textproduct: Chicago

KEY MESSAGES

- Lake effect snow will continue to result in hazardous travel across parts of northeastern IL early this evening before the main focus for lake effect shifts into northwestern IN later this evening and overnight. - Significant snowfall accumulations and dangerous travel expect near the lake in northwest Indiana tonight into Saturday.

- Lake effect snow will return to parts of far northeastern IL on Saturday. This is likely to result in some additional localized accumulations and potential travel impacts on Saturday in parts of Cook and eastern Will counties east of I-57.

- There may be a period of light snow accumulations Sunday night into Monday, followed by less cold conditions by midweek.

DISCUSSION

Issued at 323 PM CST Fri Jan 30 2026

Headlines...

Headlines are a mess, owing to the expected behavior of the lake effect band tonight through Saturday. Overall, the band of impactful snowfall looks to move east into northwestern IN tonight, then shift back west into parts of northeastern IL on Saturday. As such, we have multiple headlines in effect for portions of northeastern IL through Saturday. First, a Winter Storm Warning remains is in effect for much of Cook through this evening, with a Winter Weather Advisory covering Lake IL, DuPage (and far northern Cook) into early this evening. Then, with the expectation of the snow returning on Saturday, we have opted to go ahead and issue a second Winter Weather Advisory for all Cook County zones and eastern Will to cover much of the day Saturday. Otherwise, we continue the Winter Storm Warning tonight and on Saturday for Lake (IN) and Porter, only pushing off the start time a few hours.

Tonight through Saturday...

Lake effect snow showers have been impacting much of northeastern IL today, with the most intense snow showers as of this writing falling just inland of the lake from Chicago northward. Expect this activity to persist through late this afternoon, with localized snow rates of 1 to 2 inches. As we head into this evening the broader synoptic flow will back as the mid-level trough overhead sags to our south. This should foster a transition in the lake effect character from the ongoing multiple banded behavior, into a single dominant band of intense snow, with snow rates possible peaking in excess of 2" per hour. In fact, this behavior has been noted for several hours today across central parts of the lake.

It appears this intense band of lake effect snow will quickly shift southward down the northeastern IL shore after 6 PM this evening, before settling somewhere across southern Lake Michigan near, or just east of the Illinois and Indiana state line mid to late this evening. This thus looks to put parts of Lake County IN and adjacent areas of western Porter (and perhaps far southeastern Cook) in the target zone for periods of intense lake effect snow through the evening. With snow rates of 2"+ per hour, near white out conditions are likely at times, which will result in a period of dangerous travel tonight from near the IL and IN state line eastward along the I-80, I-90 and I-94 corridors right across Lake and into Porter counties in IN.

This lake effect band is likely to wobble, and/or shift eastward a bit overnight as a series of meso-lows track southward and crash onshore across southern Lake Michigan into northwestern IN. Accordingly, some periodic breaks in the heavier snow are likely across parts of Lake IN County overnight, (with the snow likely stopping all together across northeastern IL overnight) as the main focus (at least temporarily) shifts into Porter County. Lake induced inversion heights are expected to gradually lower late tonight into Saturday morning. However, the presence of strong boundary layer convergence is expected to persist on the lake, and will thus continue to support some heavier rates of snow within the main band into Saturday morning.

The forecast consensus continues to favor the focus for this band of lake effect snow to shift back westward towards the northeastern IL shore Saturday morning. We thus should see accumulating snow return to parts of northeastern IL on Saturday, and it could persist for several hours into Saturday afternoon before weakening into Saturday evening. While some occasional heavy rates may persist within the lake effect band on Saturday, favorable thermodynamics on the lake will continue to fade with lowering inversion heights through the afternoon. This should thus result in a lower footprint of the heavier rates of snow as the band moves into northeast IL on Saturday. Nevertheless, some localized additional accumulations could exceed 3".

