textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Isolated to scattered thunderstorms this evening with severe storms possible toward central WI. Just slight chances for storms during the overnight.

- A High Swim Risk is in effect into the early morning hours for Sheboygan and Ozaukee Counties. High waves and dangerous currents will be likely, and swimming is not advised. - Multiple rounds of strong to severe storms on Thursday. Significant severe storms are possible. Isolated tornadoes, damaging winds, and large hail are the main concerns. There is a small potential for flash flooding especially in urban areas.

UPDATE

Issued 800 PM CDT Wed Jun 10 2026

MLCAPE will continue to increase to 1500-2000 J/KG as low to mid level warm, moist advection ensues ahead of a weakening cold front over IA. The cold front will mostly dissipate late this evening into the overnight as the main upper wave over central MN lifts newd. Before then, severe storms will be possible over MQT and Green Lake Counties this evening via the line of storms approaching from Adams County. Wly 0-3 km shear of 30 kts will support potential mesovortex genesis with this line. The broken line of strong to severe storms over IA should mostly dissipate before reaching south central WI, but cannot rule out isold storms until a drier airmass arrives at 925-850 mb from 08-10Z over south central WI and 09-11Z over ern WI.

Gehring

..Severe Weather Potential Increasing This Afternoon

Rapid thunderstorm development is ongoing over eastern Iowa this afternoon beneath an approaching MCV. Thunderstorm development is ongoing within a very unstable environment with sufficient overlapping effective shear values. Very unstable conditions are in place downstream across southern Wisconsin, where surface temperatures have soared into the mid-upper 80s with dew points in the 70s. The unstable conditions will allow for continuation of the Iowa storms into southern Wisconsin through the afternoon hours, with increasing effective shear values allowing for continued maintenance of storms at severe levels. A Severe Thunderstorm Watch is now in effect for all of southern Wisconsin until 7 PM ahead of this approaching activity.

A linear convective mode affiliated with the encroaching storms will support damaging straight line winds as the predominant severe weather hazard through this afternoon. Some wind gusts could be significant (70+ MPH) given an unstable boundary layer susceptible to downward transfers of higher momentum from aloft. Line-embedded tornadoes are also possible, particularly in northeasterly line surges & any mergers with any storm development managing to occur ahead of the line. Torrential downpours will also accompany storms, though progressive storm motions should limit widespread flooding potential in this initial round of storms. Move indoors and to immediate safe shelter if a warning is issued for your area this afternoon.

Second disturbance is then forecast to pivot through the area this evening, bringing additional convective potential along with it. Peak potential for any storm redevelopment would be between 7 PM and 1 AM. Coverage & severity of storms will be heavily influenced by activity this afternoon, with current trends suggesting that available instability will be heavily depleted, leaving the intensity and coverage of storms in question. Will be monitoring trends closely through this afternoon and evening. Regardless of severity levels, any redeveloping storms would be capable of producing additional torrential downpours, which could lead to pockets of flooding in any locations that are hit this afternoon. Given lower confidence in preferred training corridors, have held off on any Flood Watches in this forecast, but will be watching trends closely through this evening/tonight.

Will then be turning attention to tomorrow's severe potential following the conclusion of this evening's activity. As a bottom line, another round of widespread severe storm development is anticipated, with the most favored locations for storms being along and south of a boundary laid down by morning showers/storms. Peak timing for storms will be between 2 to 8 PM. All severe hazards will be possible. Will be monitoring trends and providing additional details through this evening and tonight. Stay tuned to the forecast.

Quigley

LONG TERM

Issued 1220 PM CDT Wed Jun 10 2026

Friday through Wednesday:

A shortwave trough sitting over WI and a surface low pressure system are expected to move northeast over Michigan and Ontario, bringing a surface high to southern WI late Friday into early Saturday morning. Drier conditions are expected Friday with temperatures down into the 70s and humidity significantly decreasing.

Throughout Saturday, the potential for precipitation increases in the afternoon (40-50%) into the evening (50-60%) as the shortwave trough settles into WI alongside a cold front. Precipitable water values of around 1.3" increase this potential. Temperatures are expected to increase alongside humidity throughout the day into the evening.

Primarily dry and cooler conditions Sunday through Monday as surface pressure increases across the region and the shortwave trough begins to move to the east. Shower/storm chances increase into Tuesday (20-30%) as the shortwave trough begins to sink back into WI and a surface low enters from the west. A similar chance for precipitation for later Wednesday (20-30%) as the low pressure system moves west, with an approaching high over the Plains.

Zawlocki

AVIATION

Issued 800 PM CDT Wed Jun 10 2026

Local MVFR Cigs and Vsbys (BR) tnt with isolated to scattered showers and storms expected. Multiple rounds of strong to severe storms from late Thursday morning into the early evening. Areas of MVFR Cigs expected on Thu via broken stratocumulus but also in the wake of storms.

Gehring

MARINE

Issued 1220 PM CDT Wed Jun 10 2026

Showers/storms are expected to move east over Lake Michigan Wednesday night, with a high potential for precipitation in the southern half late Wednesday. Increasing fog potential over the northern half of Lake Michigan Wednesday night, with increasing potential over the entire lake early Thursday. Continued southerly winds across Lake Michigan Wednesday night with potential for gusty conditions.

A cold front/low pressure system is expected to move in Thursday afternoon (29.76 inches), increasing the potential for precipitation Thursday, with the chance of some storms becoming severe. Winds are expected to shift southeasterly ahead of precipitation, then to Westerly Friday.

Zawlocki

MKX WATCHES/WARNINGS/ADVISORIES

WI...Beach Hazards Statement...WIZ052-WIZ060 until 4 AM Thursday.

LM...Small Craft Advisory...LMZ643-LMZ644 until 1 AM Thursday.