Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

096
FXUS63 KLSX 111747
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1247 PM CDT Sat Apr 11 2026

.KEY MESSAGES...

- Scattered showers and thunderstorms are possible today as a
  warm front moves northeast across the area. Temperatures will be
  warmer, generally in the mid to upper 70s along and south of
  I-70 in Missouri and I-64 in Illinois. Mid to upper 60s are
  expected farther north.

- Next week`s weather continues to look warm and active with above
  normal temperatures and chances for showers and thunderstorms
  each day. Some storms could be severe next week, however the
  timing and extent of severe storms remains uncertain.


&&

.SHORT TERM... (Through Late Sunday Night)
Issued at 339 AM CDT Sat Apr 11 2026

A warm front will drift northeast into Iowa and west central
Missouri from near the Missouri/Arkansas border today. Most
locations will warm back into the 70s today behind the front,
however some cooler temperatures in the mid to upper 60s will
persist today across northeast Missouri and west central Illinois
where the front will take longest to reach. Short range guidance
is showing some weak to moderate low level moisture convergence
forced by a 20-30kt low level jet overrunning the front today.
Deterministic guidance spits out scattered light QPF in response
to the moisture convergence, and all CAMs produce scattered
convection to a greater or lesser extent. Given the uncertainty in
coverage, 20-40 PoPs spreading from central Missouri this morning
across much of the area this afternoon seem reasonable. GFS and
RAP show that any storms which can develop will have at most
1000-1500 J/Kg CAPE to work with, and only around 30kts of 0-6km
shear. While a strong storm or two can`t be ruled out, severe
storms are unlikely given these parameters. Guidance shows
afternoon convection dissipating quickly in the evening as daytime
heating wanes and instability drops off.

After a dry and mild Saturday night, another round of convection is
likely Sunday afternoon and evening as upper level ridging shifts
east allowing a weak short wave to move from the Plains into the
Midwest.  Still looks like convection will be triggered by the wave
over the Plains and move east into Missouri and Illinois later in
the day.  Mid level lapse rates are unimpressive over our area
leading to meager instability of 1000 J/Kg MUCAPE or less through
the afternoon into the evening.  Convection will likely be
maintained into the evening mostly through low level moisture
convergence on a broad and persistent 40-50kt low level jet.  What
meager instability there is weakens further after 06Z, the short wave
moves into the Ohio Valley leaving ridging over he Mid Mississippi
Valley, which should cause lingering convection to further dissipate
overnight Sunday night.

Carney

&&

.LONG TERM... (Monday through Friday)
Issued at 339 AM CDT Sat Apr 11 2026

Little change in the forecast for next week.  A slow moving long
wave trough over the western U.S. combined with a ridge over the
east will produce deep southwest flow over the Mid Mississippi
Valley.  Persistent southwest flow will keep above normal
temperatures, mainly in the low to mid 80s, locked in over the area.
Additionally, there will be a chance for thunderstorms each day as
weak short waves rotate around the base of the longwave to our west
and eject across the Plains triggering afternoon and evening
convection.  The LREF 500mb EOF patterns continue to indicate
variance in the speed and amplitude of each wave as it moves
northeast from the plains into the Midwest.  This is particularly
true for the main long wave Wednesday into Thursday as it attenuates
and is absorbed into the mean flow moving east into the Mississippi
Valley.  The deterministic GFS and ECMWF produce strong instability
in excess of 2000 J/Kg each afternoon through the end of the week,
however the highest instability stays over eastern Kansas and
western Missouri at least through Tuesday.  Thunderstorms should
therefore be weakening as they move east into our area from where
they develop over the Plains.  The deterministic GFS and ECMWF show
those higher CAPE values spreading into our area Wednesday afternoon
along with 40-50kts 0-6km shear as the aforementioned long wave
moves into the Plains.  With this in mind, Wednesday still looks
like the most likely day for severe thunderstorms in our area.
Thunderstorm chances continue for Thursday and Friday, however the
strongest instability and shear shift back to the west as another
long wave trough digs into the western U.S.

Carney

&&

.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1246 PM CDT Sat Apr 11 2026

Scattered showers continue to slowly drift northeastward across
Missouri with showers approaching central MO now. MVFR ceilings and
visibilities are possible within the heavier showers. Confidence is
highest in impacts at KCOU/KJEF over the next 1-2 hours, so only
added mention (PROB30) at those terminals for now. With the
scattered nature of the showers, will monitor trends in the near
term and amend KUIN/St. Louis metro terminals as needed. Surface
winds will slowly veer more southerly overnight and becoming gusty
tomorrow. Next chance of rain moves in from the west just beyond the
end of this TAF package so mention was left out for now.

Peine/Gosselin

&&

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

$$

WFO LSX