textproduct: Central Illinois

KEY MESSAGES

- A Winter Weather Advisory is in effect from Saturday morning until Saturday evening for 2 to 5 inches of snowfall near and north of I-70. The highest amounts look to center around a Macomb to Danville line. In this corridor, snowfall rates could exceed 1 inch per hour at times.

- Dangerously cold wind chills are expected Saturday night again Sunday night. The coldest wind chills will drop as low as 15 to 25 degrees below zero Sunday morning. Wind chills look to drop nearly as low again early Monday morning.

UPDATE

Issued at 543 PM CST Fri Dec 12 2025

The only change made to the forecast so far this evening was a slight increase in winds Saturday evening as the surface pressure gradient tightens between the approaching low diving southeast across the eastern Great Lakes and high pressure to our west. NAMNest forecast soundings, which often do well during cool advection in the cold season using the MYJ PBL scheme, has a shallow but well-mixed PBL during the evening and supports sustained winds around 12-15 mph with gusts to 20+ mph - potentially resulting in at least some drifting of freshly-fallen snow (which should be tapering off by that time). This increase in winds also dropped Saturday evening wind chills by a couple degrees in our forecast to -5 to -10 north of roughly I-70 by 9pm.

Bumgardner

DISCUSSION

Issued at 247 PM CST Fri Dec 12 2025

A cold front will surge into the area tonight, followed by a fast moving shortwave, currently over western Canada, Saturday. Temperatures look to plummet as low as 5 to 10 degrees by morning NW of the Illinois River, and into the teens as far southeast as I-70. Highs only look to reach the teens from around I-72 northward, and 20s to the south. Snow looks to spread into western IL around sunrise, and extend rapidly eastward through the area by mid morning. Models depict frontogenesis over the area which could result in some localized heavy bands of snow. High resolution model guidance is congregating the heaviest precipitation around a line from Macomb to Danville as of this morning's model runs, with some variation. Current expectation is generally 3 to 5 inches in the heaviest corridor, and around 2 to 4 inches to the north as well as from near Jacksonville through I-70. Some localized heavier amounts can be expected, possibly exceeding 6 inches, however pinpointing these bands can't be done at this point. Snow should be ending by mid afternoon in western IL and by 8 pm at the IN state line.

The coldest air mass still lingers behind Saturday's snow, an cold advection with 10 to 15 mph NW winds will bring lows ranging from several degrees below zero (I-72 northward) to lower single digits (south of I-70) by Sunday morning. Wind chills should range from 15 to 25 below zero. These temperatures rival record lows for the date, although in a few days these temperatures would not be as impressive climatologically. The cold high pressure system should drift across the area Sunday night, producing another night of near or below zero temperatures, albeit with lighter winds early in the night. By Monday morning, southerly winds start to develop as the high moves east, and wind chills could be well below zero before temperatures start to moderate.

Dry conditions and moderating temperatures can be expected for the first half of the work week, with highs in the mid 20s to lower 30s Monday, mid 30s to lower 40s Tuesday, and mid 40s to around 50 Wednesday.

A cold front around Thursday looks to bring the next chance for precipitation, which looks to be rain as the parent low looks to pass well to the north. Temperatures look to trim back slightly behind this front, with highs Thursday in the 40s and 50s, and highs Friday in the 40s.

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AVIATION

(For the 06z TAFs through 06z Saturday Night) Issued at 954 PM CST Fri Dec 12 2025

MVFR ceilings continue area-wide this evening ahead of a cold front coming down from Iowa. Along that front, some snow showers are resulting in localized visibility reductions, for which we've added a prob30 group to PIA from 06-08z. Elsewhere, confidence is too low in the snow holding together to add a mention, but this will need to be watched carefully over the next several hours as that front sinks south into central IL. An uptick in northwest winds is expected with this front, with sustained speeds reaching 10-14 kt and possibly a couple gusts to 20 kt. Those winds will ease somewhat and veer to a more northerly direction as a low pressure system passes to our south, bringing accumulating snow Saturday morning. HREF indicates high confidence (60-90% chance) in visibilities dropping to a half mile or less with this activity, which should taper from west to east after around 22z.

Bumgardner

ILX WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory from 7 AM to 8 PM CST Saturday for ILZ027>031-036>038-040>057-061>063-066>068.

Cold Weather Advisory from 8 PM Saturday to noon CST Sunday for ILZ027>031-036>038-040>057-061>063-066>068-071>073.