Severe Thunderstorm Warning 72, NWS Milwaukee, WI

236 
WWUS53 KMKX 171957
SVSMKX

Severe Weather Statement
National Weather Service Milwaukee/Sullivan WI
257 PM CDT Fri Apr 17 2026

WIC111-172030-
/O.CON.KMKX.SV.W.0072.000000T0000Z-260417T2030Z/
Sauk WI-
257 PM CDT Fri Apr 17 2026

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 330 PM CDT
FOR NORTHWESTERN SAUK COUNTY...

At 257 PM CDT, a severe thunderstorm was located 7 miles south of
Wonewoc, or 10 miles west of Reedsburg, moving northeast at 40 mph.

HAZARD...Two inch hail and 60 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...People and animals outdoors will be injured. Expect hail 
         damage to roofs, siding, windows, and vehicles. Expect wind 
         damage to roofs, siding, and trees.

Locations impacted include...
Reedsburg, La Valle, Ironton, Lime Ridge, and Hill Point.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Tornado Watch remains in effect until 800 PM CDT for south central
Wisconsin.

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4364 8983 4335 9019 4355 9019 4356 9020
      4356 9031 4364 9031
TIME...MOT...LOC 1957Z 213DEG 36KT 4354 9020 

TORNADO...POSSIBLE
THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...2.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

WAGNER

509 
WWUS53 KMKX 172026
SVSMKX

Severe Weather Statement
National Weather Service Milwaukee/Sullivan WI
326 PM CDT Fri Apr 17 2026

WIC111-172035-
/O.EXP.KMKX.SV.W.0072.000000T0000Z-260417T2030Z/
Sauk WI-
326 PM CDT Fri Apr 17 2026

...THE SEVERE THUNDERSTORM WARNING FOR NORTHWESTERN SAUK COUNTY WILL
EXPIRE AT 330 PM CDT...

The storm which prompted the warning has weakened below severe
limits, and has exited the warned area. Therefore, the warning will
be allowed to expire.

A Tornado Watch remains in effect until 800 PM CDT for south central
Wisconsin.

&&

LAT...LON 4364 8983 4335 9019 4355 9019 4356 9020
      4356 9031 4364 9031
TIME...MOT...LOC 2025Z 213DEG 36KT 4377 8999 

$$

HEEREN

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
244 PM CDT Fri Apr 17 2026

.KEY MESSAGES...

- Thunderstorms with higher-end severe potential and heavy
  rainfall is expected this afternoon and early evening. An
  Enhanced Risk (3 out of 5) for severe weather exists over the
  western half of the CWA. Heavy rain over saturated ground may
  lead to flash flooding.

- A Flood Watch in effect for all of southern Wisconsin until
  7am Saturday.

- Marine Dense Fog continues through tonight.

&&

.UPDATE...
Issued 244 PM CDT Fri Apr 17 2026

The storms fired along that leading cumulus field that was in
eastern Iowa right around noon. They grew and evolved into a
broken line of supercells and are now tracking a little slower
to the east. The MLCAPE is on the 2000-2500j/kg gradient and the
bulk shear is 40 to 50kt. The significant tornado parameter is
pushing 4 in this region, and the sig hail parameter is 3. These
parameters diminish as the cells congeal into a line over the
next few hours, but wind and line-embedded tornadoes will become
a higher risk.

Radar and satellite are also showing the cold frontal boundary
(just north of Twin Cities to Rochester to just east of Des
Moines) light up with numerous mini supercells. If this initial
round of storms take control for the afternoon, which they are
expected to, this will diminish the intensity of the storms
along the cold front as it tracks across southern WI during the
early evening between 6 and 9 PM. However, if this first round
underperforms, meaning does not produce widespread thunderstorms
(and a cold pool), then the storms along the frontal boundary
will be able to maintain its strength as it moves through.

The other scenario noted in the most recent small-scale model
runs is that the storms along the frontal boundary may
accelerate and catch up to this initial round. The way things
are moving, this seems like a likely scenario. The 18Z HRRR is
hinting at this. This would mean the convection would rush out
ahead of the main front and there will still be a chance for
showers and isolated thunder to linger until that front clears
our area during the overnight hours.

Heavy rain and flash flooding are still a threat due to high
precipitable water and repeated rounds of storms over already-
saturated soil.

