textproduct: Central Illinois

KEY MESSAGES

- A quick hitting winter system will bring accumulating snow on Saturday. There is high confidence of seeing at least 3 inches of snow north of a Springfield to Mattoon line.

- Dangerously cold wind chills are expected both Saturday and Sunday nights. The coldest wind chills will drop as low as 15 to 25 degrees below zero.

DISCUSSION

Issued at 256 AM CST Fri Dec 12 2025

Surface low pressure is passing by to the south of here early this morning with light snow continuing to fall north of it across central Illinois. Snow reports late Thursday evening ranged from 2 to 4 inches, with additional snow amounts looking to remain below 1 inch this morning. Precipitation will come to an end by daybreak, with cold and mostly dry conditions expected today. High temperatures were lowered by several degrees due to increased cloudiness. Forecast highs will peak in the upper 20s to middle 30s.

Accumulating snow returns on Saturday as an upper disturbance originating from the Canadian Prairies dives southeast into the Great Lakes Region. A cold front tied to this system will work through the area later today, bringing an arctic push of air southward. Overnight lows tonight will dip down into the single digits to teens for most, with low 20s south of I-70. Snow will begin nosing into west-central Illinois by daybreak Saturday ahead of an upper shortwave with precipitation chances quickly spreading east through late morning. Snow will continue through most of the day before coming to an end Saturday evening. Forecast soundings show deep moisture with synoptic lift/DGZ depth supporting occasional bursts of moderate to heavy snow, especially north of I- 72 where strong ~600-700 mb frontogenetic banding looks to slide through late morning into early afternoon. The 12.00Z HREF has a 40- 70% chance for greater than 1 inch/hour snowfall rates in this same area, which could result in a narrow band of heavy snow potentially exceeding 6 inches. Confidence is high (50-80% chance) in seeing at least 3 inches of snow north of a Springfield to Mattoon line through Saturday evening. However, lower confidence remains in regards to the upper end amounts.

Strong high pressure drops into the middle Mississippi Valley for the second half of the weekend, bringing bitterly cold temperatures over a fresh snowpack. Overnight lows Saturday night will fall into the negative single digits with brisk northwest winds sending wind chills as low as -25 degrees. Similar conditions are expected Sunday night, though somewhat lighter winds will keep minimum wind chills in the single digits to teens below zero. Cold Weather Advisories will likely be needed both of these nights.

Southerly return flow will bring a warming trend heading into the new week, with high temperatures possibly climbing into the 40s by mid to late week. Cloud cover and a residual snowpack could truncate this though, which is evident by the large spread in temperature forecasts. Precipitation chances look low through most of the week with longer range guidance showing chances increasing by the end of the week.

NMA

AVIATION

(For the 06z TAFs through 06z Friday Night) Issued at 1039 PM CST Thu Dec 11 2025

Predominantly MVFR ceilings and IFR visibilities continue this evening as an area of snow drifts southeast through the region. While this activity should be tapering to scattered snow showers between 06-10z, it will leave lingering IFR ceilings and perhaps some patchy fog in its wake. As the surface low passes to the south, 4-8 kt winds will slowly back to a northeasterly direction early Friday morning, but then switch around to the west- northwest behind a cold front late morning-early afternoon. Guidance has become a little less optimistic on improvement in ceilings Friday, especially at SPI, DEC, and CMI, where IFR conditions are forecast through the end of the period.

Bumgardner

ILX WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory until 6 AM CST early this morning for ILZ031-037-038-042>046-051>057-061>063-066>068-071>073.