NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 131757
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1257 PM CDT Mon Jul 13 2026

.KEY MESSAGES...

- Hot and modestly humid conditions are expected through most of
  the week. Expect highs in the 90s. Heat indices may reach 100
  at times, with a Heat Advisory in effect for Tuesday and
  Wednesday.

- Dry weather is expected through at least Thursday, with
  thunderstorm chances returning late in the week.

&&

.SHORT TERM...
Issued 1257 PM CDT Mon Jul 13 2026

Tonight through Wednesday:

Mostly clear skies will continue tonight into Tuesday, outside
of scattered high clouds at times. Patchy river valley fog is
likely again later tonight into early Tuesday under the clear
skies and light winds.

A strong upper level ridge across the region will largely
remain in place through at least mid-week. Surface high pressure
will be overhead through Tuesday as well, weakening a bit
Wednesday as low pressure passes by well to the northeast. The
expected hot stretch of highs in the 90s is still on track under
this ridging pattern.

Dewpoints and resultant head indices continue to be the forecast
focus for the next few days, as it will be a battle between
afternoon mixing lowering dewpoints and moisture from maturing
crops potentially bumping dewpoints up a bit. Over the last
couple days, dewpoints have trended toward the lower end of
model guidance, but seem to be more toward the middle of
solutions so far today. There does seem to be a consistent
signal that dewpoints will creep up over the next couple days
along with increasing high temps under 925 mb temps of 27-30 C.
If dewpoints end up higher into the low 70s, then heat indices
should easily reach or eclipse the 100 degree mark. If dewpoints
are lower, then temps may wind up a bit higher into the mid to
upper 90s. Either way, it looks plenty hot enough to warrant a
Heat Advisory for the entire forecast area Tue through Wed.

Westerly winds Tuesday should be strong enough to largely keep
the lake breeze offshore. There is increasing confidence that
the lake breeze will move inland Wednesday though, as the
prevailing winds become lighter out of the northwest. This could
provide some relief to the heat mid to late afternoon in the
east.

DDV

&&

.LONG TERM...
Issued 1257 PM CDT Mon Jul 13 2026

Thursday through Monday:

Southern Wisconsin is expected to stay under enough of an
influence of the upper ridge to maintain hot temps through
Friday. There will be a push of higher precipitable water values
from the south Thu/Fri though, which could open the window for
showers/storm chances if the deeper moisture gets into southern
Wisconsin. The majority of solutions are dry through Thursday,
so held off on low end precip chances until Friday. The
flattening upper ridge Friday could allow a weak wave to slide
through and interact with the increasing moisture for a few
storms. The latest ECMWF is slower to transition from a ridging
to troughing pattern than the GFS and Canadian and would be
mainly dry through Friday, so some uncertainty remains with
precip chances. Highs of 90+ are expected to linger through
Friday, especially if the ECMWF solution verifies.

By the weekend, there is pretty good agreement among models that
a troughing pattern will open the door to multiple rounds of
shower/storm chances Sat through Mon. Temps will cool a bit as
well, returning to near normal by Monday.

DDV

&&

.AVIATION...
Issued 1257 PM CDT Mon Jul 13 2026

Patchy river valley fog will be possible again tonight.
Otherwise, VFR conditions will persist through Tuesday. Outside
of scattered high clouds at times, mostly clear skies will
continue through Tuesday. Westerly winds of 5-10 knots today and
Tuesday may be strong enough to keep the lake breeze confined
to lakeshore areas. Will continue monitor marine observations
and radar for the lake breeze development and potential impact
on eastern airports.

&&

.MARINE...
Issued 1257 PM CDT Mon Jul 13 2026

High pressure of 30.2 inches over the Great Lakes region will
maintain an axis roughly from northern Iowa to southern Lower
Michigan through today and then sink into Illinois and Indiana
Tuesday and Wednesday while weakening to 30.1 inches. Low
pressure around 29.7 inches will approach from the Northern
Plains Thursday into Friday. Winds will become south-
southwesterly for today and Tuesday. A weak cold front will
bring a wind shift to the north- northeast Wednesday into
Thursday.

DDV

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Heat Advisory...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056-WIZ057-
     WIZ058-WIZ059-WIZ060-WIZ062-WIZ063-WIZ064-WIZ065-WIZ066-
     WIZ067-WIZ068-WIZ069-WIZ070-WIZ071-WIZ072...noon Tuesday
     to 8 PM Wednesday.

LM...None.
&&

$$

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