Decatur, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

771
FXUS63 KILX 241431
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
831 AM CST Sat Jan 24 2026

.KEY MESSAGES...

- A long-duration winter storm will impact the region in two waves
  spanning this afternoon through early Sunday evening. Snow
  amounts appear fairly light with the 1st wave, with 1 to 3
  inches of snow by midnight tonight (highest south of I-70).
  however, more accumulating snow arrives later tonight into
  Sunday.

- A Winter Storm Warning is in effect from Cass to Vermilion
  Counties southward from noon until 9 pm Sunday, with 5-11 inches
  of snow expected. The highest snow totals are expected
  near/south of I-70, where there is 40-70% chance for a foot or
  more of snow per NBM. A Winter Weather Advisory is posted north
  of the Winter Storm Warning, 2-4 inches of total snow is
  expected. Marshall county was added to the winter weather
  advisory which goes from noon until 6 pm Sunday.

- A Cold Weather Advisory remains in effect across central and
  southeast IL through noon. Wind chill values will range from 10
  to 20 degrees below zero with the coldest readings from I-74
  north. Another Cold Weather Advisory may be needed overnight
  Sunday night into Monday morning (80-90% chance per LREF).

&&

.UPDATE...
Issued at 830 AM CST Sat Jan 24 2026

Strong 1042-mb sfc high remains centered over WI/N IL, with dry
northeasterly flow through the low levels of the ILX CWA. 12z
RAOBs from across the region sampled this dry air, with KILX
having low RH below 800mb (~6 kft). Much further SE, KSGF
(Springfield, MO) was saturated all the way to the sfc. Regional
radar imagery from 1430z/830am showed light returns across the
region, but mPING reports and sfc obs suggest snow has mainly been
confined to MO, although just in the last 5-10 mins we`re
starting to see mPING reports east of the IL River.

Had considered slowing the onset of PoPs this morning due to the
dry low-level air, but with the steady northeastward advance of
snow reports at the sfc opted not to make any changes. The key
messages remain unchanged. For today, expect snow chances to
increase/spread northeast into the afternoon, with snow rates
expected to be less than 0.25"/hour during the daytime hours (per
the HREF).

Erwin

&&

.DISCUSSION...
Issued at 345 AM CST Sat Jan 24 2026

Continued the Cold Weather Advisory for our CWA through noon
today. Wind chills currently are 9-14 below zero in southeast IL,
and 15-25 below zero over central IL, with Bloomington having the
coldest wind chill of 26 below zero. Wind chills should elevate
to since digits below zero in southeast IL and 10-15 below in
central IL by late morning. So the Cold Weather Advisory may be
able to cancel early, but if NE winds hold up slightly higher than
this would keep lower wind chills. Temperatures were in the
single digits below zero north of I-70, and single digits above
zero southeast of a Paris to Mattoon to Litchfield line. North to
NNE winds 7-14 mph and few gusts 15-18 mph was giving the bitter
cold wind chills. A strong 1042-1044 mb arctic high pressure over
the upper MS river valley and ridging into central IL was giving
us this bitter cold airmass. A frontal boundary was near or just
south of the Gulf coast with 1010 mb low pressure in south Texas
near the Rio Grande river with a weak elongated surface trof
extending into the Ozarks in western AR and sw MO.

We continued winter storm warning from Cass to Vermilion counties
southward from noon today through 9 pm Sunday. Winter weather
advisory for rest of CWA north of here (excluding Knox and Stark
counties) from noon today until 6 pm Sunday.

Strong Arctic high pressure to slowly weaken to around 1040 mb by
sunset as it drifts eastward across the Great Lakes region.
Meanwhile a surface trof to deepen from the lower MS river valley
ne into the TN and eastern Ohio river valley into tonight. We will
see a prolonged period of overrunning/isentropic lift into
central and southeast IL this afternoon through Sunday bringing
several inches of snow to central and southeast IL, with much
lighter amounts nw CWA which will be on the nw fringe of this
winter wx system. The 1st wave of light snow to spread ne into sw
CWA by midday, and over rest of CWA during this afternoon and
continue this evening, and CAMs have trended slower with its
arrival. So the winter weather headlines have been pushed back
from a 9 am to noon start time today. Between 1-3 inches of snow
is expected by midnight, with the higher amounts in southeast IL
and less than 1 inch over Knox and Stark counties. The 06Z HRRR
model shows light snow ending nw of the IL river overnight and
most of the snow from 2nd wave late tonight and Sunday to be east
of the IL river per HRRR model. Very cold today with highs of
7-12F over central IL and mid teens in southeast IL from I-70
southeast.

