Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

524
FXUS63 KLSX 241921
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
221 PM CDT Sun May 24 2026

.KEY MESSAGES...

- Dry weather and seasonable temperatures are expected on Monday
  (Memorial Day).

- Rain chances (up to 80%) increase on Tuesday mainly across southeastern
  Missouri and southwestern Illinois, with daily rain chances
  forecast then through Saturday.


&&

.SHORT TERM...  (Through Late Monday Night)
Issued at 220 PM CDT Sun May 24 2026

The axis of an upper-level trough is pivoting through the Middle
Mississippi Valley this afternoon, with weak northwesterly flow
advecting drier air into the CWA. This has been slowly pushing low-
level clouds and associated showers southeastward out of the area,
allowing for surface heating. Locations that see plenty of sun this
afternoon will see temperatures top out around 80 degrees, while
locations across far southeastern Missouri and southwestern Illinois
will remain mostly in the mid to upper 70s.

The clearing trend will continue into the overnight hours as the
axis of a surface ridge passes through the CWA. This will cause
winds to go mostly calm, combining with the mostly clear skies to
allow for radiational cooling and potential fog development.
Southeastern Missouri and southwestern Illinois have the highest
chance of seeing fog given cooler temperatures through the day and
having had the most recent rainfall; however, high clouds moving
into this portion of the CWA during the early morning hours may
dampen radiational cooling enough to limit fog potential.

Tomorrow, upper-level ridging builds into the central CONUS as part
of a developing Omega Block. This will shift a surface high east of
the CWA, providing southerly flow to the region. Temperatures as a
result will be a few degrees warmer tomorrow afternoon compared to
those today, with this subtle warming trend being subdued over far
southeastern Missouri and southwestern Illinois thanks to persistent
high clouds.

Elmore

&&

.LONG TERM...  (Tuesday through Next Sunday)
Issued at 220 PM CDT Sun May 24 2026

Both deterministic models and ensemble clusters remain consistent on
the evolution of an Omega Block over North America Tuesday-Thursday
and the placement of its associated features. An upper-level ridge
will amplify over the central CONUS Tuesday into Wednesday, with low
to mid-level flow continuing to be weakly southerly. This flow will
support subtle warm air advection, providing a slight boost in
temperatures compared to those expected earlier in the week.
However, deterministic guidance continues to show weak disturbances
undercutting the ridge Tuesday-Thursday, and these disturbances will
impact temperatures through slight drops in low-level temperatures
and cloud cover. Warmer solutions support highs topping out in the
mid-80s, but on days when these disturbances impact portions of the
CWA, highs in the 70s will be realized. These disturbances will also
bring the daily chance of rainfall to portions of the CWA through
Thursday, though the subtlety of the disturbances and spread among
guidance continues to yield low confidence in specific timing and
placement. At the very least, guidance is converging on a solution
for Tuesday that supports rain chances (up to 80%) focused across
southeastern Missouri and southwestern Illinois.

Guidance consensus breaks down notably Friday into next weekend in
the evolution of the Omega Block, with solutions being roughly split
into two camps: one where the eastern trough of the block is
stronger and retrogrades into the Midwest, and the other where the
trough is relatively weaker and remains mostly east of the Midwest.
Both support at least a subtle drop in daily temperatures Friday
through the weekend; though, the difference is by how much. The
solutions supporting a stronger trough (majority) have daily highs
in the low to mid-70s, possibly cooler if cloud cover and rainfall
are more prevalent. Those solutions that have a relatively weaker
trough keep temperatures around to just below climatological
normals. Given the majority favor a stronger trough, this is
reflected in the current forecast.

Elmore

&&

.AVIATION...  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1225 PM CDT Sun May 24 2026

With dry air moving into the region in the wake of a weak cold
front, low-level stratus and cumulus are drifting southeastward
and dissipating, with VFR flight conditions expected the rest of
the day into early tonight at all local terminals. Calm winds and
mostly clear skies are expected overnight, leading to a low chance
for fog at the local terminals. Given the lead time, mention of
this fog and impacts has been reserved for the typical trouble
spots in river vallies (KJEF, KSUS, and KCPS). Any fog that
develops will dissipate later in the morning with the rising sun,
with VFR flight conditions expected afterward.

Elmore

&&

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

$$

WFO LSX