Marine Weather and Tide Forecast for Waukegan, IL

DISCUSSION
Issued at 304 AM CDT Sat Mar 14 2026

Through Tonight:

Early this morning, low- to mid-level frontogenesis within a northwest-southeast oriented baroclinic zone has caused multiple snow bands to flare up on regional radars from South Dakota down through central Illinois. Much of these radar returns are reflective of virga at this time with a wedge of dry air below 700 mb chewing up the descending snowflakes before they can reach the ground, though there is at least one exception to this with a few ASOS sites in southeastern and central South Dakota reporting snow from a relatively elongated band at the time of this writing.

A similar story should continue to play out through the early afternoon today as the f-gen circulations powering these snow bands drift through our area. Most snowflakes will continue to be sublimated before they are able to reach the ground, but wherever frontogenetical forcing is strongest/most persistent and mid-level lapse rates are steepest, snowflakes will have a better chance to penetrate the dry layer and reach the ground across a narrow spatial corridor. Thus, with the continued lower-end likelihood for some localized dustings of snow accumulation to occur and the expectation that most locations will not see any accumulating snowfall today, the going slight chance PoPs in our forecast grids continue to look appropriate for the situation. Any snow that does accumulate will likely only do so on grassy and colder surfaces, given that air/ground temperatures have largely remained above freezing recently and that air temperatures today should generally be in the mid-upper 30s during any precipitation.

Tonight, warm air advection will really start to ramp up as the incoming weather system for Sunday/Monday starts to get its act together over the central/northern Plains (more on that in the long term portion of the AFD below). Increasingly breezy southeasterly winds will result in a non-diurnal temperature trend into Sunday morning with surface temperatures expected to rise after midnight. A deepening mid-level cloud deck and steepening mid-level lapse rates may also support the development of precipitation somewhere over our forecast area, but at this time, it appears that the most likely outcome is that any measurable stratiform or convective precipitation that develops should remain to the north and northeast of our CWA

Ogorek

Sunday Onward:

The primary focus in the long-term period is on the strong synoptic-scale cyclone that will bring a myriad of impactful weather to our area tomorrow and Monday.

Over the next 24 hours, an upper-level shortwave moving onshore into the Pacific Northwest will undergo significant amplification wile diving southeastward across the central United States. Ensemble model guidance remains in excellent agreement that the initial surface cyclone will develop in the lee of the Rocky Mountains near the WY/SD/ND border region today, move eastward across northern Nebraska tonight and across Iowa tomorrow morning, and then shift along or just south of the Illinois/Indiana border tomorrow night before lifting toward Michigan on Monday. A broad region of upper- level diffluence within coupled jet streaks will facilitate the rapid deepening of the low as it moves into the Great Lakes tomorrow, with ensemble mean pressures falling toward 990mb (individual ensemble members falling into the mid to upper 980s).

High Winds:

As the low moves across Iowa and eventually toward the Mississippi River tomorrow, impressive pressure falls in the Great Lakes on the order of 12mb/6hr will cause low-level southerly flow to rapidly intensify in the warm sector of the approaching cyclone. Indeed, deterministic HRRR/RAP output depicts 925 and 850mb flow increasing to 50kt to 60kt, respectively, by early tomorrow afternoon (and even higher by the evening). While such strong flow will advect an EML plume northeastward into the Lower Great Lakes atop the warm sector, forecast mixing profiles depicting momentum transfer from the 925mb wind field supports a legitimate threat for surface gusts to routinely hit 55 to locally 65 mph in the warm sector particularly with eastward extent where the impacts of any low- level stratus should be minimized and surface temperatures will be warmest. So, will go ahead and hoist a High Wind Watch for damaging southerly wind gusts for areas along and east of I-55 from mid-morning through the evening. Will note that if forecast confidence is not quite there to convert the High Wind Watch to a High Wind Warning in later shifts, we almost certainly will need a Wind Advisory for the same area (as well as further to the northwest).

Severe Weather Threat:

Outside the strong synoptic winds, being in the warm sector of deepening cyclones this time of year often brings consequences in the form of severe thunderstorms. The first opportunities for thunderstorms on Sunday will be during the morning hours primarily across Illinois, as an apparent mesoscale gravity wave activates the EML plume into a northeastward-band of convection (nearly every CAM has this signal). While steep mid-level lapse rates intersecting the minus 10 to minus 30 layer will promote the development of hail, convective-layer shear looks relatively meager during the morning (only about 20 to 25 kt). Accordingly, the main threats with any morning convection should be spits of pea to dime size hail. Suppose there could be bouts of locally damaging winds where any convection is able to mix down the strong low-level wind field (doesn't quite look like a true signal for damaging wind-producing GWAC), so confidence is higher in the production of sub-severe hail.

During the late afternoon and evening hours, the surface low pressure system will move along or just south of the Illinois and Wisconsin border leading to further intensification of the low-level wind field (850mb flow progged to rocket toward 70kt).
There continues to be a signal that a narrow ribbon of low- level moisture will stream northward and just ahead of an eastward-moving cold front, setting the stage for a high- shear/low-cape (HSLC) severe weather-set up. The northern extent of these kinds of set-ups are notoriously difficult to discern, and can sometimes depend on literally every degree of both the surface temperature and dew point. Nevertheless, the signal for strong low-level convergence along the front continues to garner concern for a low-topped squall line (with or without lightning) to develop along the cold front near the Mississippi River Sunday afternoon and then sweep across the area during the evening with a threat for damaging winds. The Storm Prediction Center outlook featuring level 1 and 2 threat areas across our area, highest with eastward extent, continues to look appropriate. (Often, synoptic winds increase markedly in the 1 to 2 hours preceding the passage of strongly-forced squall lines in these regimes, as well).

