Tornado and Damaging Winds in Wisconsin, May 15, 2026

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1139 PM CDT Fri May 15 2026

.KEY MESSAGES...

- A Severe Thunderstorm Watch is in effect through 5 AM CDT from
  Iowa to Milwaukee Counties southward. This is primarily for
  damaging winds and isolated hail up to 1 inch in diameter.
  North of the watch, rain and thunderstorms are still possible,
  but are not expected to become severe.

- Isolated thunderstorm development Saturday afternoon and
  evening, with more widespread rain and storms overnight
  Saturday. A storm or two could become severe, but confidence
  is not high at this time.

- Active start to next week, with multiple rounds of showers
  and storms expected. Some storms could be severe & produce
  locally heavy rainfall.

- Trending quieter & cooler Wednesday into Thursday.

&&

.SHORT TERM...
Issued 1140 PM CDT Fri May 15 2026

Tonight through Sunday:

850 mb LLJ will strengthen existent storms as they progress
southeastward tonight along and south of the I-94 corridor late
tonight through early Saturday morning. A Severe Thunderstorm
Watch is in effect for Iowa County through Milwaukee County
southward. With storms already developing linear structure,
expecting the hail threat to be lower than previously
forecasted, although a few cores may become strong enough to
produce 1 inch in diameter hail. Cloud bases do remain high,
around 4000 ft, and combined with a stable to moist adiabatic
airmass in the low levels, expecting very low tornado threat.
An isolated tornado DOES remain possible in scenarios with an
easterly bowing segment and strong rear inflow jet. Storms are
expected to maintain intensity through the Lake Michigan
Counties, but confidence decreases farther east. Regardless of
intensity, expecting storms to exit offshore by 5 AM CDT.

Lingering light showers are possible after storms exit Saturday,
with clearing conditions through the rest of the day. Low
pressure developing in the central High Plains will bring warm
frontogenesis back into the Upper Midwest late Saturday
afternoon into Saturday night. If storms develop early enough on
Saturday (HRRR favors this solution with MUCAPE around 1000 J/kg),
probabilities for an isolated severe thunderstorm increase.
However, confidence is low (1 out of 5, or Marginal on the SPC
scale). More widespread rain and storms are expected to develop
during the overnight hours along this wing of frontogenesis.
Ingredients are not favorable for severe weather overnight, with
minimal MUCAPE and mid-level lapse rates only near 6 degrees
C/km as the surface front lingers just to the south.

Early Sunday morning, warm front finally lifts northward
through southern Wisconsin, bringing increasing instability and
shear. With overrunning precipitation, still not anticipating
any organization, but storms may become briefly surface based.
Southeasterly winds expected throughout the day Sunday, keeping
a wide temperature margin from the Lake Michigan and central
Wisconsin (low to mid 70s) to southwestern and inland counties
(low to mid 80s). Sunday afternoon, low pressure ejects into the
central Plains, bringing an additional frontogenesis region to
southwestern Wisconsin. Severe storms may become possible Sunday
afternoon into Sunday evening in this region, but confidence in
timing and placement remains in question (slower low
progression would result in less severe potential).

MH

&&

.LONG TERM...
Issued 1140 PM CDT Fri May 15 2026

Sunday night through Thursday:

Synopsis: Longwave ridging will remain entrenched over the eastern
CONUS Sunday night through the beginning of next week as a broad
upper trough gradually migrates from the Great Basin to the Northern
Plains. The upper pattern will support persistent high pressure off
the Eastern Seaboard, with broad low pressure gradually building
from the Central Plains into the upper Mississippi River Valley. The
placement of surface features will support southwesterly winds and
well-above normal temperatures through the day Monday. Muggy
conditions will accompany the warm temperatures. Temperatures will
slowly begin to trend downward Tuesday as low pressure continues to
build from Michigan's Upper Peninsula into Ontario, sweeping a cold
front across southern Wisconsin. The warm/muggy conditions &
eastward progressing upper trough, surface low and cold front will
support a continued active pattern featuring multiple chances for
additional showers and thunderstorms Sunday night into Tuesday. Some
storms could be severe, with locally heavy rainfall also possible.
Conditions will trend quieter and cooler in the wake of the departed
cold front Wednesday through Thursday.

