Area Forecast Discussion

068
FXUS63 KLSX 140423
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1023 PM CST Sat Dec 13 2025

.UPDATE...
Issued at 241 PM CST Sat Dec 13 2025

Over the last hour, freezing drizzle has been reported across
parts of central Missouri, which is associated with some light
radar returns that have developed along the I-70 corridor. While
there is some snow mixed in, traffic cameras along I-70 also
show that some light ice has collected on the lenses, which
confirms that there is at least some freezing drizzle collecting
on elevated surfaces at a minimum. While we have not yet received
reports of ice collecting on road surfaces, temperatures are
currently in the teens and low 20s in these areas, and if drizzle
becomes heavy enough, patchy slick spots will be possible on
roadways over the next few hours, particularly I-70.

BRC

&&

.KEY MESSAGES...

- Light snow and patchy freezing drizzle will gradually wind down
  over the remainder of the afternoon.

- Dangerous wind chills are expected overnight through tomorrow
  morning in many areas, and a Cold Weather Advisory remains in
  effect where wind chill values are expected to reach between
  -20 and -10 degrees.

- A rapid warmup will put and end to this bitter cold Monday
  afternoon onward.


&&

.SHORT TERM...  (Through Late Sunday Night)
Issued at 218 PM CST Sat Dec 13 2025

While some light snow continues to move through parts of northeast
Missouri and central Illinois this afternoon, rates have steadily
dropped, and the last of it is currently leaving Iowa as of this
writing. This last push of very light snow will likely bring a few
flakes farther west than most of the morning snow fell, including
St. Louis and even as far as Columbia/Jefferson City, we do not
expect much in the way of additional accumulations aside from
perhaps another dusting to an inch in the areas that have already
seen accumulations. Meanwhile, we did see a bit of very light
drizzle and freezing drizzle across mainly the northern fringes of
the Ozarks this morning and early afternoon, but thus far we have
only received sporadic reports of this sticking to windshields and
little else. Both this and the remainder of of the light snow will
gradually diminish over the next few hours, and should be mostly
concluded by 6 PM.

Attention then turns squarely to the upcoming cold, which is
expected to spill south and into the remainder of the area this
evening and overnight. The temperature and wind chill forecast
remains largely unchanged, as actual temperatures are likely to drop
to between -5 and 10 degrees by early morning, with wind chills
between -20 and 0 degrees thanks to a steady 5 to 15 mph northerly
breeze. The coldest values are expected across our northeastern
half, and a Cold Weather Advisory remains in place in the areas
where we expect wind chills to dip into the -20 to -10 degree range.
During the day Sunday, temperatures are only expected to rise into
the single digits and teens, followed by another cold night in the
single digits above zero. Fortunately, weaker winds will allow for
some modest wind chill improvement, although parts of Illinois will
flirt with -10 degree wind chills again Monday morning.

Behind this system, a cold front is likely to move through the area
sometime Thursday, bringing breezy west/northwest winds as it moves
through. Temperatures will also likely take a hit on Friday,
although we don`t expect to see anything close to the cold we`re
seeing this weekend. Instead, a return to closer to average
temperatures is much more likely, although at this time range the
specific values are relatively uncertain.

BRC

&&

.LONG TERM...  (Monday through Next Saturday)
Issued at 218 PM CST Sat Dec 13 2025

The biggest story during the work week continues to be the expected
rapid warmup early in the week, along with gradually increasing
chances for rain across mainly our eastern areas Wednesday night and
Thursday.

While morning lows Monday will be quite cold, a tightening pressure
gradient will drive breezy southwesterly low level winds and rapid
warm advection during the day. This is expected to drive a very
quick warmup during the day, perhaps by as much as 30 to 35 degrees
between sunrise and mid afternoon. This will be a welcome
reprieve from this weekend`s bitter cold, as that will be in the
rear-view mirror for much of the next week. While we don`t expect
this to be particularly impactful, this rapid warming is also
likely to result in very low humidity Monday afternoon, especially
across the Ozarks and southwest Illinois, which may combine with
the breezy southwest winds to support erratic fire behavior
wherever fuels can manage to dry out fast enough. The latter will
be a tough hurdle to climb, though, as fuel temperatures will be
very cold to start the day, and it will likely take at least a
full day of these windy and dry conditions to warm up and dry out
enough to be receptive to burning.

On Tuesday and Wednesday, persistent southwest to westerly flow and
building heights aloft will drive steady warming, and confidence
remains very high that temperatures will climb back to well above
normal values. This is especially likely Wednesday, when
temperatures are likely to reach well into the 50s and even near 60
degrees in some areas. There is a bit less certainty in parts of
northeast Missouri and central Illinois where lingering snow may
slow this warming a bit, but overall, ensemble spread remains
relatively low during this period.

Late Wednesday night through Thursday, model guidance continues to
indicate that a dynamic shortwave will dig into the central U.S. and
Mississippi Valley, driving strong southerly flow and moisture
return into the region ahead of it. As such, precipitation
probabilities continue to steadily increase (20 to 60%) across
primarily the eastern half of our forecast area, particularly in
southeast Missouri and Illinois. Given that there are still non-
trivial timing differences and that this system appears to be
somewhat progressive, there remains plenty of uncertainty regarding
exactly when and where this precipitation will fall, and how much of
that will fall in our area. We also continue to keep an eye on a
limited (less than 20%) potential for thunderstorms as well, as
there are some hints of modest warm-sector instability.

BRC

&&

.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1020 PM CST Sat Dec 13 2025

Clouds will continue to move southward tonight with VFR conditions
extending through the end of the period. Northerly winds go calm
to variable Sunday evening, before shifting back out of the south
late Sunday night.

Maples

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Cold Weather Advisory until noon CST Sunday for Knox MO-Lewis MO-
     Lincoln MO-Marion MO-Pike MO-Ralls MO-Saint Charles MO-
     Saint Louis City MO-Saint Louis MO-Shelby MO.

IL...Cold Weather Advisory until noon CST Sunday for Adams IL-Bond IL-
     Brown IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL-Jersey
     IL-Macoupin IL-Madison IL-Marion IL-Monroe IL-Montgomery IL-
     Pike IL-Randolph IL-Saint Clair IL-Washington IL.

&&

$$

WFO LSX

NWS LSX Office Area Forecast Discussion