textproduct: Chicago

KEY MESSAGES

- Bitterly cold conditions will persist through early Saturday morning.

- Fluffy accumulating snow paired with cold temperatures will likely lead to hazardous travel conditions in some locations late Saturday into Sunday. The greatest likelihood for this is currently forecasted to be near and east of Interstate 55.

- Lingering lake effect snow for far northeastern IL and northwest IN Sunday night through Monday morning. Some additional accumulation is likely.

DISCUSSION

Issued at 244 PM CST Fri Jan 23 2026

Through Sunday:

Main focus is on a synoptic accumulating snow system Saturday afternoon through Sunday. Some questions remain with exact snow amounts especially into the Chicago metro area where some lake- enhancement is likely. Expectation is that we'll end up with a general 3-6" accumulation across the southeast third to half of the cwa, and potentially parts of the Chicago metro where lake- enhancement occurs, with a sharp gradient to lower amounts farther to the northwest. Details of where exactly this gradient lays out will need further refinement, and thus in collaboration with neighbors to the east and west have held off on headline issuance just yet. However, we do anticipate the need for a winter weather advisory for southeast parts of the forecast area and near the lake as the footprint is further narrowed down.

In the near term, very cold arctic air remains in place across the area this afternoon, with temperatures still in the negative single digits across most of the area as of 2 pm CST. Winds have eased since this morning, allowing wind chills to settle around -25F or so north of I-80, and had allowed the Extreme Cold Warning to expire at noon as scheduled. Even with lighter winds however, overnight temps of -5F to -15F will support wind chills of -20F to -29F into Saturday morning, and a Cold Weather Advisory remains in effect for the entire area through 9 am CST Saturday.

Additionally, light but persistent lake-effect snow showers persist across parts of northwest Indiana, particularly northeast Porter County. Relatively shallow-topped, disorganized multi-band setup is not expected to produce impressive snowfall rates, though cold temperatures are allowing the persistent light snow to accumulate on roadways resulting in slippery travel conditions. With limited area have continued Special Weather Advisory issuance for these conditions which will likely persist into this evening. Forecast soundings overnight then depict lowering inversion heights, decreasing winds/increasing shear along with a gradual development of a land-breeze convergent zone which shifts westward toward Lake County IN with time before eventually focusing further out away from the lake shore by morning. While this scenario appears reasonable, we'll have to continue to monitor light LES trends through the night.

Attention then turns to the more widespread accumulating snow system expected to affect the area later Saturday afternoon through Sunday. Evolution of this system remains somewhat complex, involving the upper low currently off the Baja coast being kicked eastward by another wave dropping southeast across CA/NV. This results in a broad area of warm advection/isentropic ascent developing along the established baroclinic zone from the Southern Plains to the Ohio Valley Saturday and a broad synoptic precipitation shield of which the northern periphery remains progged to extend into northern IL/IN. While the strongest forcing and axis of heaviest precipitation is expected to remain south of the region, models continue to depict deepening saturation within a thermal profile which features a deep DGZ across the area from Saturday afternoon into Sunday. Ensemble probabilities of 6" or more of snowfall remain across central IL/IN for the most part, guidance is in pretty good agreement with amounts in the 3-6" range across our southeastern cwa.

Furthermore, a deepening layer of northeasterly low-level flow is likely to producing some degree of lake- enhancement into parts of the Chicago metro area, possibly with an additional small footprint of 3-5" amounts there (perhaps locally 5-6"). Will likely need a Winter Weather Advisory for at least the southeast part of the cwa from Saturday afternoon into Sunday, though with some of these details still uncertain and in collaboration with neighbors to my east and west have held off issuance at this time. Amounts should diminish quickly farther to the northwest. Synoptic snow looks to taper off/end from the west/northwest Sunday afternoon, though with some lingering lake effect lingering into Sunday night.

Ratzer

Sunday Night through Friday:

The main snow shield will be in the process of exiting the area from west to east Sunday afternoon and evening as the surface low over the Tennessee and Ohio River Valleys pushes into the Mid-Atlantic. While this will bring the snow to a close for most, a band of lake effect snow is expected to be ongoing as a couple of vort lobes within the upper trough pivot through. Now where exactly this lake effect band will be Sunday evening remains a bit uncertain, but as winds turn more northwesterly late Sunday evening and overnight the band should pivot into northwest IN and eventually into northern IN by midday Monday. Regardless of the band's location, forecast soundings do show much of the atmosphere in the snow growth region with steep low- level lapse rates (7-8C/km) and 5000-6000 ft lake induced ELs. These parameters should be sufficient to support snowfall rates around 0.5 to 1.0" per hour which will result in at least a couple inches of additional accumulation Sunday night through Monday morning. Given that surface temperatures will still be in the 5-10F range, road treatments will likely struggle to combat the snow and lead to hazardous travel beneath the lake effect band. So despite the uncertainty in location those near the lake from Chicago, IL to Michigan City, IN should be prepare for travel impacts Sunday night into Monday morning.

Outside of the lake effect, the main forecast concern for the rest of the week will be the continued below average temperatures. The reason for the continued cold will be the upper troughing that is forecast to establish over the Great Lakes this weekend and persist through at least the end of next week. As a result, northwest winds will prevail and continue to pump colder arctic air into the region keeping afternoon highs in the teens to around 20 with overnight lows in the single digits (possibly below zero at times). From a precipitation perspective, the troughing overhead will allow several shortwaves to dive across the region throughout the week and some of them could bring periods of snow. At this point, it seems guidance is favoring a period towards the later half of the week for one of these disturbances to move through but confidence remains low on its exact track and what if any impacts it will bring locally. So be prepared for additional periods of snow at times and stay tuned for more details as we get closer.

Yack

AVIATION /00Z TAFS THROUGH 06Z SUNDAY/

Issued at 553 PM CST Fri Jan 23 2026

Main Concern:

- Light snow overspreading the Chicago metro area late day Saturday into Saturday evening

VFR conditions with much lighter winds are in store through much of Saturday. This will be followed by developing light snow and associated lower flight categories towards and especially after sunset on Saturday. The main item of lower confidence in the snow forecast is onset time due to uncertainty regarding the erosion of dry air before snow reaches the surface. In the latest TAF, continued with PROB30 mention late day Saturday into the evening at ORD and MDW (and DPA at the end of 24-hr period). If snow is able to develop during this window, periodic 2-4SM VSBY appears possible.

Confidence is higher in prevailing 2-3SM light snow and gradual fluffy accumulations starting by mid to late Saturday evening with periodic ~1SM VSBY. CIGs should be in the ~2500-3500 ft range. Expect wind direction variability right over Chicago (northerly at ORD and easterly at MDW) during this time as well.

Finally, at GYY, lake effect snow showers may push westward and get close enough to result in on and off 4-6SM light snow late tonight into Saturday morning (09-15z PROB30 in TAF).

Castro

HYDROLOGY

Issued at 230 PM CST Fri Jan 23 2026

River gauges, reports from local officials, and reports from trained ice spotters continue to indicate a few ice jams across the area due to the significant increase in river ice over recent days. With continued cold weather into next week, conditions will remain favorable for river ice formation. While no widespread flooding is expected, localized ice jams may occur.

- NWS Chicago

LOT WATCHES/WARNINGS/ADVISORIES

IL...Cold Weather Advisory until 9 AM CST Saturday for ILZ003- ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013- ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ103- ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.

IN...Cold Weather Advisory until 9 AM CST /10 AM EST/ Saturday for INZ001-INZ002-INZ010-INZ011-INZ019.

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

Heavy Freezing Spray Warning until 9 PM CST this evening for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.