Monday: Widespread thunderstorm development is forecast from the
Central Plains into the mid-upper Mississippi Valley during the
afternoon/evening hours as upper troughing & a surface cold front
impinge upon a warm/moist & unstable air mass in place regionally.
An overlap of ample instability with abundant speed & directional
wind shear will be supportive for potentially substantial severe
weather hazards in thunderstorm development. Precipitable water
values in the 1.25-1.50"+ range will also be favorable for heavy
downpours & locally heavy rainfall in any convection. Certainty of
the severe weather forecast picture in the MKX CWA, however, remains
cloudier relative to areas further west, as influences from early
day showers/storms could impact the quality of the afternoon/evening
warm sector over southern Wisconsin. Further, a number of different
solutions regarding the forward progression of the ejecting upper
trough & mirroring surface features remain apparent in available
global/mesoscale forecast guidance. If slower solutions apparent in
some guidance win out, the corridor of peak severe potential would
trend further west/away from southern Wisconsin. Will thus be
monitoring forecast trends very closely through the weekend, as
small changes in expectations for early day storms and/or storm
system progression will have large ramifications on the potential
for severe weather in southern Wisconsin on Monday.

Tuesday: Could see shower/storm potential linger around the region,
particularly in the scenario of a slower storm system
evolution/delayed cold frontal arrival in southern Wisconsin.
Wouldn't be able to rule out a few stronger storms with additional
heavy rainfall in the event the cold front hangs up long enough &
instability can build back into parts of the area. Will be watching
trends over coming forecasts.

Quigley

&&

.AVIATION...
Issued 1140 PM CDT Fri May 15 2026

VFR conditions expected through the remainder of tonight outside
of organized thunderstorms. A line of strong thunderstorms
is expected to progress west to east along and south of the I-94
corridor tonight. Confidence is high in widespread thunderstorm
activity all the way to Lake Michigan, and will amend as storms
move toward terminals for updated wind speed potential. LLWS
will continue ahead of these storms as winds remain southerly at
the surface, and will diminish after the strong storms move
eastward and winds turn west-northwesterly. Expect light rain
to continue with isolated lightning for a few hours after the
line of storms exits. MVFR conditions are possible within and
behind the storms.

Storms will exit into Lake Michigan by 5 AM CDT Saturday, with
expectations for skies to remain VFR and become clear into
Saturday afternoon. Northwesterly winds will continue through
the day. Additional clouds around 3500 ft may develop Saturday
late afternoon into Saturday evening as a warm front develops.
Precipitation chances increase into Saturday night (50-70%
chance), with lightning expected in the strongest cells. Winds
will also shift to southeasterly overnight.

MH

&&

.MARINE...
Issued 1140 PM CDT Fri May 15 2026

Low pressure around 29.1 inches exiting into the Hudson Bay will
keep gusty southerly winds across the Lake through early
Saturday morning. Expect winds to shift to become northwesterly
and light into Saturday as a front crosses the lake.
Thunderstorms are expected along this front, with a few
becoming strong with gusty erratic winds possible. Storms will
end shortly after sunrise. Lighter northwest winds continue
through Saturday, with light and variable winds overnight.
Sunday, low pressure around 29.2 inches will develop in the
central High Plains, shifting winds to easterly. Winds remain
easterly through Sunday, shifting to southwesterly and becoming
gusty Sunday night through Monday night as low pressure ejects
into the western Great Lakes region. A few strong thunderstorms
are possible on Monday as low pressure crosses Lake Superior.
Potential for a few strong thunderstorms remains into Tuesday as
low pressure lingers in the region.

MH

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Gale Warning...LMZ261-LMZ362-LMZ364-LMZ563 until 1 AM Saturday.

     Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 4 AM
     Saturday.