2nd wave of light to moderate snow to lift ne over central and se
parts of CWA late tonight and Sunday morning, and a 3rd wave
lifting through areas east of the IL river during Sunday afternoon
and diminishing from west to east late Sunday afternoon/early
Sunday evening. The mixed pcpn should be se of Lawrence county
and mainly southeast of the Ohio river for Sat night into Sunday.
Models continue to show highest snowfall amounts in southeast IL
where 8-10 inches and locally up to a foot or more possible se of
I-70. Between 2-4 inches of snow over the IL river valley (1-2
inches over Knox and Stark counties) and 4-8 inches in heart of
central IL with the higher amounts further south/se you go. Will
see a sharp cutoff of snowfall amounts over nw CWA and kept Knox
and Stark counties out of the winter wx advisory. Northerly winds
increase by Sunday afternoon and Sunday night with gusts 20-25 mph
and could cause some blowing/drifting of the fluffy snow.

Another surge of arctic air arrives behind the winter wx system
Sunday night with lows Sunday night zero to 5 below and wind
chills likely reaching 10-20 below zero during overnight Sunday
night into Monday morning, when we will likely need another cold
weather advisory over much of our area. A strong Canadian high
pressure 1040 mb or stronger to move into Texas and ridge ne into
IL by midday Monday. This returns mostly sunny skies but bitter
cold temps with highs in the lower teens. Bitter cold Monday night
with lows zero to 5 below in eastern IL where wind chills could
reach near cold weather advisory criteria again. Lows in the
singles digits above zero over the IL river valley. The expected
snow cover may also make it colder especially if we have clearer
skies at night.

Slight moderation in temps on Tue with sw breezes ahead of a cold
front that moves through dry during Tue afternoon. Highs in the
mid to upper 20s Tue which is still about 10 degrees colder than
normal, and this will likely be our mildest day during next week.
A strong 500 mb low digging southward over the Great Lakes on Wed
afternoon into Wed night could bring chance of light snow to parts
of central/eastern IL Wed afternoon/evening. The ECMWF is stronger
with this system which brings higher snow chances to central IL by
Wed afternoon while GFS and GEM are much lighter with QPF. Another
Canadian high pressure settles into the area during Thu and should
bring dry/cold wx rest of week. We will be colder again Wed-Friday
with highs in the mid teens to near 20F and getting closer to
cold weather advisory criteria Wed night and Thu night. Slighter
moderation in temps next week with highs getting back into the
20s, which is still 10-15 degrees below normal.

The Climate Prediction Center (CPC) 8-14 Day Outlook for Jan
31-Feb 6th shows 35-50% chance of below normal temperatures over
central and southeast IL, while near normal temps over nw IL.
There is a 40-50% chance of below normal precipitation across IL
during the 1st week of February.

07

&&

.AVIATION...  (For the 12z TAFs through 12z Sunday Morning)
Issued at 518 AM CST Sat Jan 24 2026

A winter storm will spread -SN across the central IL terminals
from the southwest this afternoon, continuing through tonight.
IFR visibility and MVFR ceilings look to be common for the
duration of the event, which will continue past the end of this
TAF period. Northeast winds will be persistent through the next
24 hours, initially near 10 kt today then increasing to 10-14 kt
tonight.

25

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Cold Weather Advisory until noon CST today for ILZ027>031-
036>038-040>057-061>063-066>068-071>073.

Winter Weather Advisory from noon today to 6 PM CST Sunday for
ILZ029>031-036>038-040-041.

Winter Storm Warning from noon today to 9 PM CST Sunday for
ILZ042>057-061>063-066>068-071>073.

&&

$$