Marine Weather and Tide Forecast for Lake Bluff, IL

DISCUSSION
Issued at 248 AM CDT Wed May 21 2025

Through Thursday:

Cloudy, cool, and generally dreary conditions will occur into Thursday as our region remains under the general influence of broad troughing with numerous perturbations slated to drift overhead. With a surface low traversing right across the heart of the forecast area this morning, low clouds and areas of drizzle and mist/fog are expected, particularly north of a surface trough which will set up in the vicinity of the I-80 corridor. Showers are expected to expand across most the region through the rest of the overnight and into the morning as a shortwave trough presses through the area. Temperatures won't move much today with thick cloud cover forecast to hold fast.
Highs will range from near 50 across northern Illinois and near the lake to the upper 50s/near 60 across our far southern tier of counties.

Additional waves of showers will continue through tonight, particularly across the northern half of the area and especially near the lake as additional sprockets of mid-level vorticity pivot out of Wisconsin. While guidance doesn't produce much QPF tonight across our south, forecast soundings show lingering deep saturated layers up through about 700 mb. With persistent vort maxes pivoting overhead, this looks like a favorable set up for at least periods of drizzle and showers.

Forecast soundings on Thursday afternoon depict steepening low- level lapse rates in advance of yet another shortwave which will push down the lake and out of Wisconsin during the afternoon.
With the steepening low-level lapse rates, it looks like we'll build a little surface-based instability, sufficient for the development of scattered diurnally showers. Have increased PoPs a bit, particularly in the vicinity of increased convergence along the western side of the lake. Equilibrium levels will be under about 12 kft, so no thunder in the grids at this time.

Carlaw

Thursday Night through Tuesday:

There may be some lingering showers Thursday evening then dry weather is expected through at least Saturday. Confidence remains fairly low for precip chances Saturday night through early next week. There is increasing support in the GFS ensembles for precipitation Sunday/Monday, while there is decreasing support among the Canadian ensemble members with not much change among the drier ECMWF. Blended pops have increased further and are now well into chance during this time period.
Previously there had been some support of precipitation in the Monday/Tuesday time period, which is now much drier. While these blended pops look too high, made no changes this morning.

Temps will remain below normal through the period. If drier weather prevails, high temps will likely overperform guidance with lower 70s inland certainly possible over the weekend, but maintained blended highs in the 60s. Cooler temps expected near Lake Michigan with persistent easterly/onshore flow. cms

AVIATION /06Z TAFS THROUGH 12Z THURSDAY/
Issued at 1231 AM CDT Wed May 21 2025

Forecast concerns include...

Lifr/ifr cigs/vis with drizzle overnight.
Ifr cigs today/tonight with scattered showers.
Wind shift to north/northwest after daybreak this morning.

Drizzle is expected to continue and expand across the area through daybreak with visibilities likely in the 1-2sm range, possibly lower. Prevailing cigs are expected to remain lifr but some vlifr cigs are possible.

The drizzle will transition to scattered showers later this morning and showers will continue through tonight. There will likely be lulls in the shower activity but confidence is low to try to time these possible breaks in the precip. Cigs are expected to lift to ifr later this morning and remain ifr into tonight. Guidance is suggesting cigs may lift to low mvfr early Thursday morning.

Northeast winds at or below 10kt overnight will slowly turn northerly in the predawn hours and then shift to the north/ northwest after daybreak. Winds will eventually become northwest by early afternoon with gusts into the 20kt range possible. cms

LOT WATCHES/WARNINGS/ADVISORIES
IL...None.
IN...Beach Hazards Statement from late tonight through late Thursday night for INZ001-INZ002.

LM...Small Craft Advisory until 7 AM CDT this morning for Winthrop Harbor to Wilmette Harbor IL.

Small Craft Advisory from 4 AM Thursday to 1 AM CDT Friday for the IN nearshore waters.