textproduct: Central Illinois

KEY MESSAGES

- Scattered thunderstorms are expected (90% chance) on Monday. There is a level 3 of 5 ("Enhanced") risk for severe weather from all hazards.

- Outside of thunderstorms, Monday will be a windy day. There is around a 70% chance winds will gust over 40 mph from the south, resulting in difficult travel conditions for high profile vehicles, especially on west-east roadways.

- There is around a 40% chance for thunderstorms Sunday night into Monday morning. In areas that don't receive this rain, the gusty south winds on Monday could pick up dust - resulting in patchy reduced visibility which could impact motorists.

DISCUSSION

Issued at 1250 PM CDT Sat Apr 25 2026

***** PLEASANT THROUGH THE WEEKEND *****

Early Saturday afternoon, high pressure was resulting in mostly sunny skies, gentle northeast breezes, and temperatures mainly in the 60s. A weak wave will move overhead tonight into tomorrow, but CAMs suggest this will result in nothing more than some mid-high clouds. Low levels will remain dry given afternoon mixing of dry air aloft down to the surface, along with continued easterly surface winds; this will allow efficient radiational heating to add a couple degrees to high temperatures tomorrow, with mid-upper 70s common.

***** SEVERE WEATHER ON MONDAY *****

An upper level trough coming onshore in southern California this afternoon will move across the Great Basin and into the High Plains tomorrow into tomorrow night. Surface cyclogenesis will occur beneath the left exit region of this trough where strong divergence and positive vorticity advection occur tomorrow night into Monday. Global models and their respective ensembles still have some differences regarding the track of the surface low, with the cyclone's center positioned anywhere from northern Missouri to central Minnesota at 4pm Monday in both the GEFS and EPS ensembles. This is resulting in low confidence in convective evolution, risks of various hazard types, and timing of storms on Monday. For example, a further southeast surface low track would imply a nearby warm front to serve as a focus for daytime supercells capable of very large hail and long-track tornadoes; meanwhile, a low track further northwest would imply the warm front is north of our area, and without that forcing we might escape without any supercells during the day. In addition, nocturnal storms upstream Sunday night could spill into our area mainly west of I-55 during the morning (40% chance), with their outflow boundaries potentially serving as triggers for midday renewed storms. (Given elevated instability, and what appears to be a gravity wave signal in a few of the CAMs, these morning storms could still generate localized hail and damaging wind gusts.) In either case though, a strong squall line, potentially with embedded supercell-like structures, seems plausible along the cold front (most likely during the evening or early overnight), bringing a risk for damaging winds and QLCS tornadoes given 50-60 kt effective bulk shear (35-50 kt in the lowest 3km) and sufficient instability. SPC has nearly all of central and southeast Illinois outlooked in a 45-60% risk for severe weather for Monday into Monday night.

Outside of storms, southerly winds could be quite strong Monday afternoon if breaks of sunshine allow for even modest mixing, as the NAM/GFS advertise 925 mb winds of 45-50 kt. The National Blend of Models (NBM) advertises a 70-80% chance wind gusts surpass 40 mph, and even a 10-20% chance gusts top 50 mph. While windy conditions are a common spring nuisance in this area, this raises concerns for blowing dust, especially near increased field activity in preparation for spring planting. Morning storms (40% chance) would drastically lower this potential, but if we don't receive that rain prior to the gusty winds we may need a Blowing Dust Advisory to highlight the risk of reduced visibilities to motorists.

Depending on storm morphology, we may need to keep one eye on the hydro risk Monday afternoon and evening. The primary concern will be if training storms set up in our area along the warm front (or an outflow boundary), since the squall line along the cold front would be moving upwards of 50-60 mph. NBM advertises a 10-20% chance for more than 2.3 inches of rainfall with this system. This is approximately 6-hour Flash Flood Guidance (FFG), meaning if this much rain falls during a 6-hour period we can expect hydrological impacts (at least nuisance urban or small stream flooding). WPC has our area outlooked in a level 1 of 4 (marginal) risk for excessive rainfall.

***** COOLER AND LESS STORMY TUESDAY AND BEYOND *****

Behind the cold front, conditions will turn cooler Tuesday through Thursday, with forecast highs in the low 60s (north) to low 70s (south) - near to slightly below normal for late April. Global models and their respective ensembles are in agreement that upper level troughing will park itself somewhere across the Northeast CONUS late week into the weekend, with northwest flow giving us reinforcing shots of cool air from the Upper Midwest. By Friday night, NBM suggests we'll have a 20-40% chance for low temperatures cooler than 37 degrees, which is roughly the threshold for frost (given light winds).

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1150 AM CDT Sat Apr 25 2026

High pressure will favor continued VFR conditions and 7-10 kt easterly winds throughout the forecast period. The High Resolution Ensemble Forecast (HREF) suggests there will be a 30-40% chance that MVFR ceilings impact BMI and CMI from 11-14z Sunday morning. This was not yet added to the TAFs, though a TEMPO group may be needed if confidence increases.

ILX WATCHES/WARNINGS/ADVISORIES

None.