textproduct: Central Illinois

KEY MESSAGES

- Lingering Showers North Today: Isolated to scattered light rain showers will affect areas near and north of Interstate 74 through this evening, bringing little to no measurable accumulation.

- Widespread Frost and Freeze This Weekend: High confidence in cold overnight temperatures falling into the lower 30s Friday night and Saturday night. - Extended Dry Stretch Ahead: Dry and quiet weather with plenty of sunshine will prevail through at least the middle of next week as daytime highs rebound into the 60s by Monday.

DISCUSSION

Issued at 119 AM CST Thu Nov 5 2026

Water vapor imagery highlights a potent 500 mb shortwave trough digging equatorward from Ontario into the Great Lakes basin. As this vorticity maximum phases with the broader cyclonic flow, a slow-moving surface low will pivot its wrap-around moisture plume and deformation axis back southwestward across central and eastern Illinois. This setup will maintain overcast skies and generate scattered to periodic light rain showers, mostly near and north of the I-74 corridor.

A sharpening baroclinic zone and its accompanying cold front will advance southward through the state tonight. Strong cold air advection in its wake will usher in a significantly cooler, drier continental polar (cP) air mass to finish the workweek.

Deep-layer northwesterly flow following the departing trough will rapidly scour out remaining low-level moisture by Friday morning. An expansive 1024 mb surface high centered over the Canadian Prairies will build southeastward into the Midwest for the weekend, establishing a prolonged stretch of tranquil autumn weather.

Thermal profiles will feel chilly early Friday, with 850 mb temperatures dropping into the -5C to -2C range. Sensible weather over the weekend will feature crisp daytime highs in the low-to-mid 50s under mostly sunny skies. Efficient nighttime radiational cooling--driven by light winds and a clear, dry boundary layer--will foster widespread frost, as overnight lows fall into the lower 30s across the region. Agricultural and late-season gardening interests should prepare for widespread frost/freeze potential Friday night and Saturday night.

Looking ahead to next week, ensemble consensus (GEFS/EPS) shows strong agreement on an amplified synoptic pattern anchored by persistent mid/upper-level ridging over the central CONUS, flanked by an anomalous cut-off low meandering over the Deep South and Gulf Coast. This blocking regime will limit poleward Gulf moisture transport, securing dry and quiet weather through mid-week. As the air mass modifies and 500 mb heights rise, temperatures will gradually moderate back into the 60s starting Monday.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 534 AM CST Thu Nov 5 2026

A potent shortwave trough advancing from the northwest has driven a return of low-end MVFR cloud cover this morning, which will last through tonight. As synoptic forcing pivots directly overhead, scattered light rain showers are expected to develop during the late afternoon and early evening, potentially bringing localized IFR ceilings and transient MVFR visibility reductions. Sustained southwesterly breezes around 10 kts this morning will persist through the afternoon, with peak gusts approaching 20 kts. An advancing cold front will veer surface winds to the northwest by tonight.

ILX WATCHES/WARNINGS/ADVISORIES

None.