NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 211849
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
149 PM CDT Sat Jun 21 2025

.KEY MESSAGES...

- Hot and humid conditions are expected Today through Monday.
  Maximum heat indices of 100 to 105 degrees are forecast each
  day with higher heat indices between 105 and 110 expected
  through the Milwaukee Metro. An Extreme Heat Warning is in
  effect for Milwaukee, Racine, and Kenosha Counties, while
  everywhere else in southern WI is under a Heat Advisory

- High swim risk expected for Sheboygan and Ozaukee county
  beaches and moderate swim risk for Milwaukee, Racine, and
  Kenosha beaches Tuesday due to life threatening waves and
  dangerous currents, especially near breakwalls, river/creek
  inlets, and piers.

- Cold front arrives next Monday into Tuesday, but then lingers
  as a stationary boundary through much of next week. Multiple
  rounds of strong to severe storms will be possible over the
  week.

&&

.SHORT TERM...
Issued 149 PM CDT Sat Jun 21 2025

Tonight into Sunday Night:

Focus through tomorrow night continues to be on the heat. For
today, surface dew points didn't really mix at all and if
anything the moisture trapped under the inversion helped to
create a weak cu field. Dew points have climbed into the middle
70s with temps already into low to mid 90s leading to heat
indices in the low to mid 100s with the higher values in the
warning counties. With the strong southerly winds, beach hazards
remain dangerous in Sheboygan and Ozaukee counties with high
waves occurring there today.

Going into Sunday, it looks fairly similar to today with the
hot and humid air mass in place. Some subtle differences are
that the 850-700mb temperatures look to be a few degrees cooler
than today and the low level winds aren't quite as strong as
they are today. However, we'll be starting at a higher
temperature/moisture profile to start the day, so it shouldn't
take as long to get to the temps/dews we had today. Overall,
didn't see enough to change any headlines and will keep things
going as is.

Halbach

&&

.LONG TERM...
Issued 149 PM CDT Sat Jun 21 2025

Monday through Saturday:

Going into Monday, a cold front will approach southern Wisconsin
in the afternoon, which should allow for temperatures and dew
points to remain high throughout the day. The RAP/HRRR/NAM all
show a pocket of drier air advecting northeastward from the
south, which seems a bit odd considering the flow out of the
Gulf. This could lead to some lower heat indices, but will not
be changing anything since we still have heat indices going
above 100F. If this trend continues, could see where the warning
gets dropped down to an advisory after tomorrow night.

This environment ahead of the front will be highly unstable
with SBCAPE values reaching 3000 J/kg+. The wind shear profile
is unidirectional and fairly parallel to the front. The main
speed shear increase is in the lowest 0-3km, so perhaps there
could be some bowing clusters that develop and track to the
northeast ahead of the front, but overall mainly expect
multicell clusters with large hail/downbursts being the main
severe risk. The timing has been fairly consistent with the
front moving in during the late afternoon from the NW and
tracking through to the SE into the evening hours.

Beyond this, it gets a bit messy as the upper level flow goes
zonal and the boundary gets hung up somewhere in the Great Lakes
vicinity. Trying to pin down exactly when the chances for
storms/rain will occur will be difficult. Right now, my eye goes
to Thursday as there appears to be a deeper low pressure system
that develops and brings more widespread lift to the region.
Wherever the boundary sets up will be the focus for concern for
heavy rainfall or potential severe thunderstorms.

Halbach

&&

.AVIATION...
Issued 149 PM CDT Sat Jun 21 2025

The main concern through tomorrow is with the winds and low
level wind shear that will occur overnight. A locally broken cu
deck did develop this morning with ceilings dropping into the
2-3kft range briefly. Those bases have been increasing over the
past hour or so and are expected to diminish over the next few
hours. Peak wind gusts will be in the 28-34kt range this
afternoon before decoupling this evening. A Low Level Jet will
develop around 2kft toward midnight/5z which should hit 45kts.
Therefore, have left some LLWS in there for after 5z tonight as
wind gusts should subside. Winds started gusting around 12z this
morning and am expecting the same into tomorrow morning. Peak
gusts tomorrow should be slightly lower than what we're seeing
today in the 20-25kt range.

Halbach

&&

.MARINE...
Issued 149 PM CDT Sat Jun 21 2025

The main focus for higher winds and waves across the lake is
today into Sunday as a persistent southerly wind under a tight
pressure gradient helps to develop high waves from south to
north. Due to the cold water temperatures and the warm air
moving over the top of it, the amount of gusts mixing down
should be limited to just along the land/lake interaction in far
SW Lake Michigan near Chicago. These southerly winds should
continue into Monday before a cold front drops from north to
south across the lake. This front should get to the southern
shore of the lake early on Tuesday before potentially shifting
back northward over the next few days. With high pressure
pushing in from the north, winds should generally be on the
lighter side for much of next week.

Halbach

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement...WIZ052-WIZ060 until 10 PM Saturday.

     Heat Advisory...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056-WIZ057-
     WIZ058-WIZ059-WIZ060-WIZ062-WIZ063-WIZ064-WIZ065-WIZ067-
     WIZ068-WIZ069-WIZ070 until 7 PM Monday.

LM...Small Craft Advisory...LMZ643 until 4 AM Sunday.

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

&&

$$

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