textproduct: Milwaukee/Sullivan

KEY MESSAGES

- A very humid airmass will build into the region today ahead of approaching low pressure, with widespread showers and scattered thunderstorms forecast this afternoon into tonight.

- Showers and storms today will be slow moving and capable of heavy rainfall. Localized flooding is possible. General rainfall totals will be between 0.5 and 1.5 inches, but locally higher amounts will be possible. A brief, isolated, spin-up tornado also can't be ruled out.

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

- Severe thunderstorms are possible Wednesday. There is a lower risk for severe storms on Thursday.

UPDATE

Issued 612 AM CDT Mon Jun 8 2026

Scattered showers and isolated thunderstorms developed in northern IL and expanded into southern WI shortly after 1 AM. They developed along an area of vorticity advection and were also aided by the low level jet. They were widely scattered for a while, but not are in a NW to SE oriented band. Precip rates are in the 2 to 3 inch per hour range, but the band of rain is steadily tracking northward. Southeast Rock county picked up around an inch already (radar estimated).

The main area of precipitation that we're keeping an eye on is currently in eastern IA because it's associated with a mesoscale convective vortex (MCV) and the southern edge of it would be the typical spot for deeper convection, heavier rain rates, and a brief, low-topped supercell that could produce a tornado. The center of this MCV is now looking like it will track just to the WEST of the MKX forecast area.

There is currently a more intense band of rain extending from the MCV into northwest IL. This band will lift northward to the WI border by 8 AM and bring some heavier rainfall rates, but probably to areas not hit hard within the past 6 hours. We will be watching for repeated rounds of these more intense rainfall rates all day to monitor for the risk of areal flooding or flash flooding.

Steady southeast winds will prevail today and lead to high waves at beaches north of Wind Point today into this evening. A Beach Hazards Statement for a high swim risk is in effect.

Cronce

SHORT TERM

Issued 100 AM CDT Mon Jun 8 2026

Today and Tonight:

Both model guidance and observed Satellite / Radar trends suggest that the coverage of any predawn showers / storms should be lower than prior expectations, widely scattered and weak at best. The MCV currently over northern Missouri will continue to track northward this morning, heading for northeast IA (or perhaps directly overhead) this afternoon. As it approaches, we expect to see the coverage and intensity of storms gradually ramp up in a SW to NE manner, peaking late this afternoon into this evening before tapering down late tonight. With PWAT of 1.7-2.1 inches and WCL depths over 10,000 ft, all showers + storms will be very efficient rain makers. With potential for training and clustering convection, this would mean potential for localized heavy rainfall and flash flooding. The exact track of the MCV is not fully certain, but wherever it sets up, storms to the south and east of it this afternoon will experience locally backed surface winds and higher helicity, which coupled with the low LCL heights and building 3CAPE could support a brief spin-up tornado. That said, the primary hazards for today are localized heavy rainfall and lightning.

Sheppard

LONG TERM

Issued 100 AM CDT Mon Jun 8 2026

Tuesday through Monday:

Synopsis: A pronounced upper ridge axis over the eastern Great Lakes and negatively tilted trough axis over the northern Rockies will both slowly progress eastward through the rest of the work week before breaking down into a predominantly zonal pattern for this weekend. We expect the heat and humidity to peak midweek (Wednesday) followed by a slow cool down towards seasonal norms by early next week. Periodic chances for showers and thunderstorms are forecast through this period, with a particular emphasis on Wednesday and Thursday for some more organized / stronger storm potential.

Details: Predominantly dry weather expected on Tuesday, with Monday's convective activity exiting east and leaving some subsidence in it's wake. The fuel (CAPE) for a stray thunderstorm will be present in the region, particularly further south and west, though the predominantly subsident motion should keep us dry. The 18z GFS does resolve a 500mb vorticity maxima and attendant PVA crossing our region Midday (not quite in phase with peak diurnal heating), but this remains an outlier. The 00z HRRR suggests potential for Monday's convection to form an MCV that lingers long enough for widely scattered shower activity to persist into Tuesday. That said, the overall consensus is dry weather, and precip chances have been capped at 15% for now. Additional 40-60% precip chances are in place late Tuesday night, mainly on account of a dying storm complex (triggered to our west) attempting to push into southern WI.

The heat and humidity may approach Advisory levels (heat index 100-104) on Wednesday, though any remnant cloud cover from the potential overnight convection (or an earlier-than-expected convective initiation Wed afternoon) could easily hold us just shy of criteria. Our best guess is (once again) predominantly dry weather through the daytime hours, with plenty of fuel (likely 3,000 joules CAPE or more) available for a stray storm but no substantial mechanisms to trigger one. A potent 500mb trough digging into Minnesota ought to serve as the focal point for convective initiation Wednesday afternoon, likely near west- central WI / southeastern MN. Both the trough and storms would then track eastward, and depending on how early (in the evening / night) it arrives, plenty of instability would be present to support severe weather. The earlier it arrives, the worse it could be.

Yet another 500mb trough with strong PVA and shear is expected to trigger convection on Thursday, with model guidance suggesting this one will be more or less "overhead". That said, ensemble guidance substantially lowers the fuel / CAPE for Thursday, likely on account of Wed evening / night's convective activity sweeping it out and resetting the warm sector to our southeast. For now, both Wednesday and Thursday are potential candidates for severe storm activity in our region. An early arrival of convective activity Wednesday (or a failure for it to reach southern WI at all Wednesday night) would leave higher CAPE Thursday.

Such an active weather pattern leaves little in the way of 'predictability' for Friday and beyond, though the general consensus is a transition to predominantly zonal flow in the jet overhead, with temperatures trending closer to seasonal norms into early next week.

Sheppard

AVIATION

Issued 612 AM CDT Mon Jun 8 2026

Bands of showers/storms will track northward through southern and central WI today. Rainfall rates will be efficient (2 to 4 inches per hour), so any slow-moving thunderstorms or repeated rounds of storms could produce flash flooding. Ceilings will become progressively lower as the day goes on, falling to MVFR with pockets of IFR this evening. Showers and thunderstorms will gradually diminish from west to east late tonight into Tuesday morning.

Cronce

MARINE

Issued 612 AM CDT Mon Jun 8 2026

High pressure over the Lower Great Lakes will continue to shift eastward today. Light to moderate southeast winds developing over Lake Michigan will persist through this evening. A Small Craft Advisory is in effect through late afternoon. Bands of showers and thunderstorms will lift northward through WI and Lake Michigan today and tonight.

Winds will become southerly and storms become more isolated behind the front on Tuesday. A brief period of light and variable winds may occur Tuesday evening, followed by gusty south winds into Wednesday as low pressure deepens west of the region.

Cronce

MKX WATCHES/WARNINGS/ADVISORIES

WI...Beach Hazards Statement...WIZ052-WIZ060-WIZ066-WIZ071 until 7 PM Monday.

LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645 until 4 PM Monday.