textproduct: Milwaukee/Sullivan

KEY MESSAGES

- An Extreme Heat Warning remains in effect for all of southern Wisconsin through early this evening. Additional heat headlines may be needed into the rest of the week, but some uncertainty remains due to clouds and rain chances.

- There are chances (20 to 40 percent) for thunderstorms into this morning, mainly north of a Lone Rock to Sheboygan line. A stronger storm may produce hail, gusty winds and locally heavy rainfall. - There is a small chance (20 percent) of a thunderstorm this afternoon northwest of Madison. A strong to severe storm with strong winds and hail would be possible, if it develops.

- There are increasing chances (40 to 70 percent) for thunderstorms later this afternoon and tonight, with the better chances north of a Lone Rock to Sheboygan line. Some strong to severe storms with heavy rainfall may occur at times, mainly in the evening. Damaging winds and hail are the main hazards.

- There are periodic chances (40 to 60 percent) for thunderstorms Thursday into the holiday weekend. Some strong to severe storms with heavy rainfall may occur at times, though confidence remains low with the timing of each round of storms. This may impact outdoor holiday activities at times, so keep up with the forecast.

SHORT TERM

Issued 146 AM CDT Wed Jul 1 2026

Today through Friday night:

The Extreme Heat Warning will remain in effect until early this evening. An extension or a Heat Advisory issuance into later in the week may eventually be needed, depending on how many clouds and showers/storms occur. Will likely wait on how clouds and possible shower/storm trends play out overnight into later today before making further decisions on the heat headlines for the rest of the week. Heat index values in the 90s to low 100s are forecast for Thursday and Friday.

There is a chance (20 to 40 percent) for showers and storms developing into this morning, before pushing northeastward by midday. The southwesterly low level jet will be the key feature to watch, as it develops more of a nose and shifts northeastward toward the area.

CAMs seem to be favoring scattered showers and storms developing in southeast Minnesota into southwest Wisconsin by 09Z or so, shifting northeast into the morning hours. Given the setup with the southwesterly flow through a deep layer focused from Iowa into southwest and central Wisconsin, would expect any showers and storms that develop with the low level jet nose to push northeast and ride the ridge through these areas.

There is a decent amount of elevated CAPE (1500 to 2500 J/kg), with weaker deep layer bulk shear around 20 knots increasing to 30 to 35 knots in the morning. Thus, any stronger storm could produce hail, gusty winds and locally heavy rainfall, given the very moist airmass in place and storms possibly moving over the same areas.

There could be an isolated storm that develops this afternoon northwest of Madison, closer to the low level jet axis. It would be elevated in nature, but given the high CAPE over 3000 J/kg and 30 to 35 knots of deep layer bulk shear, could see a strong to severe storm occur.

CAMs suggest clusters of thunderstorms may develop along a surface boundary in north central Iowa to north central and northwest Wisconsin by early evening, then shifts east northeast with the aid of the low level jet toward and into the northern portions of the area during the evening and overnight. There is enough mean layer CAPE and deep layer bulk shear for more strong to severe storm potential, with damaging winds and hail the main hazards. Heavy rainfall may occur as well.

The low level jet should focus more into southern Wisconsin Thursday, with a surface boundary in the form of a stationary front developing as well. These features may help to focus more showers and thunderstorms at times Thursday into Thursday night, as well as into Friday. There remains a strong to severe storm risk with heavy rainfall as well for this period, as high CAPE and moderate deep layer bulk shear values persist. Details on this potential will be more clear once the convection into tonight shows its hand.

Wood

LONG TERM

Issued 146 AM CDT Wed Jul 1 2026

Saturday through Tuesday:

Active conditions continue into the holiday weekend, with multiple batches of thunderstorms expected Saturday through Sunday.

Subtropical ridging will gradually break down over the eastern CONUS this weekend, allowing for modestly cooler temperatures and heat indices. A slow-moving surface boundary will concurrently slide into southern Wisconsin, supporting daily chances for showers and thunderstorms both Saturday and Sunday. Overall storm chances are greatest (50 to 60 percent or more) on Saturday, when a shortwave trough is progged to move across southern Wisconsin.

Most favored locations for storms on Sunday will depend on where the surface boundary sets up in the wake of Saturday's storms, with boundary location remaining a source of uncertainty at this time. Will continue to monitor trends over coming forecasts.

Any weekend storms will be capable of producing cloud-to-ground lightning and heavy downpours, with a few strong to severe storms possible. Continue to monitor the forecast is planning to be outdoors. Widespread precipitation chances wane moving into the beginning of next week, as broad high pressure builds over the western Great Lakes.

Saturday/Fourth of July looks to be a potentially active Independence Day, as an upper shortwave and surface boundary move across the region. Aforementioned features will be impinging upon a still unseasonably moist airmass, which will be supportive of abundant instability. While modest, initial forecast soundings suggest bulk shear values supportive of at least loosely-organized convection, so will need to monitor for some severe weather potential over coming forecasts.

Storms will also be capable of producing heavy downpours given precipitable water values in the 1.60 to 1.80 inch or greater range. Regardless of severity, any convection will be capable of producing cloud-to-ground lightning, which will be hazardous to anybody attending outdoor holiday festivities. Keep up with the forecast if planning to be outside Saturday.

Depending on the surface boundary's location in the wake of Saturday's storms, could see another batch of convection during the afternoon/evening hours on Sunday. Have maintained 20 to 40 percent precip probabilities from the NBM in the evening forecast update, given lingering uncertainties related to surface boundary positioning.

Expect that values will continue to fluctuate with the modeled positioning of the boundary over coming forecasts, with more refined locations of favored storm development emerging during the Friday to Saturday time period. Like Saturday's thunderstorms, will need to monitor for a few severe storms with heavy downpours, in addition to lightning potential in all thunderstorms, in any Sunday activity.

Quigley

AVIATION

Issued 146 AM CDT Wed Jul 1 2026

Light southwest winds are expected into this morning. Gusty southwest winds should return by midday into the afternoon and early evening. Removed mention of low level wind shear in TAFs for now, as surface winds should remain high enough to limit this potential.

There may be broken ceilings around 5000 feet AGL into this morning for areas west and north of Madison to Sheboygan, if some showers and storms develop. Most terminals to the southeast of here should remain dry and may not see much in the way of clouds during this time.

More VFR category ceilings, along with showers and storms, may approach the Madison and Sheboygan terminals this evening and perhaps the rest of the terminals overnight tonight. Locally reduced ceilings and visibilities may occur in any showers and storms. May see gusty winds and some hail with the stronger storms during this time.

Wood

MARINE

Issued 146 AM CDT Wed Jul 1 2026

Modest to breezy south to southwest winds will prevail into Thursday, then lighter winds should occur into Friday, as high pressure around 30.1 inches remains to the southeast of the Great Lakes, while low pressure around 29.5 inches moves slowly east across central Manitoba into James Bay.

Chances for thunderstorms are forecast across the northern half of the lake through tonight. There are chances for thunderstorms across the southern two thirds of the lake Thursday into Friday evening, and across the southern half of the lake later Friday night into Sunday. Some strong to severe storms may occur at times, though confidence remains low with the timing of each round of storms.

Patchy marine fog will be possible at times, primarily over the northern half of the lake, as the warm and moist airmass moves over the lake. There may also be some patchy dense fog along the Lake Michigan shoreline into this morning.

Southwest winds may approach Small Craft Advisory levels today into early this evening for the nearshore waters, mainly near the shoreline.

Wood

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...None.