textproduct: Chicago

KEY MESSAGES

- A narrow band of accumulation snow will continue across portions of LaSalle, Grundy, Kankakee, Newton, and Jasper counties this morning. Locally hazardous travel conditions will continue through mid-morning.

- Lake effect snow showers will meander across the northeastern Illinois and northwestern Indiana shores of Lake Michgian Tuesday night into Wednesday morning, though accumulations should stay below an inch.

- Temperatures will make a run for the freezing mark toward the end of the week, marking the end of a prolonged stretch of daily highs below 32 degrees. - A pattern change toward warmer temperature (highs and lows both above freezing) may materialize by the middle of next week.

DISCUSSION

Issued at 211 CST Tue Feb 3 2026

Though Tonight:

Overnight water vapor imagery reveals an upper-level shortwave moving into western Iowa early this morning, ahead of a secondary shortwave and surface cold front dropping southward through the Great Lakes. Ahead of both features, radar imagery continues to depict a narrow band of snow slicing across eastern Iowa and northern Illinois. Dry low-level air beneath the snow band is relegating much of the returns to virga (we've only had a few flurries at our office in Romeoville). However, very steep lapse rates nearing 8 K/km in the DGZ (re: 00Z DVN RAOB) are supporting convective elements within the band of snow, leading to occasional radar reflectivity flaring to as high as 35 dBZ and an impressively narrow region (only 5 to 10 miles wide) of accumulating snow within the heart of the band.

Going forward, the snow band will continue moving across portions of LaSalle, Grundy, southern Will, Kankakee, Newton, and Jasper counties, including across portions of Interstates 39, 55, 57, and 80. Conditions will vary across short distances in the aforementioned counties, going from completely dry to 1 inch per hour snow rates across literally a mile or two. Dry air will still be problematic in the snow band, though currently expect total snow accumulations to range from 1 to locally 4 inches, again within an exceptionally narrow 5 to 10 mile wide region. Did put strong consideration into issuing a short fused Winter Weather Advisory early this morning, but felt impacts would be minimized due to relatively sparse travel volumes. With that said, have issued a strongly worded Special Weather Statement where conditions are expected to be worst this morning. After daybreak, the band of snow may begin to weaken (or just become more cellular rather than solid) as the lapse rate plume is exhausted while dropping into potions of Livingston, Ford, Iroquois, and Benton counties.

Just have to note... If we weren't dealing with dry low-level air problems this morning, the axis of 1 to 4 inches of snow probably would have been more like 6 to 12 inches (if not more) of snow. These narrow convective snow band events are the wintertime equivalent of summertime training thunderstorm events, and can just hammer the same area all day/night leading to very pronounced impacts. So, thank you dry air.

Attention then turns toward the aforementioned cold front dropping southward through the Great Lakes, which is due to move through our area after daybreak. Lake effect parameters behind the front look meager at best (inversion heights struggling to climb past 4kft), though do suspect flurries may develop along the southern shore of Lake Michigan as early as mid-morning. Low-level convergence will gradually increase after sunset tonight as a land breeze develops off of Lower Michigan, which should allow for coverage of lake effect snow showers to similarly gradually increase. Based on the expected orientation of the low-level pressure field (surface high to our northwest and surface low across the Ohio River Valley), steering flow will acquire an easterly component overnight thereby guiding lake effect snow showers toward northeastern Illinois. With all of that said, the overall marine boundary flow looks weak maybe 10 to 15 kt), and the thermodynamics will remain marginal (inversion heights struggling to climb past 5kft). So, lake effect snow shower intensity should be fairly modest with the highest coverage of showers struggling to move inland. In all, this looks like a non-event with perhaps a dusting to locally one half of an inch of snow generally from Chicago to Ogden Dunes.

Elsewhere across the area, today look quiet. In spite of clearing skies away from Lake Michigan, cold air advection will hold temperatures to the upper 20s today. Light northerly winds tonight with continued clearing skies away from the lake will support overnight lows in the single digits near the Wisconsin State Line to lower teens near the Indiana border.

Wednesday through the end of the week:

On Wednesday, a surface pressure ridge will slide through the region leading to quiescent conditions. Lake effect stratus near the IL/IN border should begin to finally eroding as inversion heights crash toward the ground, giving way to partly sunny skies across much of the area. The last vestiges of weak northerly cold air advection will maintain highs similar to Tuesday and in the mid to upper 20s.

Thursday into Friday, a pair of clipper systems will dive southward from central Canada and into the Great Lakes. The first wave on Thursday looks moisture-starved, though forecast soundings look pretty darn close to supporting a period of dry/fluffy snow, if not just flurries, from late morning to early afternoon. The follow-up wave arriving overnight into Friday morning will be the stronger of the pair, and will support a period of snow showers focused near the Lake Michigan shoreline. Aggressive warm air advection ahead of the wave may push low-level thermal profiles precariously close to supporting freezing rain as the precipitation type instead of snow, though overall moisture looks limited suggesting total precipitation amounts should be low (<0.05"). Temperatures will make a run for the freezing mark on Thursday, and perhaps into the mid 30s on Friday.

The push of cold air will lag the pair of shortwaves and arrive this weekend, though the coldest air should push moreso into Michigan and southern Ontario than our area. Highs this weekend will nevertheless fall back toward the upper 20s to lower 30s.

Next Week:

Ensemble model guidance continues to exhibit a strong signal that the stagnant upper-level northwesterly flow pattern across the central US will finally break and become replaced by broad upper-level southwesterly flow. As a result, ensemble mean temperatures trend notably upward by the middle of next week and beyond, with both high and lows well above the freezing mark. In addition, the door will open for southwest flow synoptic cyclones to lift toward the central US by next week, especially in the February 11-14 timeframe.

Borchardt

AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 525 AM CST Tue Feb 3 2026

A weak surface trough currently nearing the Chicago terminals will shift winds NNW 5 to 10 knots shortly after TAF issuance, with a second weak trough shifting winds NNE very late this morning or early afternoon. The western edge of widespread MVFR ceilings over Lower Michigan will advect over the Chicago terminals with the NNE wind shift, and perhaps produce a period of flurries this afternoon. Winds will shift back NNW this evening and NW Wednesday morning.

An area of shallow lake effect SHSN is then expected to affect GYY/MDW this evening into Wednesday morning, with the SHSN likely remaining just east of ORD. Visibility will be MVFR/VFR as extensive ice cover on Lake Michigan limits the inland extent of the heaviest showers. However, a few brief bouts of IFR visibility cannot be ruled out overnight.

Kluber

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...None.