NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 181054 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
554 AM CDT Thu Jun 18 2026

.KEY MESSAGES...

- Isolated to scattered thunderstorms are possible late this
  afternoon and evening and again Friday evening.

- Additional shower chances return on Sunday (40-60%).

&&

.UPDATE...
Issued 554 AM CDT Thu Jun 18 2026

Lingering light showers along and behind a frontal boundary will
wind down early this morning, with dry weather expected mid-
morning through at least early afternoon. Should be enough
clearing this afternoon for some instability to build.
Maintained the 20-30 percent chances for showers and storms late
afternoon into the evening.

DDV

&&

.SHORT TERM...
Issued 1145 PM CDT Wed Jun 17 2026

Rest of Tonight through Friday:

Low pressure will continue to track east across the central
portions of Lake Michigan overnight and into far eastern
Ontario and Quebec Thursday morning. This will allow for low
clouds to persist overnight through the early morning hours
before lifting after daybreak. Clouds will insulate temps and
looking at lows for early morning to hold in the mid 50s.

For thursday expect northwest to westerly winds on the backside
of the departing low. Expect lingering cloud cover and temps
only climbing into the lower 70s. May see a few isolated to
squattered showers on the backside of the low as a mid-level
shortwave trough swings through the area paired with a 30 knot
LLJ later Thursday afternoon/early evening. Overall not
expecting much from this activity other than a few sporadic
rumbles of thunder and light showers. Also cannot completely
rule out some small graupel and brief gusts of wind, but overall
strong storm chances remain on the low side.

Friday will see lighter winds and slightly warmer temps during
the day with mid to upper 70s highs as high pressure works its
way across the region. Then looking at another mid-level
shortwave trough to traverse across the Upper Midwest later
Friday bringing a slug of moisture and PWATs increasing to
around and above 1 inch. Thus looking at another potential for
some showers across southern WI. Some of the mid-ranghe models
hint at 200-900 J/kg of MUCAPE to works its way across the CWA
during this time, thus a few rumbles of thunder will be possible
as well with this activity Friday evening and diminishing
overnight.

Wagner

&&

.LONG TERM...
Issued 1145 PM CDT Wed Jun 17 2026

Saturday through Wednesday:

Weak cold advection will be ongoing on Sat in the wake of weak
low pressure and a shortwave trough. 500 mb height rises and a
weak sfc ridge will then take hold later in the day and Sat nt.
Slightly below normal temps are forecast.

A shortwave trough and low pressure area is then expected to track
from IA/MO across the nrn Ohio Valley Sun-Sun nt. There is uncertainty
on the track and how far north the rain shield will spread. At
this time 30 percent chances for rain is forecast toward central
WI increasing to 60 percent over far srn WI. Thunderstorms are not
forecast at this time. The rain may linger into Sun nt.

Shortwave ridging aloft along with sfc ridging will then prevail
for Mon into Tue with pleasant summer high temps remaining in the
70s. A shortwave trough will then approach from the northwest for
Tue nt-Wed. There also is uncertainty on the strength and timing
of this upper wave. 30-50 percent chances for showers are
forecast at this time along with small chances for storms.

Gehring

&&

.AVIATION...
Issued 554 AM CDT Thu Jun 18 2026

Lingering light showers along and behind a frontal boundary
will wind down early this morning, with dry weather expected
mid- morning through at least early afternoon. Should be enough
clearing this afternoon for some instability to build.
Maintained the 20-30 percent chances for showers and storms late
afternoon into the evening.

Conditions should return to VFR by late morning given daytime
mixing resulting in higher cloud bases and general clearing of
expected cloud cover. Mostly clear skies are then expected
tonight into Friday, with another round of shower and storm
chances in the late afternoon and evening.

DDV

&&

.MARINE...
Issued 1145 PM CDT Wed Jun 17 2026

Low pressure will track across central portions of the lake
tonight. With the tight pressure gradient will see gusty
northeast to northerly winds across the northern third of the
lake and gusty southwest to west winds for the southern third.
Occasional gusts up to 30 knots possible, especially for the
southern portions of the lake. Then as the low pressure exits
into Michigan early Thursday morning, expect all winds to shift
to the northwest and diminish gradually through the day. Winds
remain light and northwesterly through Friday as high pressure
progresses southeastward into the Lower Mississippi Valley.
Winds may briefly turn southwesterly Friday night as weak low
pressure moves through the region, but high pressure will
rapidly regain dominance by Saturday, keeping winds light and
variable. Stronger low pressure will approach from the central
Plains on Sunday, bringing more widespread rain and thunderstorms
and turning winds to northeasterly, which will continue into
early next week.

Wagner

&&

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

$$

Visit us at weather.gov/milwaukee

Follow us on Facebook, X, and YouTube at:
www.facebook.com/NWSMilwaukee
www.x.com/NWSMilwaukee
www.youtube.com/NWSMilwaukee