textproduct: Chicago

KEY MESSAGES

- Chance of snow tonight with less than an inch of accumulation mainly south of a Peru, IL to Lafayette, IN line.

- Brief warm for the end of the week, then colder with some additional snow chances over the weekend and into early next week.

DISCUSSION

Issued at 214 AM CST Wed Feb 25 2026

Main focus in the near term is on snow chances tonight across our far south/southwestern counties. Otherwise, somewhat blustery and seasonably cool conditions today will give way to dry and somewhat milder weather Thursday.

Early morning surface analysis depicts ~990 mb low pressure centered just northeast of Lake Superior, trailing a cold front which has moved east of the I-55 corridor. A subtle secondary surface trough axis was noted from central WI through the Quad Cities area, likely associated with a sheared mid-level vort trailing the more robust initial short wave from last evening. Precipitation has cleared the southeast parts of the forecast area, with skies clearing across all but the far southern tier of cwa counties as of 06Z/midnight CST. GOES nighttime microphysics RGB imagery does show an area of shallow stratocu spreading southeast across Minnesota and western Wisconsin however, which may move into northern parts of our forecast area for a time later this morning, although a good amount of sunshine is expected for most areas into this afternoon. Cold advection, on westerly winds still gusting near 20 mph at times this morning, will yield cooler than average high temps for today, ranging from the lower 30s far north to the lower 40s far south.

Farther to our northwest, GOES vapor imagery displays another sheared mid-level short wave tracking along the International border and across the northern Rockies. This wave is progged to propagate quickly to the southeast today, amplifying slightly as it moves into the lower Missouri/Ohio valleys tonight. Guidance has maintained recent trends in focusing the main axis of precipitation across central IL/IN this evening into the overnight hours, with the northern periphery of measurable precip brushing our southern counties generally south of a line from about a Peru IL to Lafayette IN. There is still a little uncertainty with the placement of this northern edge, with top- down saturation likely to struggle with considerable low-level dry air with northward extent. Nonetheless, have bumped NBM delivered pops a bit farther north by blending in some 00-03Z high-res RAP/HRRR/HREF and some 00Z GFS (which is still a little farther north with some trace precip amounts) to maintain 40-50 percent chances across our southern counties along our DVN/ILX border area. Precip should be all snow on our side of things, with minor accumulations of less than an inch possible. Farther north and east, a dry and seasonably cold night is in store with overnight lows in the upper teens and 20s.

We'll be between weather systems on Thursday, with weak surface high pressure drifting east across the area through midday. Westerly flow above the boundary layer brings some modest warm advection to the area in the afternoon, which along surface winds becoming southwest and at least partly sunny skies, should allow for moderation of temperatures back to around 40 north and into the low-mid 40s for highs.

Ratzer

Thursday night through Monday:

Low level warm advection will take off Thursday night in advance of an upper wave dropping into southern Canada. This will bring pleasantly mild conditions to Friday with highs forecast in the middle and upper 50s to around 60. That system's cold front will move across the CWA Friday night, but a big lack of moisture will keep precip chances at bay and should even allow for mostly sunny skies during the day. The baroclinic zone looks to get hung up in central IL on Saturday which could lead to a pretty big spread in temps around the area; the forecast calls for highs in the middle 30s near the WI state line to the middle and upper 40s across our south.

An upper jet max nosing into the region will drive a shortwave clipper system across northern IL on Saturday. Guidance tracks a corridor of anywhere from several tenths of an inch to a couple of inches of snow accumulation somewhere near or along the WI state line. A small majority of deterministic camps and ensemble members favor the primary axis of accumulation tracking across southern WI, but there is plenty of support for the focus to be anywhere north of the I-88 corridor. Even if not the focus, ensemble probs for at least a brush of light snow in this corridor are high. Lighter precip will be possible farther south as the wave moves across, maybe in the form of rain or a wintry mix in our southern CWA if precip occurs, but drier air with southward extent limits that potential. Timing on this precip potential would be Saturday morning through afternoon.

High pressure will drop into the Great Lakes region from the north for Sunday and advect cooler air into the region. Highs on Sunday are forecast in the lower and middle 30s. Seasonably cool conditions will continue into early next week.

An active regional synoptic pattern is anticipated for next week with a number of systems progged to track nearby and the forecast calls for frequent chances for rain and snow. The main periods to watch for next week would be the late Sunday to Monday window, Tuesday, and again on Thursday. The GFS has been especially excited about bringing impactful snow into the area with that Sunday-Monday system, but there's still tons of variability in other deterministic and ensemble guidance, including within the GEFS, where it's very tough to say how likely that is at this point. Even more uncertainty lurks beyond, but will keep a close eye on forecast trends for next week with a potentially busy week for weather ahead.

Doom

AVIATION /18Z TAFS THROUGH 00Z FRIDAY/

Issued at 1121 AM CST Wed Feb 25 2026

No major forecast concerns for the terminals for this TAF period.

The current breezy northwest winds will continue to subside through the afternoon as the winds in the column diminish resulting in speeds around 10-12 kt through sunset. Thereafter, expect light north-northwest winds to prevail tonight before turning southwesterly and increasing around 10-12 kts Thursday afternoon with gusts around 18-20 kts. That said, there is a chance that winds turn easterly for a brief period late tonight into Thursday morning as a surface high pivots through but given the very light speeds (around 2-4 kts) and short duration opted to not add another line in the TAFs for this potential.

Otherwise, expect mostly sunny skies today to give way to SCT to BKN VFR skies this evening and overnight as a shortwave disturbance swings through central IL. While a period of light snow showers and flurries is expected to develop with this disturbance, the snow will stay well south of the terminals and thus pose no issues locally. Skies will remain partly to mostly cloudy through Thursday with VFR conditions expected.

Yack

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 4 PM CST this afternoon for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.