KJB

Saturday Night through Thursday:

Active northwest flow will continue beyond this weekend's system and into next week, and will guide several disturbances across the general region through next week. Medium range guidance continues to resolve the first of these waves scooting across the Upper Midwest and Great Lakes region sometime during the Sunday PM - Monday timeframe. In general, large scale height falls don't appear all that impressive, with the main surface trough and associated low forecast to slide well to our north. However. fairly robust DCVA on the southern flanks of this feature, coupled with north-south transient bands of mid-level f-gen may be sufficient to crank out some light snowfall over parts of the area, particularly the closer to the Wisconsin state line you get. The fairly quick forward progression of this system, as well as a general lack of deeper moisture, suggests snowfall amounts will be light, probably limited to a few tenths to an an inch or so. Based on the latest guidance trends, it's possible dry air plays a role and ultimately limits snowfall chances with this feature as well.

Deterministic and ensemble guidance spread increases markedly after Tuesday, lowering overall forecast confidence during the middle and end of next week. With a lingering baroclinic zone just to our south, there's a potential for some continued precipitation chances even into Tuesday/Wednesday, but this is far from ubiquitous across the guidance suite.

While below normal temperatures are expected to continue into early next week, there' a decent model signal for at least a moderating trend during the middle and end of the week, with highs potentially pushing near and above freezing.

AVIATION /00Z TAFS THROUGH 06Z SUNDAY/

Issued at 553 PM CST Fri Jan 30 2026

Forecast concerns for the terminals...

- Band of heavy lake effect snow will persist through tonight in northwest IN resulting in LIFR visibilities.

- Lake effect wobble back west towards the Chicago terminals Saturday morning, but uncertainty remains on how far west the band gets and its intensity.

- VFR conditions expected outside of lake effect.

The initial band of lake enhanced snow is progressing southwestward across north-central IL resulting in brief periods of IFR visibilities. This band should begin to wane over the next 1-2 hours. However, the main lake effect band is developing over eastern Lake Michigan and will pivot across the Chicago terminals through 02z this evening. Beneath the band a 1-2 hour period of LIFR visibilities (as low as 1/2SM) and MVFR ceilings is expected in addition to a quick 0.5 to 1 inch of snow accumulation. As this band pivots into northwest IN by 03z this evening it is expected to slow and result in a more prolonged period of LIFR visibilities and IFR ceilings at GYY and points east. While the exact duration of the band at any one location remains uncertain, the band is expected to remain over portions of northwest IN through the night and will be wobbling between VPZ and GYY during this time. Where the band remains the longest will likely see accumulations upwards of 6 inches with locally higher amounts possible.

Heading into Saturday morning, the lake effect band is forecast to begin to swing back west towards the Chicago terminals. Despite the decent agreement in guidance on this scenario, there remains a fair bit of uncertainty as to how far west the band will get and its intensity. Therefore, have opted to maintain the PROB30s at ORD, MDW, and GYY but did opt to introduce a prevailing group of flurries at ORD and MDW to tease a slightly earlier arrival. Regardless, where the band does get to another period of IFR to LIFR visibilities can be expected. The band will gradually begin to shift back east Saturday afternoon and should weaken as it does so before finally dissipating Saturday evening. In terms of accumulation, another burst of 1-3 inches of snow is possible especially where the band sits the longest.

Outside of the lake effect, expect VFR conditions to prevail through the forecast period. Winds will also be northwest around 7-10 kts through the period, but instances of northeast winds are possible under the main lake effect band. Yack

HYDROLOGY

Issued at 230 PM CST Wed Jan 28 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...Winter Weather Advisory until 8 PM CST this evening for ILZ006- ILZ013-ILZ103.

Winter Storm Warning until midnight CST tonight for ILZ104- ILZ105.

Winter Weather Advisory from 6 AM to 4 PM CST Saturday for ILZ103-ILZ104-ILZ105-ILZ108.

Winter Weather Advisory until midnight CST tonight for ILZ108.

IN...Winter Storm Warning until 6 PM CST Saturday for INZ001-INZ002.

LM...Small Craft Advisory until 2 PM CST Saturday for the IL and IN nearshore waters.