textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Warm and dry conditions with low relative humidity today, with gusty southwesterly winds and may approach elevated fire weather conditions this afternoon.

- Increasing humidity and thunderstorm chances for late tonight through Saturday. A 1 out of 5 (marginal) risk for severe storms is forecast Friday, but the timing of the severe potential remains in question.

- On and off thunderstorm chances continue Sunday through start of next week as moisture returns to the region.

UPDATE

Issued 615 AM CDT Thu Jun 4 2026

No major changes from the previous forecast as southerly winds pick up today and temps warm into the 80s and may even approach 90F in some locations. The big question is if and how the mid and high clouds from the decaying thunderstorms/showers upstream in MN/IA impact the ongoing forecast. More cloud cover across western half of the CWA may temper temps toward mid 80s while lesser impacts for the eastern portions of the CWA where there will be better potential for upper 80s to around 90F. Will still monitor how redevelopment upstream this afternoon translates as it pushes into southern through the evening. Still expecting this activity to push east overnight into Friday morning.

Wagner

SHORT TERM

Issued 110 AM CDT Thu Jun 4 2026

Today through Friday night:

Temperatures in the upper 50s early this morning will quickly rise into the 80s by midday across all of southern Wisconsin as gusty southwesterly winds keep the lake breeze offshore. Expect highs in the mid to upper 80s in the afternoon. Cloud cover will increase throughout the day as storms develop across northern Wisconsin and Iowa. With breezy southwesterly winds and relative humidity values falling into the 25-35% range, elevated fire weather conditions may develop in the afternoon hours. Late this evening, remnant storms will sag southeastward into southwestern Wisconsin. The main hazard with these storms will be lightning, with some potential for gusty winds due to very dry low levels and therefore evaporational cooling with PWATs around 1.3 inches. However, minimal CAPE (~300-500 J/kg) will prevent storms from reaching their full potential for severe. After sunset, any lingering storms will become elevated. 300-500 J/kg of MUCAPE linger, so a few bolts of lightning remain possible through the overnight hours.

Friday morning, southwesterly winds continue, with warm frontogenesis across central to southern Wisconsin. MUCAPE increases to 1000-2000 J/kg mid-morning through the afternoon as lingering showers and thunderstorms exit into Lake Michigan. MUCAPE values may climb to as high as 2500 J/kg during the afternoon/evening hours if skies clear. Midday to afternoon evolution of additional thunderstorms remains uncertain. If skies clear, broad instability with the warm front in the region would lead to scattered thunderstorm development across all of southern Wisconsin (RAP solution). This would bring primarily an isolated hail/wind threat. However, NAM/NAM-3k/Nest and ARW indicate a remnant MCV from overnight convection in Iowa sliding across far southern Wisconsin/far northern Illinois during the midday to afternoon hours, bringing a threat for wind and isolated tornado development. Regardless, some severe potential is expected Friday afternoon. Highs in the low 80s are expected.

Friday evening, prefrontal convection developing in northern Wisconsin and LLJ-driven convection in Iowa will begin to southeastward into central Wisconsin. Model discrepancy in timing becomes more significant at this stage due to the speed of the front depending on the previous time period's convection. With MUCAPE around 1000-2000 J/kg lingering and 0-6 km bulk shear just at 35 kt, some organization may still develop with these storms. Overnight lows in the low 60s are expected. The cold front looks to work its way through southern Wisconsin late Friday night into early Saturday morning, bringing an end to any severe threat.

MH

LONG TERM

Issued 110 AM CDT Thu Jun 4 2026

Saturday through Thursday:

The main cold front will move through Saturday morning, bringing light northwesterly winds to southern Wisconsin. Even with northwest winds, temperatures are expected to climb into the mid-80s. With additional moisture aloft and continued instability, a few thunderstorms (20-30% chances) may still develop Saturday afternoon in southeastern to far southern Wisconsin where the frontal feature lingers longer.

High pressure builds back into Ontario and Quebec on Sunday, keeping the majority of southern Wisconsin dry. Isolated pop-up storms are possible in southwestern Wisconsin as moisture return from the Gulf nudges up into the Mississippi Valley. Broad low pressure will develop in the High Plains Sunday into Monday, continuing to bring moisture northward into the Mississippi Valley. Modeling is consistent regarding the low pressure ejecting northeastward into Monday, bringing higher chances for precipitation into southern Wisconsin (40-60%). This will also whittle away the edges of the high pressure sitting over eastern Canada, allowing for additional shortwaves to bring continued potential for thunderstorms on and off through midweek. With continued southerly flow, temperatures will also continue to rise, potentially reaching 90 degrees Wednesday and Thursday.

MH

AVIATION

Issued 615 AM CDT Thu Jun 4 2026

VFR conditions will prevail through today with south- southwesterly winds picking up later this morning and into the afternoon. Some mid to high level clouds expected as well. Will see more clouds move in this evening/tonight as upstream showers and storms gradually spread further east overnight. Shower chances increase for MSN between 03-06z and after 09z for the rest of southern WI terminals. A few rumbles of thunder will be possible with this activity tonight into Friday morning, but not confident enough to add in as prevailing at this time.

Wagner

MARINE

Issued 110 AM CDT Thu Jun 4 2026

Influence from the high pressure finally releases it hold over the region as it settles over the Mid-Atlantic through today. Light and variable winds early this morning will give way to gusty southerly winds over the lake as low pressure develops and deepens across Manitoba into Ontario through the day. Will see a brief window late this afternoon and evening for small craft winds and waves to develop for east-central WI nearshore waters,but will diminish by tonight as winds turn more offshore. Continue to see this low track east across the northern Great Lakes through Friday bringing prevailing southwesterly winds along with shower and thunderstorm chances tonight through Friday ahead of the cold front. Then expect the cold front to push through the region later Friday into Saturday bringing additional shower and thunderstorm chances along with a more northwest to westerly wind shift behind it into Saturday. Then winds weaken and become more variable as high pressure builds across the region later Saturday into Sunday. Looking ahead to the start of next week will bring an additional low pressure system to develop over the Plains and bring a return of southerly winds to the Upper Great Lakes.

Wagner

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Small Craft Advisory...LMZ643...2 PM Thursday to 10 PM Thursday.