textproduct: Chicago

KEY MESSAGES

- Stagnant temperatures today will warm above freezing by Friday, ending a prolonged stretch of daily highs below 32 degrees at both Chicago and Rockford.

- A pair of clipper systems will race through the area Thursday and Thursday night, bringing primarily snow showers. Little to no wintry accumulation is currently expected with either system.

- A pattern change toward warmer temperatures (highs and lows both above freezing) may materialize by the middle of next week.

DISCUSSION

Issued at 247 AM CST Wed Feb 4 2026

Through Tonight:

Baggy and somewhat disorganized aggregate upper-level cyclonic flow is in place across the Mississippi River Valley and Great Lakes this morning, atop a broad surface high pressure system centered generally near the MN/IA/WI/IL border regions. Weak convergence down the lake (a consequence of heavy clouds in Lower Michigan preventing a more formidable land breeze from developing) and meager lake-induced inversion heights (near 3500ft, per recent AMDAR soundings) have thus far kept lake effect snow activity to a minimum. At this point, feel the cat is out of the bag for anything meaningful to develop. So, will downgrade PoPs along the lakeshore to the "isolated" category and remove snow accumulations this morning.

Unlike lake effect snow, lake-induced stratus is quite prevalent across the area this morning, and is in fact increasing in coverage at press time. Easterly steering flow will stagnate by mid-afternoon, and then transition to westerly during the afternoon. Accordingly, much of the area will probably be stuck beneath clouds all day. For this reason, temperatures may not move much during daylight hours, with most areas stalling in the mid 20s.

Inversion heights should lower this evening as the back edge of the aggregate troughing slides overhead. As a result, would expect holes in clouds to develop and spread, allowing for skies to clear (this is not a guarantee, though). Assuming clouds do start to scatter out, the arrival of the center of the surface high to calm winds will support efficient radiational cooling. So, will go ahead and maintain lows tonight generally in the teens. Where clouds remain, lows could very well verify in the 20s.

Through this Weekend:

Thursday night into Friday, a pair of clipper systems will dive through the Great Lakes presenting 4 to 6 hour windows for snow showers. The first clipper will race through the area in the late morning through early afternoon hours on Thursday, with the second during the overnight/early Friday morning hours. Low- level moisture looks marginal with both clippers, especially with westward extent, so will draw a gradient in PoPs ranging from 10 to 20% near I-39 to 30 to 40% near Lake Michigan with both clippers. Precipitation type should be decidedly snow with the first clipper, but may end up a wintry mix with the second. Overall precipitation amounts look meager (<0.05") with both, so would not anticipate any impacts to roads including if a wintry mix does materialize with the latter. Will be watching for any trends upward or westward in the strength/track of the clippers though in future forecasts.

Aggressive warm-air advection ahead of the clippers should allow for temperatures to rise above freezing for much of the area on Thursday. Even on Friday, temperatures look to warm further as the push of cold air associated with the overarching upper-level troughing supporting the clippers lags behind. As a result, the stretch of days with high temperatures below freezing at both Rockford and Chicago should soon come to an end. (The final tally will be either 20 or 21 days at either site...hardly a record, but certainly not something that happens every year).

A glancing blow of another pool of seasonably cold air will render temperatures to fall this weekend. Mean GEFS/EPS highs settle into the 20s on Saturday and warm toward 30 on Sunday. Will note the NBM, which informs our extended forecast, is currently 4 to 6 degrees warmer than input ensemble suites. So, would expect our forecast highs to lower as we get closer and can more readily adjust the temperatures.

Next Week:

Ensemble model guidance remains in agreement that the upper- level flow will shift from a persistent northwesterly flow pattern to more of a southwesterly flow pattern through the course of next week. Am starting to see a fly in the ointment in a more pristine pattern shift, being a cut-off wave meandering along the US/Mexico border during the first half of the week. With that said, the signal remains in ensemble mean fields for temperatures to increase next week with highs generally in the 40s and lows generally near the freezing mark. There is still a signal for a synoptic system somewhere in the broad central US region in the February 11 to 14 timeframe, which would probably present the next opportunity for inclement weather.

Borchardt

AVIATION /12Z TAFS THROUGH 18Z THURSDAY/

Issued at 529 AM CST Wed Feb 4 2026

MVFR stratus streaming off Lake Michigan will persist through most of the day at the Chicago terminals, though ORD and especially DPA may scatter by mid-afternoon. Much of the cloud layer is shallow (under 2kft thick) and contains at least some super-cooled droplets per recent light icing reports during approach to ORD. Any agitation of the cloud layer will allow for glaciation and downstream SHSN through much of the the morning at MDW and near ORD/GYY. Precip chances should end by early afternoon as the cloud layer thins.

N/NNW winds 5-10 knots at TAF issuance will gradually back WNW through the day, and SW overnight. A quick-moving mid-level wave will track southeast across Lake Michigan on Thursday and produce a shield of SN northeast of the Chicago terminals. This SN could brush the terminals if top-down saturation is sufficient. Have included PROB30 SN with low-end MVFR visibility late in the morning, though any thorough saturation will likely yield IFR visibility.

Kluber

LOT WATCHES/WARNINGS/ADVISORIES

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