Area Forecast Discussion

085
FXUS63 KLSX 151126
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
526 AM CST Thu Jan 15 2026

.KEY MESSAGES...

- A fast round of light snow is forecast between 6PM and midnight tonight,
  mainly east of the Mississippi River. Amounts of a dusting to
  as much as 0.5" is expected.

- Scattered snow showers are expected Friday night along/behind an arctic
  cold front. While most areas will not see any measurable snow,
  isolated locations may see a dusting to 0.5".

- Very cold temperatures are forecast this weekend through
  Tuesday. Below zero wind chill values are possible each morning
  Sunday through Tuesday.


&&

.SHORT TERM...  (Through Late Tonight)
Issued at 246 AM CST Thu Jan 15 2026

A seasonably cold and dry day is in store for the bi-state area
as a surface ridge of high pressure slides eastward. High
temperatures in the 30s are expected with light winds.

Mid/high level clouds will increase quickly from the northwest late
this afternoon and early evening ahead of the next midlevel
vorticity maximum. Ascent downstream of this feature coincident with
increasing low-level warm/moist advection is likely (60-80%) to
produce a fast-hitting round of light snow between 6PM and
midnight tonight, mainly east of the Mississippi River. The main
limiting factors remain the same, with the duration of snow very
short (~2-3 hours in any given location) along with very dry
low/mid levels of the troposphere. While this dry air does help
ensure anything that does fall will be snow (via wetbulbing), the
depth (350-400 hPa) and magnitude (dewpoint depressions 15-25C)
are noteworthy. At the very least it will take multiple hours for
enough top-down saturation to occur for any snowflakes to make it
to the surface. If the forcing for ascent is just a bit weaker
and/or transient in nature, this dry air could effectively shut
down any snowfall accumulations. The current expectation is for
the forcing for ascent to overcome this dry air, but just briefly
as alluded to above. Only a 2-3 hour period of light snow makes it
difficult for much in the way in terms of accumulations. A
dusting to as much as 0.5" are possible across parts of west
central and south-central Illinois, with a quick dusting (0.1")
as far west as near the Mississippi River.


Gosselin

&&

.LONG TERM...  (Friday through Wednesday)
Issued at 246 AM CST Thu Jan 15 2026

(Friday - Friday Night)

Slightly warmer temperatures are expected on Friday ahead of another
approaching cold front. Highs in the low to mid 40s are forecast
with increasing clouds throughout the day.

The arctic front looks to move through Friday evening, with
temperatures falling quickly into the 20s. Steep low-level lapse
rates are forecast from Friday afternoon through much of Friday
night. These steep low-level lapse rates (and even some outright
CAPE) combined with an amplifying upper-level trough and
increasing low-level frontogenesis all suggest a favorable
pattern for scattered snow showers. Ahead of the arctic front,
there actually may be some light rain showers, but most of the
activity should be in the form of snow showers Friday
evening/early overnight as the boundary layer cools rapidly. While
most areas in the CWA should not see any measurable snow, I would
not be surprised to see some streaks of snow amounts from a
dusting to as much as 0.5". Some of the snow showers may have some
intensity to them as well, with reductions in visibility below
1SM possible for a duration of ~10-15 minutes.


(Saturday - Tuesday)

Confidence continues to gradually increase in what may be the
longest stretch of well-below normal temperatures so far this
winter season. High temperatures are expected to be mainly in the
20s each day, with lows in the 0s/10s. While there remains some
uncertainty on the exact timing of the second arctic cold front,
the spread has decreased quite a bit compared to 1-2 days ago.
This has led to a decrease in the spread on the NBM`s inter-
quartile range for Sunday`s highs, generally at or below 10
degrees. Just 48 hours ago, the ranges were commonly 20-25
degrees. The two coldest days should be Saturday and Monday for
most locations, though the air mass behind the second arctic cold
front continues to trend colder and colder. Given the more
amplified mid/upper level flow across Alaska, it would make sense
conceptually that the following air mass is slightly colder than
its predecessor.

Below zero wind chills are possible each morning Sunday through
Tuesday. LREF probabilities for each morning are fairly close to
each other, with the best chances (50-70%) in northeast Missouri and
west-central Illinois. For wind chill values at or below -10F,
chances drop into the 10-20% range for the same areas. This
suggests that while it looks very cold, cold weather advisory
criteria (

NWS LSX Office Area Forecast Discussion