textproduct: Chicago

KEY MESSAGES

- Two clipper systems will bring accumulating snow and slippery travel conditions this afternoon/evening and again Sunday afternoon/ evening.

- Bitterly cold conditions are expected Sunday night through Tuesday morning with wind chills 15 below to 25 below zero possible Monday morning.

DISCUSSION

Issued at 227 AM CST Sat Jan 17 2026

As the main upper level low slowly lifts northeast and opens today, another upper low is forecast to move across across the area this afternoon into this evening, when it too begins to weaken. Models are in general agreement with a period of light snow spreading and developing across the area this afternoon, continuing through mid evening and then dissipating by late evening. Not much moisture to work with in this dry airmass, but these low qpf events can still be impactful, especially with the cold temps in the upper teens/lower 20s expected today and accumulation on untreated surfaces. Have increased pops into the 70-80% range for areas along/north of I-80. Snow amounts will likely be under an inch with just a dusting further south.

Next system arrives Sunday afternoon ahead of a blast of arctic air and similar to today's system, should be a high pop/low qpf event. Boosted pops to likely for the northern half or so the cwa for Sunday afternoon/evening. Snowfall with this system could be in the one inch range, perhaps 1-2 inches across far northeast IL, to a dusting across the south. Similar temps in the upper teens/near 20 will likely allow for accumulation on untreated surfaces. Winds begin to increase as the snow ends Sunday evening. With gusts possibly into the 30 mph range, some blowing snow will likely result even after the falling snow has ended.

Temperatures will be diving Sunday night into Monday morning and lows around zero in the northwest to low single digits above zero elsewhere look on track. The strong winds will push wind chills as low as 25 below zero across the northwest to 20 below to 15 below zero for the rest of the area. Too early for any cold weather advisories, but if these trends continue, will need to consider one for the northwest cwa Monday morning. Highs barely rebound in the upper single digits/low teens Monday with lows back in the low single digits Tuesday morning, possibly just below zero across the northwest. Winds will have diminished quite a bit by Tuesday morning, but possibly still in the 10 mph range with wind chills 5 below to 15 below zero possible.

Rather good consistency in the models and their ensembles for a brief moderation of temps Tuesday into Wednesday ahead of a clipper system moving across the Great Lakes region. High temps on Tuesday back in the 20s and possibly upper 20s/lower 30s on Wednesday. Still some uncertainty for precip chances across the local area Tuesday night into Wednesday morning with this clipper. Blended guidance now has chance pops for the northern half or so of the area and that seems reasonable for now.

There remains quite a bit of uncertainty for the end of next week into next weekend with the potential for an active pattern for or near the local area. While the ensembles still show a decent spread in possibilities, this time period has looked active for the past week. Regardless of whether precip develops for the local area, current trends favor a continued cold/very cold pattern. cms

AVIATION /18Z TAFS THROUGH 00Z MONDAY/

Issued at 1123 AM CST Sat Jan 17 2026

On-and-off flurries will continue through the early afternoon as stratocumulus clouds centered in the DGZ stream overhead.

Steady snow will develop/expand across the area as a trough axis currently stretching from southern Wisconsin into central Iowa shifts southeastward. While moisture will be meager, lift centered directly in a low-centroid DGZ and filaments of frontogenesis will serve to creating dry and fluffy snow that will be effective at lowering visibility. Generally speaking, the expectation is for 2 to 4 mile visibility to prevail with periodic drops to 1 to 2 miles from late afternoon through early evening. Cigs should hold near 2000 ft during the period of snow, and winds will remain out of the south to southwest. Total accumulations of a dusting to locally 1 inch remain on track for the terminals.

Snow rates will taper to flurries during the overnight hours as the trough axis shears out while shifting eastward. Cigs may attempt to scatter after daybreak as winds begin to back southwesterly.

Yet another clipper system will approach the region tomorrow afternoon. Will go ahead and introduce 3SM -SN toward the end of the ORD/MDW 30-hour TAF windows, keeping in mind refinement in timing and visibility will take place in later TAF packages.

Borchardt

MARINE

Issued at 330 AM CST Sat Jan 17 2026

A gale watch is in effect late Sunday night through Monday afternoon for the IL and IN nearshore waters.

An arctic cold front will move across the area Sunday night bringing much colder temperatures and strong winds to the region, with a period of gales expected late Sunday night through at least midday Monday. Freezing spray is also expected, especially for the IN nearshore waters. cms

HYDROLOGY

Issued at 253 PM CST Fri Jan 16 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 9 PM CST this evening for Winthrop Harbor IL to Gary IN.

Gale Watch from late Sunday night through Monday morning for Winthrop Harbor IL to Gary IN.

Small Craft Advisory until 3 AM CST Sunday for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.

Gale Watch from late Sunday night through Monday afternoon for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.