Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

466
FXUS63 KLSX 181924
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
224 PM CDT Sun Oct 18 2026

.KEY MESSAGES...

- A gradual warmup to seasonably warm temperatures with dry
  conditions is expected this week.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 223 PM CDT Sun Oct 18 2026

Recent surface analysis reveals a surface high axis positioned
across the Ohio River Valley, which has been influencing our area
today in the form of a clear sky and light southerly winds. The
combination of these light southerly winds and abundant insolation
have led to a nice warmup today from lows this morning (mid/upper
30s), with temps now approaching the mid 60s for most locations.
This is approximately 10 degrees warmer than yesterday at this time,
thanks to 850mb temperatures that are now near 10C, or about 5C
warmer than yesterday afternoon. The surface high axis remains
mostly stationary tonight, resulting in another night of light and
variable winds for most locations, especially for river valleys/low-
lying sheltered areas. Light winds and a clear sky will once again
lead to efficient radiational cooling allowing temperatures to
quickly fall off after sunset this evening. Lows tonight are
forecast to be generally 2-3 degrees warmer for most locations,
despite very similar synoptic conditions. This is mostly because of
the warmer temps across the area this afternoon, which is a result
of the slight modification (warming) of the airmass aloft since
yesterday. Regardless, low-lying/river valley locations mostly south
of I-70 in MO and IL, should be the coolest with localized
temperatures in the mid 30s by sunrise. As a result, localized areas
of patchy frost are certainly possible tomorrow morning, but are not
expected to be widespread enough for the issuance of another Frost
Advisory. Also similar to last night, these cool temperatures should
combine with warm area waterways to produce steam fog near
ponds/lakes/rivers that will quickly fade after sunrise.

Very little change with respect to the sensible weather is expected
tomorrow as the surface ridge axis remains quasi-stationary leading
to another day with light southerly winds and a mostly sunny sky. In
fact, the HREF indicates that 850mb temperatures also stay near 10-
11C across the region, nearly the same as today. Those temperatures
would result in highs in the upper 60s/lower 70s, assuming full
mixing to that height, which is realistic given forecast soundings.
By Monday evening and into the night, scattered mid/upper level
clouds advect eastward into the area as a weak mid/level wave
traverses the Central Plains. As a result, lows are forecast to be
slightly warmer, in the 40s for most locations/upper 30s for river
valleys, with upper 40s across central/NE MO where cloud cover may
be more prevalent.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 223 PM CDT Sun Oct 18 2026

For most of the work week, the mid/upper-level pattern features
troughing across the Pacific Coast, ridging centered near the
Central Plains, and troughing across New England. The mid-level
ridge that will have influence across our area this week has
been shifted slightly to the west over the last few model runs.
This has resulted in a 1-2 degree lowering of forecast
temperatures this week, as the flow aloft is now expected to be
mostly northwesterly. As mentioned in previous forecast
discussions, the NBM has been near the warmest piece of
guidance, but has trended a bit cooler, likely due to the
westward shift of ridge placement. The LREF indicates that mean
850mb temperatures remain near 10C into Wednesday before
slightly warming to around 12C Thursday and into the weekend.
Assuming full mixing, which appears reasonable considering
abundant sunshine, this would lead to highs in the low/mid 70s
through Wednesday with some locations reaching the upper 70s to
near 80 degrees after Thursday. In addition, LREF temperature
IQRs indicate higher confidence as IQR spreads are only around
3-5 degrees for the entire week. There is a weak signal that
longwave troughing nudges eastward towards the region next
weekend, with a wide range of potential solutions leading to a
low confidence forecast by that timeframe. The general consensus
is that mid-level ridging maintains influence across the area
through most of next weekend, resulting in a continuation of dry
and seasonably warm conditions.

&&

.AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 1207 PM CDT Sun Oct 18 2026

Light southerly surface winds become light and variable for the St.
Louis metro terminals and KJEF after sunset this evening. Similar to
last night, river valley locations are forecast to reach the
mid/upper 30s. This coupled with calm winds should allow steam fog
to form on area waterways again. Confidence in visibility impacts
from river steam fog are highest at KCPS where a TEMPO for MVFR
visibilities has been included from 08-12z Monday morning.
Confidence in impacts from steam fog was currently too low to
include mention at KSUS. However, isolated/brief MVFR visbys are
possible there from 08-12z also, but are expected to be more limited
compared to KCPS. Aside from that, dry and VFR conditions with light
and variable/light southeasterly winds are forecast for all
terminals through the day on Monday.

&&

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

&&

$$

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