textproduct: Chicago

KEY MESSAGES

- Windy and warmer today, with gusts up to 40 mph this afternoon especially across north-central IL.

- Milder with periods of showers and some thunderstorms tonight into early Friday, and again from later in the weekend into early next week.

- Combined rainfall amounts tonight through Friday may exceed an inch across portions of the forecast area. This could produce new rises on area rivers and creeks.

DISCUSSION

Issued at 330 AM CDT Wed Apr 8 2026

A northwest-southeast oriented area of light rain showers, mixed with some light sleet/wet snow initially, was moving across northeast Illinois north of I-80 as of 2:30 am. This was occurring in association with warm advection on the nose of a strengthening low-level jet, downstream of a low-amplitude short wave and elevated warm front propagating through the region. At the surface, winds have turned southeast overnight allowing temperatures to rise into the mid-upper 30s (coolest north where precipitation is occurring), so no impacts are expected in the way of freezing rain, and any sleet/snow should be short lived and non-accumulating. Precipitation should taper to spotty rain sprinkles by sunrise, and end shortly after.

Otherwise, early morning surface analysis places ~1000 mb low pressure over southwest South Dakota near the Nebraska border. A surface warm front extends southeast from the low, across eastern Nebraska and Kansas west of the Missouri River. The surface low is forecast to lift quickly northeast into the upper Mississippi Valley today, combining with deeper low pressure developing toward the northwest shore of Lake Superior by early this evening. In the process, the warm front will lift quickly north across the forecast area early this afternoon, with a windy warm sector air mass spreading across the area. Decreasing cloud cover by this afternoon should help temperatures to surge into the mid-upper 60s across the area, with a few spots tagging 70 degrees across our western cwa. Southwest winds will gust as high as 35 to 40 mph, especially across north-central IL where the the gradient will be a little stronger. Some higher gusts are possible late this afternoon, especially if boundary layer mixing ends up deeper than currently expected.

As the aforementioned surface low tracks north of Lake Superior tonight, it will trail a slow-moving cold front southeast across the area. A line of showers and isolated/embedded thunderstorms along and ahead of the front will move into north- central IL mid-late evening, and slowly work its way east- southeast across the area overnight as the front slowly advances. Forecast QPF amounts are generally in the 0.25-0.30 inch range, focused across the northern half of the cwa. Showers shift south of I-80 Thursday morning, weakening as stronger forcing passes off to the northeast and the front slows its southward push, stalling across or just south of the southern cwa Thursday evening. Another mid-level shortwave is progged to transit the region Thursday night into Friday morning however, inducing redevelopment of another round of showers and thunderstorms along/north of the frontal zone. This is accompanied by an axis of deeper moisture (PWATs over 1.25"), which looks to produce greater rainfall amounts (generally 0.50-075"+) across the forecast area. Exact location of higher amounts is of low confidence just yet, though combined QPF from tonight and Thursday night/Friday in excess of an inch appears possible. This would likely cause additional rises on area rivers which are still in flood stage in some locations due to previous heavy rains.

Surface high pressure is progged to build across the upper Midwest and Great Lakes region Friday night into Saturday, pushing the front south of the area and allowing for at least a brief respite from additional rainfall.

Global ensemble guidance continues to show good agreement in the upper pattern becoming more amplified from this weekend into early next week, as a deep west-coast long wave trough develops and induces southwest flow downstream into the Midwest and Great Lakes region. Return of warmer/moist air aloft appears to bring rain chances back to the forecast area as early as Saturday night with the returning warm front and indications of a low-amplitude mid-level wave emerging from the base of the western upper trough. This looks to begin a period warmer but also more active weather from Sunday into early next week. Ratzer

AVIATION /18Z TAFS THROUGH 00Z FRIDAY/

Issued at 1205 PM CDT Wed Apr 8 2026

- Gusty southerly winds expected into tonight ahead of an approaching cold front - Band of SCTD -SHRA expected to move across the terminals during the predawn into the early morning

Area of dense OVC cirrus currently over the terminals is tamping down mixing a bit right out of the gate for the 18z TAFs. As the dense cirrus will move east of the terminals early-mid afternoon, look for wind speeds/gusts to increase with prevailing 30-35kt gusts expected with a few brief higher gusts. Wind will likely remain gusty this evening, though likely slightly lower magnitude. The gusty winds this evening are precluding the inclusion of LLWS in the TAFs, if winds are lighter than anticipated then there would likely be LLWS. Also of note this evening, winds/gusts could be higher at ORD and MDW due to the effects of the urban heat island.

A cold front will move across the terminals early Thursday morning. Ahead of the front, a band of scattered showers is expected to move across the terminals. Generally expecting VFR conditions with any showers. In the wake of the front, winds will becoming more west to west-northwest around 10kt.

- Izzi

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 4 AM CDT Thursday for the IL nearshore waters.

Small Craft Advisory until 7 AM CDT Thursday for the IN nearshore waters.