Marine Weather and Tide Forecast for Kenilworth, IL

DISCUSSION
Issued at 309 AM CST Thu Nov 6 2025

Today through Friday Night...

Surface high pressure is shifting east across the region early this morning and will be replaced by steady pressure falls today as the next area of low pressure develops well to our north.
Light and variable/calm winds will trend southeasterly and southerly later this morning and afternoon, and we'll pick up some intermittent gusts to around 20-25 mph mainly west of the Fox Valley as some slightly stronger flow arrives late in the day. Once again, have considerably undercut NBM-delivered dewpoints today as another very dry airmass rolls overhead.
Based on how dewpoints responded to similar airmasses this past week, have nudged dewpoints down towards the WRFARW, UKMET, and ECMWF blend, which results in afternoon RH values falling into the 20-30 percent range. The lone exception might be right at the lakefront across Lake County, IL where southeasterly winds may push some higher moisture values inland a bit. Even though grasses/fine fuels are dry, the overlap of the very low RH with marginal southerly breezes will be limited today, so no plans currently for a Special Weather Statement, but will indicate the dry and somewhat breezy conditions in the Fire Weather Forecast.

An area of elevated showers and some thunderstorms will blossom this evening and overnight as warm advection intensifies. While the parent surface low will track across the UP of Michigan and Lake Superior, large scale forcing looks significant down this way as 120 to 150 m/12 hour mid-level height falls and significant DCVA overspread the area overnight. Have boosted PoPs a bit, with the expectation of widespread precipitation.
That said, this will be a quick bout of precip which will limit totals generally to a quarter inch or less, although some very localized amounts over of a half inch to inch will be possible within corridors of heaviest thunderstorms.

Precip will clear the area by mid morning Friday if not earlier with mainly dry conditions through the rest of the day. The one exception will be late in the afternoon and into Friday evening across northern Illinois as the true push of cold advection arrives. Model guidance suggests a sliver of low-level CAPE (0-3 km) developing during this period ahead of an well-defined 700-500 mb shortwave. While the deepest boundary layer moisture is forecast to remain near and north of the WI state line, the fairly strong nature of incoming ascent supported the introduction of some slight chances for showers mainly north of I-88. If deeper and more organized showers are able to develop, couldn't entirely rule out the potential for a rogue 50 mph gust near the WI state line given 30-40 kts flow in the column.
The attendant cold front will deliver some gustier northwest winds to the region Friday evening.

There is a chance that some loosely-organized lake effect precipitation (rain) develops Friday night into Saturday morning as subfreezing 850 mb temperatures spread across the lake. The parameter space isn't particularly supportive, though, with progged inversion heights under about 7 kft.

Carlaw

Saturday through Sunday Morning...

The main story in the extended portion of the forecast is the expectation for our area to receive its first shot of true winter weather this cool season in the late Saturday through Monday time frame.

Ensemble guidance continues to show strong support for a mid- latitude shortwave trough and an associated surface cyclone bringing precipitation to the region late Saturday into early Sunday, followed by an incursion of Arctic air that will linger into the beginning of the upcoming workweek. Confidence in these two aspects of our forecast continues to remain high as a result. Confidence in how much wintry precipitation will be observed in our forecast area and where during this time frame remains a bit lower, but the range of possible outcomes depicted across the Grand Ensemble continues to shrink in a way that has increased our confidence in at least parts of our forecast area seeing their first snowflakes of this cool season, but with little/limited impact through Sunday morning at least.

The main forecast uncertainties with respect to potential snowfall during the Saturday evening/Sunday morning period remain tied to the evolution of a sprawling upper-level Polar low and the Arctic air mass that it will be associated with. Ensemble guidance remains in fairly good agreement that the upper low will hover over Hudson Bay for a couple of days before deforming and diving southward into the Great Lakes over the weekend, accompanied by a blast of anomalously cold air. For context, this air mass is progged by both the ECMWF and the GFS to be characterized by 500 mb temperatures of around -40C and 850 mb temperatures between -10 and -15C as it spills into the Great Lakes, which would be at or near record levels for this time of year in sounding climatology at GRB.

How quickly this colder air will get dislodged and reach the Great Lakes has been the main point of contention across the suite of available model guidance. A quicker southward release of the cold air would likely cause rain in many areas here to become mixed with or change over to snow before the main wave of synoptic precipitation comes to an end Sunday morning. On the other hand, if the cold air were to remain bottled up over Canada longer before arriving later, then most precipitation here would end before the cold air's arrival would give it a better chance to reach the ground as snowflakes.

The EPS had been the main proponent of the latter solution, but over the past day or so has trended a bit more in line with the GEFS which has remained steadfast in its support for the former outcome. Still, the ECMWF/EPS remains notably slower than the GFS/CMC and those ensemble systems, and a bit closer to the even slower/milder UKMET.

For this forecast issuance, did end up further expanding the snow mention eastward late Saturday night, but did some work to limit the potential across Chicago and downwind of the still mild lake. The general multimodel consensus seems to suggest that the main stratiform precipitation shield will be exiting eastward prior to the arrival of the coldest airmass, and have seen a persistent downward trend the GFS's snowfall forecast output. In fact, the latest GFS snow depth output, which is likely a better proxy for actual surface accumulations in this marginal thermal environment, show perhaps a tenth of two of snow at most prior to the cessation of precipitation Sunday morning. If colder air ends up being more formidable and arriving more quickly, AND more significant banding develops, then the potential for slushy accums would increase, but currently not seeing support for this outcome in the ensemble guidance.

