Area Forecast Discussion

KEY MESSAGES

- Sprinkles possible in southeast WI this afternoon.

- A very humid airmass will return Monday and Monday night ahead of approaching low pressure with widespread showers and scattered thunderstorms forecast.

- Hot and humid conditions expected mid to end of next week with some potential for Heat Advisory conditions late next week.

UPDATE

Issued 634 AM CDT Sat Jun 6 2026

Showers and storms that were over southwest WI dissipated just before they reached the IL border. Despite the outflow boundary/effective front being south of the WI border, our dewpoints are still in the lower 60s. These will drop into the mid 50s today, but with temps topping out in the lower to mid 80s and plenty of sunshine, it is going to feel very warm and humid today, especially with the light winds.

We should see diurnal cumulus clouds today due to the high dewpoints. They should focus along the lake breeze convergence area in southeast WI this afternoon. Models are hinting at the potential for a few sprinkles out of them.

Cronce

SHORT TERM

Issued 104 AM CDT Sat Jun 6 2026

Overnight through Saturday Night:

The east-west broken line of storms will continue to slide southward and exit southern WI between 1 and 2 AM. There is one area of additional storms that are developing between La Crosse and Wisconsin Dells. This is associated with the back edge of a weak shortwave trough sliding through southern WI. The vorticity advection with that feature will help whatever ongoing storms progress into northern IL around daybreak. The main thing we need to watch overnight is for training storms. With precipitable water around 1.5 inches, the storms are efficient rain producers.

High pressure will return to the Upper Great Lakes on Saturday (today). We can expect mostly sunny skies and warmer temperatures than yesterday, with highs in the mid 80s. We will still be within the warm and humid air mass with dewpoints in the 60s. The lakeshore will see some relief from from the heat in the afternoon with a lake breeze, but the lake breeze is not going to make it very far inland until the evening. Temps will drop into the 50s for east central and southeast WI Sat nt as drier air briefly moves in.

Sunday through Monday:

A closed upper low that will be over Texas today will make its way into the Plains on Sunday. The position of this upper low as it approaches the Upper Midwest will draw moisture up from the Gulf and we can expect widespread showers with thunderstorms over southern WI on Monday. They should spread in Sunday night and exit Monday night, although the movement of this weak upper low has uncertainty. This should bring another soaking rain. There could be a few strong storms with this system on Monday, given the negatively tilted upper trough, but the overall system lacks the strong synoptic forcing for a bigger severe event.

Cronce

LONG TERM

Issued 104 AM CDT Sat Jun 6 2026

Tuesday through Saturday:

Broad low pressure in the Great Plains will continue to pivot 500 mb shortwaves northeastward through the Great Lakes region Tuesday and Wednesday, leading to on and off thunderstorm potential (20-30% chances). Meanwhile, stiff southwesterly winds will develop on Wednesday, bringing a warm, humid airmass into southern Wisconsin. Expecting highs in the low 90s, with high temperatures reaching all the way to Lake Michigan as southwest winds keep the lake breeze offshore.

Thursday, low pressure ejects into the Canadian Prairies and brings an occluded warm front through southern Wisconsin. This is a potential trigger for additional storm development in the afternoon (~35%), which may prevent temperatures from rising as dramatically as Wednesday. However, highs in the upper 80s to near 90 degrees are expected as southwest winds continue to bring in plenty of warm, moist air from the Gulf. Thunderstorm potential continues through Thursday night (20-35%) as winds shift northwesterly and bring in upper 60s for the overnight hours.

Winds shift back to southwesterly Friday as low pressure lifts into northern Ontario and additional low pressure develops in the central High Plains. Heat and humidity will increase again, with heat index values potentially rising into Heat Advisory levels. Pop-up thunderstorms are possible, but confidence is low at this time (15-20%). Friday night, expect low pressure to eject into the Plains. Model discrepancy develops as to the path this low takes, but either solution (northern would result in more cloud cover and less warming, southern would result in easterly winds off Lake Michigan) would lead to a respite in high temperatures with the most likely solution in the mid-80s.

MH

AVIATION

Issued 634 AM CDT Sat Jun 6 2026

With low level moisture lingering over southern WI today, expect diurnal cumulus clouds to develop by mid morning. The bases may begin with a few pockets of MVFR around 2500ft in far southern WI but quickly become VFR for the rest of the day. Clouds may concentrate along the lake breeze convergence this afternoon and produce a few sprinkles. Clear skies and light winds are expected tonight into Sunday.

Cronce

MARINE

Issued 634 AM CDT Sat Jun 6 2026

Low pressure will exit Ontario this morning as high pressure builds into the Upper Great Lakes. Warm and humid air will linger over the relatively cool waters of Lake Michigan with a light wind regime and cause areas of fog through early afternoon, mainly over the north half. Fog may return tonight into Sunday as the high strengthens. Low pressure develops in the Great Plains Monday, bringing south- southeasterly winds through at least midweek. Additional chances for thunderstorms develop Monday and Tuesday.

Cronce

MKX WATCHES / WARNINGS / ADVISORIES

WI...None. LM...Dense Fog Advisory...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565- LMZ567-LMZ669-LMZ671-LMZ868-LMZ870-LMZ872 until 1 PM Saturday.