Cronce

&&

.SHORT TERM...
Issued 1207 PM CDT Fri Apr 17 2026

Tonight and Saturday:

Nearly all of southern WI has sunshine as of 1130 this morning.
The fog and low stratus are hanging on over east central WI, but
the increasing southerly winds will help that to erode quickly
through the early afternoon. Temperatures are rising quickly,
with areas west of Madison already in the lower 70s. Dewpoints
are rising as well, with lower 60s in the southwest. Gusty winds
are developing as we start to mix out our low layer inversion
and diurnal cu are also popping up. This is all conducive for
priming our environment for convection this afternoon.

The main change for today is that we are expecting storms to
develop and move into southwest WI earlier than forecast, now
between 1 and 5 PM. Storms triggered along a gravity wave just
south of the Twin Cities around 8 am. If we trace that gravity
wave down into Iowa on satellite, the cumulus clouds are
focusing along it. The leading edge of this is now entering
northeast IA and far southeast MN. The timing of it to arrive
in Madison is 230PM/1930Z, give or take a half hour. There is no
lighting in eastern IA yet, but we are watching for that to
happen within the next 30 to 60 minutes.

Whatever develops in IA and tracks eastward is our main show in
southern WI for today. All hazards are on the table. High CAPE,
shear and helicity all point to a large hail (greater than 2
inches), damaging wind and tornado potential. If tornadoes
develop, they would be on the strong side. As any discrete cells
congeal into a line as they head into eastern WI, the severe
threat will be mainly for damaging wind and QLCS tornadoes. With
0 to 3 km shear vectors up to 50 kt and aligned perpendicular
to the line of storms (and streamwise vorticity of 45-50 kt),
brief spin- up tornadoes are favorable along the leading edge
within any notches/bowing line segments.

There is still a chance that the storms that develop in Iowa
could skirt just to the south of WI and be the strongest across
northern IL this afternoon. If I had to guess, the strongest
storms should be over the south half of southern WI. However,
there is still a severe threat for all of WI, including north
central all the way to Green Bay.

The actual cold front is back in south central MN and central
IA. This is a very strong front, with over a 20 degree temp drop
behind it. Storms will be well ahead of the front, but once our
afternoon storms clear, we will still have a chance for
scattered showers and thunderstorms (not severe) until the
actual front passes during the late evening and overnight hours.

Cronce

&&

.LONG TERM...
Issued 244 PM CDT Fri Apr 17 2026

Saturday through Friday:

Gusty west-northwest winds up to 30 mph are expected behind the
cold front Saturday. Sunshine should be prevalent, although
cyclonic flow aloft will allow for some high-level diurnal
cumulus clouds. Saturday highs will only be in the 40s, a stark
contrast to the highs today. Lows Saturday night should dip
below freezing nearly everywhere except the immediate Lake
Michigan lakeshore.

The upper low will remain over Ontario Sunday and a shortwave
trough digging into central and southern WI may steepen lapse
rates enough to produce a few flurries. It looks like moisture
will be very limited with this feature, but the forcing is
certainly there. Highs Sunday will be similar to Saturday but
with slightly lighter northwest winds. Lows Sunday night have a
better chance of dropping below freezing, with lows forecast in
the 25 to 30 degree range.

As high pressure departs the Upper Great Lakes on Monday,
southerly winds will usher milder air back into southern WI.
The sunshine will also help temps get into the mid 50s inland
and lower 50s near the lakeshore. A clipper system will cross
Ontario and Lake Superior Monday night, but southern WI will
remain dry. However, this could push a cold front down Lake
Michigan Tuesday. Not all models have picked up on this
potential yet, so the forecast highs Tue are in the lower 70s
inland and mid 60s lakeshore. Lakeshore temps could end up being
colder, but the highs will depend on when that back door cold
front actually makes it onshore.

There will be a stark temp gradient across southern WI from
west to east on Wednesday as low pressure develops in the
Plains. It looks like the storms associated with the warm front
of this low will be over northeast MN and northern WI Thu. All
We should see temps get back into the upper 70s inland over
southern WI. The next potential for showers and thunderstorms,
potentially severe, looks like next week Friday.