Lake effect snow potential Sunday through Monday night...

The anomalously cold air spreading over a Lake Michigan whose water temperatures are still in the low-mid 50s will result in conditions that will be very favorable for lake effect precipitation Sunday into Monday. Much of this lake effect precipitation would be expected to fall as snow, particularly Sunday night through Monday night with temperatures dropping into the 30s and 20s as the Arctic air mass engulfs the region.

It's still not entirely clear how much residence time this lake effect precipitation will have in our forecast area compared to areas farther to the east as ensemble guidance still exhibits subtle, but non-trivial variations in the synoptic flow configuration aloft stemming from uncertainties in the evolution of the inbound Polar trough and how far west its centroid will track. Conceptually, the vast majority of any precip would tend to be confined to northwest Indiana as flow turns northwesterly, but we continue to see indications either of a strong land breeze and/or surface trough axis rolling through lower Michigan Sunday night which could shift the boundary layer flow northeasterly enough to point LES into northeast Illinois, including Chicago. With temperatures falling below freezing during this period, some increased concern for winter impacts exist as LES parameters would be quite supportive of heavier snowfall rates. Given the mild lake temperatures, snowfall accumulations may end up being limited to areas away from the immediate lakefront.

At this range, still can't do more better than chance PoPs for snow showers Sunday night and Monday morning across northeast Illinois, but this a time period we'll continue to keep a close eye on. Through Monday night, any lingering LES potential should tend to shift eastward into Lake/Porter counties in NW Indiana and then coming to an end through early Tuesday morning.

A stratocumulus deck may end up developing squarely within the dendritic growth zone over northern Illinois and/or northwest Indiana, even away from any lake influence, Sunday and into Monday. If this ends up coming to fruition, then pattern recognition suggests that periodic flurries could be observed across a good chunk of the area during this timeframe.

Highs on Sunday and Monday may struggle to get out of the mid 30s, while widespread well below freezing temperatures (possibly as low as the upper teens) are likely to be observed during the nights and mornings while we remain entrenched in the Arctic air mass. However, the deep troughing over the Great Lakes will shift eastward early next week, allowing for a warming trend to commence going into mid-week.

Ogorek/Carlaw

AVIATION /18Z TAFS THROUGH 00Z SATURDAY/
Issued at 1132 AM CST Thu Nov 6 2025

Aviation forecast concerns for the 18Z TAFs:

- South-southeast winds gradually increase later this afternoon.
ORD/MDW may vary 190-170 deg initially, becoming more 160-ish toward sunset.

- South-southwest winds become strong/gusty tonight. 50-55 kt low level jet around 2 kft will support LLWS conditions especially away from urban sites which maintain stronger sfc winds/gusts.

- Period of SHRA overnight. Isolated TS possible, but greater chances south of terminals.

- MVFR cigs possible overnight in precip, possibly lingering early Friday morning.

- Breezy west winds Friday with gusts around 25 kts.

Surface low pressure currently over South Dakota will deepen tonight as it tracks into the northern Great Lakes through Friday morning. Locally, this will induce increasing south winds especially tonight as a 50-60 kt southwesterly low-level jet develops. This should make for gusty surface winds, especially for the urban ORD/MDW locations where gusts 25+ kts are likely to be more persistent. Other locations are more likely to decouple a little more, with somewhat lower surface wind/gust speeds making for a more pronounced LLWS setup with 50-55 kt southwest winds at 2 kft AGL and 60+ kts above that.

Moist ascent ahead of an accompanying mid-level disturbance is expected to produce a period of rain showers from around midnight into the predawn hours. Can't rule out isolated TS, though better chances per high-res ensemble guidance appear to pass south of the terminals and thus did not mention in TAFs.
Forecast soundings do indicate the potential for MVFR (or even brief IFR) ceilings within precipitation, and potentially lingering into early Friday morning before mixing out.

As the aforementioned low tracks across the northern Lakes into early Friday morning, a trailing cold front will move across the terminals and result in a wind shift to the west. Breezy conditions are then expected through the day with gusts around 25 kts.

Ratzer

MARINE
Issued at 453 AM CST Thu Nov 6 2025

An area of low pressure near 29.5 inches will gradually deepen tonight as it moves east across the Upper Great Lakes. Southerly winds will increase quickly in response across the Illinois and Indiana nearshore waters this evening, with frequent gusts over 30 knots expected. There is a brief window tonight between roughly 9 PM and 3 AM where occasional gales to 35 to 40 kts will be possible, particularly a few miles offshore. If confidence in the frequency of gale gusts increases, a brief Gale Warning may be needed during this period.

A Small Craft Advisory is in effect from 6 PM this evening to 6 AM Friday. An extension in time to the Illinois nearshore portion of the advisory into Friday afternoon may also be needed in future forecast updates.

Carlaw

LOT WATCHES/WARNINGS/ADVISORIES
IL...None.
IN...None.
LM...Small Craft Advisory from 6 PM this evening to 6 AM CST Friday for the IL and IN nearshore waters.