textproduct: Central Illinois

KEY MESSAGES

- Scattered storms are forecast late Thursday night into Friday. There is a low (5%) chance for severe weather, with locally damaging wind gusts the main risk.

- Another round of thunderstorms is likely (80% chance) Sunday night through Monday. There is at least a low risk for severe weather with these storms.

DISCUSSION

Issued at 115 PM CDT Wed Apr 22 2026

***** WARM AND BREEZY THROUGH THURSDAY *****

Water vapor satellite shows an upper level trough across the Great Basin and PacNW, with the RAP's 18z mesoanalysis indicating a 990mb low pressure system in central Montana. Meanwhile, a shortwave ridge remains in place across the Midwest to favor above normal temperatures in the mid to upper 70s again this afternoon. Tomorrow, this ridge will shift east into the Ohio Valley with the approach of the upper level trough from the west. The resultant sharpening pressure gradient will bring strong warm advection, with afternoon highs in the low 80s and southerly winds gusting to around 30 mph.

***** SHOWERS AND STORMS EARLY FRIDAY *****

Numerous storms are forecast to form along a cold front across the east-central Plains and Midwest tomorrow afternoon and evening, with weakening convection reaching our area late in the overnight period and lingering through Friday morning. Given the strengthening sfc pressure gradient and 40-50kt LLJ, we may stay sufficiently mixed for a wind threat to materialize with those storms - hence, SPC's marginal (level 1 of 5) risk for severe weather extends all the way east to I-57. However, CAM depictions of convective activity have it falling apart or becoming very messy in our area; thinking is that briefly heavy rain, localized small (up to dime-size) hail, and scattered gusty (40-50 mph) winds will be the worst we see.

The front becomes ill-defined and stalls near/south of I-72 on Friday, which could favor continued storms and a conditional severe weather risk throughout the day in our southeast counties. SPC's day 3 marginal (level 1 of 5) risk along and south of I-70 seems fitting given the uncertainty in northward extent of instability.

***** NEXT CHANCE OF STORMS SUNDAY NIGHT AND MONDAY *****

High pressure will settle over the region on Saturday, giving us a moment of repose before a southern stream wave lifts into the Midwest late Sunday into early Monday. Deterministic models and their respective ensembles have differences in the timing and strength of this system, but there seems to be a decent shot at severe weather. The Low Resolution Ensemble Forecast (LREF) system gives a 40-70% joint probability (highest south) for more than 45 kt of 0-6km bulk shear and more than 1000 J/kg MUCAPE, which would be more than sufficient for organized convection. This is highlighted with 15-30+% risks for severe weather from various machine learning models. At this time, SPC's Day 6 outlook for Monday keeps the 15%+ probabilities for severe weather south of our area, but we suspect this may expand further north in subsequent outlooks barring a large shift in global model/ensemble guidance.

This system will also bear watching for heavy rain if training storms form along the warm front late Sunday night into Monday. Confidence in if and where this occurs is low, but the National Blend of Models (NBM) advertises a ~10% chance for more than 2 inches of rainfall in any given location across central and southeast Illinois. Outside of showers and storms, it will be breezy on Monday with south winds likely (50-60% chance) gusting upwards of 35 mph during the late morning and afternoon.

***** TURNING LESS WARM MID NEXT WORK WEEK *****

Behind the cold front, conditions will turn cooler Tuesday into Wednesday. In fact, NBM advertises a 50-70% chance high temperatures fall short of 70 degrees each day. It's worth noting that while this will feel cooler than what we've become accustomed to the past few weeks, average highs for late April range from the mid 60s to low 70s (from north to south) across the area.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 628 PM CDT Wed Apr 22 2026

VFR conditions will prevail at all sites next 24hrs. Skies should be clear through the period. Southwest winds will decrease and be less than 10kts through the night, then increase tomorrow out of the south with gusts of 25-27kts at all sites.

ILX WATCHES/WARNINGS/ADVISORIES

None.