Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

941
FXUS63 KLSX 180826
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
326 AM CDT Sun Oct 18 2026

.KEY MESSAGES...

- Confidence is high in dry weather through this upcoming
  workweek. Hazardous conditions are not anticipated.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 324 AM CDT Sun Oct 18 2026

Water vapor imagery shows broad, low-amplitude ridging building into
the Midwest as a surface high shifts to be centered over the Ohio
Valley. The influence of this high is still enough over the CWA so
that skies are clear and winds are mostly calm, leading to another
round of efficient radiational cooling. In addition to a frost
threat due to temperatures falling into the mid 30s, warm water
temperatures will contribute to steam fog on area waterways through
sunrise.

The placement of the surface high will lead to increasingly
southerly low-level flow through the day, providing subtle warm air
advection. Temperatures as a result will top out in the in the upper
60s to around 70 degrees area-wide this afternoon. With this pattern
holding into tonight, temperatures are expected to be a few degrees
warmer than the last couple of nights, mitigating a frost threat
outside of low-lying areas in the Ozarks.

The upper-level ridge holds in place over the region on Monday, as a
tropical disturbance in the Atlantic pushes the surface high then
located over the eastern CONUS north-northeastward. This will
keep the high`s influence over the CWA similar to that on
Sunday, with low-level temperatures holding steady. Surface
temperatures will therefore warm to or just above Sunday`s
values.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Issued at 324 AM CDT Sun Oct 18 2026

The most notable change to the forecast for this issuance is that
guidance consensus has trended further westward with the placement
of an upper-level ridge relative to the Middle Mississippi Valley.
While at the start of the period on Tuesday the axis will be
roughly along the Mississippi River, it will quickly retrograde
to over the Great Plains by Wednesday. The positioning of this
ridge will place the CWA beneath northwesterly flow and keep the
ridge`s thermal component west of the region. The result is
that while temperatures are still expected to gradually warm,
the degree of warmth has been muted compared to recent previous
forecasts. The NBM (mid to upper 70s) is still a couple of
degrees warmer than the global ensemble members (low to mid
70s), but at least is now more in line with guidance consensus
than as of late.

Late in the period (Saturday), a trough ejects out into the Plains
and pinches the ridge; however, deterministic and ensemble guidance
varies drastically in the phasing of these features. Therefore,
confidence in our local weather is very low Saturday into the
weekend.

&&

.AVIATION /06Z TAFS THROUGH 12Z MONDAY/...
Issued at 1144 PM CDT Sat Oct 17 2026

Calm winds, rapidly cooling air temperatures, and warm waters
are contributing to steam fog along area rivers. The most
favorable conditions for steam fog are at KSUS and KCPS, though
light southerly winds at KJEF may advect what little fog that
develops there over the terminal. There is a low potential that
visibility may drop below what is currently forecast. Any fog
that develops will dissipate shortly after sunrise, with VFR
flight conditions expected after then.

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Frost Advisory until 9 AM CDT this morning for MOZ036-042-
     049>052-059>063-065-072>075-084-085-099.
IL...Frost Advisory until 9 AM CDT this morning for ILZ058>060-064-
     065-069-070-074-079-098>102.

&&

$$

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