LONG TERM...  (Tuesday Night through Sunday)
Issued at 245 AM CST Mon Feb 23 2026

The front arrives Tuesday evening, though the heart of the airmass
lags behind the boundary itself. As a result, overnight lows will
still be fairly warm compared to the last few nights. The base of
the post-frontal high will enter the bi-state Wednesday, and while
most will experience a slightly cooler day compared to Tuesday,
there`s some uncertainty in temperatures at any one location owing
to where the ridge axis will be. Right now, a consensus exists in
southeast winds across a good portion of Missouri warming those west
of the Mississippi River into the 50s, while those in Illinois stay
on the slightly cooler side of the high.

Meanwhile, a weak, progressive mid-level shortwave responsible for
our next widespread precipitation chances will drop from the
northern Rockies into the central Plains by late Wednesday evening.
Deterministic guidance and most ensembles continue to develop a weak
surface low and light precipitation associated with this wave,
though there are some timing and amplitude differences evident that
will impact when rain starts and how widespread it will be at first.
The wave is still expected to amplify a bit as it traverses the Mid-
Mississippi Valley, further maturing the surface low and leading to
more widespread precipitation overnight Wednesday into Thursday
morning. NBM probabilities of exceeding 0.50" of rain remain fairly
low (10-20% at the most), which lends credence to this system
threatening nothing more than beneficial rain. I can`t completely
rule out a rain/snow mix across northeast Missouri and west-central
Illinois, where model soundings are a bit more supportive of
dendritic growth, but no accumulations are forecast given the
marginal environment overall. There is also a small chance for
isolated thunderstorms across the Ozarks, where some ensemble
support exists for modest MUCAPE to develop, but any convection that
manages to percolate will be weak amidst relatively-neutral height
tendency aloft.

Confidence is high (70-80%) that temperatures warm back into at
least the 60s behind this system with a southerly flow regime back
in place across the region. Beyond there, significant uncertainty
enters the forecast with longwave troughing likely to take hold of
most of the CONUS this weekend. A potent cold front associated with
the longwave trough drops into the central U.S., though its
southward progress is still a sticking point in the guidance. NBM
IQRs for high temperatures are consistently in the 20-25 degree
range from Sunday onward. Chances for precipitation exist through
early March, but hinging greatly on the front`s position and any
shortwaves in the longerwave trough that affect the region.

MRB

&&

.AVIATION...  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 504 AM CST Mon Feb 23 2026

A stubborn stratus deck is currently impacting the St. Louis metro
terminals with low-end VFR to high-end MVFR conditions and
occasional flurries. Conditions should improve at these terminals
imminently with VFR stratus just upstream, and dry VFR conditions
are forecast through the rest of the TAF period. There is a
threat for low-level wind shear overnight in central Missouri with
a surface high departing and a 50-60kt LLJ overhead. The biggest
question is whether that jet makes it to the central Missouri
terminals before the surface winds intensify, which would mitigate
the LLWS. Mention of this threat was not included in the TAFs,
but this potential will be monitored for central Missouri. Winds
strengthen out of the south/southwest during the late morning
Tuesday, gusting as high as 30kts ahead of a cold front.

MRB

&&

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

$$

WFO LSX