Marine Weather and Tide Forecast for Waukegan, IL

UPDATE
Issued at 845 AM CST Sat Feb 28 2026

A narrow band of radar returns indicative of snow stretches from northern South Dakota through southern Minnesota, far northeastern Iowa, and southern Wisconsin. Surface dew point depressions of 15 to 20 degrees and cloud bases of 7000 to 8000 feet beneath the radar returns east of the Mississippi River are indicative of a wedge of dry low-level air, which has thus far rendered all local radar returns to virga. Indeed, radar reflectivity returns from KMKX and and KDVN continue to exhibit the classic doughnut-shape, as the radar beam samples the concentric outer-edge of where snow is sublimating into the wedge of dry air.

As the morning progresses, continued sublimation of snowflakes should gradually whittle away at the depth of the low-level dry layer. Indeed, have already noted the top of the dry layer fall from around 600 to 700 mb in the past few hours in AMDAR soundings from MDW. Such a process can also be inferred across far northern Iowa, where broken clouds near 3500 feet have developed in tandem with reports of snow reaching the ground.
And, have noted a very modest "shrinking" in the donut hole shape in recent KMKX reflectivity data particularly on elevated radar elevation angles. As a result, there appears to be a somewhat brief (2 to 4 hour) window where snow may ultimately reach the ground from late morning through early afternoon as the peak in forcing traverses along the Illinois and Wisconsin state line. The inherited forecast carrying likely (>55%) PoPs generally along and north of IL-176 handles such a possibility well.

With a somewhat limited time window for snow, a residual dry low-level airmass, and marginal surface temperatures near freezing, still suspect that snow may struggle to accumulate where it does reach the ground. Accordingly, the inherited forecast for up to about an inch of snow near the Wisconsin state line remains quite appropriate. Of course, there remains a possibility (implied 40 to 45% chance or so given the aforementioned PoPs) that snow never actually reaches the ground locally.

Elsewhere, today looks rather banal with increasing cloud cover and gradually increasing east to northeasterly flow. Highs will stall generally near 40 along the I-88/I-80 corridors and rise to around 50 near US-24.

Updated products will be sent soon.

Borchardt

DISCUSSION
Issued at 316 AM CST Sat Feb 28 2026

Through Monday:

We are monitoring a narrow band of snow approaching the region that currently extends from southwest North Dakota across South Dakota into southwest Minnesota. This feature is associated with a frontogenetical response to divergence aloft in the left exit region of an upper level jet streak. The fgen layer appears to reside within 850-750mb which is situated beneath a rather deep layer of saturation within the DGZ paired with fairly steep lapse rates within that layer, indicative of embedded locally high snowfall rates of 1"+ per hour. The key forecast challenge is whether this feature will maintain its east southeastward progression into portions of northern Illinois and whether it can overcome pronounced low-level dry air here locally. 00Z guidance had largely maintained the idea that this band would begin to trend more east than southeast through the morning keeping accumulations largely north of the Wisconsin state line. However, the current position of the snow band has remained mostly south of these earlier solutions, more in line with the 0Z ARW and now likely being picked up by the recent 06Z NAMnest which bring the snow across portions of northern Illinois.

As a result, it felt prudent to nudge up snowfall amounts (~0.5 to 1") near and north of a Rockford to Evanston line (highest toward the Wisconsin state line). It remains lower confidence as to whether this will lead to travel impacts here locally with pavement temperature observations still above freezing after an unseasonably warm Friday. Thus, with this in mind and daytime timing with fairly strong last day of February sun, suspect that any accumulations would be mainly confined to grassy and untreated elevated surfaces (including bridges and overpasses).
However, if locally higher snowfall rates can be achieved late morning into early afternoon when the fgen signal is maximized, a brief (1-2 hr) period of pavement accumulations would be possible, leading to a greater coverage of slippery travel conditions. Lastly we will have to monitor for any additional southward adjustments to the track of the band of snow which could include more of the Chicago metro area but there should be a fairly sharp southern edge to the snowfall.

Temperatures today will feature a fairly sizable gradient from north to south, with lower to mid 30s for highs north of I-88 closer to the potential band of snow. In contrast, warmer mid 40s to around 50 possible are likely south of I-80.

In the wake of today's snow system this evening, a lake effect snow band may try to set up and orient into northeast Illinois toward daybreak Sunday. Lake effect parameters don't look especially impressive at this time but some high-res guidance suggests there could at least be a light dusting near the lake before it ends in the afternoon on Sunday. Have maintained slight chances (~20%) near the lake to account for this.

Model guidance for the Sunday night system continues to trend farther south with blended guidance keeping the accumulating snow largely south of the area. Have held onto low snow chances south of I-80 with this update given there has been some variability in the position of the band the past few days.
Suspect this may end up not much more than flurries given there will be dry air to contend with amidst expanding surface high pressure over the Upper Midwest and Great Lakes region.

