textproduct: Chicago

KEY MESSAGES

- Accumulating snow is expected tonight, likely resulting in hazardous travel conditions.

- Isolated to scattered gusty snow showers late Friday afternoon into early evening may produce locally slippery travel for the evening commute.

- Several clipper-like systems within northwest flow aloft will bring periods of snow showers and renewed bouts of very cold and windy conditions. Bitterly cold conditions are expected Sunday night through early Tuesday.

DISCUSSION

Issued at 250 PM CST Thu Jan 15 2026

Through Early Friday Afternoon:

Afternoon water vapor imagery depicts a shortwave impulse working across Minnesota en route to Wisconsin. Regional radar imagery shows a few pockets of snow showers on the leading edge of this wave working into northwestern portions of WI. Ahead of the snow showers is a plume of snow aloft that doesn't appear to be making it to the ground owing to dry low level air preceding the wave. The system will work across north-central WI tonight and drag its cold front across the CWA providing our next opportunity for accumulating snow. Isentropic ascent will kick off late this afternoon in the low level warm advection wing in advance of this wave. However, with the low levels being so dry, there won't be much moisture to loft initially and we too may end up with a few hour period of virga snow showers or possibly a few flurries. The snow shower potential will really pick up during the mid-late evening period while the low levels quickly moisten up. From there, we expect a few hour period over any given location of light accumulating snow into the overnight. This should lead to reductions in visibility, possibly down to or even below one mile from time to time, and slippery road conditions.

Model guidance likes the idea of a few hour lull in activity ahead of the storm's cold front in which we may end up dry or with only lingering flurries late overnight into very early Friday. The front will approach our western CWA during the predawn hours and a second push of accumulating light snow is anticipated along and immediately ahead of the boundary. The time window for this second push would be predawn in our west through about mid-morning to exit to our east. This will reinforce the visibility and slippery travel concerns for the morning commute. While this doesn't appear to be an overly impactful event, at the least expect a slower-moving commute tomorrow. By the end of tomorrow morning, widespread accumulations around or just over an inch are forecast with 2" being on the higher end of expectations. After the trough axis shoves the main body of precip to our east, the late morning through early afternoon period could feature scattered flurries around the area.

There is a weak signal among some camps for us to lose out on cloud ice during a few hour window overnight and again during the morning. Forecast soundings from the GFS and NAM are most bullish on this potential, but even then the signal is very marginal and neither model resolves any freezing precip outright. Latest RAP and HRRR soundings depict a deeper saturated layer through the night which would favor all snow. If anything, the signal is slightly stronger tomorrow during the late morning and early afternoon, but this would come after the system precip and in the form of only a brief period of light freezing drizzle, if at all. Plus, temperatures should be pushing above freezing right around this time which should further limit any potential impacts. Expectations for now are for precip to remain in the form of snow with no formal mention of freezing rain/drizzle in the forecast, but will keep a close eye on observations as the system moves across.

The cold air will really begin to fill in aloft during the afternoon. This will steepen up low level lapse rates as a secondary trough axis and vort lobe are progged to swing across the CWA. This will provide yet another chance for accumulating snow, possibly heavier at times. More details on this afternoon/evening potential can be found in the long term discussion below.

In other news, the warm advection later today will keep temperatures rather steady in the lower and middle 20s from now through most of the overnight. The stronger warm advection just in advance of the cold front will drive temperatures up a few degrees prior to daybreak and we should wake up to middle and upper 20s. We're looking at middle and upper 30s for the afternoon. Gusts will also begin to pick up overnight with the initial push of snow and stay up through the day on Friday. Southwest to west winds will gust to between 25 and 30 mph, with the strongest winds expected overnight and Friday afternoon.

Doom

Late Friday Afternoon through Thursday:

Stout ridging currently developing over the eastern Pacific toward the Gulf of Alaska will dislodge a series of arctic disturbances SSE toward the Great Lakes region this weekend through early next week. Bitterly cold conditions are expected, especially Sunday night into Tuesday. Each shot of colder air as well as persistent cyclonic flow aloft will support periodic snow showers and flurries during this time.

