Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

846
FXUS63 KLSX 180007
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
707 PM CDT Sat Oct 17 2026

.KEY MESSAGES...

- A Frost Advisory is in effect tonight across portions of
  southern Missouri and southern Illinois.

- A gradual warmup with dry conditions is expected into the
  work week.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 144 PM CDT Sat Oct 17 2026

As of early this afternoon, a broad surface ridge axis stretches
from Lake Michigan southwestward through the region, which has aided
in the continuation of calm/variable winds and a clear sky today.
This surface ridge axis will slide southeastward into the evening,
becoming centered over the southeastern half of the area tonight. As
a result, the coolest temperatures by tomorrow morning (mid 30s) are
forecast along and to the south of I-44 in MO and I-70 in IL, where
a Frost Advisory remains in effect until 9am Sunday. Some river
valley/low-lying locations across the area mentioned above will be
the coldest with some localized areas that may approach the freezing
mark. The remainder of the area should cool off into the upper 30s
to lower 40s tonight. These seasonably cool temperatures combined
with the warm water temperatures that remain in area lakes/rivers
may result in areas of steam fog that could be locally dense early
in the morning before fading shortly after sunrise.

A quicker warmup will be in store on Sunday compared to what was
realized today, as 850mb temperatures will be about 10C warmer by
Sunday morning than this morning. The warmer low-level temperatures,
coupled with light southerly flow and abundant sunshine, should
result in highs that reach the mid 60s to lower 70s by tomorrow
afternoon. The surface ridge axis should remain near the
southeastern half of the area Sunday night, which may allow for
another night of efficient radiational cooling, resulting in lows
that could reach the mid 30s for some leading to patchy frost.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 144 PM CDT Sat Oct 17 2026

For nearly the entire week, the prevailing large-scale pattern will
feature mid-level troughing across the Pacific Coast with ridging
centered from the Central Plains to the Middle Mississippi Valley. A
gradual warmup is forecast through the week as LREF 850mb
temperatures slowly climb from near 10C at the beginning of the week
into the low teens (10-14C) by mid-late week. The NBM continues to
be on the warmer end of guidance but has come down a few degrees on
the latest run. Now it is more closely aligned with other members
and more representable of the low-level airmass (850mb temperatures)
that the LREF indicates. As a result, the latest LREF temperature
IQRs reveal near normal temperatures are expected into Tuesday with
above normal temperatures forecast to make a comeback by Thursday
lasting into next Saturday. Mid-level ridging remains nearly
stationary across the area this week, resulting in high confidence
that dry conditions prevail into next Saturday.

&&

.AVIATION /00Z TAFS THROUGH 06Z MONDAY/...
Issued at 706 PM CDT Sat Oct 17 2026

High pressure continues to bring calm conditions and a clear
sky. Expect VFR conditions to continue tonight and Sunday with
winds eventually turning light out of the south.

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Frost Advisory from 1 AM to 9 AM CDT Sunday for MOZ062-065-
     072>075-084-085-099.
IL...Frost Advisory from 1 AM to 9 AM CDT Sunday for ILZ060-064-065-
     069-070-074-079-100>102.

&&

$$

SHORT TERM...Peine
LONG TERM...Peine
AVIATION...Kimble