Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

376
FXUS63 KLSX 171130
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
630 AM CDT Sat Oct 17 2026

.KEY MESSAGES...

- A Frost Advisory is in effect Saturday night across portions
  of southeastern Missouri and southern Illinois where
  confidence is highest in widespread temperatures in the mid
  30s.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 216 AM CDT Sat Oct 17 2026

An expansive area of high pressure has settled into the Great Plains
and is edging into the Middle Mississippi Valley. This has allowed
for our skies to clear and winds to die off, leading to effective
radiational cooling across much of the area. Where skies have been
clearest longest over northeastern Missouri and west-central
Illinois, temperatures have dropped into the 30s. With a few hours
left before sunrise, a drop of another few degrees is expected, with
the ongoing Frost Advisory remaining in good shape.

This high pressure and a building ridge aloft will dictate our
weather today, with skies remaining most clear and conditions calm.
Ample sunshine and rising low to mid-level temperatures will yield
highs in the 60s this afternoon; nearly 5-10 degrees warmer than
what was experienced Friday. Despite the bump in temperatures,
another night of clear skies and calm winds will lead to portions of
the area seeing the threat of frost once again. Across southeastern
Missouri and southern Illinois where these conditions will be
maximized due to proximity to the surface high, temperatures will
drop into the mid 30s to just above freezing. Where confidence in
this happening is highest, another Frost Advisory has been issued
for Saturday night into Sunday morning.

With the axis of the upper-level ridge moving overhead on Sunday as
the surface high moves further east, southerly to southwesterly flow
will deepen over the region and begin weakly advecting warm air into
the CWA. The result is another 5-10 degree bump in temperatures on
Sunday compared to today. There is a low chance (30%) that portions
of the area could be cold enough for frost again Sunday night.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 216 AM CDT Sat Oct 17 2026

Little change is seen among the most recent model initializations
compared to the forecasts over the last 24 hours. With nearly steady
troughing over the western CONUS and upper-level ridging southeast
of the Middle Mississippi Valley, the CWA will be beneath
southwesterly flow. This flow will be weak due to a slack pressure
gradient aloft, with little in the way of warm air advection or
passing disturbances. This translates to a gradual warming trend
with little to no chance for rain through Saturday. While confidence
is high that temperatures will be above normal by mid-week,
confidence in specific values is still low. The NBM and its bias-
corrected components are warmer than a majority of ensemble guidance
at this point, with its solution favoring highs in the low to mid
80s by the end of the week. This is nearly 5-10 degrees above the
75th percentile of ensemble guidance, but is still within the
envelope of reasonable outcomes. Therefore, adjustments will not be
made to the forecast until lead time and ensemble spread decrease
further.

&&

.AVIATION /12Z TAFS THROUGH 18Z SUNDAY/...
Issued at 629 AM CDT Sat Oct 17 2026

Dry and VFR flight conditions are anticipated at each of the
local terminals through the forecast period.

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Frost Advisory until 9 AM CDT this morning for MOZ018-019-026-
     027-034>036-042-052.
     Frost Advisory from 1 AM to 9 AM CDT Sunday for MOZ062-065-
     072>075-084-085-099.
IL...Frost Advisory until 9 AM CDT this morning for ILZ058>060-
     095>099.
     Frost Advisory from 1 AM to 9 AM CDT Sunday for ILZ060-064-065-
     069-070-074-079-100>102.

&&

$$

SHORT TERM...Elmore
LONG TERM...Elmore
AVIATION...Elmore