textproduct: Central Illinois

KEY MESSAGES

- Precipitation chances have increased modestly for Wednesday, though the chances of greater than a quarter-inch of total rainfall are still limited (20-30%).

- After a stretch of high temperatures largely in the 60s from Sunday through Wednesday, another notable cool-down is anticipated later next week. There is a 50-80% chance of high temperatures below 50 degrees on Friday.

DISCUSSION

Issued at 146 PM CST Sat Nov 7 2026

Light winds are in place across central and southeast Illinois this afternoon, influenced by a surface high centered over north-central MO. Some high cloudiness associated with a weak positively-tilted short-wave trough over NE and KS is affecting the region, but dry weather and slightly below normal temperatures for early November persist.

A fast-moving short-wave trough will transit across the Great Lakes from tonight through Sunday afternoon, mainly bringing a band of high clouds through central Illinois Sunday morning but with at least some chance of morning stratus, given nearly saturated forecast soundings below about 2-3 kft. Otherwise, anticipate a shift in winds back to the west-northwest with an increase in wind speeds on Sunday afternoon, but temperatures on Sunday should be around 10 degrees warmer than they were today.

Once winds relax early Monday morning and temperatures cool, look for fog potential to increase due to strong radiational cooling and saturated near-surface conditions. REFS member forecasts are currently split on whether visibilities below one-half mile will develop, but the potential will need to be watched. Forecast soundings are favorable, with a strong low level inversion and light wind speeds.

For Monday and Tuesday, anticipate steadily warming daytime temperatures and dry conditions through a period of zonal flow aloft. From Tuesday night into Wednesday, the upper level pattern begins to amplify with a strong ridge developing over the western US and a deep trough being carved out east of that. The typical variability exists at this time range regarding timing and placement of individual short-wave troughs embedded in the flow and the relative strength of the main ridge/trough, but given that every cluster has the same general pattern, confidence in that is relatively high. Concurrently, there has been a modest increase in precipitation chances for Wednesday as the initial wave makes its way into Illinois. Mean ensemble precipitable water values are at around 0.6-0.8 inches, but the 90th percentile (10 percent chance of exceedance) is up to around 1 inch. Given the variability in placement/timing of individual short waves, there remains only around a 20-30 percent chance of greater than a quarter inch of total rainfall from early Wednesday morning through early Thursday morning.

Though precip potential remains on the modest side at this point, we can be fairly confident in a notable cool-down late next week after being largely in the 60s from Sunday through Wednesday. The pattern in the latter half of next week indicates northerly flow and perhaps multiple pushes of cool air. Though nothing highly unusual for mid-November is anticipated at this point, look for a 50-80% chance of high temperatures below 50 degrees on Friday, with a 20-40% chance of high temperatures below 45 degrees. About half of the ensemble membership translates the ridge eastward and begins warming temperatures on Saturday next week, while the other half shows a persistent trough over the eastern US and would likely continue colder temperatures into next weekend.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 1026 PM CST Sat Nov 7 2026

VFR conditions continue next 24 hours. Light southwest winds tonight will veer west late morning, with some gusts near 20 kt through Sunday afternoon.

ILX WATCHES/WARNINGS/ADVISORIES

None.