textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Chances for thunderstorms on and off this morning through this evening. A Marginal Risk for severe thunderstorms develops this 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.

UPDATE

Issued 550 AM CDT Wed Jun 24 2026

06z guidance remains roughly in agreement with the 00z guidance for today's thunderstorm setup... The existing elevated convection (showers and thunderstorms) over northeastern IA and southwestern WI will continue to track east-southeastward, crossing southern and southeastern WI through the rest of this morning. Instability with it will be quite limited (generally 700 joules or less MUCAPE), and the storms will not have an opportunity to become surface-based, meaning the only real concern will be lightning. Based on their current motion vector as well as interim model guidance, these showers (and rumbles of thunder) should take until at least midday to move clear of far southeastern WI, and the associated cloud cover will block much of the sunlight through peak heating today, making it really difficult for far southeastern WI to destabilize this afternoon.

For east-central, central, and southwestern WI, a different story... the existing showers + weak storms and associated cloud cover should clear out much earlier in the day, perhaps allowing some of the sunlight at midday / peak heating to get through to the ground. Nighttime microphysics cloud imagery over the past 3 hours corroborates this assessment, and as I write this (5:45am CDT) I am seeing mostly clear skies in south-central MN. The exact effect of the morning convection on this afternoon's effective warm front remains disputed amongst model guidance, but the general consensus is for southwesterly surface winds behind the morning convection to lift it northeastward across southwestern WI, stalling it diagonally across the CWA (which could allow it to be a focal point for storms in southwestern and perhaps south-central WI this afternoon and early evening. Further north into central and east-central WI, we aren't expecting this boundary to lift that far north, though some lighter synoptic southwesterly flow will still be present here, the clouds should still break apart (particularly further west), and models hint that your mid-level lapse rates might be a little bit steeper (which makes conceptual sense closer to the core of the low pressure system). Hence, the airmass in these areas may recover this afternoon as well, perhaps enabling some strong storms in these areas. Generally watching the 2:00 PM to 8:00 PM timeframe this afternoon and early evening for the stronger storm potential. Frequent lightning, hail, and gusty winds remain the primary concerns.

Sheppard

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 600 AM CDT Wed Jun 24 2026

A morning round of showers and weak thunderstorms tracks east- southeastward across southern WI this morning, taking until roughly midday to move clear of far southeastern WI. Expect MVFR visibilities (in some cases briefly IFR) from the moderate to locally heavy rainfall and some rumbles of thunder. Cloud ceilings have been generally VFR with this activity so far, though model guidance suggests a lowering to predominantly MVFR is likely for most areas later this morning.

Cloud ceilings improve to predominantly VFR in a west to east manner early this afternoon, but chances for more intense thunderstorms build in from west to east shortly thereafter. Gusty winds, hail, and frequent lightning would be a concern with any stronger storms if applicable, mainly in southwestern, central, and east-central WI terminals. Generally weaker storm activity expected as the convection tracks into southeastern WI, but still a lightning threat.

Storms weaken and clear out in a west to east manner later this evening. Dry weather likely across the region after midnight tonight.

Sheppard

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.