textproduct: Chicago

KEY MESSAGES

- Lake effect snow will continue to result in hazardous travel across parts of northwest Indiana tonight. - 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.

UPDATE

Issued at 957 PM CST Fri Jan 30 2026

Overall the forecast remains on track with only minor adjustments made to capture current observational trends.

The earlier multi-banded lake effect snow has shifted east into northwest IN over the past couple of hours. A more dominant single band is starting to organize just offshore of Porter County at this hour. A 01z sounding out of Valparaiso University did showcase steep low-level lapse rates around 6C/km right through the heart of the DGZ which in combination with lake induced ELs around 800 mb should support peak snowfall rates within the band upwards of 2" per hour. While some uncertainty remains as to how fluid the band will be overnight, there is a decent signal in guidance for the band to set up over portions of Porter County for a good part of the night. If this is to occur then a localized corridor of 6-8 inches of snow may be seen with higher amounts certainly possible. These snow amounts in combination with very low visibility will result in dangerous travel across portions of northwest IN through Saturday morning. For this reason a Winter Storm Warning remains in effect for Lake (IN) and Porter Counties through 6 PM Saturday.

Heading into Saturday morning, guidance continues to be very adamant that the band will begin to shift back west and ooze into northeast IL between 7-9 AM. As this occurs a building subsidence inversion should begin to limit the extent of the instability, but the steep lapse rates coinciding with the DGZ should still be able to squeeze out some 0.5 to 1 inch per hour snow rates at times. That said, the inland extent of the lake effect should be more limited than today since winds are expected to remain northwesterly through Saturday afternoon. So expect the higher snowfall amounts (upwards of 3-4 inches) to likely reside closer to the lake tomorrow. Regardless, some localized hazardous travel is expected to materialize for portions of Cook and eastern Will Counties where a Winter Weather Advisory remains in effect from 6 AM to 4 PM Saturday.

Finally, the lake effect may attempt to wobble back east again Saturday afternoon but it looks as if the better instability should be waning by this time. Therefore, expect snow rates to be on the decrease through Saturday afternoon with the band fully dissipating during the evening hours.

Outside of the lake effect, another night of single digit temperatures can be expected before temperatures rebound into the low to mid-20s Saturday afternoon.

Yack

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 /06Z TAFS THROUGH 12Z SUNDAY/

Issued at 1103 PM CST Fri Jan 30 2026

Forecast concerns for the terminals...

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

- Lake effect to wobble back east Saturday morning resulting in a period of IFR to LIFR visibilities at the Chicago terminals.

- VFR conditions outside of lake effect.

The band of lake effect snow continues to organize offshore of Porter County, IN. While there remains some uncertainty as to where the band will remain the longest, the general consensus is for the band to remain mostly over Porter County tonight before starting to wobble back east around 09-10z. Regardless, under the band expect LIFR visibilities and snow rates upwards of 2"/hr which could lead to localized accumulations of 6-8 inches with higher amounts possible.

Heading into Saturday morning, the band is expected to continue to drift east towards the Chicago terminals. Guidance remains adamant that the lake effect will ooze back inland by 14-15z Saturday resulting in another period of IFR to LIFR visibilities. Though, with the instability expected to be weakening it seems snow rates will be less (around 1"/hr) and possibly another 1-4 inches of accumulation. That said, how long the band parks over the Chicago terminals remains uncertain so while the the current PROB30s have been maintained through Saturday afternoon, there is a chance the snow pushes back east sooner. The snow is finally expected to dissipate late Saturday evening which will return the terminals to VFR conditions.

Outside of the lake effect, expect VFR conditions to prevail through the forecast period. However, some MVFR clouds may drift over northern IL tonight resulting in brief periods of MVFR ceilings. Winds will also remain northwest around 10 kts through the period before becoming light westerly winds Saturday night. Though, periods of northeast winds will occur within the lake effect snow.

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 from 6 AM to 4 PM CST Saturday for ILZ103-ILZ104-ILZ105-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.