textproduct: Central Illinois

KEY MESSAGES

- Areas north of Interstate 70 face a high chance (60-70%) of widespread light wintry precipitation tonight and into Thursday morning. Additionally, a conditional threat exists for locally heavy snowfall within one or two narrow corridors. However, the probability of these corridors receiving 1 inch or more of snow is currently low to moderate (30-50%).

- Additional wintry precipitation is possible (40-60% chance) early next week.

DISCUSSION

Issued at 355 AM CST Wed Feb 25 2026

A cold front has settled just south of the region early this morning, which will keep us on the cool side of the boundary today with afternoon highs near 40 degrees. This boundary could then sharpen a bit late tonight and into Thursday morning as mid-level shortwave energy and its attendant surface low track across the Central Plains and into the Ozarks, bringing forth our next weather-maker.

Forecasting tonight's event remains challenging due to several uncertainties, primarily the placement of any enhanced mid-level frontogenesis and the precise thermal profile, which will dictate precipitation type. Currently, there are two potential outcomes worth considering.

Scenario A, the most probable outcome, suggests only limited, sub- advisory weather impacts. In this scenario, the surface-low pressure system moving across the Ozarks late tonight is poorly defined. Weak mesoscale forcing (FGEN) across Illinois would prevent the development of enhanced snow bands, leading instead to light snow generally north of Interstate 72.

South of Interstate 72, the precipitation may transition to sleet. Thermal profiles indicate partial melting between 2,000 and 3,000 feet, followed by refreezing near the surface. Soundings also show weak instability approaching from the south, which could increase the likelihood of graupel near and south of Interstate 72, extending toward Interstate 70.

The period around sunrise Thursday morning is expected to bring a shift to patchy freezing drizzle. This occurs as cloud ice nuclei rapidly diminish while residual low-level omega and low-level relative humidity briefly align before dissipating.

Scenario B presents an alternative, albeit less favored, outcome supporting heavier snow and sleet across central Illinois. This scenario involves a more organized surface-low tracking through the Ozarks and a sharper baroclinic zone, which would result in stronger mesoscale (FGEN) forcing over Illinois, increasing the potential for heavy banded snow.

Evidence for this scenario is seen in the 03z RAP, which depicts two distinct 700mb FGEN circulations between 9 PM and 5 AM. The first band is centered approximately along Interstate 74 give or take 40 miles north or south, with a second band developing later between Interstate 72 and Interstate 70.

Should the stronger mesoscale banding depicted by the RAP take shape and even over-perform, then the upshot would be a 1-3 inch snowfall along a narrow corridor or two in the areas outlined above. Specific models supporting this narrative include yesterday's 12z HRRR and this morning's 06z RRFS run.

Even under Scenario B, patchy freezing drizzle remains plausible into Thursday morning.

Quiet and mild weather then returns by the end of the week as a ridge of high pressure settles in behind our midweek precip event. Temperatures for Friday look to be near 60 degrees until a backdoor cold front sags across the area by late Friday night into Saturday, eventually pushing temperatures back down toward seasonal norms for Sunday and Monday.

For the second night in a row, global deterministic guidance is resolving a high-impact winter storm targeting central Illinois in the Sunday night to Monday morning timeframe. The synoptic setup, featuring a large surface high over the Great Lakes and a signal for overrunning precipitation across the Central Plains, Ozarks, and Mid-Mississippi Valley, climatologically favors icing conditions. While the model spread in temperatures for this period remains too large to have high confidence in the ice versus snow potential, the overall pattern is noteworthy.

MJA

AVIATION

(For the 12z TAFs through 12z Thursday Morning) Issued at 532 AM CST Wed Feb 25 2026

Mid-level clouds will slowly push south this morning with VFR conditions expected through this evening. An upper disturbance will bring a quick shot for snow showers and MVFR conditions late tonight into Thursday morning. Probabilities for IFR ceilings/visby are nonzero, but appear low at this time. Northwest winds will veer to the north-northeast tonight with speeds around 12 kts or below through the period.

NMA

ILX WATCHES/WARNINGS/ADVISORIES

None.