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 18z TAFs through 18z Friday Afternoon) Issued at 1214 PM CDT Thu Mar 12 2026

VFR through the period. There is a low chance (20-30%) for a few SHRA tonight ahead of a cold front. Due to the dryness of the airmass, this should not impact category so just included VCSH. The main impact of the front for all of the central IL terminals will be an increase in wind speed and gusts later this afternoon, through the remainder of the forecast. Initially west winds early this afternoon will back southwest to south ahead of the front tonight, then veer back southwest and eventually west after the frontal passage tonight into Friday morning. Gusts will increase to 20-30 kt tonight, and 30-40 kt after sunrise, highest near and north of the I-74 corridor. A 55 kt low level jet will bring marginal LLWS criteria overnight, and included this mention at all terminals.

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ILX WATCHES/WARNINGS/ADVISORIES

Wind Advisory from 10 PM this evening to 4 PM CDT Friday for ILZ027>031-036>038-040>057-061>063-066>068-071>073.