Area Forecast Discussion

551
FXUS63 KLSX 270344
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
944 PM CST Mon Jan 26 2026

.KEY MESSAGES...

- Wind chill values below -10 degrees are forecast tonight across
parts of south central and southwest Illinois.

- Dry conditions with mostly sub-freezing temperatures will continue
through Wednesday.

- Another blast of arctic air is expected late this week into this
weekend with the potential for below zero lows and dangerous wind
chills.


&&

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 219 PM CST Mon Jan 26 2026

A strong surface ridge of high pressure is located from southwest
to northeast, roughly bisecting the CWA. This ridge will quickly
move off to the southeast into the mid south-Upper Ohio Valley.
This means an increase in southwesterly return flow at the surface
and rising temperatures overnight tonight. Before that happens
though, temperatures are expected to drop into the single digits
in eastern Missouri and southern Illinois. The coldest
temperatures are forecast across southern Illinois, and a period
of wind chills around -10 degrees are still forecast. Therefore,
the cold weather advisory still is on track for tonight, though
may be able to be cancelled before 1200 UTC Tuesday as
temperatures warm overnight.

Another cold front approaches the area very early Tuesday morning
and moves through from northwest to southeast, exiting around
midday. Winds will turn back to the northwest behind this boundary,
and also bring some colder air. This air mass moving in however is
not as cold as those which have been impacting the area the past
several days. In fact, parts of southeast Missouri have >60%
probabilities for above freezing high temperatures. The deep, still
fairly fresh snow pack though does lead to lower than normal
confidence in actually achieving the mid 30s that are forecast down
there however. Further north, highs are expected to range from the
mid 20s to near 30 degrees from north to south.


Gosselin

&&

.LONG TERM...  (Tuesday Night through Next Monday)
Issued at 219 PM CST Mon Jan 26 2026

(Tuesday Night - Wednesday)

Another very cold night is expected Tuesday night as a seasonably
strong (~1030 hPa) surface anticyclone settles into the bi-state
area. These conditions are very favorable for radiational cooling
with a clear sky and calm winds. The snow pack will still be here of
course, though a bit older so the albedo isn`t as high as it is
currently. Lows near zero are forecast, with the best chances of
subzero minimums (>50%) from the NBM in parts of south central and
southwest Illinois. With very little/no wind, it appears the chances
of needing another cold weather advisory are fairly low.

A quick "warmup" is again expected on Wednesday, similar to tomorrow
as winds turn out of the southwest ahead of another cold front.
Highs should be mostly below the freezing mark, with possible
exceptions across central/southeast Missouri where mid 30s are
forecast.


(Wednesday Night - Sunday)

This next air mass coming in certainly looks colder than its
predecessor, with its origins coming from northern Canada northwest
of Hudson Bay. Another period of much-below normal temperatures is
in the offing later on this week through the weekend. The coldest
period of time appears to be between Thursday and Saturday. Highs in
the teens to mid twenties are expected, with lows near or slightly
below zero each night. The best chances of subzero lows are Friday
and Saturday mornings where the NBM has probabilities of 30-60%
across the region. Exact values will likely come down to the timing
of the next surface high, and if there are clouds are not. Given the
strength of this air mass however, I would fully expect subzero lows
with a clear sky and favorable timing of the high. Well-below zero
lows would also be possible in that scenario. The incoming air mass
peaks Friday into Saturday when 850-hPa temperatures on the EPS/GEFS
mean drop to near -20C (99th percentile of climo) surface
high entering the Upper Midwest Friday evening. Give the potential
for subzero lows, we will have to watch for the possibility of
dangerously cold wind chills again. At the moment, Friday
night/Saturday morning may have the best potential given there
should be a northwest wind around 5-10 mph with the surface high
likely still to the northwest. LREF probabilities for minimum wind
chills Saturday morning are in the 70-90% range across the area.

In terms of precipitation chances, we will have to watch for the
potential for some light snow in any northwest flow shortwaves.
Nothing appears distinct however at this time range, with dry
weather favored throughout the period. The "best" chances for any
measurable light snow are Friday/Friday evening (~10% on the NBM)
and Sunday (10-20%).


(Sunday Night - Next Monday)

Moderating temperatures are forecast heading into early next week as
mid/upper level heights rise and 850-hPa temperatures climb closer
to -5C. While not as cold, temperatures still should be below normal
even through next Monday. Even the 90th percentile of the NBM
just barely gets highs on Monday back to around normal.


Gosselin

&&

.AVIATION...  (For the 06z TAFs through 06z Tuesday Night)
Issued at 942 PM CST Mon Jan 26 2026

Dry and VFR conditions are expected through the end of the period.
Southwesterly winds will turn out of the northwest on Tuesday
behind a cold front and will gust between 18-24 knots at times.

Britt

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...Cold Weather Advisory until 6 AM CST Tuesday for Bond IL-Clinton
     IL-Fayette IL-Macoupin IL-Madison IL-Marion IL-Monroe IL-
     Montgomery IL-Randolph IL-Saint Clair IL-Washington IL.

&&

$$

WFO LSX

NWS LSX Office Area Forecast Discussion