textproduct: Central Illinois

KEY MESSAGES

- Severe weather is possible Sunday afternoon and evening, primarily east of Interstate 55, with damaging winds as the primary hazard. - A sharp transition from rain to snow occurs Sunday night behind a strong cold front, accompanied by wind gusts over 40 mph and rapidly falling temperatures.

- Sub-freezing high temperatures and minimum wind chills between 0 and -10 degrees for Monday and Tuesday before a significant warming trend takes over for the last half of next week.

DISCUSSION

Issued at 157 PM CDT Fri Mar 13 2026

Current surface analysis shows a departing 989 mb low over the northern Great Lakes, leaving central Illinois in a brisk westerly gradient flow. High-resolution guidance indicates wind gusts will gradually subside this afternoon and early evening as a transient surface ridge builds in. Will keep the northeast sections of the Wind Advisory going until 4 pm expiration as we're still seeing some gusts near 45 mph there. Later tonight into early Saturday morning, a wing of warm advection increases cloud cover, and HREF probabilities suggest a slight chance for light snow or flurries over the far northern CWA. Airmass remains quite dry so we don't have any accumulation mentioned.

A strong mid-latitude cyclone is slated to impact the region Sunday, as a deepening surface low (sub-990 mb) tracks from the Central Plains into the Great Lakes. Ahead of the cold front, southerly gradient winds increase significantly, with gusts gusts reaching 35-45 mph midday and afternoon. A robust 850 mb low- level jet in excess of 70 knots will facilitate moisture return and strong kinematic support. While thermodynamic instability remains limited (MLCAPE ~500 J/kg), the intense deep- layer shear and strong linear forcing suggest a squall line and potential QLCS event. Model consensus is high regarding the severe threat being concentrated east of I-55 with an Enhanced Risk (Level 3 of 5) east of I-57.

Behind the front, intense cold advection takes hold Sunday night. Precipitation transitions to snow within the deformation zone of the departing low. 12z guidance has backed off on the intensity of the deformation zone snows this far south, and latest blended guidance has decreased accumulations to 1-3", highest north. However, the combination of falling snow and northwesterly gusts over 40 mph could create hazardous travel conditions and will be monitoring need for headlines Sunday night. A flash freeze may also be in play due to initially warm ground/melting on roads followed by plummeting temps.

An unseasonably cold, late season Arctic airmass will dive southeast across the Midwest behind the storm. The ECMWF EFI shows values between -0.7 and -0.8 for Monday and Tuesday, indicating an unusual cold event for mid- March. Latest blended guidance shows 20s high temperatures Monday and lows in the single digits Monday night. Breezy conditions through the period will likely drive wind chills to the single digits above zero Sunday night and single digits below zero Monday night.

Medium range guidance shows a clipper crossing the Midwest Tuesday night. Depending on the track of this low, minor accumulations would be possible.

For mid to late week, the deep upper low departs the region, allowing for significant height rises and moderating temperatures. NBM indicates a return to 60s highs Thu/Fri, which aligns with the CPC 6-10 day outlook favoring a transition toward above- normal temperatures across the central United States by late next week.

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AVIATION

(For the 00z TAFs through 00z Saturday Evening) Issued at 621 PM CDT Fri Mar 13 2026

A weak disturbance featuring warm advection and frontogenesis aloft looks to shift rapidly east through the area late tonight into early Saturday morning, and could bring a few light flurries around KPIA-KBMI around 12Z, although it appears conditions will remain VFR. Otherwise, periods of mid and high clouds with winds decreasing and turning clockwise from NW to SE is on track for the next 24 hours.

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ILX WATCHES/WARNINGS/ADVISORIES

None.