823
FXUS63 KLSX 072031
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
231 PM CST Sun Dec 7 2025

.KEY MESSAGES...

- A mix of very light drizzle/rain and snow is possible this
  evening across the Ozarks and southwest Missouri, but impactful
  accumulations are not expected.

- A round of light accumulating snow is possible (20-60%)
  Thursday, but confidence is low.

- While tomorrow will be chilly, much colder temperatures are
  expected Thursday through the weekend, particularly Saturday.

&&

.SHORT TERM...  (Through Late Monday Night)
Issued at 227 PM CST Sun Dec 7 2025

It has been a brisk, gloomy day throughout the area so far today,
with breezy northerly winds and persistent low level cloud cover.
While there are minimal potential hazards to discuss today, we do
continue to keep an eye on the potential for light
drizzle/sprinkles, and perhaps even some flurries/light snow showers
later this afternoon.

The primary driver of this latter potential appears to be weak
upslope flow thanks to northerly winds moving atop the Ozarks, along
with increasing low level saturation. So far this has only amounted
to persistent low clouds and perhaps some faint fog, but most CAMS
have latched onto the idea of some light precipitation developing in
southeast Missouri and southwest Illinois later in the afternoon and
evening, roughly between 4 PM and midnight. Model soundings are
somewhat varied, but all show some variation of a deep saturated
layer developing in the low levels, perhaps up to about 5 to 7kft,
albeit with very modest low level lift propped up a bit by upslope
flow over the Ozarks. While there is some uncertainty as to whether
or not this will be enough forcing alone to actually get
precipitation development, there is just enough evidence to carry a
mention of drizzle into the late evening hours, transitioning to
light snow gradually after sunset as the profile cools enough to
allow for cloud ice.

Meanwhile, we will also need to keep an eye on a very limited
potential for freezing drizzle, due to the fact that most model
soundings (besides some CAMS) do not bring any part of the saturated
layer to -10C or lower until very late in the evening. The primary
concern here is that if surface temperatures cool below freezing
before precipitation ends, and before cloud ice can form, then you
have a recipe for a brief period of freezing drizzle/very light
rain. To be clear, this is an unlikely (20% or less) worst-case
scenario, and the chances of enough of this to form, stick to roads,
and cause impacts are likely even lower. Meanwhile, almost all of
the precipitation-producing CAMS generally transition from liquid
rain directly to light snow. This is a lot of writing for something
that is not likely to occur, but considering that FZDZ can be
uniquely impactful when it does materialize, we felt that it was
worth explaining in spite of the low probability.

Overnight, steady cold air advection behind the front will slow as
high pressure settles in, with morning temperatures likely dipping
into the teens and 20s. Coldest temperatures are likely across
northern Missouri and central Illinois, where skies are already
clearing, winds will weaken, and snow cover remains. Monday is
expected to be dry and cold as well, with afternoon highs only in
the 30s.

BRC

&&

.LONG TERM...  (Tuesday through Next Sunday)
Issued at 227 PM CST Sun Dec 7 2025

While we will get a reprieve from these chilly temperatures Tuesday,
a series of cold fronts will usher in a much colder airmass over the
latter half of the week. We may also see another potential for light
snow accumulations on Thursday, although confidence in the latter
remains low.

For the next week, the synoptic pattern will remain relatively
stable across the CONUS, with a nearly stationary longwave trough
across the eastern CONUS, northwest flow atop the Mississippi
Valley, and a steady stream of shortwaves moving through this
northwest flow. While there will be several of these waves, there
are two in particular that will impact our local weather. The first
of these will move through the upper Mississippi Valley Wednesday
night, and it`s primary impact will be to increase the pressure
gradient and drive breezy southwesterly surface winds ahead of it
Tuesday. Warm air advection will lead to a rapid jump in
temperatures Tuesday, perhaps as much as 20 degrees higher than the
day before in all areas that do not still have substantial snow
cover. This would equate to highs reaching into the 50s in many
areas, and perhaps as much as 5 to 10 degrees above average.

On Wednesday though, a cold front will mute this warming trend,
beginning a steady cooldown that will continue through the weekend.
This initial front will not bring the coldest air with it just yet,
though, as the second, deeper shortwave will drive the core of an
arctic airmass into the area Thursday through Saturday, when the
lowest temperatures are expected. While there remains some non-
trivial ensemble spread in forecast temperatures, this has
narrowed over the past 24 hours, and confidence is now very high
that we will see temperatures dipping to around 20 to 30 degrees
below average by Saturday. That equates to morning lows in the low
teens to single digits almost everywhere by Saturday morning, and
highs only in the teens and 20s later that afternoon.

As for precipitation, the next reasonable opportunity does not
arrive until Thursday when the second shortwave begins to impact the
area. Even then, forecast precipitation amounts remain very light,
and confidence is low to moderate that this precipitation will
materialize locally (20-60% over 24 hours). However, temperatures
will likely be cold enough to support snow if we do see
precipitation from this system, and possibly enough to cause minor
impacts if some of the higher percentile forecast amounts are closer
to verifying.

BRC

&&

.AVIATION...  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1150 AM CST Sun Dec 7 2025

The primary concern for the 18Z TAF period is the persistence of
low clouds. Widespread MVFR ceilings continue to impact all local
terminals at the start of the period, and this is likely to
continue through the overnight hours and into at least sometime
tomorrow morning, and possibly longer, for all terminals except
for UIN. At UIN, the edge of the low clouds will likely pass the
terminal later this afternoon, with a much earlier return to VFR
conditions than the other terminals.

While some brief light drizzle or even a few snow flurries will
be possible in the St. Louis area late this afternoon and evening,
this is more likely to remain south of STL/SUS/CPS. A few flurries
are also possible at UIN overnight tonight, but this is more
likely farther north.

BRC

&&

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

$$

WFO LSX