The first arctic front will sweep across the area late Friday afternoon into mid-evening. Low-level moisture profiles appear marginal for snow showers with the front, but a modestly deep layer (up to 10kft) of steep low-level lapse rates combined with temps quickly falling through the 20s and WNW winds gusting to 30 mph or higher does raise concern for localized snow squall conditions roughly in the 4-8pm window. Given that this aligns with the peak Friday evening commute time, it would not take long for impacts to quickly mount. Still feel moisture availability will be the limiting factor for genuine robust squalls, though upstream trends across Iowa earlier in the afternoon should provide some lead time if coverage and/or intensity is higher than currently expected.

Another pair of trough axes will bring a renewed chance of snow showers Saturday evening and again Sunday afternoon into the evening. Inversion heights lowering to under 6kft will limit intensity, but with the cloud layer residing mostly in the DGZ for both periods, even meager moisture will result in at least some lighter snow showers.

Expect daytime highs this weekend to settle in the mid to upper teens amid gusty WNW to WSW winds, resulting in wind chills topping out only just above zero. A next push of arctic air will arrive late Sunday afternoon and evening, with notably colder conditions Sunday night into Tuesday. Minimum wind chills Monday morning are expected to be around -20 degrees, with the potential that a Cold Weather Advisory (-25 degrees) is needed for at least some of the area. With the cold start to the day, highs Monday may struggle to reach 10 degrees, with maximum wind chills remaining solidly below zero. Winds will begin to diminish Monday night as a surface high passes south of the area, but wind chills as low as -15 degrees can be expected Tuesday morning.

Beyond Tuesday, strong baroclinicity developing across the central CONUS will support a more active period of weather near or south of the area. Still a lot of discrepancies in the broader model/ensemble systems chiefly due to uncertainty as to where the baroclinic zone resides with respect to out area.

Kluber

AVIATION /06Z TAFS THROUGH 12Z SATURDAY/

Issued at 1126 PM CST Thu Jan 15 2026

Key Messages:

- A brief period of snowfall with IFR visibility will occur at the beginning of the TAF period at the Chicago metro terminals.

- Another brief period of steady snowfall with IFR visibility is expected around sunrise this morning.

- Gusty snow showers will likely affect the terminals this afternoon/evening.

- MVFR ceilings are expected to be prevalent through much of the TAF period.

Multiple rounds of snow are expected during the 06Z TAF period as a sprawling weather system traverses the Great Lakes. An initial round of snow is ongoing at press time and is on track to conclude by 07-08Z at the Chicago metro terminals. Briefly IFR visibilities are likely to occur prior to the snow ending. Thereafter, a 4-6 hour lull in the steadier snowfall is expected overnight, with a temporary return to VFR ceilings likely as well.

A second wave of steady snowfall will arrive at the terminals towards daybreak. Much like the first round of snow, this follow-up round of snow will also likely last no more than 2-4 hours at any one location while also producing IFR visibilities and another quick coating of accumulation. Couldn't rule out some brief LIFR visibility with this round of snow as well, but opted to hold off on introducing any lower visibilities into the TAFs at this time.

Another lull in the snowfall is expected from the mid-late morning through the early afternoon tomorrow. However, scattered snow showers are likely to develop during the afternoon and produce on-and-off visibility reductions through at least the early evening tomorrow. Air temperatures warming into the mid 30s by this point should tend to limit any dustings to colder and grassy surfaces, if that. A few of the more robust snow showers could also produce wind gusts near or in excess of 30 kts.

Aside from the probable period of VFR ceilings overnight, ceilings are generally favored to stay in the MVFR flight category from this morning through most of the rest of the TAF period, though there is some chance for IFR ceilings to be observed both during and just after the steadiest snowfall this morning. Winds will remain out of a southwesterly direction through the morning, gusting in excess of 20 kts on at least an occasional basis. They will then shift westerly behind a cold front this afternoon, though similar (or slightly higher) wind magnitudes are expected to be retained behind the front.

Ogorek

HYDROLOGY

Issued at 1209 PM CST Thu Jan 15 2026

The upcoming extended period of very cold temperatures will likely result in the rapid development of ice on area rivers and streams which may increase the chance of localized ice jam flooding. Last week's heavy rainfall has resulted in increased streamflow in several basins, including the Fox, Des Plains, and Illinois River basins. This higher streamflow will result in a greater potential for freeze up ice jam flooding.

- Izzi

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 6 PM CST Friday for the IL and IN nearshore waters.