Winter Weather Threat:

Sunday night into Monday, the low pressure system will lift into Lower Michigan. Expansive upper-level diffluence in the left exit region of an impressive 125kt 500mb jet streak lifting into the Lower Great Lakes will allow the surface low to continue rapidly deepening (toward the lower 980mb range?) as well as support the development of a "comma head" precipitation region along the backside of the low. Precipitation type should change from rain to snow as temperatures tumble behind the system, though a 2 to 3 hour period of a wintry mix cannot be ruled out as the transition occurs.
The southern extent of the snow on the backside of the system remains somewhat varied in model guidance, likely owing to subtle differences with exactly how fast and where the low matures. Indeed, ensemble IQRs for snowfall from the EPS and GEFS at Rockford range from 1 to 6 inches, with tails reaching double-digit totals. With that said, there is a reasonably strong signal that measurable if not plowable snow will be observed across parts of our area, favoring those northwest of I-55. Note that a dusting to an inch may still fall elsewhere across the area.

Snowfall totals are rarely the only entity that makes wintry weather impactful. Indeed, impressive pressure rises along the backside of the system around 10 mb/6hr (by virtue of a 1030mb+ surface high settling in the northern Plains) suggest that northwesterly winds will quickly pick up and routinely gust 40 to 50 mb as the snow is falling and low pulls away. Snow character should start quite wet with a ratio near 10:1, which may initially limit accumulations on the wet/road ground.
However, the rapidly cooling low-level thermal profile will allow snow to become increasingly more fluffy with time. So, conditions should become more hazardous with time, particularly after midnight Sunday night. Snow should then taper from south to north throughout the day on Monday as the low pulls away.

Headline decisions for the winter portion of the event are not straight forward, especially considering we are now about 48 hours away from when the first snowflakes would fall. Normally, we use 6 inches of snow in 12 hours as an "entry point" to consider a Winter Storm Watch, and then use other factors such as temperatures, wind speeds, and time of day to ultimately leverage a decision. With this particular system, the eventual snow accumulations may struggle to reach that 6 inch entry point, though the potential overlap of strong wind gusts with falling snow leads to a heavy pull toward needing a product.
All things considered, will issue a Winter Storm Watch for Lee, Ogle, Winnebago, and Boone Counties where confidence is the overlap of plowable snow and strong winds is currently highest.
With that said, can easily envision an off-ramp to issue a Winter Weather Advisory instead of a Winter Storm Warning if it does look like we're looking more at a 2 to 4 inch snowfall versus 4 to 6+ inch event. Note that conditions may remain hazardous even after snow is done falling due to blowing and drifting due to the continuation of strong northwesterly winds.

Rest of the long-term period:

Monday night into Tuesday will feature a brief hit of chilly air as unseasonably cool 850mb temperatures bottoming out near -20C slosh into the region behind the departing storm system.
Lows Monday night are expected to fall into the single digits which, with continued gusty northwest winds, will feel more like 5 to 15 below zero. Ensemble guidance hints at a threat for a clipper-like system in the Tuesday night to Wednesday timeframe before a warming trend becomes reestablished across much of the country by the end of the week.

Borchardt

AVIATION /12Z TAFS THROUGH 18Z SUNDAY/
Issued at 548 AM CDT Sat Mar 14 2026

A surface high pressure system currently centered over the Great Lakes will shift eastward throughout the day, allowing for winds to settle on an east to southeasterly direction will gradually increasing in magnitude toward 10-12kt. Various mid- to upper- level clouds and virga will stream overhead through the day associated with ephemeral frontogenesis acting upon a northward-moving baroclinic zone. There is a low (10% or so)
chance that snow makes it to the ground at some point this morning, though any accumulations should be minimized to a dusting at worst.

Tonight, winds will turn more southeasterly and increase in magnitude in response to initial pressure falls in the Great Lakes ahead of a developing storm system in the northern Plains.
A southerly low-level jet will develop and intensify toward 45-50 kt with time, leading to LLWS criteria being threatened (including a 30 deg directional change).

After daybreak, winds will turn south to southwesterly and increase in speed with gusts approaching 30 kt by mid-morning.
The eastward advection of a plume of mid-level lapse rates and increasing low-level warm air advection will support the development of a few showers and storms toward late morning. So, will introduce PROB30 groups for the last 3 hours in the outgoing ORD/MDW TAFs.

Borchardt

LOT WATCHES/WARNINGS/ADVISORIES
IL...Winter Storm Watch from Sunday evening through Monday evening for ILZ003-ILZ004-ILZ008-ILZ010.

High Wind Watch from Sunday morning through Sunday evening for ILZ023-ILZ032-ILZ033-ILZ039-ILZ108.

IN...High Wind Watch from Sunday morning through Sunday evening for INZ001-INZ002-INZ010-INZ011-INZ019.

LM...Gale Watch from Sunday morning through Sunday evening for the IL and IN nearshore waters.

Small Craft Advisory until 10 AM CDT this morning for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.