NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 301146
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
646 AM CDT Tue Jun 30 2026

.KEY MESSAGES...

- Extreme Heat Warning in effect for all of southern WI today
  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 Wednesday night through Friday. An isolated storm during
  this period may become severe.

&&

.UPDATE...
Issued 646 AM CDT Tue Jun 30 2026

Some chances for showers and storms in central to southwestern
WI today, with a lingering EML/warm nose preventing the majority
of development. However, a high amount of CAPE (over 3000 J/kg)
is available for any storms that do punch through the EML. This
would require a strong forcing mechanism, which is currently
lacking. Right now, expecting any showers/storms to develop off
of outflow boundaries, so should remain generally cut off from
surface instability and sub-severe.

MH

&&

.SHORT TERM...
Issued 1142 PM CDT Mon Jun 29 2026

Tonight through Tuesday:

Low pressure around 991 mb continues to deepen over srn Manitoba
and will deepen to 985 mb over sw Manitoba by 12Z Tue as the
main upper wave swings nwd from the Dakotas. The initial squall
line ahead of the cold front in sw MN has mostly dissipated, but
there is shower development within the low level jet axis over
ne IA into west central WI but moving newd. Thus the night is
looking mainly dry but muggy for srn 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. The flow aloft then becomes more wswly for Wed nt-Thu
with a vorticity maximum in the flow. Less capping and high CAPE
will remain with 60-80 percent chances for showers and storms
mainly over south central WI with much lower chances toward MKE.
Some of these showers and storms could linger into Thu.

Gehring

&&

.LONG TERM...
Issued 1142 PM CDT Mon Jun 29 2026

Thursday night through Monday:

500 mb cluster analysis is generally showing positive anomalies
over and north of the western Great Lakes region Thursday night
into Saturday night, with a modest ridge remaining just east of
the region. There should still be west northwest flow over the
region during this time, with various 500 mb vorticity maxima
shifting through at times. At the surface, a stalled warm front
may remain over or near the area Thursday night into Friday,
lingering into Independence Day or Saturday night per ensemble
mean output from the ECE/GEFS.

The low level jet may pivot more over the area during this
period, helping to maintain warm, moist advection. This should
continue to support periodic rounds of showers and thunderstorms
Thursday night into Saturday night. Ensembles show most members
with measurable precipitation as well. Temperatures and heat index
values during this time will be highly dependent on clouds and
precipitation. Still, very warm and humid conditions are expected
to continue through this period and are supported by ensembles.

The 500 mb ridge axis should shift further east Sunday into
Monday, and may allow for high pressure to build in. This may
allow for some drier conditions to work into the area at times,
and chances for showers and storms may lower in later forecasts
if this trend continues. It will remain warm and humid during this
time.

Wood

&&

.AVIATION...
Issued 646 AM CDT Tue Jun 30 2026

VFR conditions are expected throughout today into Wednesday.
Southwesterly winds will become gusty at 20-25 kt by midday.
Winds will diminish to become steady at 10-12 kt overnight, with
LLWS around 40 kt developing across much of southern Wisconsin
during this timeframe. Winds will remain light around 10 kt and
LLWS will diminish into Wednesday morning.

MH

&&

.MARINE...
Issued 1142 PM CDT Mon Jun 29 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 Great Plains. Areas of dense fog may develop at
times this week due to a very humid airmass flowing over the
cooler waters of the lake. Scattered thunderstorms are forecast on
most days, especially over the north half.

Gehring

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

$$

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