textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Widespread showers and scattered thunderstorms expected today into tonight. Still monitoring an isolated risk for a few severe storms (hail/wind) late afternoon into the evening, though the greatest chances will be to the south of the area. - A Small Craft Advisory and High Swim Risk are both in effect for nearshore regions and beaches through late tonight. Gusty southeast winds will lead to high waves and dangerous currents.

- The next substantial chance for thunderstorms arrives Sunday (45-65% chances), although on and off periods of isolated to scattered storms are possible through much of the week.

SHORT TERM

Issued 255 PM CDT Wed Jun 17 2026

Tonight through Thursday:

Light rain continues across the WI/IL border into this evening, with the line of expected thunderstorms along a cold front progressing eastward from southern Minnesota. Expecting storms to arrive in southwestern Wisconsin around 5 PM CDT, progressing to southeastern Wisconsin by 7 PM CDT. With plenty of cloud cover and very little instability building into the region (MUCAPE 500-750 J/kg riding just ahead of the cold frontal boundary), expecting the primary hazard with this activity to be lightning. An isolated storm may become severe in primarily southwestern Wisconsin, with wind and hail as the main threats. Storms will exit into Lake Michigan by sunset, with only a few showers in central and southeastern Wisconsin lingering after dark.

Winds are also expected to build waves up along Lake Michigan beaches, with a High Swim Risk expected throughout this afternoon and tonight. Stay out of the water and away from dangerous areas like piers and breakwalls!

Winds become northwesterly overnight as low pressure exits to the east, with gusty conditions possible in southeastern Wisconsin Thursday morning before becoming steady midday. Thursday afternoon, isolated thunderstorms along a weak 500 mb shortwave are possible. No severe weather is expected with these storms, but lightning is anticipated.

MH

LONG TERM

Issued 255 PM CDT Wed Jun 17 2026

Thursday night through Wednesday:

Drier conditions are expected Thursday night as a surface high pressure system begins to move in from the Plains following a surface low. There is a slight chance for isolated precipitation Thursday night (10-20%). As the high pressure enters from the west Friday morning behind a cold front, primarily stable and drier conditions are expected. However, the development of a NW- SE jet streak over the region could bring a chance for precipitation (20-40%) due to the upward motion following the pattern. Temperatures for both Thursday and Friday suggest highs in the low to mid-70s.

Into Saturday, an upper-level trough propagates eastward, with the geopotential height gradients tightening around the upper- level jet streak. A shortwave ridge in this region decreases the chance for precipitation Saturday (<10%) with temperatures rising into the upper 70s. With the tropical jet and polar jet enhancing the jet streak, conditions favor the intensification of a low pressure system in the Plains Saturday night, which could create showers and thunderstorms in our region (50-70%). As low pressure moves through Sunday, temperatures are expected to drop into the low 70s.

Conditions are expected to become dry and warmer Monday, as a surface high pressure system and upper-level ridge favor these conditions. Tuesday and Wednesday still pose uncertainty with the position of an eastward-propogating trough and a surface low in the Plains moving toward the Mississippi River Valley. There is a potential for showers on both Tuesday and Wednesday (10-30%), but likelihood depends on the location of these systems.

Zawlocki

AVIATION

Issued 255 PM CDT Wed Jun 17 2026

Southeasterly winds remain gusty at 25 to 30 kt outside of a band of rain slowly moving across the I-94 corridor. Inside of rain showers, gusty winds up to 20 kt are expected. Expecting ceilings to continue to fall to become IFR by this evening and through the overnight. Lightning chances have diminished greatly for the afternoon, with the better chances for thunderstorms now looking to arrive between 21Z and 00Z. A few of these storms earlier in the evening may become capable of producing damaging wind and hail. These storms will exit into Lake Michigan by sunset, with showers lingering into the overnight hours in southeast and central Wisconsin. Winds will shift to become northwesterly overnight as well. Northwest winds will continue into Thursday, with steady winds between 12 and 15 kt expected through much of the day. Thursday afternoon, isolated (~15% coverage) thunderstorms are possible.

MH

MARINE

Issued 255 PM CDT Wed Jun 17 2026

Southeasterly winds gusting consistently around 30 kt will build waves in the southern half of Lake Michigan into this evening as low pressure around 29.2 inches approaches. Winds will become northeasterly in the northern half and westerly in the southern half as low pressure crosses central portions of the open waters late tonight. Winds in the southern half will continue to gust near 30 kt. For both periods, a few gales are expected. Isolated thunderstorms are also expected across the southern half this evening.

As low pressure exits into Michigan early Thursday morning, expect all winds to shift to become northwesterly and diminish gradually into Thursday. Winds remain light and northwesterly through the remainder of Thursday and through Friday as high pressure around 30.0 inches progresses southeastward into the Lower Mississippi Valley. Winds may briefly turn southwesterly Friday night as weak low pressure moves through the region, but high pressure will rapidly regain dominance by Saturday, keeping winds light and variable. Stronger low pressure will approach from the central Plains on Sunday, bringing more widespread rain and thunderstorms and turning winds to northeasterly. Northeast winds will continue into early next week.

MH

MKX WATCHES/WARNINGS/ADVISORIES

WI...Beach Hazards Statement...WIZ052-WIZ060-WIZ066-WIZ071-WIZ072 until 4 AM Thursday.

LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 4 AM Thursday.