Cold air advection paired with northeast winds off Lake Michigan will likely keep temperatures in the 30s across the area on Sunday. After a chilly Sunday temperatures then trend warmer on Monday with highs mainly in the 40s (upper 30s near the IL lakeshore) as we transition into a warmer and wetter pattern, more on that below.

Petr

Monday Night Onward:

A significant large scale weather pattern shift is expected during this coming week. The pattern will transition to the negative phase of the Pacific North American (PNA) teleconnection pattern, which is characterized by western CONUS mid and upper level troughing and eastern CONUS ridging. While the day-to-day specifics of this pattern remain somewhat unclear, there is above average forecast confidence that this pattern will favor periods of active weather, including notable rainfall amounts and thunderstorms, along with above average temperatures through next weekend. Our current forecast does advertise at least some lower end chances for rain each day Tuesday through next weekend. In spite of this, do not expected to be raining constantly, as there will be periods of dry time.

Our first favored period of rain is late Monday night into Tuesday in association with increasing warm air advection (isentropic upglide) setting up across a surface frontal boundary downstream of an impulse traversing the Colorado Rockies. There's a non-zero chance that the initial rain will fall while temperatures and/or surface wet bulbs over parts of the area are at or just below freezing in the overnight/pre-dawn hours of Tuesday. With east-southeasterly flow coming from a region of 20s dew points to our east associated with departing strong surface high pressure, there might be enough of a delay in surface warming to result in a brief period of freezing rain. The primary zone of interest for this lower end potential would be near and north of I-90 in far northern Illinois. Even if a period of freezing rain materializes, fairly mild antecedent pavement temperatures may serve to mitigate travel impacts. We'll hold off a few more cycles in terms of ramping up messaging for the current slight/20% chance of freezing rain in parts of far northern Illinois.

Ultimately, there is a strong signal for rainfall during the late Monday night and Tuesday period, with roughly 70 to 90+ percent of the ensemble members producing rain across a good portion of the area. Thereafter, ensemble spread increases, particularly with the speed and timing of the the next impulse expected to shift into the lower Great Lakes region sometime Wednesday into Thursday. The GEFS and to a lesser extent the Canadian ensemble system have remained on the faster side of the guidance envelope for Wednesday, which would entail rainy/inclement conditions.
Meanwhile, if the slower solutions advertised by about half of the ensemble suites (the ECMWF and UKMET ensembles) pan out, a good chunk of Wednesday could be dry (especially with northward extent)
before rain chances increase again Wednesday night into Thursday.
On either side of the faster to slower spectrum with respect to rain trends Wednesday-Thursday, temperatures may end up a good deal cooler than the official forecast in parts of the area due to onshore flow from Lake Michigan. This is particularly the case on Thursday near the lake in northeast Illinois.

Regardless of exactly how the mid to late week period evolves, precipitable water of 250-300% of average/normal for early March could certainly spell corridors of heavy rainfall and an associated flooding threat. The extent (or lack thereof) of embedded thunderstorms will likely play a role as well. Finally, the exceptionally mild and moist cyclone warm sectors in the upcoming pattern may also feature a threat for organized strong to severe convection within in the general region. Next Friday may be a "day to watch" in this regard. Even at this lead time, the various ensemble systems have a strikingly strong signal for a northward surge of anomalous dew points in the 50s to possibly 60F+ in spots coinciding with an approaching cold front and seasonably strong wind fields.

Castro/KJB

AVIATION /12Z TAFS THROUGH 18Z SUNDAY/
Issued at 556 AM CST Sat Feb 28 2026

Main Concern:

- Potential for a period of snow and associated VSBY impacts at the northern Illinois terminals today

The southern extent of a fairly narrow snow band today remains uncertain. Recent upstream radar and observational trends have been a better fit for near-term guidance that shifted a bit south from previous model cycles. This still places the northern Illinois terminals on the sharp southern edge dividing line between snow with impacts to VSBY and VFR flurries at most. For this issuance, maintained PROB30 mention, though with IFR VSBY at RFD and ORD where there's a better chance for a period of higher snowfall rates. Given mild pavement temperatures going into today and the fairly strong end of February sun, pavement accumulations would probably be limited (a relatively higher chance at RFD).

CIGs should build down to a period of prevailing MVFR at the Chicago metro sites this evening due to strengthening north- northeast flow. This could eventually yield intermittent lake effect flurries near the lake, with little/no impacts expected if they occur. Once winds shift east of north this morning, they're expected to remain east of north through Sunday. Expect the strongest winds late today and especially this evening when gusts near the lake may reach as high as 20-25 kt at times.

Castro

LOT WATCHES/WARNINGS/ADVISORIES
IL...None.
IN...None.
LM...Small Craft Advisory from 2 PM this afternoon to 3 PM CST Sunday for Winthrop Harbor IL to Burns Harbor IN.

Small Craft Advisory until 3 PM CST Sunday for Burns Harbor to Michigan City IN.