Marine Weather and Tide Forecast for Reedsburg, WI

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 1249 AM CDT Thu Jun 25 2026

Clear skies, light winds, and recent rain make the environment favorable for fog overnight. Patchy dense fog is already developing, mainly in the favorable low spots, marshy areas, and river valleys. But it is also developing in the areas where nearly 2 inches of rain fell yesterday. Southeast WI is showing signs of the more widespread fog via IR satellite. With the fog, IFR/VLIFR ceilings may also develop.

Fog and low clouds will diminish quickly with sunrise and we can expect mostly sunny skies for much of the day. Convergence along the lake breeze and also an upper level disturbance rolling through central WI will bring a chance for showers and thunderstorms to east central and portions of southeast WI this afternoon.

Cronce

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...None.