textproduct: Central Illinois

KEY MESSAGES

- Wind gusts up to 50 mph develop tonight and continue through midday Friday, necessitating a Wind Advisory for all of central and southeast Illinois.

- A strong cold front Sunday brings a risk of severe storms for the afternoon and evening, followed by a changeover to snow Sunday night.

- Sharply colder air behind the storm system will drive wind chills below zero for Sunday night and Monday night.

DISCUSSION

Issued at 208 PM CDT Thu Mar 12 2026

The primary short-term forecast concern involves impactful wind gusts tonight through Friday afternoon. As a sub-990 mb surface low tracks across the Upper Midwest, the tight pressure gradient between this low and high pressure over the Southeast CONUS results in sustained southwesterly winds of 20-30 mph, gusting near 45 mph tonight. Forecast soundings from the RAP and HRRR show a 50-60 mph low- level jet at 1-2 kft AGL. While a near-surface stable layer often limits overnight mixing, the strength of the gradient supports advisory level winds during the overnight period. Lift ahead of a southeastward advancing cold front will bring in increase in mid level clouds tonight, and a 20-30% chance of sprinkles/showers mainly north of I-72. Any showers would have the potential to mix down the higher momentum air aloft, making a few 50+ mph gusts possible. Winds back WSW to WNW behind the frontal passage Friday morning. Diurnally increasing mixing depths to the base of the waning LLJ will bring a quick surge of higher wind gusts after sunrise, likely in the 45-55 mph range, with the higher end gusts gradually lowering through midday. This will be close to High Wind Warning criteria (sustained 40+ mph or gusts 58+ mph) and we'll be monitoring the need for eventual headline upgrade, mainly across the northern CWA. Winds to rapidly decrease Friday afternoon and evening as surface ridging builds in from the west.

Attention then shifts to Sunday as a medium range guidance shows a classic deepening mid latitude cyclone affecting the Midwest. Ahead of the low, warm- sector temperatures will surge into the 60s Sunday. Deep- layer shear of 45-50 knots supports organized convection along/ahead of the advancing cold front Sunday afternoon to evening. At this point low-level moisture return remains a limiting factor for widespread severe weather, however the strong background wind field and deepening low make damaging gusts a concern within any developing lines of storms. CSU-MLP highlights areas east of I-55 for the better severe potential, while the latest SPC outlook keeps the northern edge of the risk area over southern IL.

Robust cold advection behind the front will drive a transition from rain to snow from the northwest Sunday evening/night. 12z deterministic guidance shows a respectable deformation zone on the back side of the low, and correspondingly the latest runs of the NBM have increased snowfall accumulations over central IL. Tight MSLP gradient on the back side of the low will bring another round of high winds to the area Sunday night and Monday. Today's WPC guidance shows a 60-80% chance of minor impacts and 20-30% chance of moderate impacts. This system will need to be monitored over the coming forecast cycles as it appears impactful winter weather will occur in the region, though confidence on the track of the low and associated snow band is low-medium.

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 below zero for most of the CWA Sunday night and Monday night.

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AVIATION

(For the 06z TAFs through 06z Friday Night) Issued at 1247 AM CDT Fri Mar 13 2026

VFR conditions will prevail at all TAF sites next 24hrs. Mid clouds will move across the sites overnight with PIA, BMI, and CMI possibly getting some light showers. Cloud bases are high, so some of it will be virga. However, close to the cold front back in IA, some is reaching the ground. Will have PROB30 for these 3 TAF sites for several hours. SPI and DEC will not have any precip or lots of Virga. Clouds will remain high through the period and become scattered in the morning and continue into the afternoon and evening. Breezy winds are expected ahead of the front, but then get even stronger behind the front with gusts around 40kts possible. Winds decrease in the afternoon and then gust will be gone in the evening. Models show strong wind shear possible at all sites with 50-55kts close to 1.5kft now through 13-14z.

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ILX WATCHES/WARNINGS/ADVISORIES

Wind Advisory until 4 PM CDT this afternoon for ILZ027>031- 036>038-040>057-061>063-066>068-071>073.