textproduct: Central Illinois

KEY MESSAGES

- Dangerous cold persists through tonight, with wind chills as cold as 15 to 30 degrees below zero at times.

- Areas of blowing snow are possible late tonight into Monday morning. This could result in localized, sharp visibility reductions, as well as drifting of snow onto roadways. The greatest impacts will be on east-west oriented roads.

- A warming trend is expected this week, with highs in the mid 40s to mid 50s by Thursday.

DISCUSSION

Issued at 325 AM CST Sun Dec 14 2025

*** DANGEROUS COLD ***

Saturday's event brought a stripe of 5-8" of snow roughly from Galesburg/Macomb east to Danville, with slightly lower amounts of 3- 6" southward to the I-70 corridor. Snow has long since ended and strong sfc high pressure (1040 mb) has settled over the central Plains, with clear skies across the ILX CWA overnight/early Sun AM. Dangerous cold remains the top concern, with air temps ranging from the single digits south of I-72 to the single digits below zero along/north of I-72/Danville. With the sfc high still off the to west, northwest winds of 5 to 15 mph have resulted in widespread apparent temps of 10 to 20 below zero, with some locations dropping as low as 25 below at times. The extreme cold warning/cold weather advisory for Sunday morning were not changed.

The bitter cold air mass will remain in place through the day, with the snow cover further helping to limit warming during the day despite ample sunshine. The result in highs stuck in the single digits above zero. The sfc high will shift almost directly overhead by this evening, resulting in favorable radiational cooling during the evening. Accordingly, anticipate temps will drop sharply after sunset, with some of the coldest temps of the night occurring during the evening/late evening hours (single digits below zero). The high will continue shifting east through the night, resulting in the development of southerly flow that steadily increases in strength, peaking at 10-20 mph. Despite this southerly wind warming temps slightly during the overnight, the net result of the winds will be to push the apparent temps back to advisory criteria (as low as 20 below). The latest HREF (14.00z) gave a 50-80% chance of meeting advisory criteria, roughly along a Macomb to Shelbyville line (and eastward), thus the cold weather advisory was extended in these areas through 6 AM Monday.

*** BLOWING/DRIFTING SNOW ***

With no melting anticipated today, the lack of a surface crust on the fresh snow pack will leave the region susceptible to blowing/drifting snow during periods of elevated winds. Some patchy blowing snow is possible early this morning, but winds are currently around 15 mph or less, with weakening expected into the day as the sfc high approaches. A better chance will be late Sun night into Mon morning as those southerly winds develop and become breezy. Added a mention of blowing snow to the forecast during this time frame. The greatest impacts will be on east-west oriented roads. Localized, sharp visibility reductions are possible in any areas of blowing snow.

*** MID-WEEK WARM UP ***

Below normal temps have dominated the forecast since Thanksgiving, but mercifully, some warmer conditions are on the horizon. After southerly flow on Mon, a sfc low is set to track north of the Great Lakes on Tues, keeping southerly winds locally. However, with the seasonably deep snow pack in place, it's going to be difficult to warm much above freezing, and the NBM keeps highs in the mid/upper 30s in most locations. Combined with the breezy winds, I don't think it will feel mild, but at least it's not more bitter cold.

However, the warming trend steadily persists through the week, with the warmest day expected to be Thurs as very breezy southerly flow develops ahead of an approaching cold front. Temps are forecast to climb into the mid 40s (north of I-74) to mid 50s (south of I-70), but once again, the breezy winds will prevent it from being all that enjoyable. The associated sfc low will track towards the northern Great Lakes on Thurs, with a greater than 50% chance of sfc pressure falling below 990 mb, which will result in the strong pressure gradient across IL. Will need to keep an eye on the potential for a wind advisory Thurs, as the latest NBM has a 40-70% chance for gusts over 40 mph. Precip appears likely along/ahead of the cold front, with the temps favoring primarily rain, although a brief transition to a rain-snow mix can't be ruled out, depending on how quickly cold air surges in behind the front. Guidance currently has a 20-60% chance for over a quarter inch of liquid precip with this system, with probabilities increasing with eastward extent.

Depending on the timing of the front, we may experience non- diurnal temp trends on Thurs (temps falling during the day following the frontal passage), but will need to evaluate higher resolution guidance to better assess these specifics. At any rate, another push of cold air will move in by Thurs night, albeit nothing as extreme as the current air mass. The NBM has just a 20-40% chance of air temps falling into the single digits north of I-70.

Erwin

AVIATION

(For the 12z TAFs through 12z Monday Morning) Issued at 504 AM CST Sun Dec 14 2025

VFR conditions are favored through the period, although patchy blowing snow could result in localized vis reductions during the first few hours of the period. Northwest winds, around 10 knots currently, will weaken through the day and eventually become light and variable during the afternoon. South-southwesterly winds develop overnight into Monday morning. Will need to monitor the potential for marginal LLWS around 12z Mon as a 45 kt LLJ shifts overhead. Blowing snow is also possible Monday morning as the southwesterly flow increases. For now, did not include LLWS or BLSN in the TAF for Mon AM.

Erwin

ILX WATCHES/WARNINGS/ADVISORIES

Cold Weather Advisory until 6 AM CST Monday for ILZ027>031-036- 037-040>042-048-051-062-063.

Extreme Cold Warning until noon CST today for ILZ038-043>046- 052>057-061.

Cold Weather Advisory from noon today to 6 AM CST Monday for ILZ038-043>046-052>057-061.

Cold Weather Advisory until noon CST today for ILZ047-049-050- 066>068-071>073.