Marine Weather and Tide Forecast for Old Mill Creek, IL

UPDATE
Issued 445 AM CDT Sun Oct 11 2026

Forecast remains on track this morning. Temperatures will warm quickly once again today under largely clear skies, with most locations away from the immediate Lake Michigan shoreline climbing into the upper 70s and low 80s. Current forecast highs fall just shy of record values at Madison (84 in 1928), but similar to yesterday observational trends will need to be closely monitored. In the event overperformance occurs, could see records come within reach.

Quigley

SHORT TERM
Issued 1015 PM CDT Sat Oct 10 2026

Sunday and Sunday night:

Dry weather and a light south breeze continue through the period, with clear skies for Sunday and broken high-altitude cloud cover arriving Sunday night. Unseasonably warm conditions continue, with inland highs around 80 and lows in the low 60s.
A weak lake breeze may ventilate far eastern WI, holding daytime highs to the low 70s (or even the upper 60s along the immediate shoreline).

Sheppard

LONG TERM
Issued 1015 PM CDT Sat Oct 10 2026

Monday through Saturday:

Oblong low pressure spanning from the High Plains to the Upper Mississippi River Valley regroups northeastward on Monday, drifting into WI. Warm / moist advection ahead of this system yields some low chances (~10-20%) for showers in the daytime hours Monday. The 10.18z GFS allows a shortwave trough to crest the ridge midday as well, though that stands as an outlier for now.
The increasing heat and humidity (near record high temps and near record warm low temps for MSN, dewpoints entering the low 60s)
will bring increasing levels of instability with it, sufficient for some thunderstorms (~1,500 joules CAPE on most model guidance). That said, shower and storm chances remain fairly low until Monday evening / Monday night when the core of the low pressure system crosses central / south-central WI (20-45% precip chances). An isolated stronger storm cannot be ruled out as the low crosses the region, but severe weather appears unlikely at this time. Hail (elevated convection) would be the main concern if applicable.

The cold front associated with this system crosses our region Tuesday morning, bringing northwest winds and dry weather in behind it. Predominantly dry weather expected midweek, though ensembles hint at a stalled baroclinic zone just south of the state, yielding some additional 10-30% rain chances on Wednesday, mainly towards the IL border. There is plenty of disagreement among model guidance for the late half of the work week, particularly pertaining to the presence of / intensity of a clipper-system that could yield additional rain showers Thursday into Friday (40-50% chances until things become clearer).

The general consensus is then for strong high pressure to descend from western Canada into the Dakotas late this week, eventually drifting overhead at some point this weekend. This should lead to strong CAA, much colder temperatures, and frost potential for our region. If the aforementioned Thursday/Friday clipper system winds up being present, the pressure gradient between the incoming high pressure and departing clipper system could drive some very gusty northwest winds late this week.

Sheppard

AVIATION
Issued 445 AM CDT Sun Oct 11 2026

VFR flight categories prevail through the period at all terminals. Expecting surface winds to remain largely south- southwesterly this afternoon, but will need to monitor for south-southeasterly winds at lakeshore terminals in the event a lake breeze develops. Have held any mentions out of the upcoming 12Z forecast, but will be monitoring observational trends through today. Skies will remain entirely to largely clear through early evening, with a BKN deck based between FL150-FL250 moving in closer to and after midnight. An increasing low level jet across the Upper Mississippi Valley could lead to periods of LLWS early Monday morning, particularly at western sites where proximity to the feature will be greatest. Have thus accounted for this potential in the coming 12Z forecast at MSN and JVL, and will monitor for possible mentions further east into today.

Quigley

MARINE
Issued 1015 PM CDT Sat Oct 10 2026

Open Waters / Synopsis: Light to modest south winds continue Sunday through Monday as oblong low pressure lingers over the High Plains and Upper Mississippi River Valley. This low pressure, around 29.6 inches, will tighten up and track northeastward across central Lake MI late Monday into early Tuesday, with rain showers likely and chances for thunderstorms. Northwest winds arrive behind the associated cold front into Tuesday, veering northerly or even northeasterly into Wednesday.

A stronger low pressure system is possible later this week, which could bring gusty east to southeast winds and shower / storm chances into Thursday. The associated cold front and incoming strong high pressure may then yield gusty northwest winds Friday into Saturday, with gales possible.

Nearshore Zones: A few lingering gusts to 25 kt and elevated waves expected through the overnight hours and early Sunday morning. A Small Craft Advisory remains in effect until 1 AM Sunday north of Wind Point and until 7 AM Sunday north of Port Washington. Winds and waves generally expected to remain below Advisory thresholds for the rest of Sunday and through much of the early half of this week. Gusty onshore winds and high waves are looking possible Thursday and Thursday night. Gusty NW winds are possible Friday into Saturday, and gales cannot be ruled out.

Sheppard

MKX WATCHES/WARNINGS/ADVISORIES
WI...None.
LM
Small Craft Advisory
LMZ643 until 7 AM Sunday.