textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Isolated to scattered storms may develop late tonight into Wednesday morning, with large hail a possibility if storms form. Confidence is on the low end with this storm potential.

- Fog is possible tonight along Lake Michigan. Marine Dense Fog is also likely.

- A High Swim Risk is in effect tomorrow mid afternoon into the evening. High waves and dangerous currents will be likely, and swimming is not advised at Sheboygan and Ozaukee beaches.

- Multiple rounds of storms are expected Wednesday and Thursday. Severe thunderstorms are likely at times. An Enhanced Risk for Severe Weather exists both Wednesday and Thursday.

- Hot and humid conditions expected Wednesday and Thursday, with some potential for Heat Advisory conditions on Wednesday if we get enough sunshine.

UPDATE

Issued 745 PM CDT Tue Jun 9 2026

Quiet weather is expected this evening, with slowly falling temperatures due to the humid airmass. It still looks like there could be some fog near the lake by late evening and continuing into early Wednesday given the high dewpoints and relatively chilly waters of Lake Michigan.

The other concern tonight into early Wednesday is the potential for a round of thunderstorms. The activity over the Dakotas early this evening is expected to largely lift northeast through the top of the upper ridge, staying more closely tied to the shortwave. These storms could clip the northern forecast area roughly between 7 am and 11 am tomorrow morning, though latest short term model trends largely keep this activity to the north.

Another possibility for showers and storms tonight will be as an area of warm advection aloft and higher precipitable water advect in from the southwest. There are still a couple models that try to pop a few storms as this airmass moves in, though there has been an overall downward trend in models for this scenario to unfold.

Will continue to monitor upstream radar and satellite trends this evening to watch for potential storm impacts across southern Wisconsin tonight. Plenty of elevated instability tonight along with modest shear and steep mid-level lapse rates would lead to a potential for large hail if storms do fire. In general though, confidence in widespread showers/storms across the forecast area has decreased a bit for tonight into early Wednesday.

As 00Z models roll in, the picture will hopefully become more clear with what may then happen mid-day Wednesday into Wednesday evening. Still some lingering uncertainties with that period as well.

DDV

SHORT TERM

Issued 152 PM CDT Tue Jun 9 2026

Tonight through Thursday Night:

A remnant MCV continues to churn over northern Lake Michigan. Cyclonic flow around this feature, daytime heating from breaks in the clouds, and high surface moisture may allow for some isolated to scattered thunderstorms over southern WI from the mid afternoon into this evening. Given the high moisture in the environment, these showers/storms will feature heavy downpours.

Fog is possible tonight, primarily along Lake Michigan where it may become dense in spots.

Attention then turns to an approaching trough tomorrow. Low to mid level warm advection is expected to kick off a line of storms during the pre-dawn hours on Wednesday that should track into WI. Models vary on coverage, but there is some potential these thunderstorms may impact southwest through central WI from 5AM to 10AM Wednesday. These storms would be elevated, and feature the potential for large hail, given steep mid level lapse rates around 7.5 C/km, MUCAPE of 2500 J/kg, and the potential for supercells in the 30 knots of effective shear that will be present.

Models then vary wildly with what will occur through the day. One constant seems to be that there will be a line of storms that comes through during the mid to late evening on Wednesday. In between the morning round and evening round however, two things could happen. Another afternoon round looks to develop in most of the CAMs along the WI/IL border early afternoon. This line would then track east and exit over Lake Michigan form 4 to 6 PM. Some models do not develop this round however, which increases the likelihood for hot and humid conditions Wednesday afternoon and a heat advisory may be needed. Right now, the afternoon round of thunderstorms scenario looks most likely, which would limit the potential for a heat advisory, but contribute to a higher all hazards threat for the storms during the afternoon, given very unstable CAPE of 4000 J/kg in RAP and HRRR soundings and good low level turning in the hodographs.

Wednesday evenings round of storms would then primarily feature a wind threat given shear would be more boundary parallel during this time.

