textproduct: Central Illinois

KEY MESSAGES

- A quick hitting winter system will bring 2 to 5 inches of accumulating snow north of I-70 today. A narrow corridor of amounts exceeding 5 inches is most likely near or north of a Macomb to Champaign line.

- Dangerously cold wind chills are expected tonight into Sunday morning, and again Sunday night into Monday morning. The coldest wind chills will drop as low as 15 to 25 degrees below zero.

DISCUSSION

Issued at 324 AM CST Sat Dec 13 2025

An upper low is entering the northern Great Lakes Region early this morning with a surface low just north of there in Ontario. A cold front stretches southward through the Midwest states, with it approaching I-70 as of 3 am. Winds are brisk behind the front with gusts up to 20 mph being observed. Temperatures will continue to tumble behind the front with readings already in the single digits across eastern Iowa. Most will reach their daytime highs this morning as temperatures steadily fall throughout the day. Midday temperatures will range from the single digits near Galesburg, teens over central parts of the state, and low to middle 20s south of I-70. Even colder air arrives tonight... more on that later.

Accumulating snow is expected today as an upper shortwave swiftly slides across the area. Snow will begin nosing into west-central Illinois by daybreak with chances quickly overspreading most locations north of I-70 by 9 or 10 am. Snow will continue through this afternoon before pushing east of here early this evening. Forecast soundings show strong synoptic lift overlapping the dendritic growth zone (DGZ) between 500-700 mb, with a secondary DGZ located in the lowest ~900 mb. Light winds and high snow ratios (15-20:1) will favor light, fluffy dendrites that will lead to quick snow accumulations. A narrow corridor of moderate to heavy snow is expected where strong ~600-700 mb frontogenetic banding slides through later this morning, which appears most likely near or just north of a Macomb to Champaign line. The 13.00Z HREF highlights a 50-70% chance for 1"/hour snowfall rates in this same area between 11 am and 2 pm. Confidence is high that most areas north of I-70 will receive 2 to 5 inches of snow with amounts exceeding 5 inches most likely near or just north of a Macomb to Champaign line. A Winter Weather Advisory remains in effect until this evening.

Strong high pressure drops into the middle Mississippi Valley by Sunday. Skies will clear with the approaching high overnight, allowing low temperatures to fall below zero. A tight pressure gradient ahead of the approaching high will lead to brisk northwest winds with gusts upwards of 25 mph tonight, potentially leading to some blowing and drifting of fresh snowfall. Wind chills will plummet with coldest readings expected to range from 15 to 25 degrees below zero through Sunday morning. Temperatures will remain bitterly cold during the day Sunday with highs looking to near or break record lowest maximum temperatures for the day. Winds will become light on Sunday as the center of the surface high moves right overhead, allowing wind chills to improve some. Sunday night lows will fall below zero once again, with winds expected to increase as the surface high slides off to our east. Wind chills Sunday night into Monday morning will bottom out between 15 to 20 degrees below zero. A Cold Weather Advisory is in effect for tonight into Sunday morning, with another likely needed Sunday night into Monday morning.

Southerly return flow will bring warmer temperatures heading into the new week, with highs looking to approach the 40s to near 50 by midweek. Our next chance for precipitation comes in the form of rain as a cold front moves through later in the week.

NMA

AVIATION

(For the 12z TAFs through 12z Sunday Morning) Issued at 454 AM CST Sat Dec 13 2025

A quick hitting winter system will bring accumulating snow to central Illinois today. Flight conditions will worsen as snow arrives between 14-15Z, with visibility dropping as low as 1/2 to 1/4 mile. Ceilings will range from MVFR to IFR, with higher chances (60%) for <1k ft ceilings with the precipitation. Snow will come to an end later this afternoon or early this evening, with skies clearing and ceilings improving to VFR later tonight. Northwest winds will increase to 10-15 kt overnight as an area of strong high pressure approaches from the northwest.

NMA

ILX WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory until 8 PM CST this evening for ILZ027>031-036>038-040>057-061>063-066>068.

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