Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

208
FXUS63 KLSX 071947
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
247 PM CDT Fri Aug 7 2026

.KEY MESSAGES...

- There is a chance for showers and thunderstorms this afternoon
  and evening across parts of southeast Missouri, as well as
  northeast Missouri into west central Illinois. A few strong
  storms capable of gusty winds, some hail, and locally heavy
  rain are possible.

- The weather will turn hot and humid again this weekend, with
  heat index readings in the 100-108 degree range by Sunday. The
  heat is expected to continue into the middle of next week.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 238 PM CDT Fri Aug 7 2026

An MCV is moving slowly east-southeast from Kansas into Missouri
this afternoon.  Most deterministic guidance including CAMs
redevelop convection ahead and in the vicinity of the MCV this
afternoon.  Convection continues at least through early evening
across parts of southern Missouri energy from daytime heating
persists.  CAPE values reach 2000+ J/Kg before sunset this evening,
but 0-6km bulk shear is less than 30kts east of the MCV.  This isn`t
particularly favorable for severe thunderstorms, however MCVs can be
unpredictable so a few marginally severe storms/clusters aren`t
out of the question. Additionally, a cold front will move from
northwest Iowa into northern Missouri and west central Illinois
late tonight. Could see thunderstorms race ahead of the front
into northern parts of the forecast area, or isolated
thunderstorms persisting or redeveloping along the front
overnight.

The front stalls early Saturday morning and then lifts back to the
north late Saturday into Saturday night.  Temperatures Saturday look
similar to today`s, however models are hinting that surface moisture
will pool along the front during the afternoon which will push heat
index values up to around 100 degrees along and south of I-70.
There`s another shot at convection in northeast Missouri and west
central Illinois Saturday night as the front moves north, however
most guidance remains dry at this time.

The front should be well to our north by Sunday, and the eastern
edge of the upper level ridge over the western CONUS slides into the
lower Missouri/Mid Mississippi Valley by Sunday afternoon.  This
looks like the first of at least three widespread 90-95 degree days
ahead.  Southerly flow will feed low level moisture into the region
to produce dew point temperatures in the mid 70s Sunday afternoon.
This pushes heat index readings up to 105-109, mostly in central and
east central Missouri (including the STL Metro Area) as well as
southwest Illinois.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 238 PM CDT Fri Aug 7 2026

Next week continues to look warm and humid with limited chances for
precipitation...at least through Thursday.  Medium range guidance
shows the relatively stagnant upper pattern persisting through the
week.  Long wave ridging over the western 1/2 of the CONUS and a
long wave trough over the east will keep the Mid Mississippi Valley
in weak west to northwest flow aloft through the end of the week.
The upper level ridge tries to build east into the Mid Mississippi
Valley briefly on Monday and Tuesday, and as a result these will
likely be the two warmest days of the week with highs in the low to
mid 90s.  Persistent low level southwest flow will keep dew point
temperatures high as well; consequently heat index values are
forecast to rise to 100-108 across most of the area.  There is some
uncertainty in the temperature forecast Monday and Tuesday as weak
short waves dip through the Midwest causing afternoon convection.
Latest deterministic guidance shows these convective complexes
missing our area to the north both days, but a small shift in the
track of the waves could produce convection farther south and lower
afternoon temperatures.  The LREF acknowledges this possibility, and
the IQR for max temps Monday and Tuesday is 5-8 degrees,
particularly across northeast Missouri and west central Illinois
which will be closer to wave track.  The short waves sharpen up the
long wave trough over the eastern U.S. by mid-late week.  The
deepening trough allows a cool surface high to build over the Great
Lakes which pushes a back-door cold front southwest into the Mid
Mississippi Valley.  Models vary on where the front will end up
later in the week, but the consensus is that the heat will break
Wednesday/Thursday as the front moves into the vicinity with
increasing chances for convection.

&&

.AVIATION /18Z TAFS THROUGH 00Z SUNDAY/...
Issued at 1229 PM CDT Fri Aug 7 2026

VFR flight conditions are expected to prevail through the
period. Scattered thunderstorms may redevelop farther to the
northwest than current activity this afternoon as a compact low
moves across southern Missouri. Some storms could produce
40-50kt wind gusts and hail up to 1 inch in diameter this
afternoon and evening. A few thunderstorms are also possible
across northern Missouri into west central Illinois after 05Z as
a weak cold front drifts into the area. If storms do develop,
they are not expected to be particularly strong or widespread
overnight.

&&

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

&&

$$

SHORT TERM...Carney
LONG TERM...Carney
AVIATION...Carney