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.

- Additional chances for showers and thunderstorms through the rest of this week, with potential ingredients for stronger thunderstorms Wednesday and Thursday.

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 100 AM CDT Mon Jun 8 2026

Scattered shower and thunderstorm activity is expected to slowly lift northeastward into the region through this morning, becoming more widespread with additional rounds of showers + storms this afternoon into tonight. In the TAFs this appears as PROB30 groups for the predominantly scattered activity, with prevailing / FM groups for the more intense / widespread activity. Predominantly southeast winds expected through this entire timeframe.

Predominantly VFR cloud ceilings expected with the initial rainfall / thunderstorms, with repeated rounds leading to lowering ceilings. A decline to MVFR ceilings is expected in a west to east manner later today, followed by potential for IFR (or even LIFR) cloud ceilings late tonight.

Sheppard

MARINE

Issued 100 AM CDT Mon Jun 8 2026

High pressure of 30.1 inches over the Upper Great Lakes will shift east through this morning, deepening to 30.2 inches. Working with broad low pressure over the Great Plains, this will drive light to moderate southeast winds over Lake Michigan today through tonight. Scattered showers and thunderstorms are expected over southern portions of the lake this afternoon, becoming more numerous and widespread tonight as a warm front lifts northward.

The southeast winds this morning through early this afternoon are forecast to raise nearshore wave heights to around 4 feet. Hence a Small Craft Advisory is in effect through Monday afternoon from Wind Point to Sheboygan.

Winds turn south and storms become more isolated behind the front (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.

Sheppard

MKX WATCHES/WARNINGS/ADVISORIES

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

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