Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

565
FXUS63 KLSX 221055
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
555 AM CDT Sat Aug 22 2026

.KEY MESSAGES...

- Temperatures will be near or a few degrees below normal in the
  low to mid 80s this weekend, with relatively low humidity.

- Temperatures warm back up to the mid to upper 80s by midweek
  with slight chances for showers and thunderstorms.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 254 AM CDT Sat Aug 22 2026

The Mid Mississippi Valley remains locked in northwest flow aloft
with an amplified upper level ridge centered near the Four Corners
Region, and a long wave trough digging through the Ohio Valley into
the Southeastern U.S.  A subtle short wave embedded in the northwest
flow aloft is pushing a weak cold front south through Missouri and
Illinois this morning.  A line of thunderstorms is moving south
through central Illinois along or just ahead of the front.  Expect
these storms to continue moving south and out of our forecast area
by 09-10Z.  Temperatures behind the front will be 2 or 3 degrees
cooler today in the mid 80s, and dew point temperatures will be 5+
degrees lower in most locations.  High pressure drops into the
Mississippi Valley behind the front with light winds and a clear sky
overnight tonight.   These excellent radiational cooling conditions
along with the drier air behind the front will allow overnight lows
to drop into the low 60s in most locations by Sunday morning.  The
urban heat island of St. Louis will hang on to a little more warmth,
but temperatures should still drop into the mid 60s which will be
the coolest lows since the beginning of August.  The cool start to
the day will be followed up by a cooler Sunday under the high
pressure with highs in the low to mid 80s.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 254 AM CDT Sat Aug 22 2026

The overall weather pattern persists through next week with a ridge
to the west and a trough to the east and northwest flow aloft over
the Mississippi Valley.  The long wave trough does attenuate
somewhat in the Monday-Tuesday timeframe.  This allows the ridge to
to drift eastward which brings warmer temperatures and higher
humidity back to the region.  This doesn`t look like extreme heat,
just more "normal" late August heat and humidity.  After another
cool start to the day Monday, and highs in the low 80s, temperatures
rise back into the mid and upper 80s through at least Wednesday or
Thursday. Deterministic guidance shows another short wave diving
southwest from south central Canada into the Great Lakes region late
in the week.  This pushes another cold front through the Mid
Mississippi Valley with the potential for some precip and perhaps
cooler temperatures for Friday.  However, the LREF cluster analysis
is showing variance in both the amplitude and speed of the late-week
short wave.  The timing and strength of the cold front along with
the chance for precip that it brings is therefore questionable. Have
left NBM temps and PoPs alone for the end of the week, which keeps
highs in the mid to upper 80s and only sporadic slight chance PoPs.

&&

.AVIATION /06Z TAFS THROUGH 12Z SUNDAY/...
Issued at 552 AM CDT Sat Aug 22 2026

VFR flight conditions are expected to prevail through the
period. There are patches of river valley fog, mainly along the
Missouri river locally reducing the visibility to 1SM or less.
This fog should dissipate rapidly after sunrise. Additionally,
isolated showers and possibly a thunderstorm will move across
southwest and south central Illinois through 12-13Z. While most
of this precipitation won`t be heavy enough to reduce the
visibility, isolated heavier showers will be capable of reducing
the visibility to 2SM or less for a brief period.

&&

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

&&

$$

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