Cronce

&&

.AVIATION...
Issued 1207 PM CDT Fri Apr 17 2026

See the main part of the discussion for thunderstorm chances.
Timing of the storms for southern WI looks earlier than
previously forecast. All severe hazards are possible.

A strong cold front will cross southern WI late tonight. Showers
and a few storms will remain possible until the front clears.
MVFR ceilings are expected behind the front on gusty WNW winds,
and IFR ceilings are possible for a few hours early Saturday
morning. Saturday ceilings should recover to VFR by mid/late
morning and probably scatter out.

Cronce

&&

.MARINE...
Issued 1207 PM CDT Fri Apr 17 2026

Winds will become southerly this morning as a surface low of 29.5
inches approaches from the central plains. Dense fog will
continue over the lake through this evening and likely during
the overnight hours until the cold front clears the lake. This
surface low will quickly move from Omaha to Duluth from this
morning into the afternoon. Winds will become gusty and
southeasterly tonight, and strong to severe storms will cross
the lake as a cold front sweeps through the area. Winds then
become northwesterly behind the cold front Saturday morning.
Breezy northwesterly winds then continue Saturday through Sunday
as the low then races northeast toward Hudson Bay. Winds ease
Monday morning as high pressure tracks southeast over the upper
Great Lakes.

Cronce

&&

.HYDROLOGY...
Issued 1207 PM CDT Fri Apr 17 2026

This afternoon / evening's convection is expected to produce an
additional 0.50 to 1.25 inches of rainfall across the region,
with locally higher totals up to 2.00 inches possible. Probs of
exceeding 2.00 are only 10% or less based off of most guidance.
Highest rainfall potential exists in the western half of the
CWA, given the potential for initial supercells with heavy rain
followed by additional showers / storms along the advancing cold
front (eg. multiple rounds of heavier precip). Further east,
still expecting a good burst of heavy rain from short line
segments or QLCS to be more progressive / fast- moving by that
time of day, but increased the storm total amounts toward an
inch.

Cronce/Sheppard

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Flood Watch...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056-WIZ057-WIZ058-
     WIZ059-WIZ060-WIZ062-WIZ063-WIZ064-WIZ065-WIZ066-WIZ067-
     WIZ068-WIZ069-WIZ070-WIZ071-WIZ072 until 7 AM Saturday.

LM...Dense Fog Advisory...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-
     LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 until 4 AM
     Saturday.

     Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 10 PM
     Saturday.

&&

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Hazardous Weather Outlook
National Weather Service Milwaukee/Sullivan WI
108 AM CDT Fri Apr 17 2026

WIZ046-047-051-052-056>060-062>072-180615-
Marquette-Green Lake-Fond du Lac-Sheboygan-Sauk-Columbia-Dodge-
Washington-Ozaukee-Iowa-Dane-Jefferson-Waukesha-Milwaukee-
Lafayette-Green-Rock-Walworth-Racine-Kenosha-
108 AM CDT Fri Apr 17 2026

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

.DAY ONE...Today and Tonight

Dense fog this morning. Dense Fog Advisory in effect and may need
further expansion. Marine Dense Fog continues through today.

A Flood Watch is out for all of southern Wisconsin from 1pm
today to 7am Saturday for more heavy rain this afternoon and
evening.

Another round of heavy rainfall, flooding, and severe
thunderstorms is expected this afternoon into tonight. An
Enhanced Risk (3 out of 5) for severe weather exists over the
western half of the CWA.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter reports of flooding this morning are appreciated. Spotter
activation will be needed again on Friday for severe weather.

LMZ643>646-180615-
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-
108 AM CDT Fri Apr 17 2026

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

.DAY ONE...Today and Tonight

Dense fog continues for the whole nearhsore through today
possibly into tonight.

Small Craft Advisory in effect at noon today for high waves and
strong southerly winds

Chances for thunderstorms return for today, with some strong to
severe storms possible for the evening.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Small Craft Advisory will continue through Saturday for breezy
west to northwest winds.

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-180615-
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-
108 AM CDT Fri Apr 17 2026

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

.DAY ONE...Today and Tonight

Dense fog continues through today possible lingering through tonight.

Chances for thunderstorms return for today, with some strong to
severe storms possible for the evening.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

No hazardous weather is expected at this time.

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