Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

649
FXUS63 KLSX 020005
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
705 PM CDT Sat Aug 1 2026

.KEY MESSAGES...

- Drizzle and intermittent showers continue through late this
  evening with gradual drying through Sunday. Rain chances
  return late Wednesday into Thursday.

- Temperatures gradually warm through the upcoming week, though
  Sunday`s temperatures remain well below normal.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 212 PM CDT Sat Aug 1 2026

A fall-like upper level system continues to slowly rotate through
the central U.S., accompanied by clouds, drizzle, and intermittent
showers. Showers become less numerous this evening, though isolated
showers and drizzle linger into early Sunday before diminishing
completely.

An anomalous, stacked 500mb low (~575dam) is nicely depicted in
regional satellite loops as it rotates over the Mid-Mississippi
Valley this afternoon. These heights rank in the 1st percentile of
upper level climo data with northerly flow and ample cloud cover
holding afternoon temperatures in the upper 60s to mid-70s. 2D
planes show small lobes of mid-level vorticity wrapping around the
parent upper low through 00z before gradually pulling to the
southeast through Sunday morning. RAP model soundings indicate
saturation extending from just off the surface through roughly 10k
feet directly under the system. Drizzle will remain possible through
late this evening with occasional showers through diurnal peak.
Thunder looks unlikely (15% or less) with CAPE values several
hundred J/kg lower than depicted in yesterday`s guidance. While the
system continues to move southeast, its progression slows a bit as
it remains cutoff from the main flow and briefly pivots over the
Ohio/Tennessee Valley. Low low chance (<50%) probabilities linger over
the far eastern sections of the CWA (east of I-55) through Sunday
afternoon. However, most locations see more dry time as an inverted
surface ridge builds into the region from north to south Sunday into
Monday.

Temperature profiles do not change significantly through early next
week, though increasing sunshine and better mixing will help boost
temperatures several degrees Sunday with a more subtle increase
Monday. Temperatures remain cooler than normal with highs in the 80s
and low in the 60s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Issued at 212 PM CDT Sat Aug 1 2026

The upper level pattern becomes less amplified through the
course of the week as the western ridge breaks down and the
departing system ejects northeastward into the eastern Canadian
Provinces. The axis to the western ridge attempts to shift east
into the Mississippi Valley but de-amplifies as it does so. The
end result is a subtle day-to-day warming trend with no strong
temperature advection to account for through at least Thursday.

By midweek, upper ridging attempts to reestablish itself over
the east coast with southerly return flow drawing warm, moist
air back into the central U.S. Meanwhile, a surface low over
Canada occludes near the Hudson Bay at the eastern edge of an
upper level, longwave trough. This system sends a cold front
southward into the central U.S. Wednesday into Thursday. Ahead
of the front, a narrow envelop of dry air remains around the
inverted surface ridge, but gradually gives way to increasing
moisture. Global guidance is in decent agreement with the
overall synoptic pattern, but differs in placement and timing of
small scale features.

There is some semblance of a surface system over the central
Plains that rides along the front Wednesday night into Thursday.
This, along with subtle timing/placement differences in the
front will impact precipitation chances, but the general trend
will be toward showers and thunderstorms as the front
approaches, and especially if the disturbance over the central
U.S. becomes any better organized. LREF IQR spreads are greatest
along the front, which is positioned over Iowa Wednesday night.
By Thursday, these spreads narrow quite rapidly along with the
reduction in overall precipitation amounts. These trends may be
a telling sign of a stalling front as upper and lower IQR
6-hourly precipitation data falls below 0.05. This seems
plausible with the build of the eastern ridge (southerly push
over the Midwest) and the front`s increasing departure from
it`s origin (Canadian low). That being said, should the front
drop farther south and stall, it may become a focusing mechanism
for additional disturbances. Considering that PWATs near 2
inches showers and thunderstorms could be efficient rain-
producers should support materialize. This will be something to
monitor to fine tune the placement of heavy rain potential
through late week into next weekend.

Daily highs stair-steup upward through the 80s this week with
90s possible by Friday into next weekend. Low temperatures in
60s give way to warmth and lows in 70s expand across the region
between Wednesday and Friday nights.

&&

.AVIATION /00Z TAFS THROUGH 06Z MONDAY/...
Issued at 703 PM CDT Sat Aug 1 2026

A fall-like system will continue to slowly rotate through the
Midwest this evening through Sunday. As a result, MVFR cigs will
continue with intermittent IFR cigs and DZ through this evening and
into Sunday morning. Then on Sunday morning the central MO terminals
will clear to VFR conditions, while the St. Louis metro terminals
will remain in MVFR conditions until the afternoon as the system
moves out of the region. At the same time, winds and gusts will
decrease through the overnight hours and into Sunday. VFR conditions
will return to all terminals by Sunday afternoon.

&&

.CLIMATE...
Issued at 221 PM CDT Fri Jul 31 2026

Unseasonably cool temperatures are expected today. High
temperatures will be near the record coolest high temperature
for August 1st. Below are the record min max values for each
climate site:

SiteRecord (Year)Forecast

St. Louis   73 (1985)76
Columbia 71 (1985)73
Quincy73 (1973)74


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

&&

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

&&

$$

SHORT TERM...Maples
LONG TERM...Maples
AVIATION...Asel/MRB
CLIMATE...Kimble