Marine Weather and Tide Forecast for Cedarburg, WI

UPDATE
Issued 650 AM CDT Thu Jun 25 2026

Stagnant rain-humidified air over central portions of Lake Michigan has lead to an area of marine dense fog north of a Port Washington to Whitehall MI line for which an Advisory has been issued. Models expect this fog to erode out by mid to late morning. Patchy dense fog over land areas (low-lying marshy areas and river valleys in central WI) will burn off much faster (early this morning) under the sunshine.

Continuing to monitor the potential for widely scattered showers (and possibly a few weak thunderstorms) to develop over portions of eastern and east-central WI this afternoon, mainly between Noon and 6 PM CDT. These should be very brief / widely scattered / weak if applicable, lightning should be the only concern.
Modeled SBCAPE fields only hit 300-750 joules in this area.

Sheppard

SHORT TERM
Issued 1249 AM CDT Thu Jun 25 2026

Overnight through Sunday:

Storms diminished and most of southern WI is suddenly under clear skies. With that and the light winds and the recent heavy rain, we are now seeing patchy fog developing. Patchy dense fog can be expected through 7 AM. It is uncertain how transient or widespread this fog will be, but we will issue a dense fog advisory as necessary.

The combination of a lake breeze convergence and a weak mid level shortwave will combine over central/east central WI this afternoon and give us a chance of diurnally-driven thunderstorms.
The model soundings show weak CAPE up to 500 j/kg (HRRR shows MU CAPE of 500 to 750 j/kg) and up to 30 kt bulk shear. This supports scattered thunderstorm development with a very small chance for a stronger cell or two, but this is not a severe-type setup. Lightning is the main hazard.

With surface high pressure over the Upper great lakes and onshore flow over southern WI on Friday, highs be cooler than normal in the lower to mid 70s (except upper 70s west of Madison).

A weak shortwave trough is expected to track across the Central Plains on Saturday, but storms associated with this feature should remain south of southern WI due to the easterly winds over us holding that warm front south. However, we have small chances of storms in the forecast due to the close proximity of the forcing. The upper level ridge should push into southern WI on Sunday, so our chance for storms is lower that day.

Cronce

LONG TERM
Issued 1249 AM CDT Thu Jun 25 2026

Sunday Night through Tuesday:

A closed upper low will sit over the Pacific Northwest and southwest Canada from Saturday through Tuesday. Another low will follow for the rest of the week. This will create a surface low in the Northern Plains and draw warm, moist air into the Upper Midwest on southerly winds from the Gulf. This air mass is expected to arrive behind a warm front Sunday night-Monday morning and generally remain in place all week. It looks like the warm front should lift through southern WI quietly (without storms) due to the timing.

The main story is the heat and humidity that will impact southern WI next week. It looks like the models are trending a little later with the arrival time of this heat, but once it moves in (by Monday morning), temps should be in the lower 90s since 925mb temps are forecast to be around 25C with dry adiabatic low level lapse rates. If these temps pan out due to the dry low levels, then it seems unlikely that we will actually achieve dewpoints in the mid 70s like what is currently in our forecast. Models have a pretty high dewpoint bias, so I am skeptical about the forecast heat index values we have in the extended.

The other scenario is that our dewpoints end up in the mid 70s, but then we would not have that dry adiabatic mixing and end up with highs in the upper 80s. So realistically, heat indices should be around 100 which is heat advisory criteria. I am uncertain about reaching the extreme heat warning criteria of 105 for southern WI due to the above reasons.

In addition, all it would take to lower the temps/heat indices during this warm spell would be clouds and remnant showers/storms from storms that develop to our north or northwest along the "ring of fire" at the top of the ridge where the low level jet will be pointing. There are differences between the models about how close this area will be to southern WI, so this will be something to watch.

Cronce

AVIATION
Issued 650 AM CDT Thu Jun 25 2026

Areas of fog and low stratus over east-central WI and the WI river valley should burn up and clear out rapidly under the strong sunshine early this morning. After that, looking at diurnal cumulus clouds between 4,000 and 7,000 ft AGL across the region, with chances for widely scattered showers and weak thunderstorms over eastern and east-central WI terminals this afternoon (PROB30 groups included in TAFs where applicable).
These should be relatively weak / minimally disruptive storms if applicable, instability in the atmosphere appears quite limited.
A light northwesterly breeze expected across the region today, with a lake breeze developing right along the shoreline of Lake MI this afternoon and making some inland progress later this afternoon. Generally 10 kt or less sustained wind speeds with all of this.

Dry weather tonight with nearly calm winds. Some scattered high-altitude clouds (generally over 20,000 ft) should help to reduce fog potential tonight. The best shot at seeing any fog would likely be in the WI River Valley as usual.

Sheppard

MARINE
Issued 1249 AM CDT Thu Jun 25 2026

Weak low pressure over northeast Wisconsin will slide into northern Lower Michigan by Thursday morning. Patchy fog is possible overnight. High pressure over Ontario and the western Great Lakes will dominate Friday through Saturday with light north to northeast winds likely. Sunday, low pressure deepens over the Central Plains, bringing breezy southeasterly winds to the lake. Winds turn southerly and strengthen into Monday as low pressure exits into the Canadian Prairies. On and off thunderstorms become more likely during this time.

Cronce

MKX WATCHES/WARNINGS/ADVISORIES
WI...None.
LM
Dense Fog Advisory
LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-LMZ643- LMZ669-LMZ868-LMZ870 until 11 AM Thursday.