Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

617
FXUS63 KLSX 240724
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
224 AM CDT Sun May 24 2026

.KEY MESSAGES...

- While some areas will see lingering light rain through this morning,
  for the most part seasonably warm and dry conditions can be
  expected today and again on the Memorial Day Holiday.

- Multiple rounds of showers and weak thunderstorms are expected
  between Tuesday and Friday, with limited day-to-day confidence
  in the coverage of this activity.

&&

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 219 AM CDT Sun May 24 2026

Early this morning, remnants from deeper convection yesterday
evening continue to very slowly move eastward across the area. This
activity has weakened considerably from yesterday, likely due to the
loss of daytime heating and also mid-level dry air/subsidence.
Still, at least some light rain will continue to push east and most
areas of eastern MO / southwest IL will see at least a few sprinkles
to perhaps a few hundredths of an inch of rain between now and
roughly noon. Immediately behind these showers, some patchy fog has
quickly developed in central Missouri as well, due to the
combination of diminishing cloud cover and residual moisture from
earlier rain. While we don`t expect widespread dense fog, a few
spots may dip to near 1/4 mile visibility before sunrise.

Over the course of the day, a weak cold front will slowly push
southeastward and settle across our southeastern periphery, pushing
the higher moisture content largely outside of our area. However, we
may still see a stray redeveloping shower or two along the boundary
in southeast MO / southwest IL later this afternoon, with some CAMS
(notably the HRRR) producing a smattering of showers as far north as
I-44. In any case, even if this were to materialize we expect that
coverage would be very isolated, and most areas are more likely to
remain dry. Otherwise, expect a relatively comfortable and dry day
with highs very near seasonal averages (upper 70s to low 80s).

Thanks to a persistent surface ridge of high pressure draped across
the area, very similar conditions can be expected tomorrow, leading
to a seasonably warm and mostly dry Memorial Day holiday. Once again
we will need to keep an eye out for a redeveloping shower or two
along our southeastern periphery, as the stalled front will remain
in this area through tomorrow. However, latest model projections
have consistently pushed this activity further and further
southeast, and the vast majority of our area is expected to remain
dry.

BRC

&&

.LONG TERM...  (Monday Night through Saturday)
Issued at 219 AM CDT Sun May 24 2026

A rather abrupt pattern shift Tuesday will see the rapid development
of an amplified upper ridge across the U.S. and Canadian Plains,
resembling an Omega Block pattern. However, at the base of this
ridge a weak trough is expected to slowly emerge from the southwest,
drawing deep Gulf moisture northward and into our area from Tuesday
through the end of the work week. While critical mesoscale
features remain unresolved at this stage, confidence continues to
grow that the first of several waves of showers will move
northward into our area sometime during the afternoon Tuesday as
rich PWAT air arrives from the Gulf. Ensemble guidance has been
quite consistent in producing PWAT values approaching the 95th
percentile of climatology during this period, along with moderate
instability (500-1000 J/kg of SBCAPE). While this is expected to
generate scattered to numerous diurnally driven showers and
thunderstorms Tuesday afternoon, weak wind shear is expected to
significantly limit the potential for strong or severe storms,
even in the presence of the aforementioned upper trough.

For the next several days thereafter, the upper trough and rich
moisture are expected to remain largely in place, leading to
repeated episodes of afternoon showers and thunderstorms. Confidence
in the details progressively lowers each successive day, as the
coverage and placement of redeveloping activity will likely be
augmented by the previous day`s activity, and may be focused on
lingering outflow boundaries or other features that are not easily
resolvable at this time range. However, confidence is also growing
that late in the work week a trough will begin to slowly dig into
the eastern CONUS, gradually driving a backdoor cold front into our
area, and eventually a a milder, drier airmass behind it. Before the
latter arrives though, this front may act as a local focus for
shower/thunderstorm development, particularly Thursday and Friday,
and may play a big role in the distribution of precipitation across
the area. In any case, it appears that the southern half of Missouri
will be better positioned to see repeated rounds of rain and higher
precipitation totals, as these areas will remain south of this front
for a longer period.

Otherwise, the other item of note is temperatures, which remain
generally on track to remain near or slightly above seasonal
averages through the end of the work week. As has been discussed at
length over the past few weeks, the NBM continues to be affected by
a known warm-bias, and has been manually adjusted downwards during
this period. Over the weekend, a modest cooling trend may be in
store as the cold and post-frontal airmass finally pushes through
the area.

BRC

&&

.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1044 PM CDT Sat May 23 2026

A broad area of light to occasionally moderate rain will drift
east from central and northeast Missouri across the area tonight
into early Sunday morning. The confidence is low in the intensity
and areal coverage of the rain as it continues east tonight,
however VFR flight conditions are expected to prevail, with
pockets of MVFR visibilities possible. Fog/low stratus may develop
in central Missouri behind the rain if the sky clears sufficiently
to promote radiational cooling. Any fog that develops should
dissipate rapidly after sunrise. VFR flight conditions are
expected to prevail after any lingering rain exits the area
through south central Illinois Sunday morning.

Carney

&&

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

$$

WFO LSX