textproduct: Milwaukee/Sullivan

KEY MESSAGES

- A very humid air mass will linger through this week.

- Showers and isolated thunderstorms will continue this evening into tonight.

- Hot and humid conditions expected mid to late week, with some potential for Heat Advisory conditions on Wednesday.

- Severe thunderstorms are possible Wednesday and Thursday.

UPDATE

Issued 740 PM CDT Mon Jun 8 2026

Showers will continue this evening as weak low pressure slowly approaches from the southwest. With the loss of daytime heating, the thunder threat should continue to diminish this evening, though a few rumbles will be possible into overnight. Overall rainfall rates should be less this evening into tonight as well.

DDV

SHORT TERM

Issued 240 PM CDT Mon Jun 8 2026

Tonight through Tuesday night:

A compact MCV continues to churn over eastern Iowa as dew points in the low 70s and PWATs from 1.8 to 2 inches continue to circulate around the feature. A bit of a lull in convection behind morning activity has allowed for breaks in the sun to occur in pockets over southern WI. This has allowed for modest SBCAPE of 1000 to 2000 J/kg to build over the area. The presence of the MCV and surface instability should support additional thunderstorms late this afternoon into this evening. Very heavy downpours will be possible with any thunderstorms that occur this evening owing to the tropical environment that will be present. Generally an additional 0.1 to 0.5 inch of rain is expected areawide into the evening, but far larger local amounts from 1 to 3 inches will be possible beneath any stronger storms.

With the potential for water loading in downdrafts this afternoon, some wind gusts from wet microbursts can't be ruled out. Shear is far lower than projected yesterday by models, lessening the potential for an isolated, brief tornado. However, some funnel clouds can't be ruled out.

The MCV is projected to slowly meander from NE IA over southern WI tonight, reaching the Lake Michigan shoreline Tuesday morning, where it then becomes a bit ill-defined in the models heading into Tuesday afternoon. Some remnant influence from the MCV, and a low level trigger from a lake breeze circulation may allow for some scattered pop- up thunderstorms along the Lake Michigan shoreline Tuesday afternoon. These storms may be capable of gusty winds and small hail, particularly during the mid to late afternoon when instability is maximized.

CMiller

LONG TERM

Issued 229 PM CDT Mon Jun 8 2026

Wednesday through Monday:

Low to mid level warm advection Wednesday morning may bring in a line of storms into our southwest. CAM soundings show these storms being slightly elevated but feature 2000 J/kg of MUCAPE, and mid level lapse rates around 7 C/km. Some hail will be possible as these storms move in just before sunrise, with some potential for gusty winds if the stable layer gets broken through. Through Wednesday, a warm front is projected to lift north over the area, exposing southern WI to a hot and humid environment. Highs will be in the low 90s, amid dewpoints between 70 and 75 degrees. This will lead to heat indices approaching 100 and borderline Heat Advisory conditions. We'll have to watch Wednesday for cloud cover, as increased cloud cover will decrease temps and heat indices and vice versa.

Wednesday afternoon, diffluent flow aloft from an approaching trough will kick off thunderstorm activity over central MN. These storms are expected to quickly form into a line amid the boundary parallel shear and track toward southern WI Wednesday evening around and after sunset. GFS and NAM soundings show great turning in the low levels, but weak flow aloft. This may support an initial tornado/hail threat over Central MN and northern WI, but may mean more in the way of wind for us as the line tracks our way as the weak shear makes the storms outflow dominant. We'll need to watch timing and where storms initiate, as that will determine what severe weather hazards we see Wednesday night. Closer initiation to southern WI and storms earlier in the evening would support all hazards, rather than favoring wind.

Thursday, another chance for severe weather exists, but the threat will highly depend upon where a remnant boundary from Wednesday night's convection sets up. The presence of the boundary will drive storm formation Thursday afternoon. Runs of the RRFS that are in range would suggest all severe weather hazards would be possible.

Beyond, a front swings through, lowering dew points heading into next weekend. Ill-defined chances for showers and storms at time then linger Saturday through Monday.

CMiller

AVIATION

Issued 740 PM CDT Mon Jun 8 2026

Showers will continue this evening as weak low pressure slowly approaches from the southwest. With the loss of daytime heating, the thunder threat should continue to diminish this evening, though a few rumbles will be possible into overnight. The chance for showers will generally wind down southwest to northeast overnight into Tuesday morning, though a few showers and isolated thunderstorms may linger in the east

Ceilings are expected to decrease this evening into tonight, as the low pressure system moves into southern Wisconsin. If fog develops over Lake Michigan, some lower visibilities will be possible in the east tonight into early Tuesday, especially north of Milwaukee.

Light southeast winds this evening will gradually become west to northwest by Tuesday morning as the low passes through the region. Winds will likely turn onshore near Lake Michigan by late Tue morning or early afternoon.

DDV

MARINE

Issued 211 PM CDT Mon Jun 8 2026

Warm and humid air brought from the south along a warm front over the cool lake into the evening and overnight will bring the potential for fog over Lake Michigan, primarily over the northern half Monday night into Tuesday morning, with increasing fog potential in the north Tuesday evening. Showers and thunderstorms are expected to increase tonight over the southern portions of the lake.

Continued southeasterly winds over the lake overnight and into Tuesday morning ahead of an MCV and a surface low pressure, with winds shifting southwesterly in the south and northerly in the north. Into Wednesday, westerly winds alongside a pressure decrease will bring gusty conditions with the potential for showers/thunderstorms over southern Lake Michigan Wednesday afternoon and evening.

Zawlocki

MKX WATCHES/WARNINGS/ADVISORIES

WI...None.

LM...None.