&&

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Hazardous Weather Outlook
National Weather Service Milwaukee/Sullivan WI
227 PM CDT Fri May 15 2026

WIZ046-047-051-052-056>060-062>072-161930-
Marquette-Green Lake-Fond du Lac-Sheboygan-Sauk-Columbia-Dodge-
Washington-Ozaukee-Iowa-Dane-Jefferson-Waukesha-Milwaukee-
Lafayette-Green-Rock-Walworth-Racine-Kenosha-
227 PM CDT Fri May 15 2026

This Hazardous Weather Outlook is for portions of east central
Wisconsin, south central Wisconsin and southeast Wisconsin.

.DAY ONE...Tonight

A line of strong to severe thundestorms expected to develop and
push across southern WI overnight tonight after 10 PM.
Strong/damaging winds and some hail will be the main threats,
especially toward the WI/IL border.

.DAYS TWO THROUGH SEVEN...Saturday through Friday

Rounds of thunderstorms are expected Saturday night through
Tuesday. The best chance for strong to severe storms will be later
on Sunday and Monday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will be needed tonight. Overnight wind and
hail reports would be appreciated.

LMZ643>646-161930-
Sheboygan to Port Washington WI-
Port Washington to North Point Light WI-
North Point Light to Wind Point WI-
Wind Point WI to Winthrop Harbor IL-
227 PM CDT Fri May 15 2026

This Hazardous Weather Outlook is for the nearshore waters from
Sheboygan Wisconsin to Winthrop Harbor Illinois.

.DAY ONE...Tonight

Small craft conditions this evening/tonight.

There is a chance of thunderstorms tonight.

.DAYS TWO THROUGH SEVEN...Saturday through Friday

There are chances for thunderstorms at times Saturday night
through Tuesday.

Periods of small craft conditions at times into early next week.

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-161930-
Lake Michigan Michigan City IN to St. Joseph MI 5 NM offshore to
mid-line of lake.-
Lake Michigan from Seul Choix Point to Rock Island Passage 5NM
offshore to Mid Lake-
Lake Michigan South of a line from Seul Choix Point to the
Mackinac Bridge and North of a line from Charlevoix MI to South
Fox Island 5NM offshore-
Lake Michigan from Charlevoix to Point Betsie MI 5NM Offshore to
mid lake-
Lake Michigan from Point Betsie to Manistee MI 5NM offshore to
Mid Lake-
Lake Michigan from Rock Island Passage to Sturgeon Bay WI 5NM
offshore to mid lake-
Lake Michigan from Sturgeon Bay to Two Rivers WI 5NM offshore to
Mid Lake-
Lake Michigan from Two Rivers to Sheboygan WI 5NM offshore to Mid
Lake-
Lake Michigan from Sheboygan to Port Washington WI 5NM offshore
to Mid Lake-
Lake Michigan from Port Washington to North Point Light WI 5NM
offshore to Mid Lake-
Lake Michigan from North Point Light to Wind Point WI 5NM
offshore to Mid Lake-
Lake Michigan from Wind Point WI to Winthrop Harbor IL 5NM
offshore to Mid Lake-
Lake Michigan from Winthrop Harbor to Wilmette Harbor IL 5NM
offshore to Mid Lake-
Lake Michigan from Wilmette Harbor to Michigan City in 5NM
offshore to Mid Lake-
Lake Michigan from Pentwater to Manistee MI 5NM offshore to Mid
Lake-
Lake Michigan from Whitehall to Pentwater MI 5NM offshore to Mid
Lake-
Lake Michigan from Grand Haven to Whitehall MI 5NM offshore to
Mid Lake-
Lake Michigan from Holland to Grand Haven MI 5NM offshore to Mid
Lake-
Lake Michigan from South Haven to Holland MI 5NM offshore to Mid
lake-
Lake Michigan from St Joseph to South Haven MI 5NM offshore to
Mid Lake-
227 PM CDT Fri May 15 2026

This Hazardous Weather Outlook is for the open waters of Lake Michigan.

.DAY ONE...Tonight

Southerly gales are expected for the northern third into tonight.
A Gale Warning remains in effect.

Thunderstorms are possible late tonight.

.DAYS TWO THROUGH SEVEN...Saturday through Friday

Gales may be possible again Monday and Tuesday.

There are chances for thunderstorms at times Saturday night into
early next week.

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