Marine Weather and Tide Forecast for Chicago, IL

UPDATE
Issued at 1106 AM CST Sat Jan 24 2026

No big forecast changes planned this morning. Did cancel the wind chill advisory early as wind chills have inched their way above the -20F criteria.

Radar shows virga has overspread northern IL and northwest IN with very slow top down saturation noted as a closing "donut hole" on our WSR-88D. This top down saturation process should continue through the day with some light snow likely to eventually develop from west to east across the area this afternoon. It's possible this process may be a tad quicker than progged in current pops, so may eventually need to tweak the timing up a bit. Initially, snow should be very small flake size which should be very slow to accumulate.

The stubborn lake effect snow band has now moved offshore, however there is a narrow band of lake effect clouds and flurries that snakes its way inland across northern Lake County into eastern Will and southeast Cook County. There are probably some light flurries falling from this based on the weak radar returns. As top down saturation continues, suspect that this band of flurries could intensify as seeder-feeder process ramps up from the virga falling into this narrow band of flurries.
Radar suggests that this seeder feeder process could start soon, will wait to make any pop changes until we see how much intensification we see as this takes place. This narrow band is expected to continue drifting northwestward around 5 mph across the southern Chicago suburbs into the south side of Chicago this afternoon.

- Izzi

DISCUSSION
Issued at 327 AM CST Sat Jan 24 2026

Through Sunday Night:

It's another frigid morning out there as the well-advertised Arctic air mass continues to make its presence known. Air temperatures at press time are below zero across the area with wind chills generally between -20 and -30F, coldest across our northern counties. These readings will not change much until after sunrise, and even then, a relatively thick cirrus canopy will hamper warming efforts to some degree, keeping today's high temperatures in the single digits to at or slightly above 10F.
Did opt to extend the going Cold Weather Advisory until noon to better align that with the advisory expiration times of our neighboring WFOs, but the overall message of another frigid morning has not changed, so bundle up in multiple layers if you need to go outside!

Also ongoing this morning is a stubborn ribbon of lake effect snow in northwest Indiana. Will continue to message the likelihood of resultant slick travel conditions in northern Porter County (and possibly northern Lake County, IN later on)
with Special Weather Statements. Eventually, the lake effect snow band will retreat offshore and back over Lake Michigan later this morning as near-surface flow on the band's eastern flank veers from an easterly to a southerly direction with time.

This weekend's weather headline-maker is the absolute unit of a winter storm that will produce significant wintry impacts across a large swath of the central and eastern CONUS, including portions of the Deep South. The storm's massive size can be attributed to the Arctic air mass clashing with a substantial poleward influx of Gulf and sub-tropical Pacific moisture. This has yielded an expansive swath of precipitation across the southern central CONUS this morning, which is only expected to grow in size today into Sunday as a strengthening sub-tropical jet continues to funnel moisture into the CONUS while a cut-off upper low off the coast of Baja California begins to eject northeastward while undergoing a complex phasing process with two northern stream troughs. Aided by broad upper-level divergence in the right entrance region of a westerly polar jet streak, this storm's precipitation will spread into our forecast area from southwest to northeast in the form of snow by as early as this afternoon. System snow will then likely continue across at least a portion of our forecast area all the way through late Sunday afternoon/evening. Lake enhancement will also likely start to occur Saturday night/Sunday morning, before transitioning to a more bona fide lake effect snow and lingering beyond the end time of the system snow until closer to midnight.

One lingering point of forecast uncertainty remains how far northwest the steadier snowfall will be able to spread with a strong Arctic high to our northwest supplying a feed of dry air into the area. While our northwestern counties could still see a period of light snowfall this evening, the steadier snowfall will remain focused in the southeastern half of our CWA (and within any lake effect snow bands) thereafter as the drier air attempts to gradually creep eastward. A sharp snowfall gradient will likely occur across our forecast area as a result -- one that will likely be tighter than what can reasonably be depicted in our gridded forecast database.

Wherever the steadier snowfall does end up occurring, an exceptionally deep dendritic growth zone and the aforementioned cold air temperatures will yield a dry, powdery type of snow with snow-to-liquid ratios favored to average out around or just above 20:1. With the more pronounced mesoscale forcing mechanisms remaining displaced to our south, snowfall rates aren't expected to be exceptional -- generally remaining at or below 0.5"/hour. Briefly higher rates closer to 1"/hour aren't out of the question, though, in the more robust lake effect banding and in our far southeastern counties during the height of the synoptic snowfall late Saturday night/Sunday morning as an increasingly coupled jet structure strengthens broad-scale ascent. However, even without eye-popping snowfall rates, the prolonged duration of the snowfall will still allow for anywhere from a few to several inches of snow accumulation to be observed wherever the steadier snowfall has some staying power.

Have hoisted a Winter Weather Advisory for roughly the southeastern half of our forecast area (plus Lake County, IL), where confidence is highest in multiple inches of snow accumulation occurring and hazardous travel conditions materializing as a consequence of the cold air temperatures making it easier for snow to accumulate on roadways. It is possible that some locations could end up seeing snowfall totals of 6" or greater, and did give consideration to a Winter Storm Warning for a portion of our southeastern CWA for that reason.
However, with our presently forecasted snowfall amounts being borderline for a Winter Storm Warning issuance and most other headline decision factors (long snowfall duration, less-than- stellar snowfall rates, winds not expected to be particularly strong, etc.) pointing towards the issuance of an advisory over a warning, elected to go with an advisory headline. Did segment the advisory product accordingly to account for where snowfall totals may be higher relative to other areas. That said, if confidence increases in solidly 6+" snowfall totals being observed somewhere, then an upgrade to a Winter Storm Warning may eventually be warranted for those locations.

