NWS-Milwaukee/Sullivan Forecast Discussion
FXUS63 KMKX 280032 AAA
AFDMKX
Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
732 PM CDT Mon Jul 27 2026
.KEY MESSAGES...
- Strong to severe thunderstorms ending this evening over south
central WI.
- Extreme Heat Warning in effect for south central Wisconsin
into early evening.
- High swim risk conditions are developing earlier (now) and
will continue into Wednesday morning along all Lake Michigan
beaches due to high waves and currents. A Beach Hazard
Statement is in effect.
&&
.UPDATE...
Issued 732 PM CDT Mon Jul 27 2026
Looking at surface observations, satellite and radar early this
evening, we have a few distinct boundaries. There is a wind
convergence zone along a line from Wisconsin Dells to Madison
to Janesville. Winds are southeast on the east side of it and
west- northwest on the west side. Then an area with lower
dewpoints (in the mid 60s) worked its way into far southwest WI
and is converging on that other wind boundary. Very warm and
moist air in the vicinity of this convergence zone is helping a
few showers and thunderstorms to pop up. The one we are
currently watching is right over and south of the Janesville
area. The environment is still very unstable within this zone
and severe is possible.
The other boundary to watch is the cold front. This is sliding
southward from northern WI and has north-northeast winds behind
it and falling dewpoints. There is a line of weak storms along
it and now they are just starting to interact with the wind
shift boundary that stretches into central WI. Expecting this
cluster of storms to slide southward. They may perk up at times,
but mid level dry air may start to get in their way of
strengthening much.
The other afternoon surprise is the steady south-southeast winds
that are persisting over the lakeshore after the last main
round of storms exited. These winds are at Small Craft Advisory
Levels and could build high waves of 3 to 5 feet quickly, so we
moved up the start time of the Beach Hazards Statement to 6 PM.
We may see a lull in the winds for a few hours, but then north-
northeast winds should push in on the cold front by late
evening and continue to build the high waves.
Cronce
&&
.SHORT TERM...
Issued 156 PM CDT Mon Jul 27 2026
Tonight through Tuesday night:
Much of the strong to severe convection will exit se WI late
this afternoon. Otherwise, low pressure around 1000 mb over
central WI will track sewd to the Lower Great Lakes by 09-12Z
Tue. Its cold front will pass late this afternoon and evening
but with only slight chances for showers and storms due to the
lack of upper dynamics and warm air aloft. The low and its
upper wave will then slow and occlude over the Mid Atlantic
States to New England through Thursday. Nly winds will cool high
temps to lower to middle 80s for Tue including much lower
relative humidity. A ridge of high pressure will then prevail
Tue nt-Thu AM with pleasant summer wx and high temps rising each
day in the 90s.
Gehring
&&
.LONG TERM...
Issued 156 PM CDT Mon Jul 27 2026
Thursday night through Monday:
Nwly flow aloft will prevail during this period with embedded
shortwave troughs. Shower and storm chances will rise to 50-60
percent for Fri-Sat. High temps in the 80s are expected each
day.
Gehring
&&
.AVIATION...
Issued 732 PM CDT Mon Jul 27 2026
Thunderstorms will continue to be possible in southern WI until
a cold front pushes in from the north during the late evening.
Not enough confidence to add a PROB30 at any TAF location at
this time. JVL has a thunderstorm near it due to the close
proximity of a wind direction (surface convergence) boundary.
Madison is also along this boundary, but may have more dry air
aloft to prevent storms.
A period of MVFR ceilings is possible during the early morning
hours in the wake of the cold front. This should be short-lived
and dry air will help to mix out the low clouds by mid-late
morning.
Cronce
&&
.MARINE...
Issued 732 PM Mon Jul 27 2026
There was an afternoon surprise with the steady south-southeast
winds that are persisting over the lakeshore after the last
main round of storms exited. These winds are at Small Craft
Advisory Levels and could build high waves of 3 to 5 feet
quickly, so we moved up the start time of the advisory. We may
see a lull in the winds for a few hours, but then north-
northeast winds should push in on the cold front by late evening
and continue to build the high waves.
Thunderstorms will continue to be possible over Lake Michigan
through late evening. Otherwise low pressure around 29.5 inches
over central Wisconsin will move to the lower Great Lakes for
Tuesday morning. Its cold front will move north to south across
Lake Michigan during the evening. Northerly winds are expected
to gust around 30 kt over central and southern Lake Michigan
tonight through Tuesday. Much lighter northerly winds are then
expected late Tuesday night into Wednesday as high pressure
around 30.0 inches builds into the northern Great Lakes. The
high will maintain light winds for Thursday and Friday as well.
Gehring/Cronce
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement...WIZ052-WIZ060-WIZ066-WIZ071-WIZ072
until 10 AM Wednesday.
LM...Small Craft Advisory...LMZ643-LMZ644 until 1 AM Wednesday.
Small Craft Advisory...LMZ645-LMZ646 until 7 AM Wednesday.
&&
$$
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