textproduct: Central Illinois

KEY MESSAGES

- Periods of showers and storms will bring mostly beneficial rain to the area through early Saturday. There is a low (5-15%) risk for localized flooding in areas that already received heavy rainfall.

- There is a level 2 of 5 risk for severe weather from roughly 2-10 pm today, except a level 3 risk north of a Macomb to Pontiac line. The primary hazard will be damaging wind gusts, but there is also a low chance for tornadoes and large hail.

- From roughly 11am to 6pm today, strong winds will blow from the south, causing difficult driving conditions for high profile vehicles on west-east roadways. Gusts are likely (60-80% chance) to peak over 45 mph.

- There is a low chance of a severe thunderstorm Friday afternoon and evening, with all hazards in play. There is a higher chance for thunderstorms after midnight Friday night, mainly west of I-55. Damaging wind gusts will be the main risk with that second wave, but there is also a low chance of a tornado.

- Overnight lows are likely (50-80% chance) to fall into the mid 30s or lower each morning Sunday through Tuesday. Action may be needed to protect newly-emerged, tender vegetation.

DISCUSSION

Issued at 307 AM CDT Thu Apr 2 2026

***** WINDY WITH SCATTERED STORMS TODAY *****

At 3am, periods of showers with a couple embedded thunderstorms were lifting northeast through an expansive warm conveyor ahead of an upper level trough over the Central Plains. Temperatures across central Illinois were in the 40s, but these are progged to climb sharply as a warm front surges north later this morning. Moisture advection will be robust behind that front given vigorous southerly winds, with dewpoints climbing solidly into the 60s area-wide by noon.

Temperatures and winds today were a tricky forecast due to model disparities in if/when we'll have breaks in cloud cover. HREF suggests 40-60% (80%+) chances for low (high) cloud cover through mid afternoon, with decreasing chances west of I-55 thereafter. Our forecast looks a lot like the National Blend of Models (NBM), though these mid 70s highs north of I-70 might be a tad optimistic if we don't see many afternoon breaks of sunshine.

With a low level capping inversion and prolific clouds, mixing depth and hence magnitude of these winds is unclear. Even so, Bufkit forecast soundings from several CAMs indicate a 1-3 hour period in any given location (between 11am and 6pm) when the 40-45 kt winds at 900mb may mix down, resulting in frequent southerly gusts over 40 (sporadically 50) mph. In coordination with neighboring offices, the Wind Advisory was expanded to encompass the entire forecast area.

Late morning into early afternoon, a prefrontal trough will tap into 500-1000 J/kg surface based instability to generate scattered thunderstorms across the area. Mid level lapse rates are paltry and low level moisture will be on the high side, but strongly clockwise- curved hodographs resulting in 200-350 m^2/s^2 of 0-3km SRH could favor a few cells capable of severe hail. Additionally, RAP/HRRR LCLs are less than 500m, favoring at least a low tornado risk given 30+ kt 0-1km shear. The primary risk, however, will be strong to locally damaging wind gusts given the aforementioned kinematic profile. Damp soils in areas that received heavy rainfall Tuesday night will be especially vulnerable, with a few shallow rooted trees potentially toppling (resulting in roof damage and/or power outages) where gusts surpass 60mph.

As those storms exit the forecast area by early evening, there is potential for a second wave mainly west of I-55 where a couple hours of surface heating may generate 1000-2000 J/kg uncapped MLCAPE in a modestly sheared (30-40 kt 0-6km) environment characterized by low LCLs. In this volatile airmass where sigtor values are modeled (HRRR/RAP) at 2-5 (locally higher), it's unclear whether storms will fire given optimal upper level forcing will be displaced well to our north across Iowa, but if convection erupts all severe hazards would be in play from roughly 5-10pm.

***** MORE STORMS TOMORROW INTO SATURDAY *****

A more potent upper level low is progged to move northeast from the Central Plains into the Upper Midwest tomorrow into Saturday. Ahead of the surface low and attendant cold front, a line of severe storms is slated to develop upstream across Iowa, Missouri, Kansas, and Oklahoma tomorrow afternoon. While we may see a few stronger cells with the northward-lifting warm front from 2-7pm, the best opportunity for severe weather will come with the decaying line of storms that will enter west-central Illinois around midnight and cross the county warning area during the pre-dawn hours Saturday morning. The primary risk will be gusty to locally damaging winds, though a QLCS tornado cannot be ruled out, especially west of the Illinois River Valley where instability will be highest (and CIN lowest) ahead of the storms.

***** COOLER WEATHER RETURNS SATURDAY *****

Late Saturday morning into early afternoon, the cold front should cross central and southeast Illinois, bringing cool conditions to the region by Easter Sunday, when forecast highs are in the low to mid 50s. Frost/freeze headlines could become necessary any night Saturday through Tuesday, as temperatures likely (50-80% chance) fall into the mid 30s or cooler each night.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 606 AM CDT Thu Apr 2 2026

A warm front lifting through the area will bring an end to LIFR ceilings, IFR/MVFR visibilities, and LLWS over the next several hours, while scattered showers continue through the morning. During the afternoon, instability will increase favoring a few thunderstorms, with the highest confidence at CMI between 21-23z when a few models are showing a line of storms blowing through. A second wave of thunderstorms may develop along a cold front later this evening from 00-05z. Outside of storms, south winds will be quite strong, especially from 17z-00z when gusts may reach 40 kt at times. Those winds will ease and shift to a more westerly direction behind the front late this evening.

ILX WATCHES/WARNINGS/ADVISORIES

Wind Advisory from noon today to 7 PM CDT this evening for ILZ027>031-036-037-040-041-047>050. Wind Advisory from 10 AM this morning to 7 PM CDT this evening for ILZ038-042>046-051>057-061>063-066>068-071>073.