Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

093
FXUS63 KLSX 050844
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
344 AM CDT Sun Jul 5 2026

.KEY MESSAGES...

- Temperatures will be closer to early July normals today and at
  least into the early work-week.

- There`s a chance for showers and thunderstorms again today,
  mainly during the afternoon across parts of southeast Missouri
  into southern Illinois. Some strong storms capable of gusty
  winds, frequent lightning, and locally heavy rain are possible.

&&

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 343 AM CDT Sun Jul 5 2026

The primary forecast challenge in the short term be timing/location
of showers and thunderstorms over the next 24-36 hours.  An upper
level short wave is digging into the Mid Mississippi Valley this
morning.  The wave will push a weak cold front through the area
today.  Temperatures across the area should be around 3-5 degrees
cooler than yesterday in the mid to upper 80s, and dew point
temperatures should also be a few degrees cooler.  While it will
still feel warm and humid, the heat won`t be as oppressive as it was
last week.

The short wave trough will produce broad-scale lift to
assist in generating convection again this afternoon.  Forecast
soundings are weakly capped with 1500-2500 J/Kg SBCAPE this
afternoon.  Surface triggers may be hard to come by across most of
the area as the front will be over southeast Missouri this
afternoon.  However, think 40-50 PoPs are warranted in the vicinity
of the front with at least 20-30 farther to the north as localized
wind shifts from north to northeast increase surface convergence.
While there isn`t as much instability as yesterday, forecast
soundings are still showing an inverted-V signature, and P-wats are
generally 1.50-1.75, so some gusty winds and locally downpours are
possible. Instability drops slowly after sunset so some convection
will probably linger after sunset.

The trough axis continues sliding south Monday and is forecast to be
draped over southeast Missouri by Monday afternoon.  Guidance is
showing around 1500 J/Kg CAPE building again Monday afternoon with a
weak cap.  Surface triggers will once again be subtle and weak so
any convection that develops will likely be isolated.  Temperatures
Monday should continue in the mid to upper 80s behind the front

Carney

&&

.LONG TERM...  (Monday Night through Saturday)
Issued at 343 AM CDT Sun Jul 5 2026

Deterministic guidance in the medium range continues to show some
differences in how they handle the upper level trough.  The GFS
still develops a closed low Monday night into Tuesday, but keeps it
connected to the mean flow which ushers it across the Lower Ohio
Valley and across the Appalachians to the East Coast by Thursday
afternoon.  The ECMWF cuts the closed low off over far southeast
Missouri Tuesday afternoon and it sits over southeast
Missouri/southern Illinois through 00Z Thursday when it finally
opens up and gets shunted east.  The ECMWF is therefore a wetter
solution for southeast Missouri and southern Illinois thorough
midweek.  The majority of the LREF members (other than the ECMWF)
favor the drier solution on Tuesday, and even the ECMWF members drop
off Wednesday.  Am therefore leaning dry with a mostly clear sky and
slowly increasing temperatures Tuesday and Wednesday.  Rain chances
return again Thursday through Saturday as a series of short waves
move across the Midwest.  Thursday may be the warmest day of the
week with temperatures climbing into the upper 80s to mid 90s just
ahead of the first short wave.  Temperatures moderate back into the
mid to upper 80s Friday and Saturday as a a long wave trough deepens
along and east of the Mississippi and northwest flow aloft becomes
prevalent.

Carney

&&

.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1058 PM CDT Sat Jul 4 2026

Thunderstorms that moved through the region earlier this evening
have been a stabilizing factor for this evening. Aside from a
stray shower, most of the night remains dry with VFR conditions
with light and variable surface winds. A few showers and
thunderstorms are possible around the metro terminal Sunday.
Unlike Saturday, Sunday`s thunderstorms are expected to be less
impactful with respect to intensity, though a brief, localized
heavy downpour will be possible through peak heating (18z-23z or
so).

Outside of weather-related impacts, smoke/haze have affected some
terminals with 4th of July celebrations. Low level smoke could
linger for a couple of hours before scouring out through late
tonight. Localized visibilities may drop to MVFR levels.

Maples

&&

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

$$

WFO LSX