Area Forecast Discussion

523
FXUS63 KLSX 172005
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
205 PM CST Sat Jan 17 2026

.KEY MESSAGES...

- Light snow showers and flurries will continue on and off across
the forecast area through this afternoon and again on Sunday.

- The first half of the work week will be largely dry with
  temperatures near to below normal despite multiple warm up-cool
  down cycles. Wind chills will drop below zero in many locations
  Monday morning.


&&

.SHORT TERM...  (Through Late Sunday Night)
Issued at 203 PM CST Sat Jan 17 2026

This mornings snow showers have exited the forecast area, leaving a
combination of stratus and broken cumulus across the region. The
cumulus is indicative of the steep low-level lapse rates we have
across the area, which combined with a mid-level disturbance, will
keep the chance (15%) for flurries going areawide through the
remainder of the afternoon. Across northeast Missouri and west-
central Illinois the mid-level disturbance and steep low-level lapse
rates will combine with a surface trough and some weak low-level
frontogenesis to produce snow showers. Some of these can be seen in
far northern Missouri and southern Iowa. These will also come to an
end during the early evening as the mid-level disturbance slides
southeast out of the region.

Another cold front will sink into the forecast area tomorrow, it`s
attendant low across the Great Lakes area. Ahead of the front,
southwesterly low-level flow will help boost temperatures into the
30s. Another round of sprinkles/flurries is expected area wide
tomorrow starting mid-morning and continuing through the early
evening, driven by another day with steep low-level lapse rates.
Sprinkles are most likely across central and southeast Missouri
where temperatures will be warmest, but will quickly transition to
flurries as temperatures cool. Across northeast Missouri and west-
central Illinois weak 850mb frontogenesis and low-level omega will
be able to produce isolated to scattered snow showers. Accumulations
are expected to be highly localized and less than 0.2". Uncertainty
exists in how far south into the forecast area they will form, but
where they do, brief periods of light to moderate fluffy snow are
expected. The frontogenesis and omega will shift eastward during the
evening with the surface front, bringing snow showers to an end.


Delia

&&

.LONG TERM...  (Monday through Next Saturday)
Issued at 203 PM CST Sat Jan 17 2026

Northwest mid-level low will continue into the work week as a deep
trough remains centered over the Hudson Bay region, extending all
the way to the Gulf. Multiple disturbances will pass through this
flow through the week, creating a pattern of warm up-cold front-cool
down that will repeat a few times over the week. The first of these
started this weekend, with Sunday`s warm up and cold front, which
will result in cooler temperatures Monday with a renewed push of
cold air advection. Along with this cooler air will come wind chills
in the negative digits Monday morning north of I-70, while south of
the interstate wind chill will be in the single digits. Another cold
front will roll through Wednesday, though moisture return ahead of
the front is not currently expected to be enough to overcome the dry
Arctic air that will be in place.

By the weekend, most clusters with the LREF depict a surface low
moving through the Mississippi Valley, bringing a chance of
precipitation to the region. Significant timing and location
differences exist with this feature and its evolution. This is
reflected in both the long duration of pops in the extended
forecast, as well as the increasing interquartile spread for high
temperatures Friday through the end of the period (15-20 degrees).

Delia

&&

.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1115 AM CST Sat Jan 17 2026

Snow has lingered across the St. Louis metro terminals this
morning, but is finally exiting eastward. This will allow ceilings
to lift to VFR and improve visibilities to VFR as well. Another
round of light snow is expected to move into west-central Illinois
this afternoon, impacting KUIN. Uncertainty exists where these
snow showers will develop, so have left the mention at PROB30 for
now. Elsewhere, flurries are possible on and off throughout the
day but are not expected to have any impact at the terminals.

The moisture bringing this second chance of snow is also
increasing low end VFR cumulus across the area. MVFR ceilings are
most likely at KUIN. Across the remainder of the terminals, MVFR
ceilings are not expected to prevail, but there is a 20% chance
for brief periods of MVFR ceilings through the afternoon.
Precipitation is expected to end early this evening and conditions
will improve to VFR across all terminals.

Flurries are expected areawide again tomorrow along with a 20-30%
chance for snow showers mainly north of I-70 during the day.
Confidence is too low in where and when these showers will
develop, so have left the mention out of the TAF period for now.

Winds will prevail largely from the northwest to west, gusting
into the 20s through early this evening.

Delia

&&

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

$$

WFO LSX

NWS LSX Office Area Forecast Discussion