textproduct: Central Illinois

KEY MESSAGES

- A Cold Weather Advisory remains in effect through midday for wind chill values of 10 to 20 degrees below zero. The threat of cold to occasionally very cold weather will return later this week.

- Near daily chances (10-30%) for light snow exist throughout this week and upcoming weekend, but with little or no new accumulation.

DISCUSSION

(through next Monday) Issued at 325 AM CST Mon Jan 19 2026

Periods of cold to occasionally very cold temperatures remain the primary forecast concern for the Midwest over the next 7 to 10 days. The pattern will largely be driven by a significant alignment of atmospheric teleconnections: the Arctic Oscillation (AO), North Atlantic Oscillation (NAO), and East Pacific Oscillation (EPO) are all deeply negative.

Analysis of this morning's northern hemisphere 5-wave chart confirms this setup. A massive ridge of high pressure is currently stationed over the Gulf of Alaska, which is a hallmark of a deeply negative EPO. At the same time, an anomalous ridge is impinging upon the North Pole, characteristic of a deeply negative AO. This configuration promotes the equatorward displacement of the Polar Vortex. Consequently, lobes of arctic air are expected to periodically slide down the eastern Pacific ridge toward the Great Lakes through the remainder of the month. The net impact will be occasional periods of below-normal temperatures, with readings projected to be 10 to 20 degrees below seasonal averages. This means there will be a handful of days forthcoming where afternoon highs struggle to rise into the 20s while overnight lows fall near or below zero.

An active storm track will coincide with this cold air, bringing a wavetrain of disturbances across the Upper Midwest. These quick- hitting, clipper-like systems may occasionally impact central Illinois directly; however, they are not expected to develop into significant mid-latitude cyclones, and therefore are not forecasted to produce significant snowfall over the next week.

The trend in the Eastern Pacific Oscillation (EPO) is a key teleconnection to watch. While currently deeply negative, the index is projected to trend toward neutral by the end of the week. This shift promotes a slight weakening and repositioning of the Alaskan ridge.

The change will allow moisture to leak under the ridge, a development supported by most model guidance. Specifically, a closed upper low is expected to meander past the California coast by Friday, drawing both Pacific and Gulf moisture into the southern US.

This pattern is anticipated to lead to a substantial overrunning event this weekend. Warm, moist air will ride over a strong cold dome descending across the Midwest, creating a threat of sleet and freezing rain across the South, and accumulating snow across parts of the Ozarks and Tennessee Valley.

For central Illinois, however, recent forecast cycles have indicated a colder and drier trend for the weekend, with the most impactful wintry precipitation likely tracking just south of the area.

MJA

AVIATION

(For the 12z TAFs through 12z Tuesday Morning) Issued at 401 AM CST Mon Jan 19 2026

Early morning satellite imagery depicts narrow ribbons of stratus embedded in cyclonic flow. Upstream observations across central and southeast Iowa reveal that these ceilings have generally been in the MVFR category with even scattered snow showers accompanying them.

The central Illinois terminals will remain on the southern periphery of these lower clouds and scattered showers throughout the morning.

Have ultimately designated the coverage of clouds as SCT and not BKN, and believe that coverage will continue to wane throughout the morning as drier air moves in amid diurnal heating.

A period of mostly clear skies is likely this afternoon before an area of mid-level clouds push across the region by this evening.

Surface winds will remain from the west with sustained speeds between 10-15 kts and occasional gusts between 20-30 kts, diminishing this evening as high pressure passes just south of the region.

MJA

ILX WATCHES/WARNINGS/ADVISORIES

Cold Weather Advisory until noon CST today for ILZ027>031- 036>038-040>057-061>063-066>068-071>073.