textproduct: Central Illinois

KEY MESSAGES

- Well above normal temperatures persist through Friday, with highs climbing to the mid 70s to around 80 degrees, around 15 degrees above normal.

- Scattered light showers are possible Thursday through Saturday along a weak frontal boundary, but rain amounts will be light and localized.

- A pronounced pattern shift this weekend through early next week brings high confidence in more widespread rainfall and cooler temperatures.

DISCUSSION

Issued at 1223 PM CDT Tue Oct 27 2026

Latest water vapor imagery and upper air analysis indicated a shortwave trough tracking into northwest MO. Ahead of this feature, high clouds have increased west of I-57. Regional radar mosaics showed scattered showers over IA and northern MO, though surface obs indicate most of this is virga south of I-80 due to dry air in the deep sub-cloud layer. Short range guidance including the HRRR and RRFS indicate some radar returns over the area late afternoon to early evening, however, forecast soundings continue to show quite dry air in the lowest 10k feet of the atmosphere. Thus, feel anything reaching the ground will be limited to sprinkles. Otherwise, mostly cloudy skies and seasonably warm weather will continue, with highs likely a couple degrees cooler than yesterday thanks to increased cloud cover.

Well above normal temperatures will continue through the end of the week, as we remain in southwest to zonal flow, on the northern periphery of strong mid level ridging centered over the southeast U.S. Highs in the upper 70s to around 80 will be common. These readings are a few degrees short of records which are generally in the mid 80s for late October. We'll begin to see a bit of a north- south temperature gradient develop on Thursday and Friday, as a weak front slips south into the area. Model consensus through this period shows moisture advection remains limited, keeping PoPs low and QPF light through Saturday with a few periods of isolated to scattered showers.

Medium range model guidance shows good agreement on a significant pattern change beginning later this weekend and persisting early next week. A powerful upper level trough is forecast to dig across the Rockies and into the Plains Sunday- Monday. Most solutions favor an amplified, slow-moving system tracking across the Midwest early next week. This would allow a plume of rich, sub-tropical moisture to advect north. Various guidance shows PWATs surging above 1.8", or near the top of climatology for early November. At this range we still see significant differences on timing and location of best forcing, but for now the NBM shows highest PoPs (likely category) Monday and Tuesday. An early look at QPF from the LREF shows around an 80% probability of exceeding a half inch, and 60% chance of exceeding 1 inch, with the highest probabilities west of I-55. With the increased areas of precip and cloud cover, temperatures should trend down, though latest NBM still shows readings several degrees above normal through Tue.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 655 PM CDT Tue Oct 27 2026

Cloud cover around 12000 ft AGL will lower to around 8000 ft by 16Z, but VFR conditions are expected to continue. Winds S around 5 kts, increasing to around 10 kts by 16Z.

ILX WATCHES/WARNINGS/ADVISORIES

None.