Area Forecast Discussion

104
FXUS63 KLSX 112330
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
530 PM CST Sun Jan 11 2026

.KEY MESSAGES...

- This week will start warm with highs peaking on Tuesday. A
  series of cold fronts will keep temperatures cooler through the
  rest of the week.

- Largely dry weather is forecast through at least Saturday.


&&

.SHORT TERM...  (Through Late Monday Night)
Issued at 212 PM CST Sun Jan 11 2026

The beginning of the work week will be uneventful. The cold airmass
that brought us a seasonably cold morning today will continue to
push east and out of the region. Low-level ridging has established
itself in its place, and warm air advection has begun to ramp up.
Monday morning`s lows will be similar to this morning`s, but a lack
of strong pressure gradient winds will mean wind chills will be much
closer to the ambient temperature. Strengthening warm air advection
Monday will launch highs into the upper 40s to mid-50s, well above
normal. Lows Monday night will be equally as anomalous, only
falling into the 30s areawide. These overnight temperatures are on
par with the average highs for mid-January.

Jaja

&&

.LONG TERM...  (Tuesday through Next Sunday)
Issued at 212 PM CST Sun Jan 11 2026

West-southwesterly surface winds will ramp up further on Tuesday
ahead of our next system, yielding even warmer conditions than
Monday. According to NBM probabilities, areas south of I-44/I-64
have a 70 - 90% chance of reaching the low-60s. If it wasn`t for
incoming mid to high level cloud cover and a lack of true,
persistent southwesterly winds, temperatures would likely warm
further. As it stands, however, the probability of reaching 65
degrees falls to 10 - 20%. Locations to the north are forecast to
remain solidly in the mid to upper 50s. Surprisingly, this places
KUIN only a few degrees off from breaking their daily high
temperature record (58 - 1932). Breaking the record shouldn`t be
easy given that KUIN will have at least partial cloud cover all day.
Ensembles corroborate this, giving KUIN only a 10 - 15% chance of
reaching 58 degrees.

A cold front will pass through the region Tuesday night. The cold
air behind the front will lag, reaching our northern border sometime
after sunrise. The late arrival of the airmass will result in steady
temperatures if not incremental warming during the day with daily
highs occurring near midnight for most if not all of the CWA. Rain
may accompany the front, but anything that falls will be very light.
LREF probabilities of 24 hour precipitation > 0.05" peak at 35% in
our far eastern Illinois counties. Signals for post-frontal
precipitation are increasing as well, with more deterministic models
catching on. This introduces a chance of a brief rain/snow mix in
portions of south-central Illinois as the colder airmass moves in.
Accumulations are not expected given the brevity of any snow that
may fall, the fact that it would very likely be mixed with rain, and
warm ground temperatures.

Thursday will be the coolest day of the work week as we experience
the full influence of the cold airmass. Widespread 30s are
forecast - a far cry from the 50s and 60s two days prior. A quick
hit of low- level warm air advection will tease the region with a
push into the 40s on Friday, but this will be short-lived.
Another more potent cold front is forecast to push through the
region Friday into Saturday. Highs are forecast to differ by 10+
degrees between Friday and Saturday with our warmest locations
peaking at or just above the freezing mark. NBM probabilities
reflect this, showing a 60% - 100% chance of highs 

NWS LSX Office Area Forecast Discussion