textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Chances for thunderstorms on and off this morning through this evening. A Marginal Risk for severe thunderstorms develops Wednesday afternoon and early evening, with the main hazards damaging winds and hail, especially in areas that see clearing in the early afternoon hours.

- Active pattern develops Sunday through Wednesday next week.

- A strong warming trend is expected early next week, potentially nearing Heat Advisory criteria Monday through Wednesday.

SHORT TERM

Issued 117 AM CDT Wed Jun 24 2026

Today through Thursday night:

A warm front draped from southern Minnesota through eastern Iowa will lift northward into this morning as a decaying MCS progresses eastward along the northern edges of this front. Expecting overrunning precipitation across the majority of southern Wisconsin through this morning as the front slowly moves through the region, with the main threat being lightning. Warm front will lift into southern Wisconsin after sunrise.

Latest mesoscale modeling shows the weak warm front struggling to get farther north than the I-94 corridor, resulting in additional rounds of precipitation through much of the day across the I-94 corridor southward. The parent low finally propagates into northern Wisconsin during the afternoon hours, with a cold front slowly progressing southeastward through the state. With additional rainfall/cloud cover becoming more likely across the southernmost tiers of counties through much of day, intensity of storms developing along the cold front is more in question. Areas farthest north toward central Wisconsin and the Wisconsin River Valley stand the best chances of seeing isolated stronger storms due to the increase in instability near the core of the low (still expected to rise to 1000-1500 J/kg) and the increased shear values along the front (0-6 km shear around 30 kt, definitely a downward trend from previous model runs) during the mid afternoon hours. Storms that do tap into the available ingredients may become capable of producing damaging winds and hail. Elsewhere, generally expecting lightning to be the main threat.

Storms along the cold frontal boundary will progress southeastward through the remainder of the afternoon and evening, with potential for additional development along the front into the evening hours, although coverage is expected to diminish (20-40%, isolated to scattered). Storms will end west to east by midnight, with lows in the mid to upper 50s. Winds are expected to remain light, but steady enough to inhibit fog development at this time.

Winds become northwesterly into Thursday as low pressure exits into Lower Michigan, with an additional shortwave propagating along the mean flow through central to southeastern Wisconsin during the afternoon hours, leading to additional scattered showers and thunderstorms (20-40% coverage). Highs in the mid 70s are expected.

Winds shift to become northeasterly Thursday night as low pressure develops in the Middle Mississippi Valley. A few showers and storms along the north side of the low may progress into far southern Wisconsin, but probabilities are low due to the low track through central/southern Illinois (~20%). Lows in the low to mid 50s are expected.

MH

LONG TERM

Issued 117 AM CDT Wed Jun 24 2026

Friday to Wednesday:

High pressure builds into the Great Lakes region on Friday, as low pressure continues to propagate across the Ohio Valley. A few showers (15-20%) may continue across far southern Wisconsin, but this likely will trend even lower due to the strength of the northern high. Easterly winds off Lake Michigan will keep temperatures cooler in the low 70s in southeastern WI while temperatures in southwestern WI reach the upper 70s. This pattern persists through Saturday, but with plenty of sunshine on Saturday as the Ohio Valley low exits, expect highs in the mid to upper 70s in southeastern WI and highs in the low 80s in southwestern WI. Low pressure then developing in the northern High Plains will shift winds to southeasterly going into Sunday, with WAA and weak convergence across the area leading to chances for showers and thunderstorms (15-25%) as low pressure continues to deepen in the Plains. Temperatures will climb into the mid-80s and even the upper 80s in areas that do not see showers/storms.

Southerly winds continue through Sunday night, with lows only in the low 70s. By Monday, plenty of surface WAA combined with increasing humidity will lead to highs in the upper 80s to even low 90s (potentially reaching heat index values over 100 degrees). Winds shifting to become southwesterly as low pressure propagates into Ontario will allow for high heat index values all the way to the Lake Michigan shoreline. Monday night into Tuesday, a frontal feature from the exiting low will bring in scattered shower and storm potential (20-40%). Some models show this front stalling through midweek, but confidence in exact timing of any additional showers and storms remain in question. As high pressure builds across the Southeast U.S. through early next week, additional heat and humidity will build into the region. With overrunning cloud cover, Heat Advisory criteria becomes less confident, but conditions are ripe for some areas that see additional sunshine during the daylight hours to also see heat index values above 100 degrees.

MH

AVIATION

Issued 117 AM CDT Wed Jun 24 2026

VFR ceilings with visibilities between 2 and 5 SM within a cluster of rain with embedded thunderstorms will progress southeastward through this morning, stalling along and south of a line from MSN to MKE by late morning. Expecting light rain to dominate, with increasing chances for thunderstorms after mid-morning as instability increases. However, expecting coverage to decrease (30-50%, or scattered). A broken line of storms looks to develop across central to southwestern WI this afternoon, progressing southeastward this evening. These storms will not linger over any terminals for long durations, but may produce briefly gusty winds or small hail, especially in southwestern WI. Storms will gradually end into the overnight hours.

Light and variable winds will become southwesterly and gusty into this afternoon, diminishing and becoming westerly into the evening to overnight hours as storms exit. Winds shift to northwesterly into Thursday morning.

MH

MARINE

Issued 117 AM CDT Wed Jun 24 2026

Weak low pressure around 29.9 inches in northern Minnesota this morning will allow for winds to shift to southwesterly as low pressure pushes eastward through northern Wisconsin through today. Thunderstorms are expected to develop this evening as low pressure pushes across the open waters into Lower Michigan, turning winds to northerly into Thursday. High pressure around 30.0 inches over Ontario and the western Great Lakes will dominate Friday through Saturday for light northerly winds shifting to northeasterly. Sunday, low pressure deepens to 29.4 inches in the northern High Plains, bringing strong southeasterly winds to the lake. Winds turn southerly into Monday as low pressure exits into the Canadian Prairies. On and off thunderstorms become more likely during this time.

MH

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...None.