textproduct: Central Illinois

KEY MESSAGES

- Cooler today, with highs in the 20s, but a modest warm up is expected to push highs into the upper 30s and low 40s by Friday.

- A more notable warm up is expected next week, with a 50-80% chance for highs above 50 degrees each day Tuesday through Thursday (February 10th through 12th).

DISCUSSION

Issued at 129 AM CST Wed Feb 4 2026

*** TODAY ***

A low-impact stretch of weather is forecast across central IL through at least the next several days. Early Wed AM, an upper level Rex Block was anchored over the western US, while a weak trough persisted over the Midwest. At the sfc, a weak sfc high (1030 mb) was present over the upper Midwest, keeping light northerly winds across the ILX CWA.

The main forecast challenge early this morning is the short-term temperatures, as low-level moisture advection off Lake Michigan has led to a stratus deck extending as far south as Mattoon as of 07z/1am (encompassing areas along and east of I-57 to the north of Mattoon). Areas beneath the stratus deck remain in the low 20s, while cloud free areas are in the low teens. NT microphysics satellite imagery shows scattered low clouds developing west of the current deck, so some expansion of the stratus appears likely through daybreak. Expect some variable temperature readings across the area this morning, with the cloud covered areas warmer than the cloud-free areas.

Based on low-level RH fields, models suggest these lake-enhanced clouds will persist into the day Wed, most prevalent east of the IL River. Highs today are expected to be cooler than previous days, only in the 20s, with upper 20s west of the IL River where better insolation is expected. Lows Wed night could once again be impacted by the sky cover. Low clouds could linger near/east of I-57 into the evening, then a shortwave digging into the upper Great Lakes will lead to mid/high clouds overspreading the ILX CWA from the northwest after 06z Thurs/midnight. The low temps were nudged a few degrees warmer than previous forecasts, with values in the teens.

*** REST OF THE PERIOD ***

Two clipper systems pass by to the north late this week, with one on Thurs and another on Fri. In both cases, PoPs for the ILX CWA are less than 10%. These waves will induce southwesterly sfc flow locally that results in a minor warming trend through Fri, when highs reach the low to mid 40s across most of the CWA. The Fri clipper will send a cold front through, with an expansive high pressure shifting over WI Fri night. While we do trend cooler for Saturday, this will only be a glancing blow of cold air, as the Arctic air associated with this system instead pushes into New England. (By Saturday morning, 850mb temps over the ILX CWA will range from -1 to -5 degC, compared to below -20 degC over New England).

After Saturday, a more notable warming trend begins into next week as the amplified upper pattern breaks down and height rises occur over the Plains/Midwest. Ens guidance favors highs in the 40s for much of the area Sun/Mon, then 50s Tues/Wed. Touching 60 degrees isn't out of the question either, with a 20-40% chance (increasing with southward extent) each day Tues-Thurs of next week.

Some deterministic models continue to hint at another clipper system on Sun. Can't rule out precip, but for now ensembles keep the probability below 10%. There are rain chances next week, although specific timing and amounts are low confidence at this range. The NBM offers a 30-40% chance of total rainfall exceeding a half inch through Thursday of next week. That won't bust the ongoing Extreme D3 (D3) drought across portions of eastern IL, but any rainfall will be welcome.

Given the unseasonably warm temps and rain chances, it's understandable to wonder if the environment could support severe thunderstorms. As is often the case in the cool season, the instability is the potential limiting factor. The LREF depicts low- end probability of a marginally supportive environment during the middle of next week (10% chance of both CAPE over 250 J/kg and 30 kts of bulk shear). The LREF mean also has bulk shear over 30 kts through next week (at times over 50 kts), so as expected it is the instability that is holding these probabilities back. We'll keep an eye on how this evolves, but for now the threat appears low.

Erwin

AVIATION

(For the 12z TAFs through 12z Thursday Morning) Issued at 425 AM CST Wed Feb 4 2026

Main challenge this period is the evolution of MVFR stratus. As of 1025z, satellite showed overcast skies along and east of I-57, with scattered/inconsistent cloud development to the west. Confidence is highest that MVFR ceilings persist at KCMI, but models do suggest a westward progression of the stratus. Ultimately went with some mention of MVFR ceilings (either prevailing or TEMPO) at all sites today. Ceilings should gradually rise into the afternoon, along with increasing breaks in the cloud deck. Light north-northeasterly winds will become variable this evening, then develop out of the southwest late in the period. Broken mid/high clouds will overspread the region from west to east towards the end of the period.

Erwin

ILX WATCHES/WARNINGS/ADVISORIES

None.