Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

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FXUS63 KLSX 240946
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
446 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 12z TAFs through 12z Monday Morning)
Issued at 439 AM CDT Sun May 24 2026

While light rain continues to impact UIN/SUS/STL/CPS at the time
of this writing, this is largely expected to move east of these
terminals by 12Z, and the remainder of the period is very likely
(90%) to be dry. Meanwhile, patchy fog may impact COU/JEF for an
hour or two at the start of the period, but will quickly dissipate
after sunrise. VFR conditions are expected the remainder of the
day, with only a very low (10%) chance of a redeveloping afternoon
shower or two near St. Louis area terminals.

Overnight, calm winds and lingering humidity may allow for some
patchy river valley fog redevelopment, and an MVFR mention has
been included at JEF/SUS to account for this.

BRC

&&

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

$$

WFO LSX