Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

243
FXUS63 KLSX 141101
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
601 AM CDT Tue Apr 14 2026

.KEY MESSAGES...

- Warm and humid conditions continue through most of this week.
  The best chances for thunderstorms, some potentially severe,
  are tonight and Wednesday.

- A strong cold front brings seasonably cool temperatures for the
  weekend.


&&

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 256 AM CDT Tue Apr 14 2026

The overall weather pattern across the US consists of surface high
pressure near the southeast US coastline with a rich plume of Gulf
moisture (60+ dewpoints) circulating around this high from central
Texas northeast to the Chicago area. The western edge of this
moisture plume is bounded by a dryline, oscillating back and forth
each day with daytime heating and the passage of shortwave troughs
aloft. The northern extent is bounded by a quasi-stationary
front/trough stretching from Nebraska to Michigan. Looking aloft,
upper level ridging is centered over the Gulf with a trough over the
Southwest US moving from around Las Vegas to the Four Corners during
the day today. Between the Gulf ridge and the Southwest US trough
exists a southwesterly jet with embedded shortwave troughs. The rich
low level moisture on the edge of the upper level ridge has led to
an axis of instability within which multiple patches of
thunderstorms will continue to generate over the coming days.
Seasonably strong mid level flow combines with the instability to
produce conditions favorable for supercell thunderstorms and
occasional convective clusters where thunderstorms form.

Zooming in on our forecast area, although instability maximizes this
afternoon with daytime heating (temperatures nearing 90!), the
influence of the ridge aloft is expected to maintain capping through
much of the day, inhibiting convective development. We`ll be in
between disturbances to our northeast and southwest leading to a
local minimum in convective potential. The primary focus for
development will be more toward the periphery of the ridge and along
the surface boundaries: the warm/stationary front to the north and
the dryline to the west. High resolution guidance is in good
agreement that convection will be suppressed locally during the day
today. That said, if we are able to get any local areas of lift
along a local convergence zone or in an area of locally maximized
low level moisture (reducing capping), then a storm or two could
develop. The environment is primed for supercell thunderstorms if
this occurs, with large hail and damaging winds the main threats.
The better chance for thunderstorms locally will be from leftover
storms which formed to our west tracking into our area during the
late evening or overnight hours. While wind shear will still be
sufficient for organized thunderstorms, surface based instability
will be on a downward diurnal trend by the time any such activity
reaches our area, limiting the severe weather potential.

On Wednesday the southwest trough opens up and lifts northeast
through the Plains. This leads to greater mid level lift supporting
more widespread showers and thunderstorms across the instability
axis including through our region. While we continue to see moderate
to strong mid level flow sufficient for storm organization, more
widespread cloud cover is expected to limit the development of
surface based instability to just patches of stronger instability
where cloud cover is less extensive. As a result, our confidence in
the timing and location of the severe weather threat on Wednesday is
lower, though the threat is likely to favor the afternoon hours when
the potential for surface based instability is greatest during the
heat of the day. We may not have greater clarity on these points
until Wednesday morning when the effects of morning clouds and
showers can be a bit better known.

Kimble

&&

.LONG TERM...  (Wednesday Night through Monday)
Issued at 256 AM CDT Tue Apr 14 2026

The passage of the trough Wednesday into Wednesday night will also
shove the front southeastward, pulling in some slightly drier air
and shifting the instability axis southeastward. Showers and storms
may still be ongoing Thursday morning, with the focus for convective
activity shifting toward the Ohio Valley with time. Most of our area
sees gradually clearing skies with continued warm temperatures near
80 degrees.

While ridging briefly builds back in behind Wednesday`s departing
trough, a stronger trough will be moving out of the Pacific
Northwest and into the Plains on Friday. We`ll see moisture return
northward ahead of this approaching trough setting up the potential
for another round of severe thunderstorms. Where that severe weather
threat materializes depends on the speed of the front. At the
moment, timing of the front favors a greater severe thunderstorm
threat to our west as the front moves through our area mostly during
the overnight Friday night into the first half of the day on
Saturday. However, if the front speeds up a bit, this could shift
the threat more into our area. Alternatively, if it slows down a
bit, then another threat could develop during peak heating on
Saturday. At this stage it`s too soon to have much confidence in a
severe weather threat locally given the current expected frontal
timing, but it`s a time period to watch for any changes that could
shift the threat into our area.

The air mass behind this front is MUCH cooler than what we`ve been
dealing with as of late. This air mass has origins in the Arctic
which is still cold this time of year. There remains some
uncertainty in how cold it will be by the time it reaches our area,
but there is strong confidence that we`ll see at least one day of
below normal temperatures. NBM interquartile range for high
temperatures on Sunday is around 10 degrees, with the warmer end of
that range right around normal for mid April while the cooler end is
several degrees below normal. Dewpoints also drop into the 20s
suggesting that if we were to get a clear, calm night that
temperatures could approach levels where a frost or freeze could
develop. At this time, NBM probability of 32 degrees or colder is
only 5 to 15 percent across the region as the likelihood of seeing
the clear, calm conditions necessary to realize this air mass`s full
potential is low. We will begin to warm back up again early next
week as amplified ridging rather quickly replaces this weekend`s
trough.

Kimble

&&

.AVIATION...  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 600 AM CDT Tue Apr 14 2026

Gusty SSW winds are expected area wide today under VFR clouds. The
main questions regard the potential for thunderstorms and the
timing at each terminal. For the most part, the day should be dry,
although there`s an outside chance (less than 20 percent) of
thunderstorms popping up this afternoon. The better chance will be
with storms moving into the region from the southwest during the
overnight hours. This is most likely to affect COU, JEF, and UIN
while the St Louis area`s thunderstorm chances are too low to
mention in the TAF at this time.

Kimble

&&

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

$$

WFO LSX