Area Forecast Discussion

166
FXUS63 KLSX 292048
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
248 PM CST Sat Nov 29 2025

.KEY MESSAGES...

- Parts of the Winter Storm Warning and most of the Winter Weather
  Advisory have been cancelled. Precipitation will end from west
  to east this afternoon into this evening as a cold front passes
  through the area.

- Another system will bring the area snow Monday into Monday
  night. This could produce additional significant snow
  accumulations.

- Temperatures are expected to remain below normal through the end
  of next week.


&&

.SHORT TERM...  (Through Late Sunday Night)
Issued at 241 PM CST Sat Nov 29 2025

Precipitation will taper off from west to east through the remainder
of the afternoon into this evening.  Nearly the entire forecast area
is above freezing at 200 PM, and the rain/snow line, which stalled
earlier, looks like it`s moving northward again.  Have therefore
dropped most of the Advisory and a bit  of the warning early, and I
anticipate being able to drop the remainder of the headlines early
as well.  The short wave causing our wintry weather has taken on a
negative tilt, and the surface low is lifting northeast through
Missouri at this time.  This will continue to pull the warm front
north, and continue to increase temperatures this afternoon.   The
latest RAP shows the cold front moving from near Columbia MO at 23Z
to near Salem Illinois by about 04Z.  Cold dry air behind the front
will bring an end to any lingering precipitation.  The dry air should
 help roads dry out as well, particularly with the strong and gusty
winds expected behind the front. However, temperatures are expected
to fall below freezing within 2-4 hours after the front passes, so
any remaining water on roadways will be in danger of freezing.
Expect lows ranging from the mid teens to the low 20s across the
area.  Strong and gusty winds will diminish on Sunday as high
pressure builds into the Midwest.  Highs on Sunday will be around 10
degrees colder on Sunday in the mid 20s to low 30s.  Lows Sunday
night drop into the teens in most locations.

Carney

&&

.LONG TERM...  (Monday through Next Saturday)
Issued at 241 PM CST Sat Nov 29 2025

Attention turns to the next upstream short wave which looks
increasingly likely to bring us another round of snow on Monday and
Monday night. The atmosphere will be cold enough through this event
that all the precipitation will be snow, and snow/liquid ratios are
forecast to be in the 10-15:1 range. Additionally, the ground will
be cold leading into the event due to the cold airmass which builds
in the day before, so everything that falls will accumulate.
There now looks to be an initial wave of warm advection snow forced
by southerly 850mb flow ahead of the wave. However, the surface high
will be over the Ohio Valley, pushing dry air at low levels back
into our area.  This will make it difficult for the snow to reach
the ground, at least initially. The low levels will eventually
moisten up enough for the snow to reach the ground late Monday
morning into the afternoon...generally along and north of the I-70
corridor.  Another round of snow will develop as the short
wave move through Monday evening/overnight forced by mid-level
frontogenesis.  NBM probability of 1 inch or greater from 6 AM
Monday to 6 AM Tuesday is 60+ percent along and north of I-70, and
as high as 80-85 percent in a band across northern Missouri into
central Illinois.  The probability of 2 inches or greater drops to
around 60 percent in this band and only 30-50 percent farther south.
 This may be under done.  Frontogenetical forcing tends to produce
bands of heavier precipitation which can linger over one spot for
long periods of time.  There are early indications in the CAMs that
go out that far, particularly the HiRes-FV3.  The NBM is unlikely to
pick up on f-gen bands that far out.  I would not be surprised to see
snowfall totals in excess of 3 inches in some spots by the time the
snow ends.

The short wave pushes another cold airmass into the Mississippi
Valley into the Gulf.  Temperatures on Tuesday will struggle to
reach the upper 20s to mid 30s again as the high builds across the
region.  Temperatures will be warmer Wednesday on the northwest side
of the high in return flow.  Current indications are that most of
the area will warm above freezing into the the mid 30s in northeast
Missouri and west central Illinois to the mid 40s across the eastern
Ozarks.  Ensemble guidance begins to show divergence in the pattern
beyond Wednesday.  Another short wave moves into the Midwest
Wednesday/Wednesday night which could produce another round of light
precip.  However, there are signs that the high to our southeast
will block moisture return, so the wave may not have much to work
with.  One way or another, the wave ushers another cold high
pressure system into the Mississippi Valley.  It`s unclear how far
south the cold air will push therefore there is a great deal of
uncertainty in the temperature forecast. LREF temperature IQRs
increase from only 3-4 degrees on Wednesday to as much as 8-12
degrees on Thursday through Saturday.

Carney

&&

.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1138 AM CST Sat Nov 29 2025

Precipitation will continue across the area this afternoon, with
snow changing to rain from south to north through 21-00Z. Snow may
mix with sleet at times as the transition zone moves north. Flight
conditions will largely remain IFR in the snow, and will improve
to MVFR once precip transitions to rain. A cold front will move
through the area this evening which will bring any lingering
precipitation end. Gusty south-southeast winds this afternoon will
turn to the west-northwest behind the cold front and remain strong
and gusty into Sunday morning.

Carney

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Winter Storm Warning until midnight CST tonight for Knox MO-
     Lewis MO-Marion MO-Pike MO-Ralls MO.

     Winter Weather Advisory until midnight CST tonight for Monroe MO-
     Shelby MO.

IL...Winter Storm Warning until midnight CST tonight for Adams IL-
     Brown IL-Calhoun IL-Greene IL-Jersey IL-Macoupin IL-
     Montgomery IL-Pike IL.

     Winter Weather Advisory until midnight CST tonight for Bond IL-
     Fayette IL.

&&

$$

WFO LSX

NWS LSX Office Area Forecast Discussion