NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 181151
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
651 AM CDT Mon May 18 2026

.KEY MESSAGES...

- Some weak pulse thunderstorms are possible this morning.

- Another round of showers and storms late tonight into Tuesday
  with a potential for strong to severe storms.

- Cool and drier weather then returns for midweek.


&&

.UPDATE...
Issued 643 AM CDT Mon May 18 2026

A few thunderstorms have popped up this morning over south
central to southeast Wisconsin, riding some of the better low to
mid level warm advection from an LLJ into the area. These storms
should be fairly pulse like, having quick spikes in intensity,
following by core collapses. Sub-severe hail and gusty winds, as
well as lightning will be the main hazards.

CMiller

&&

.SHORT TERM...
Issued 1200 AM CDT Mon May 18 2026

Today through Tuesday:

The nrn portion of the QLCS over ne IA and se MN has recently
produced severe wind gusts but gradual weakening is expected as
it moves into greater CIN. Farther to the south, the gust front
is outrunning the convection but sporadic wind gusts of 40-50
mph are still occurring. For srn WI, gusty winds and scattered
storms will continue to initiate along and behind the gust front
during the early morning hours. MUCAPE of 1500-2000 J/KG will
be present but with high LFCs at 650-700 MB. The high LFCs
should aid in the further dissipation of the organized line
and/or transitioning to elevated scattered storms.

During this time, a wave of low pressure will track across MN
to wrn Lake Superior and be the catalyst to shifting the warm
front nwd into central WI. Thus the low stratus and areas of fog
toward central WI will come to an end during the early morning
hours. Some showers and storms will likely linger through later
this morning, but capping will set in again and will aid in
some scattering of clouds and temps nearing 80F for the
afternoon.

Another wave of low pressure will develop from the central
Great Plains to nrn WI from late Mon afternoon until 12Z Tue,
while the main shortwave trough tracks from the central Rockies
to nw WI. The actual trailing cold front will likely not pass
until Tue, but there is some confidence in another round of
showers and storms for mainly after midnight (early Tue AM) as
another MCS moves into srn WI from the west. The MCS may already
have reached the dissipating stage at this time, but there is
uncertainty with the timing of the evolution. Once again,
damaging wind gusts would be the main concern. Finally, there
may be some shower and storm development with the cold frontal
passage Tue afternoon with severe probs are low at this time.

Gehring

&&

.LONG TERM...
Issued 1200 AM CDT Mon May 18 2026

Tuesday night through Sunday:

Gusty northwest winds remain in place through Tuesday night as
high pressure builds in from the northwest. Winds gradually
diminish into Wednesday as high pressure settles into the region.
Temperatures are expected to be back into the 60s and low 70s for
highs and lows in the upper 30s to mid 40s through midweek. High
pressure remains dominant through Thursday before propagating
eastward into the Northeast U.S. Low pressure will begin to deepen
in the lee of the Colorado Rockies, ejecting into the Plains
Friday morning. With high pressure remaining over the Northeast,
models are indicating a split low progression, with one portion of
upper level energy propagating through the Lower Mississippi
Valley along a Gulf humidity axis, and the other portion following
the long wave pattern northeastward into the western Great Lakes.
A few showers and thunderstorms may work their way in as early as
Thursday night into Friday (15-25%), with more potential for
widespread showers and thunderstorms into Friday night and
Saturday as the cold front from the Midwest low phases with the
southern low. Confidence in timing and placement remains in
question due to model discrepancies, so maintained NBM
probabilities for this update. Precipitation exits Saturday night
as ridging begins to build back into the southern Wisconsin from
the central Plains. Expect temperatures to return to the upper 70s
and low 80s Sunday as winds shift to southerly, with additional
chances for storms Sunday night into Monday.

MH

&&

.AVIATION...
Issued 645 AM CDT Mon May 18 2026

Mostly VFR conditions are expected today save for drops in
flight category with any showers and storms. There is some
potential for fog for lakeshore terminals this afternoon. Winds
will be out of the south southwest and breezy. Tonight ceilings
lower to MVFR and potentially IFR as a line of thunderstorms
moves through from the west.

CMiller

&&

.MARINE...
Issued 1200 AM CDT Mon May 18 2026

A warm front will move from southern Lake Michigan to northern
Lake Michigan this morning. East to northeast winds will become
breezy out of the south. Areas of dense fog may occur at times
until the front passes. Breezy south winds will then continue
through today into Tuesday followed by a wind shift to the
northwest late Tuesday afternoon and evening with the passage of
a cold front. High pressure and light and variable winds will
then take hold from late Wednesday into Thursday.

A Marine Dense Fog Advisory is in effect from Sheboygan to North
Point Lighthouse until 3 AM CDT today. The fog will dissipate
once the warm front moves to the north, and south winds and
milder temperatures arrive.

Gehring

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643 until 7 PM Tuesday.

     Small Craft Advisory...LMZ644-LMZ645-LMZ646...4 AM Tuesday to
     4 PM Tuesday.

&&

$$

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