Ogorek

Monday through Friday:

Following the weekend system, an energetic and active upper pattern will remain in place with fast, northwesterly flow aloft likely to guide additional disturbances across the Upper Midwest and Great Lakes region through the week. Regarding late Sunday night/Monday morning: latest guidance suggest we may need some additional cold weather headlines during this period to start the week with wind chills in the 15 to 25 below range.

Latest indications point to generally precip-free conditions on Monday as fairly robust mid-level height rises spread in from the west through the afternoon. The nose of a ~130 kt jet streak will impinge on the region late in the day, but at this time only looks like it'll drag some increasing mid and high- level cloud cover overhead. Northwest to west-southwest breezes with a lingering fairly tight surface pressure gradient will hold wind chills largely below zero through the day.

On Monday night, a fast-moving and fairly robust disturbance is slated to press southward out of the Minnesota Arrowhead Region and across the Great Lakes. Latest guidance currently takes the bulk of the most intense large scale forcing with this system to our north, and will continue with a dry forecast in our area as a result. The associated surface low will eventually drag a reinforcing cold front through the area on Tuesday which will send air temperatures back down to around 0 degrees Tuesday night with colder wind chills. In the wake of the front, forecast soundings look a bit more supportive of some intermittent flurries as lobes of strong shear vorticity meander southward through the afternoon and evening with increased saturation in a thin layer at the base of a deep DGZ. Good agreement that the boundary layer flow will remain westerly enough to keep an follow-up LES to our east.

Another, potentially even more intense shortwave is forecast to drop more solidly across our area on Wednesday and Wednesday night. Guidance generally appears supportive of a period of light snow somewhere in the vicinity, although noting a fair amount of north- south spread in the current deterministic and ensemble output. At this point, didn't see any reason to stray from the NBM-delivered chance PoPs during this period. Where snow does fall, very cold temperatures in the single digits and teens will once again lead to travel impacts.

Beyond this time, forecast confidence breaks down a bit, but there's an interesting signal of a fast-moving vort lobe backing southwest across lower Michigan sometime during the late Wednesday night - Thursday timeframe. This could potentially restart the LES potential in our area, but confidence is pretty low in specifics at this time.

Carlaw

AVIATION /18Z TAFS THROUGH 00Z MONDAY/
Issued at 1221 PM CST Sat Jan 24 2026

Forecast concerns for the terminals...

- Snow will spread into the area this evening resulting in a period of IFR visibilities overnight.

- A band of lake effect snow is expected to develop early Sunday morning and result in IFR to LIFR visibilities at the Chicago terminals and GYY.

The arctic high that brought us the bitter cold the past couple days continues to drift eastward over MI as a storm system begins to organize over the southern Plains. The lingering influence of the high will continue to promote VFR conditions and light northerly winds through this afternoon. Though, wind directions will become more northeasterly later this afternoon and evening as the aforementioned storm system approaches. While mostly dry conditions are expected through this afternoon, a few flurries cannot be ruled out as mid-level moisture increases.
Furthermore, there is also a band of lake effect snow just off shore of GYY which has a band of MVFR clouds associated with it.
So far any snow with these MVFR clouds has been flurries, but the concern is growing that as the aforementioned mid-level moisture increases that it may generate more robust snow showers from these clouds. Given that this is lower confidence have opted to just maintain a 6SM flurry mention at the Chicago area terminals for now.

Heading into this evening, the main snow shield with the aforementioned storm system will begin to spread into northern IL and northwest IN between 02z and 04z. As the snow arrives visibilities should diminish into the IFR (1-2SM) range shortly after snow begins. While the snow itself will persist through the night, it appears that the better forcing may drift east of the area after 07z which may allow for some improvement in visibilities into Sunday morning. However, a band of lake effect snow is expected to develop early Sunday morning and begin to move over the Chicago terminals and eventually GYY. Given the decent lake induced instability the lake effect band should be able to produce a period of 0.5-1" per hour snow rates which will result in IFR to LIFR visibilities at ORD, MDW, and GYY under the band. Additionally, winds under the band may also become breezy with northerly gusts around 20 kts.

Confidence on the lake effect band occurring remains high, but confidence on how long it persists over the terminals is much lower. For now have opted to capture the potential for the lowest LIFR visibilities in a PROB30 between 13z and 18-19z when guidance has a general consensus of the band being over the terminals. However, will maintain a longer period of IFR visibilities through Sunday afternoon to account for a slower band progression. Regardless of what the lake effect band does, the cold surface temperatures will result in at least 2-4 inches of accumulation (locally higher where the lake effect band goes) across much of northeast IL and northwest IN. Though, lighter snow amounts are expected near RFD (accumulations around a couple tenths to locally 1 inch).

Outside of the snow, expect MVFR conditions overnight to improve to VFR once the snow concludes. Winds will gradually become more northwest on Sunday with speeds remaining in the 5-10 kt range.

Yack

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...Winter Weather Advisory from 6 PM this evening to 6 PM CST Sunday for ILZ006-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023- ILZ032-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.

Winter Weather Advisory from 6 PM this evening to 9 PM CST Sunday for ILZ033-ILZ039.

IN...Winter Weather Advisory from 6 PM CST /7 PM EST/ this evening to 9 PM CST /10 PM EST/ Sunday for INZ010-INZ011-INZ019.

Winter Weather Advisory from 6 PM this evening to midnight CST Sunday night for INZ001-INZ002.

LM...None.