New Berlin, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

479
FXUS63 KMKX 300115
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
815 PM CDT Mon Jun 29 2026

.KEY MESSAGES...

- Extreme Heat Warning in effect for all of southern WI tonight
  through Wednesday. 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 Tuesday night through the end of
  the week as the hot and humid pattern continues.

- High swim risk conditions for Ozaukee and Sheboygan County
  beaches this evening, with moderate swim risk conditions for
  Milwaukee and Racine Counties.


&&

.UPDATE...
Issued 815 PM CDT Mon Jun 29 2026

Convective initiation is occurring near the cold front over the
ern Dakotas into ne NE early this evening. The associated low
pressure area of 995 mb over ern ND will deepen to 985 mb over
sw Manitoba by 12Z Tue as the main upper wave swings nwd from
the Dakotas. Thus the cold front will weaken as it lifts newd
from wrn MN into ne MN. The 850-300 mb flow remains swly tnt
over said region, while the forward propagating corfidi vectors
have a sswly flow. Thus expect any MCSs to track newd through
MN toward nw WI. Otherwise sswly sfc winds will maintain a hot
and humid airmass over srn WI into Tue and Wed. The Extreme
Heat Warning is in effect through Wed at this time.

Showers and storm chances of 20-40 percent are forecast Tue nt
along and west of a line from Darlington to Madison to Sheboygan
then shifting even farther toward central WI on Wed as the main
shortwave track runs from the central Great Plains to MN and
nrn WI.

Gehring

&&

.SHORT TERM...
Issued 247 PM CDT Mon Jun 29 2026

Tonight through Wednesday:

Hot and humid is the name of the game through the first half of
the week as the upper-level ridge is set up over the Midwest
with a blocking high over the southeastern CONUS. Extreme Heat
Warning has been extended through at least Wednesday at this
point given the prolonged nature of daytime heat indices
expected to rise above 100F each afternoon and overnight heat
indices in the upper 70s. Areas immediately along the lakeshore
of Lake Michigan along with any onshore wind component may be
cooler by a few degrees, but still will see impacts from the
heat/humidity regardless. Even with cloud cover lingering this
afternoon, we are seeing heat indices above 100F and even higher
with pockets of clearing and dewpoints running warmer than
models suggested. Thus, have higher confidence of seeing similar
heat indices Tuesday into Wednesday.

While the hot and humid conditions are the main story, these
conditions are also favorable ingredients for thunderstorm
activity. It will not take much to trigger a storm or two to
develop with these conditions, however, it needs a trigger to
initiate development and tap into the moisture and instability
settled across the region. Each CAM has a different solution and
potential trigger for any activity overnight and Tuesday, but
its tough to pinpoint if and what type of trigger would be. The
12z NAM nest, and ARW have convection upstream be the focus for
some showers and storms to develop overnight and track across
and north of the area, with the RRFS being more aggressive with
deeper develop more into Tuesday off of something coming off
the storms that may develop in the Plains tonight (which seems
most unlikely scenario, but not impossible). Meanwhile the HRRR
and NSSL keep us dry and any convection to the north. So while
potential is there and cannot rule out seeing a few storms
trigger along remnant boundaries or a gravity wave from upstream
storms, the influence and subsidence from the ridge may
ultimately limit any of this activity Tuesday, but Wednesday
might have better potential as the ridge axis shift further east
and upper- level jet influence creeps toward our western CWA.
Nevertheless, it does bear watching the mesoscale trends and how
the environment evolves overnight through Tuesday.

Wagner

&&

.LONG TERM...
Issued 247 PM CDT Mon Jun 29 2026

Wednesday night through Monday:

Hot and humid conditions persist into the second half of the
week with additional heat headlines possible given persisting
+100F heat indices. However, pattern remains more uncertain as
the ridge axis slide further east and potential for daily shower
and thunderstorm chances increase. Models hint at a bit more
upper-level support in the form of mid-level vorticity lobes
overrunning the ridge along with LLJ and upper-level jet
moving more in place. Thus, could see the extreme heat pattern
break down a bit into the holiday weekend. Nevertheless, still
looking at above normal temps and muggy conditions accompanying
the daily storm chances for the end of the week.

Wagner

&&

.AVIATION...
Issued 815 PM CDT Mon Jun 29 2026

Sct035-045 cumulus or stratocumulus will continue tnt-Wed with
areas of broken cloud cover possible at times.

Gehring

&&

.MARINE...
Issued 247 PM CDT Mon Jun 29 2026

Southerly winds will continue this afternoon into the evening
but gradually shift southwesterly. Given the humid airmass and
cooler airmass will be potential for fog over Lake at times,
particularly the northwestern quadrant of the Lake along
northeastern WI to mid lake. Otherwise, with low pressure
developing over the Plains and high pressure lingering over the
Southeast US, expect breezy conditions to continue through much
of the week. The hot and humid airmass settled over the region
will also bring daily thunderstorms chances to portions of the
lake through the end of the week.

Wagner

&&

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

LM...Dense Fog Advisory...LMZ563 until 7 AM Tuesday.

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

&&

$$

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