Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

431
FXUS63 KLSX 130545
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
1145 PM CST Thu Nov 12 2026

.KEY MESSAGES...

- Seasonably cold conditions last into the weekend with
  widespread hard freezes expected both Friday and Saturday
  night. Temperatures gradually warm to seasonal normals next
  week.

- Aside from a few patches of sprinkles/flurries that are
  possible across southern Illinois tomorrow morning, dry
  conditions are expected through the middle of next week.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 242 PM CST Thu Nov 12 2026

Recent mid-level water vapor imagery reveals broad cyclonic flow
centered across the Great Lakes region placing our region under deep
northerly flow. Within this post-frontal flow regime, low-level CAA
has been stronger than the dry air advection, working to increase
moisture, especially between the 900-700mb layer. In addition to
that, CAA has steepened low-level lapse rates with soundings
indicating small amounts of shallow instability across the region.
Currently, isolated patches of rain showers are moving north to
south, mostly across IL, thanks to the factors mentioned above along
with a shortwave within the mid-level northerly flow providing broad
ascent across the area. In nearly all forecast soundings, the moist
layer is below the DGZ, meaning that super-cooled drops are favored
aloft and dendrites are not likely. However, with surface
temperatures in the 40s and steep lapse rates, wet-bulb zero heights
are only 2-3kft AGL. Some drops that manage to freeze while falling
through the sub-freezing layer aloft, may not fully melt before
reaching the ground. As a result, a few ice pellets are possible in
isolated instances this afternoon, generally limited to the heavier
showers with no impacts due to surface/road temperatures that are
well above freezing.

Later tonight and into early tomorrow morning, a secondary mid-level
shortwave pivots southward across the region, driving another cold
front through the area and leading to more broad scale ascent. This
feature will reinforce low-level CAA and also bring another low
chance for precipitation. Moisture in the low-levels will be less by
then making precipitation more dependent on where the moisture being
drawn off Lake Michigan ends up. As a result, measurable
precipitation is expected to be across eastern IL/IN, with a 10-20%
chance for pockets of sprinkles and flurries across parts of
central/southern IL tomorrow morning. As seasonably cold air
continues to filter in tonight, temperatures are forecast to be in
the upper 20s/low 30s across the region by tomorrow morning. These
temperatures combined with strengthening 10-15mph winds after
sunrise, will lead to wind chills in the 20s, which will be quite a
shock from the 70s we had yesterday afternoon. A rather muted
diurnal curve is forecast tomorrow with continued CAA and
intermittent cloud cover, leading to highs in the 40s across the
area tomorrow.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Issued at 242 PM CST Thu Nov 12 2026

By Friday night, the pressure gradient weakens as an Arctic high
slides into the Midwest, leading to light surface winds and a mostly
clear sky. This synoptic setup, with the surface high just to the
north providing calm/light northerly flow, will allow for efficient
radiational cooling across the entire area. As a result, Saturday
morning will feature the coldest air of the season with a widespread
hard freeze expected as lows reach the 20s across most the area.
Some low-lying sheltered locations may lower into the upper teens in
localized instances. The slow moving surface high will maintain
close influence on the area through the weekend allowing both
Saturday and Sunday night to drop below freezing across most of the
region. Highs will gradually moderate Saturday into Sunday thanks to
a slight airmass modification as 850mb temperatures warm to around
1-2C, allowing temperatures to reach near 50 by Sunday afternoon.

Mid-level ridging slides into the region from the Great Plains by
Tuesday with the surface high sliding east as well, bringing a
return to southerly WAA. This will allow for a gradual warming trend
from Tuesday to next Thursday as LREF mean 850mb temperatures reach
>5C by the middle of next week. Assuming full mixing, that would
correlate to highs in the upper 50s/low 60s in the afternoon. Light
surface winds are forecast each night until Wednesday night, meaning
that if there is a lack of cloud cover, most rural areas have the
potential to fall below freezing each morning despite a gradual
warming of high temperatures.

Mostly dry conditions are forecast to continue through at least the
middle of the week with good model consensus in long-range guidance.
The LREF has <10% chances for measurable precipitation until at
least the middle part of next week. By next Thursday, rain chances
return as guidance suggests the return of western longwave troughing
that would favor moist southerly flow back into the region.

&&

.AVIATION /06Z TAFS THROUGH 12Z SATURDAY/...
Issued at 1136 PM CST Thu Nov 12 2026

VFR flight conditions and northwest flow is expected to prevail
through the period. Some patches of lower ceilings around 3000
feet will move through the area overnight, but it looks like
those MVFR ceilings will be transient and short-lived.

&&

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

&&

$$

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