Area Forecast Discussion

247
FXUS63 KLSX 052010 CCA
AFDLSX

Area Forecast Discussion...CORRECTED
National Weather Service Saint Louis MO
210 PM CST Fri Dec 5 2025

.KEY MESSAGES...

- A round of light rain and snow is likely (50-70%) Saturday night
  and Sunday morning. Snow accumulations ranging from a trace to 1
  inch are most likely (80%) where snow manages to occur.

- Below average temperatures continue through Monday, with some
  moderation and possibly (30-50%) another round of light rain
  Tuesday night and Wednesday.


&&

.SHORT TERM...  (Through Late Saturday Night)
Issued at 143 PM CST Fri Dec 5 2025

Quiet, but chilly conditions are in place this afternoon as we
await the arrival of Saturday night`s clipper system and
associated round of light wintry precipitation. As of 1 PM, clouds
have largely cleared across the area, revealing a clearly defined
snowpack covering a large portion of northeast Missouri and the
northern 2/3rds of Illinois, including just barely the St. Louis
metro area. In the areas where snow is prevalent, temperatures
have been much slower to warm, with afternoon readings generally
only in the low 30s. Farther south, temperatures are much more
comfortable, even reaching into the mid-40s across parts of the
Ozarks.

Overnight through tomorrow morning, a weak cold front is expected to
slowly push into the area, bringing a round of low clouds that may
linger much of the day tomorrow. In addition to keeping skies gray
in many places, this should also help to reinforce the cooler
temperatures in our northern areas especially. Overall, we can
expect a similar distribution of afternoon temperatures tomorrow to
what we are seeing today.

Attention then turns to the arrival of a fast-moving "clipper" low
pressure system, which is expected to move roughly along the MO/IA
border overnight tomorrow. This track is slightly further north than
previous forecasts, and as such, the corridor of more significant
frontogenesis-driven precipitation has shifted slightly further
north as well. However, we remain likely to see a brief round of
light rain and potentially some light accumulating snow overnight
and early Sunday morning, driven largely by isentropic ascent.
During this period, soundings generally support a mix of rain and
wet snow, without much evidence to suggest other precipitation types
like freezing rain and sleet, although some model guidance continues
to depict an occasional smattering of such here and there (most
notably the NBM). As such, we will continue to remove mention of
freezing rain for the time being, as this potential continues to
appear very tenuous at best. Instead, expect a mix of light rain and
snow, with snow accumulations most likely to range from a trace to a
light dusting. Best chances for more notable accumulations (1-2
inches) will be along our far northern fringes in NE MO and WC IL.

Behind this initial round Sunday morning, we do also note that dry
air aloft may scour out most of the ice-producing mid and higher
level clouds later in the morning and afternoon, while leaving
behind some sub-freezing low level saturation and lift. During this
brief window we can`t completely rule out some light freezing
drizzle that eventually transitions to flurries, but the potential
for impacts to roads is very low (10-20%). Meanwhile, a more robust
cold front will push through the area throughout the day Sunday,
reinforcing well below average temperatures early in the week.

BRC

&&

.LONG TERM...  (Sunday through Next Friday)
Issued at 143 PM CST Fri Dec 5 2025

From Monday onward, the overall synoptic pattern looks to remain
relatively consistent, with a broad longwave trough remaining nearly
stationary across the eastern CONUS. This scenario maintains
northwest flow aloft locally, and keeps our region within the path
of a series of modest clipper systems. The next such system of any
note is likely to move through the area sometime late Tuesday and
Wednesday, following a similar track as it`s predecessor and
bringing another round of light precipitation. While still several
days away, currently forecast temperatures suggest that this is
more likely than not to produce all liquid rain, although it
remains just cool enough that we can`t completely rule out some
light frozen precipitation depending on the exact timing (day vs.
night).

Otherwise though, the primary implication of this pattern is that it
will put a ceiling on temperatures for at least the next week, with
some moderation back to near seasonal averages Tuesday and
Wednesday, followed by likely another surge of colder air behind
Wednesday`s system through the end of the work week. It should also
be noted that while the large scale pattern remains relatively
consistent, confidence in day-to-day temperatures decreases
considerably Thursday onward, owing largely to differences in trough
amplitude among ensemble members in the long range. In spite of this
though, confidence is high (70+%) that temperatures will dip back to
below average values.

BRC

&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1143 AM CST Fri Dec 5 2025

VFR conditions are expected for the remainder of the day and much
of the overnight hours. However, a cold front is expected to bring
a round of low stratus overnight through the day tomorrow, likely
to at least MVFR and potentially IFR as well. Much of this stratus
may hold off until after the 18Z TAF period at COU/JEF, but it
has been included in the UIN/STL/SUS/CPS TAFS.

BRC

&&

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

$$

WFO LSX

NWS LSX Office Area Forecast Discussion