Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

367
FXUS63 KLSX 121058
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
558 AM CDT Sun Jul 12 2026

.KEY MESSAGES...

- Typical summertime heat and humidity will prevail for the week
  ahead with limited chances for precipitation.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 304 AM CDT Sun Jul 12 2026

Seasonal conditions are expected to take hold the next several
days. Rain chances remain limited with respect to both time and
space, limiting concerns for impacts.

GOES-19 IR satellite imagery shows mostly clear skies extending from
the Great Lakes through the central Plains early this morning thanks
to an elongated surface ridge coinciding with the broad area of
clearing. The active boundary that kept the region busy the last few
days has shifted southward, and now stretches from the southern
Plains through the Tennessee and Ohio Valleys. Dewpoints have fallen
since yesterday (mid-60s/low-70s), though the drop isn`t
significant. Surface observations show dewpoint depressions ranging
from 0-7 degrees with saturation more so confined to lower
elevations and river valleys. Light and variable surface flow,
coupled with recent moisture deposited by heavy rain, could give
rise to patchy fog. Beyond patchy fog, the forecast is relatively
worry-free. Guidance is in good agreement with respect to a
potentially record-setting (LREF 100th percentile/~600dam) upper
level ridge (Rex Block pattern) to our west/northwest and surface
high pressure that holds the active track to the south. The only
potential for precipitation comes as we approach Tuesday afternoon.
Even this is limited to far southeast Missouri with trends shifting
further south in the last couple of days. Model soundings show a
shallow saturated layer centered around 850mb, rapidly drying
above/below this layer. HREF/LREF spreads boost confidence in a
largely dry forecast as the 75th percentile bounds a few hundredths
of an inch of precipitation to around KFAM and south. Aside from a
stray, diurnally-driven shower, trends suggest most locations will
remain uneventful through the end of the short term period.

Temperatures will hover close to normal with highs in the 80s
through Monday. Temperatures slowly climb through midweek, flirting
with 90 degrees in urban areas by Tuesday. Lows range from the mid-
60s to low-70s.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Issued at 304 AM CDT Sun Jul 12 2026

Summer heat is favored to make a gradual return through the course
of the week with limited precipitation potential. The magnitude of
the heat will rely on the orientation and strength of the upper
level ridge, along with available surface moisture.

By Wednesday, the upper level ridge remains in command across the
center of the CONUS. It`s notable that LREF shows some weakening,
and yet the center of the ridge remains near the 100th percentile
with respect to climatological means. While this brings record heat
potential to the northern Plains and Upper Midwest, the northward
departure should initially spare the local area with seasonable
warmth and humidity. The upper level shortwave that supported
showers and thunderstorms in recent days was modeled to temporarily
stagnate over western Tennessee before being pulled back to the west
and northwest in some fashion. Trends have decided otherwise,
however, as the ridge has delayed this potential and pushed it
further south. Wednesday afternoon brings the best chance (30% or
less) for rain south and east of I-44. The greater impact to
sensible conditions is the gradual increase in moisture as the
cutoff system retrogrades toward the west and draws dewpoints back
into the 70s within an areas of weak easterly flow. While the change
isn`t negligible, LREF statistics show similar precipitation
potential as Tuesday with the detailed differences evident among
GFS/ECM ensemble members. A number of the individual members
show precipitation over Southeast Missouri, although a large
number of those member are at or below 0.1". If not for this
potential, much of the week remains dry with heat slowly
building through the end of the period. NBM IQR spreads are
rather small (<5 degrees) through Friday before increasing next
week. At that point, the upper ridge weakens below its record
heights and shifts westward. This places the area in the more
active northwesterly flow with MCS potential, though these
small scale features are less certain at this distance in time.

High temperatures return to the low to mid-90s with lows in the
upper 60s to mid-70s.

&&

.AVIATION /06Z TAFS THROUGH 12Z MONDAY/...
Issued at 553 AM CDT Sun Jul 12 2026

KSUS has been the only site affected by MVFR visibility this
morning. The couple of instances that visibility dipped was
likely attributed to localized, shallow ground fog than what is
more typical with synoptic conditions. These conditions are
expected to improve over the next hour with river valley fog
potential waning beyond 13z. A TEMPO group was included for the
first hour to cover this with other site remaining unrestricted.

Outside of the patchy fog potential this morning, VFR
conditions are expected to persist throughout the TAF period.

&&

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

&&

$$

SHORT TERM...Maples
LONG TERM...Maples
AVIATION...Britt