Thursday's storm threat then depends upon where any remnant boundaries set up after Wednesday's storms. Some of the CAMs that are in range of Thursday suggest that another day with multiple rounds of storms may occur with all severe weather hazards possible. But the details of where/when remain murky given Wednesday hasn't played out yet. Early indications favor the southern half of the CWA for any potential severe weather Thursday.

Additionally, breezy southeast winds will drive high onshore waves tomorrow late afternoon into the evening at beaches in Sheboygan and Ozaukee Counties. A High Swim Risk has been issued for the high waves and dangerous currents. Swimming is not advised during this time.

CMiller

LONG TERM

Issued 152 PM CDT Tue Jun 9 2026

Friday through Tuesday:

Light to modest wly surface winds, dry weather, and near normal temps will return for Friday in the wake of a cold front Thu nt. Otherwise zonal flow will prevail the weekend into early next week, but with a tendency for 500 mb heights to fall especially over Ontario and the nrn Great Lakes.

A weak trough in the low to mid levels will approach from the west Sat afternoon and pass Sat nt. Weak low to mid level warm, moist advection, but slightly stronger frontogenesis in that layer will support 40-60 percent chances of showers and thunderstorms.

Weak high pressure will follow for Sun-Mon but weak shortwave troughs may bring 20-30 percent chances for showers and storms. 30-40 percent chances for showers and storms is forecast for Tue as a more organized shortwave trough may affect the region. Temps are expected to be slightly above normal for Fri-Sat then slightly below normal for Sun-Mon.

Gehring

AVIATION

Issued 745 PM CDT Tue Jun 9 2026

Lower ceilings and visibilities may move into the eastern forecast area from Lake Michigan this evening, possibly lingering into Wednesday morning. Already seeing signs of this via observations and webcams from Sheboygan to Manitowoc.

There is also the potential for a round of showers and storms later tonight into early Wednesday. Confidence is not high in these storms though, as the current activity of the Dakotas may scoot by just to the north early tomorrow. Will continue to monitor upstream trends though, as any storms that do develop could have the potential for some large hail.

Confidence is a bit higher for storm chances Wednesday afternoon into Wednesday evening. Some uncertainty remains though, as afternoon storms tied to a weak shortwave and vortmax could move through southern Wisconsin and rob the local environment of instability for the potential evening storms. Any storms that do move through the forecast area tomorrow afternoon and evening would have the potential to be severe.

Light and variable winds this evening will become south to southwest and breezy by late Wednesday morning ahead of an approaching shortwave.

DDV

MARINE

Issued 152 PM CDT Tue Jun 9 2026

Marine Dense Fog currently exists over the northern half to two thirds of Lake Michigan. Models project this fog to gradually spread to encompass the entirety of the lake tonight as a surface warm front approaches the lake. A Marine Dense Fog Advisory has been preemptively issued for the fog potential late this afternoon and into tonight.

Light generally northerly winds will continue through this afternoon and into tonight, until the warm front lifts north over the lake around midnight CDT and flips winds around to southerly and southeasterly. Winds will then remain southeasterly through Wednesday as low pressure of 29.3 inches approaches from the northern plains. The winds may become moderately breezy late Wednesday afternoon into the evening.. Thunderstorms are expected over the lake at times on Wednesday, with some strong storms favored Wednesday afternoon and night.

Winds come around to southwesterly Wednesday night into Thursday, with winds then returning to southeasterly ahead of an approaching cold front on Thursday, with additional storms possible.

CMiller

MKX WATCHES/WARNINGS/ADVISORIES

WI...Beach Hazards Statement...WIZ052-WIZ060...4 PM Wednesday to 4 AM Thursday.

LM...Dense Fog Advisory...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563- LMZ565-LMZ567-LMZ643-LMZ644-LMZ645-LMZ669-LMZ671-LMZ673- LMZ675-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876- LMZ878 until 10 AM Wednesday.

Small Craft Advisory...LMZ643-LMZ644...4 PM Wednesday to 1 AM Thursday.