textproduct: Chicago

KEY MESSAGES

- Accumulating lake effect snow will result in travel impacts across parts of NW Indiana (Porter County in particular) through Monday.

- Monitoring potential for accumulating snow somewhere in the region in the Wednesday night-Thursday timeframe. Too early to have much confidence in track of system and any local impacts just yet.

DISCUSSION

Issued at 252 AM CST Sun Feb 22 2026

Through Monday...

A broad upper wave is transversing the region early this morning and has been providing periods of snow showers to the area. A brief burst of ~1"/hour rates over Chicago even brought a quick inch+ to parts of the city late last evening. As the vort lobe responsible in big part for the showers is peeling off to the east, focus for the more appreciable snowfall has recently shifted into far northwest IN with some lake enhancement ongoing as well, but flurries continue around much of northern and northeastern IL. We should see snow showers continue to favor northwest Indiana through the morning. Recent forecast soundings and model QPF would even suggest that the primary axis of snowfall from daybreak through the end of the morning could focus east of the CWA, if not brush northeast portions of Porter County. But amid the persistent cold advection today and a several thousand-foot DGZ immediately overtop the area, flurries could continue around the rest of the CWA pretty much all day.

Guidance is in solid agreement on a secondary vort max dropping south into the area this afternoon. With cooler air aloft in its wake, the passing of the wave will boost lake-effect parameters for the afternoon and even moreso for the evening and night. The low level wind field will also veer from NW to more NNW, and snow coverage is expected to slosh back westward into our northwest Indiana counties as a result. Coverage during the afternoon looks somewhat broad around the southern end of the lake and may try to expand back into parts of extreme northeastern IL at times. During the evening and into the night, expectations are for a multi-banded structure to develop and possibly congeal into one heavy cohesive band overnight and into Monday morning. Coverage during this time is heavily favored to largely target Porter and La Porte Counties, but could ebb into Lake County at times. Moderate to heavy snow may continue through the morning before some incoming dry air chips away at chances for the latter half of the day. Light snow showers may remain in northwest Indiana through the afternoon and let up to only flurries by dusk. Significant travel impacts are looking likely for the Monday morning commute, and possibly afternoon as well, particularly in northern Porter County. No changes made to the going Winter Weather Advisory in Porter County. Still expecting accumulations in the 3 to 5" range in northern and eastern portions of the county through the end of Monday with locally higher totals possible.

Low level winds will be ramping up here over the next several hours and we'll see gusts most of today in the 25 to 30 mph range out of the northwest. Winds will remain breezy through the night and Monday morning before stepping down during the afternoon. Highs are forecast in the middle and upper 20s this afternoon, but the wind chill will cause it to feel like single digits this morning and teens during the afternoon. It will be a frigid start to the work week with Monday morning wind chills forecast in the single digits to near or slightly below zero.

Doom

Monday Night through Sunday...

Northerly low-level winds will likely maintain shallow lake- induced stratocu across parts of northwest Indiana Monday evening, which forecast soundings indicate will still reside within the DGZ thermal range. Thus while inversion heights of less than 4500 feet are forecast, some non-accumulating snow flurries should remain for areas east of Gary during the evening. These should come to an end overnight however, as large-scale subsidence and drying in the wake of the deep east coast upper trough works to further lower inversion heights, decrease winds and erode the stratocu layer. An associated north-south oriented surface high pressure ridge will transit the forecast area overnight, allowing light winds to turn southerly by morning.

Meanwhile, guidance remains in good agreement in depicting a clipper system dropping east-southeast toward the upper Midwest toward daybreak Tuesday, with its surface tracking from northern Minnesota into the northern Lakes during the day while deepening to around 995 mb. While guidance continues to track the mid-level vort and strongest ascent north of the forecast area, the diffluent/divergent left exit region of a 150 kt upper level jet streak associated with the wave is progged to provide additional forcing to cool and saturate mid-levels, steepen lapse rates aloft and potentially produce some precipitation as far south as far north/northeast IL and far northern IN Tuesday. NBM blend has maintained the trend of 20-30% pops north of the I-80 corridor, highest toward the IL/WI border. P-type would be snow during the morning/midday, with some rain or rain/snow mix later in the day as surface temps warm on strong south-southwest winds. Some guidance lingers light precip into Tuesday evening across our eastern cwa, with ensembles then trending dry overnight. Speaking of those winds, as the surface low deepens to our north, gusts approaching 30-35 mph appear likely. Drier ECMWF/EPS guidance still indicates daytime RH values to the 25- 30% range in the afternoon. This would continue to present some potential for a heightened grass/brush fire threat across our south/southwest counties where precip is less likely and temps warm into the low-mid 40s.

00Z global ensembles have currently come into better agreement with their depiction of an amplifying short wave tracking southeast from the Northern Plains into the Midwest during the Wednesday night through Thursday timeframe. EPS/GEFS/CMCE means remain loosely clustered with a surface low track near/south of our forecast area, and in the potential for accumulating snow across parts of the region. Confidence remains low in the fine details at this distance however, given differences in degree of phasing and amplitude of the wave. Nonetheless, this period bares watching for the potential for some wintery impacts associated with this system.

Ratzer

AVIATION /12Z TAFS THROUGH 18Z MONDAY/

Issued at 541 AM CST Sun Feb 22 2026

Aviation forecast concerns for the 12Z TAFs:

- Prolonged period of flurries and occasional light snow showers into tonight. Late morning/afternoon and this evening may be periods of somewhat greater coverage of snow showers and brief MVFR vsbys for Chicago area terminals.

- Periods of MVFR ceilings especially midday through tonight.

- Blustery northwest winds with gusts 25-30 kt becoming more north-northwest later tonight into early Monday.

An upper level trough will linger across the western Great Lakes region before slowly drifting east of the area Monday morning. Several smaller embedded circulations will rotate through the trough, modulating periods of light snow showers. Timing these with precision is somewhat difficult, though it appears that one will bring a period of snow showers to the Chicago terminals later this morning into this afternoon. Another is expected to move southward over Lake Michigan this evening, though greater snow shower coverage this evening may remain just east of ORD/MDW while likely affecting GYY. These snow showers may produce brief MVFR visibilities and ceilings, along with a dusting of accumulation. Additional lake effect snow showers will set up across northwest IN tonight into Monday morning, but are expected to focus east of GYY. Outside of these periods of light snow showers, non-accumulating flurries are expected through tonight.

Surface low pressure will deepen east of the area later today and tonight, helping to maintain a fairly tight surface pressure gradient across the western Lakes. This will support blustery northwest winds gusting 25-30 kts through much of the period. Winds will eventually become more north-northwest late tonight into Monday morning, while slowly easing.

Ratzer

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...Winter Weather Advisory until noon CST Monday for INZ002.

LM...Small Craft Advisory until 3 AM CST Tuesday for Winthrop Harbor IL to Gary IN.

Small Craft Advisory until 6 PM CST this evening for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.

Gale Warning from 6 PM this evening to 3 PM CST Monday for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.