Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

183
FXUS63 KLSX 051139
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
639 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 12z TAFs through 12z Monday Morning)
Issued at 634 AM CDT Sun Jul 5 2026

Scattered showers and thunderstorms are expected today, mainly
this afternoon along and south of I-70. A few pop-up thunderstorms
are possible this morning, but are not expected to last long. The
strongest storms will be capable of producing gusty winds and IFR
flight conditions in locally heavy rain. Otherwise, VFR flight
conditions and light northerly winds are expected outside of
thunderstorms.

Carney

&&

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

$$

WFO LSX