Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

172
FXUS63 KLSX 121739
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
1139 AM CST Thu Nov 12 2026

.KEY MESSAGES...

- Temperatures remain below average through the weekend with the
  coldest temperatures so far this season and widespread hard
  freezes. Temperatures will warm to average next week.

- Aside from isolated showers/drizzle today, dry conditions are
  expected through mid-next week.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 238 AM CST Thu Nov 12 2026

Within deep, cyclonic flow, the next shortwave trough is approaching
the region from the Upper Midwest, per early morning mid-level water
vapor imagery. As this shortwave trough passes today, broad ascent,
lingering moisture, and CAA-steepened lapse rates in the vicinity of
a secondary cold front will support isolated light showers/drizzle
or sprinkles late this morning through afternoon. REFS probabilities
of measurable rainfall are 20 to 30 percent along/east of the
Mississippi River, indicating the highest confidence in
showers/drizzle in those areas. A cooler post-frontal airmass is now
in place this morning with temperatures around 20 F cooler today
than Wednesday with highs only in the 40s and 50s F beneath
widespread stratocumulus, but the aforementioned shortwave trough
and secondary cold front will be accompanied by a stronger,
reinforcing round of CAA arriving late this afternoon continuing
into tonight. As another shortwave trough passes overnight and
northerly to north-northeasterly low-level flow carries moisture
southward from Lake Michigan, some sprinkles and/or flurries
will be possible across south-central/southwestern IL into early
Friday morning as CAA also significantly lowers the wet-bulb 0C
height.

The core of the seasonably cool airmass will reach the CWA on
Friday, accompanied by the coldest temperatures the CWA has seen so
far this season with highs in the 40s and lows in the 20s F
resulting in a hard freezes. This airmass will be locked in place
through Sunday morning by a nearby surface anticyclone. Efficient
radiational cooling is most likely Friday night when a few sheltered
locations reach the upper teens F cannot be ruled out, but upper-
level clouds may increase late Saturday night/Sunday morning west of
the Mississippi River potentially limiting the window of efficient
radiational cooling.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Issued at 238 AM CST Thu Nov 12 2026

On Sunday, cyclonic flow will give way to upper-level shortwave
ridging or a general weakness in flow as longwave troughing across
the Great Lakes and Northeast finally progresses eastward. In this
process, the surface anticyclone will be slow to retreat
northeastward early next week with only a very gradual moderation of
temperatures toward average, mainly from airmass modification versus
advection at least through Tuesday. Global model guidance is in
reasonable agreement that the anticyclone will retreat enough for
low-level southerly WAA to increase after Tuesday with temperatures
warming above average. Otherwise, confidence has further increased
in CWA-wide dry conditions prevailing through this period with
global ensemble model probabilities of measurable rainfall now below
10 percent with the weakening upper-level trough trending further
south of the CWA Sunday into Monday.

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 1139 AM CST Thu Nov 12 2026

A field of low-VFR/MVFR stratocumulus is pivoting cyclonically from
north to south across the region. In general, to the west of the
Mississippi River is where this field is mostly scattered, with more
widespread broken ceilings to the east of the river in Illinois. As
a result, TEMPO groups have been added to KUIN and the STL metro
terminals for these broken MVFR ceilings. Left mention of MVFR
ceilings out at COU/JEF for now since the cloud field is more
scattered across central MO, but will continue to monitor short term
upstream trends and amend as needed. Along with this cloud field are
isolated patches of light showers across central IL. These patches
are expected to stay across IL as they move north to south with
about a 10% chance that any of these briefly impact the STL metro
terminals this afternoon. Strong sustained northwesterly winds with
intermittent gusts to 25kts continue through the afternoon before
weakening to 5-10kts after sunset this evening.

&&

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

&&

$$

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