Decatur, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

109
FXUS63 KILX 222310
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
510 PM CST Sun Feb 22 2026

.KEY MESSAGES...

- Bitterly cold wind chills as low as -5 below are expected
  tonight, especially west of I-55. There is a 60-80% chance for
  sub-zero wind chills west of I-55.

- Strong south winds will develop Tuesday, with gusts potentially
  (20-50% chance) reaching 45 mph. These winds may impact travel
  for high-profile vehicles.

- Widespread rain is likely (70% chance) Wednesday night into
  Thursday. Most areas will see rain, but snow or a wintry mix is
  possible for areas near and north of the I-74 corridor where
  there is a 20-40% chance for an inch of snow.

&&

.DISCUSSION...
Issued at 140 PM CST Sun Feb 22 2026

Today and Tonight: Cold and Breezy Conditions
A robust 1055+ mb high pressure system remains centered over the
Canadian Prairies, with its associated ridging extending south
across the Great Plains. Concurrently, a pair of low pressure
systems are influencing the pattern to our east: one situated over
the Great Lakes and another tracking along the mid-Atlantic
Coast. The moderate north/northwesterly pressure gradient
established between these features is maintaining breezy and cold
conditions across central Illinois today.

Temperatures will only reach highs mainly in the 20s this
afternoon before dropping back into the teens overnight. The
combination of cold temperatures and persistent wind will lead to
sub-zero wind chill values. Based on LREF guidance, a 60-80%
chance for sub-zero wind chills exists along and west of I-55,
with a 20% chance extending eastward toward the I-57 corridor.

Monday and Tuesday: Transition and Gusty Winds
The surface ridge axis will progress across central Illinois on
Monday, providing a brief period of lighter winds during the later
part of the day. Following the passage of the ridge axis Monday
night, a return to southerly flow will spread across the region,
marking the beginning of a gradual warming trend. High
temperatures are forecast to rebound into the 40s and 50s
beginning Tuesday and persisting through the remainder of the work
week.

Ahead of the next system, gusty winds are expected across central
Illinois on Tuesday. A shortwave digging across the Great Lakes
Tuesday and Tuesday night will tighten the pressure gradient
sufficiently to produce strong gusts. NBMs 75th percentile peak
gust on Tuesday aligns closely with our Wind Advisory criteria of
45 mph. At this time, any precipitation associated with this wave
is favored to remain north of the I-74 corridor.

Mid-Week Precipitation Potential
Attention turns to the next in a series of shortwaves traversing
the region. A wave moving through Wednesday night into Thursday
presents the best chance for any meaningful precipitation locally.
Confidence is high for a wetting rain, with NBM probability for
0.1" QPF across the area registering between 60-70%.

The primary forecast challenge remains the potential for wintry
precipitation. The chance for an inch of accumulating snow is
currently 20-40% along and north of the I-74 corridor, decreasing
to low but non-zero probabilities (around 10%) south to the I-70
corridor.

Analysis of thermal profiles and forecast soundings from the GFS
model suggests that precipitation will primarily fall as rain
across the majority of the area. However, a mix including freezing
rain and sleet will be possible near the I-74 corridor, with a
transition to snow favored further north. The slightly warmer
ECMWF solution suggests a more widespread rain event across
central Illinois. As is typical several days out, there is still
plenty of time for fine-tuning these details regarding
precipitation type and placement.

Deubelbeiss

&&

.AVIATION...  (For the 00z TAFs through 00z Monday Evening)
Issued at 510 PM CST Sun Feb 22 2026

Central Illinois falls between high pressure over the Plains and
low pressure over the Great Lakes. Moderate northwest flow
continues with gusts into the mid 20 kt range expected to
continue through midday Monday. MVFR level cold air stratocumulus
stretches from near KPIA northwest through southern MN. As this
shifts southeast tonight we expect MVFR ceilings to be common
across the central IL terminals, then scattering out by late
morning.

25

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$