NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 302023
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
323 PM CDT Tue Jun 30 2026

.KEY MESSAGES...

- Extreme Heat Warning in effect for all of southern WI tonight
  through Wednesday evening. Additional heat headlines may be
  needed for the second half of the week, but some uncertainty
  remains due to clouds and rain chances.

- Thunderstorm chances return this evening through the end of
  the week as the hot and humid pattern continues. Best chances
  are tonight (mainly north of a line from Lone Rock to Fond du
  Lac), through Friday on a more areawide basis. Strong to
  severe storms may occur at times.

&&

.SHORT TERM...
Issued 255 PM CDT Tue Jun 30 2026

Tonight through Wednesday night:

Hot and humid conditions continue into tonight with heat index
values remaining in the 100 to 105 range. Tonight, heat will
remain a concern, as overnight lows will only drop into the mid
to upper 70s.

The ridge held fast through today keeping storm activity north
of the area, but tonight, models depict some storm activity over
central increasing through the overnight hours as the
environment uncaps and the LLJ kicks off convection. Storm
motion vectors would carry any storms over central WI to the
northeast sparing most of the area, but areas north of a line
from Lone Rock to Fond du Lac may see a glancing blow from
thunderstorm activity. Given the steep mid level lapse rates,
large hail may occur with any storms, and there may be some wet
microburst potential give the high PWATs and low shear. This
activity would move through just before and just after dawn on
Wednesday.

After morning thunderstorm activity, more hot and humid
conditions are expected with highs in the low to mid 90s, with
heat indices above 100.

CMiller

&&

.LONG TERM...
Issued 256 CDT Tue Jun 30 2026

Thursday through Tuesday:

The upper level ridge begins to flatten Thursday allowing more
thunderstorm activity into the area. There looks to be some
potential for a morning round, followed by a late afternoon and
evening round. The latter round may feature more of the severe
threat, given the potential for instability to build through
Thursday.

Beyond, the ridge sinks southward, allowing a more favorable
band of flow aloft to pass over the area into the weekend. Daily
thunderstorm chances look possible, but each days chances will
be highly dependent upon where the previous day's rounds of
storms force an outflow boundary to flow and act as a storm
trigger. As such a high amount of uncertainty will linger into
the 4th of July weekend regarding storm timing/position.

Hot and humid conditions will linger through Friday. with highs
near or into the 90s. Temps "cool" this weekend with highs in
the 80s, but dewpoints will remain elevated into next week,
prolonging the mugginess.

CMiller

&&

.AVIATION...
Issued 253 PM CDT Tue Jun 30 2026

Breezy southwest winds continue this afternoon amid a mixture of
MVFR cigs and SCT to CLR skycon in some spots. Cumulus clouds
and wind will linger until sunset, when daytime mixing subsides.

Overnight, thunderstorms activity may for over west central WI,
adding high cirrus to the skies. Storms are mainly expected to
stay north of a line from KLNR to KFLD tonight into early
Wednesday.

Storms are expected to move off by late Wed morning and then a
similar mix of VFR and MVFR conditions may take hold again
tomorrow afternoon.

CMiller

&&

.MARINE...
Issued 245 AM CDT Tue Jun 30 2026

Modest to breezy southerly winds will prevail into Thursday then
lighter into Friday as high pressure remains to the southeast
of the Great Lakes, while troughs of low pressure continue over
Canada into the northern Great Plains. Scattered thunderstorms
are forecast across the northern half tonight through Wednesday
night, and across the southern two thirds Thursday into Friday,
and across the whole lake Friday into Saturday as a cold front
shifts winds to northerly. Patchy marine fog will be possible at
times, primarily over the northern half of the lake, as a warm
moist air mass moves over the lake.

CMiller

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 10 PM
     Tuesday.

&&

$$

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