Severe Thunderstorm Warning 129, NWS Milwaukee, WI

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
407 PM CDT Sat Aug 16 2025

.KEY MESSAGES...

- Area of storms moving into south central WI is anticipated to
  stall over southern WI this evening. This would enhance our
  risk of flash flooding. Additional storms are possible
  overnight into Sunday morning. Flash Flood Watch in effect
  until 10 AM.

- Multiple rounds of showers and thunderstorms are likely into
  early next week. Locally heavy rainfall is possible. There
  remains a lot of uncertainty with storm placement and timing
  over the next few days.

- The rain over the next few days could lead to river rises
  again, with the potential for a few locations to return to at
  least minor flood stage.

- Drying out and becoming less humid by mid to late next week.

&&

.SHORT TERM...
Issued 407 PM CDT Sat Aug 16 2025

Tonight and Sunday:

We are focused on our second round of convection moving into
south central WI now. These developed along some elevated warm
air advection and potentially assisted by a remnant MCV. Looking
at visible satellite, we can see a stationary boundary that is
over northern Iowa and stretches into southwest WI through
Grant and Iowa County. There are several outflow boundaries
associated with the ongoing convection, and they seem to be
meeting over Grant or Iowa county right now. This stationary
boundary probably translates eastward through Madison and
potentially West Bend. This line of storms moving into south
central WI is expected to become west-east oriented and slow
down as it starts to line up along that stationary boundary.
This seems like a glimpse of where our region of storms may
stall this evening.

The low level jet will ramp up this evening and point into this
stationary boundary. The lift from this feature is expected to
help regenerate showers and thunderstorms along the stalled
boundary. This is our region of concern for flash flooding.
There is still uncertainty in exactly where any flash flooding
will occur, as that type of convection is a very small scale
feature. However the current idea (and concern) is that it
would be within the I-94 corridor. However, if the boundary gets
shunted a bit from outflow, then I-90 and southwest, including
Madison, have a risk of that persistent convection overnight (a
third round).

While we are not trusting any convection allowing models due to
their poor track record lately, the 19Z HRRR and 18Z NAM Nest
develop storms late this evening along the boundary from
southern MN, northeast IA, and south central WI. This scenario
depicts what our thoughts are at this time. However, these
models want to race the line of storms into northern IL and I am
not sure how much I trust that idea.

Sunday weather continues to be uncertain. If a big complex of
storms diminishes right over southern WI late tonight, then it
will be a while before storms can re-develop. If the storms blow
through and we have a chance to get some sun on the northern
edge of the storm remnants over northeast portions of our
forecast area, then additional storm development would be
possible already Sunday morning.

Gusty northeast winds are expected to rush down Lake Michigan
Sunday morning and bring elevated waves to the nearshore and
beaches Sunday afternoon and evening. A Beach Hazards Statement
may be needed.

Cronce

&&

.LONG TERM...
Issued 407 PM CDT Sat Aug 16 2025

Monday through Saturday:

Another storm complex will be possible over central or southern
WI on Monday as a more robust shortwave trough tracks across
central MN. With a frontal boundary draped from west central WI
to southeast WI, we have will continue to be in a position for
another round of storms Monday afternoon into the evening. The
high precipitable water values of around 2 inches will continue
to sit over the area, the risk of heavy rain will continue. The
current flash flood watch may need to be extended or have a new
one issued.

It looks like high pressure will finally win over the Upper
Great Lakes area by Tuesday evening, which will end our chance
for storms. One caution to that idea is that a weak trough may
stall over the eastern Great Lakes and clip Lake Michigan (and
far southeast WI) with surprise showers and/or storms on
Wednesday. Thursday and Friday look quiet for southern WI.

Cronce

&&

.AVIATION...
Issued 407 PM CDT Sat Aug 16 2025

Another round of storms is pushing into south central WI late
this afternoon may produce severe winds. This line is expected
to stall over southern WI this evening.

MVFR ceilings are expected with areas of convection through late
evening, and then IFR ceilings become more likely for east
central and portions of southeast WI Sunday morning. Improvement
is expected through Sunday afternoon, although more storms are
possible.

Cronce

&&

.MARINE...
Issued 407 PM CDT Sat Aug 16 2025

The risk for thunderstorms will be in place along a stationary
boundary that is draped across central and southern WI through
at least Monday. Gusty winds are the main threat.

A period of gusty north-northeast winds in the wake of a cold
front dropping down Lake Michigan late tonight through Sunday
morning will produce high waves. A Small Craft Advisory will
likely be needed.

Cronce

&&

.HYDROLOGY...
Issued 407 PM CDT Fri Aug 15 2025

There is a flash flood risk this afternoon through Sunday
morning due to repeated rounds of heavy rain. A Flash Flood
Watch is in effect until 10 AM.

One Flood Warning and one Flood Watch remain in effect in the
Milwaukee metro area, in the wake of the heavy rainfall this
past weekend.

The Lower Fox River at Waukesha remains in minor flood stage at
this time, but will continue to decrease in stage height. It
may remain in flood stage until at least early Sunday morning.

The Fox River at New Munster may reach minor flood stage early
next week, and is being monitored with a Flood Watch.

Ponding of water in areas immediately near each river segment
will remain possible until each can fall below flood stage by
later this week. Continue to heed any road closures in all
impacted areas until river stages recede further and Flood
Warnings are allowed to expire.

There is potential for localized heavy rainfall again this
afternoon through Monday, and area rivers (particularly in the
Milwaukee metro area and surrounding counties) will be monitored
for potential rises.

Cronce

&&

.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 10 AM Sunday.

LM...None.
&&

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Hazardous Weather Outlook
National Weather Service Milwaukee/Sullivan WI
317 PM CDT Sat Aug 16 2025

WIZ046-047-051-052-056>060-062>072-172030-
Marquette-Green Lake-Fond du Lac-Sheboygan-Sauk-Columbia-Dodge-
Washington-Ozaukee-Iowa-Dane-Jefferson-Waukesha-Milwaukee-
Lafayette-Green-Rock-Walworth-Racine-Kenosha-
317 PM CDT Sat Aug 16 2025

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

.DAY ONE...Tonight

The Fox River in Waukesha will remain above flood stage.

There are chances for thunderstorms through tonight with the main
risk being gusty winds, hail, heavy rain and the possibility for
flash flooding.

.DAYS TWO THROUGH SEVEN...Sunday through Saturday

The Fox River in Waukesha will remain above flood stage until at
least early Sunday morning.

There will be continued chances for thunderstorms through the
first half of next week. Locally heavy rainfall is possible,
particularly in locations experiencing repeated rounds of storms.

.SPOTTER INFORMATION STATEMENT...

CoCoRAHS rainfall reports will be appreciated through next week.

LMZ643>646-172030-
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-
317 PM CDT Sat Aug 16 2025

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

.DAY ONE...Tonight

There are chances for thunderstorms through the overnight hours.
Gusty winds are the main hazards.

.DAYS TWO THROUGH SEVEN...Sunday through Saturday

There will be continued chances for thunderstorms through the
first half of next week.

Gusty northeast winds in the wake of a front Sunday morning will
produce high waves through Sunday evening.

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-172030-
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-
317 PM CDT Sat Aug 16 2025

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

.DAY ONE...Tonight

There are chances for thunderstorms into the overnight hours.
Gusty winds are the main hazards.

.DAYS TWO THROUGH SEVEN...Sunday through Saturday

There will be continued chances for thunderstorms through the
first half of next week.

A wind shift to the northeast will contain gusts up to 30 kt and
building waves in the wake of a cold front on Sunday.

MRC

www.weather.gov/mkx

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