Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1033 PM CST Thu Jan 29 2026
.KEY MESSAGES...
- Temperatures remain seasonably cold through Saturday. Friday
night will be the coldest, with a 60-80% chance for wind chills
lower than 10 degrees below zero.
- On Friday evening, lake effect snow showers may (30% chance)
impact areas north of a roughly Macomb to Paris line. While
accumulations would be light, sharp reductions in visibility may
accompany the heaviest showers.
- There is a 30-40% chance for light accumulating snow on Sunday,
with amounts generally staying under an inch. Locally slick
roadways would be the main impact.
- A corridor of accumulating snow may impact a portion of central
or southeast Illinois Tuesday into Wednesday, but confidence is
low on precisely where. At this time, there is a 20-40% chance
for more than one inch of accumulation area-wide.
&&
.DISCUSSION...
Issued at 134 PM CST Thu Jan 29 2026
***** COLD WEATHER CONTINUES *****
Early Thursday afternoon, scattered mid to high clouds, light winds,
and temperatures generally in the teens were observed across central
and southeast IL, under the influence of expansive 1030-1032mb
surface pressure across the southern Canadian Prairies, Northern
Plains, and Midwest. There have been a couple mping reports of snow
across portions of east-central MO where ceilings area a little
lower (5-7kft), though surface dewpoint depressions suggest little,
if any, of this activity will make it into our neck of the woods;
we`ve included a mention of flurries in our southwestern counties
through the evening to account for the low chance of a couple
flakes. HREF generally suggests a 30-50% chance of mid-high cloud
cover overnight, which would offset radiational losses, but given
the light winds temps could sink like a rock if we get some
clearing, especially given the snow cover. We`ll monitor observation
and model trends through the evening in case we need to make
adjustments, but for now Friday morning`s lows are forecast to
generally run from 5 below to 3 above, with wind chills a couple
degrees cooler.
***** SNOW FRIDAY AFTERNOON-EVENING? *****
A compact but potent shortwave trough will drop south into the
region from the Upper Midwest/Great Lakes tomorrow afternoon,
bringing a sharp drop in temperatures aloft with HREF mean 850mb
temps dropping to around -20 degC. This will result in steep lapse
rates off the surface and perhaps even some instability poking into
the DGZ, so even with anemic low level moisture we will likely see
some snow shower activity. Virtually all of the 12z CAMs bring a
brief burst of snow (even if light) into our northern counties
tomorrow evening, though there are differences among them in
intensity of snow, along with precise timing and location. If there
were going to be impacts, it would likely be from a sudden drop in
visibility from briefly moderate snow accompanied by wind gusts to
25-30 mph. The short duration of snow in any given location suggests
accumulations should be light; HREF probs for more than 0.56" snow
(uses 10:1 SLR) generally keeps the chance for more than 1" of
accumulation (assuming our 18:1 SLR is correct) at generally less
than 10% area wide.
***** COLDER FRIDAY NIGHT INTO SATURDAY *****
Given the semi-tight pressure gradient across the area and 15-18kt
PBL winds advertised on forecast soundings Friday night into
Saturday, we felt NBM`s 10-15 mph winds were a bit low and boosted
them to 15-20 mph with gusts to 25 mph, which lowered wind chills
into the -10 to -16 range area-wide. Taking REFS, HREF, and LREF
apparent temperatures together, we think a Cold Weather Advisory is
possibly (40-60% chance) going to be needed for this coldest night
in the 7 day forecast.
***** SNOW POTENTIAL LATE SUNDAY, TUESDAY-WEDNESDAY *****
Temperatures will gradually moderate next week, with highs making a
run at the freezing mark each day Monday through Wednesday. However,
we`ll need to keep an eye on a couple disturbances slated to take
aim at the district: the first late Sunday, and another Tuesday into
Wednesday. Generally, ensemble guidance suggests low chances for
substantial accumulations with the clipper system on Sunday, with
only a 5-15% chance for more than an inch from NBM. The second
system, however, will bear a little more watching, as a brief period
of deep southwesterly return flow ahead of the upper level wave
offers our area with a little Gulf Moisture. Temperatures aloft may
warm sufficiently that the initial p-type is rain or freezing rain,
but then as conditions cool again on the low`s northwest side a
portion of our area may receive some accumulating snow with various
iterations of deterministic models advertising a band of 3+ inches,
though discrepancies in specifically where. For what it`s worth, NBM
chances for more than an inch generally range from 25-40% in our
area, highest near and north of the I-74 corridor.
Bumgardner
&&
.AVIATION... (For the 06z TAFs through 06z Friday Night)
Issued at 1033 PM CST Thu Jan 29 2026
Main aviation concerns will begin around midday Friday, as
ceilings begin to lower while an upper disturbance drops into the
area. Ensemble guidance currently is in the 40-60% range for
ceilings below 3000 feet at all TAF sites, generally focused on a
period from about 22z-04z, though this may be more associated with
a band of snow showers that will push south. Greatest confidence
of this occurring is currently at KPIA/KBMI, and will include a
PROB30 for lowered ceilings/visibilities with the showers.
Guidance is more mixed on whether that will make it south to the
KSPI-KCMI corridor, though KCMI may see more of a focus with lake
effect snow toward 06z or just after.
