NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 121048 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
548 AM CDT Tue May 12 2026

.KEY MESSAGES...

- Showers will move through the area this morning (40 to 70
  percent chances). A passing cold front this afternoon may
  bring some thunderstorms (20 to 40 percent chances). Gusty
  winds and small hail may occur with the strongest storms, if
  they develop.

- A period of south gales is expected over the middle third of
  the open waters of Lake Michigan from middle morning to middle
  afternoon today. A Gale Warning is in effect for this area, as
  well as for the nearshore waters from Sheboygan to Port
  Washington.

- Gusty south to southwest winds are expected today. Gusts of 35
  to 40 MPH are expected at times. A gust or two to 45 MPH may
  occur, but most gusts should remain below Wind Advisory
  levels.

- Relatively warm and humid conditions with increasing storm
  chances returns Thursday night into the weekend.

&&

.UPDATE...
Issued 548 AM CDT Tue May 12 2026

An area of showers will move east through the area during the
morning hours, within focused warm air advection in the low
levels with the low level jet transporting moisture into the
region. CAMs suggest that this activity may exit the area by
midday, or linger in southeast Wisconsin later this morning
into early or perhaps middle afternoon. They vary with how much
additional showers and some storms develop from middle to late
afternoon across the area with the cold frontal passage.

The main thing to watch will be how long the showers and
associated clouds linger into this afternoon, and if we can get
any sunshine and instability to develop. If so, there should be
enough skinny mean layer CAPE (300 to 600 J/kg) with strong deep
layer bulk shear (around 50 knots) for some storms to produce
gusty winds and small hail. This would be supported
synoptically aloft by an advancing 500 mb shortwave trough into
the area. Would need more than 1000 J/kg of mean layer CAPE for
severe storms, which seems unlikely at this time. Will need to
monitor the mesoscale environment into this afternoon. This
should exit to the east by early this evening.

In addition, forecast soundings are showing steep low level
lapse rates allowing for robust mixing in the boundary layer
today. Gusts of 35 to 40 MPH are expected over most of the area,
and there could be a gust or two to 45 MPH. For now, think most
gusts will remain below Wind Advisory levels today. Warm
temperatures are expected today, with highs into the middle to
upper 70s. If more sunshine occurs, it may reach 80 degrees or
higher.

Gusty winds will shift west to northwest behind the cold front
this evening, with gusty northwest winds later tonight into
Wednesday lingering. The cyclonic flow at 500 mb into Wednesday
should allow for scattered to broken, or perhaps more overcast,
stratocumulus clouds to linger. Cold air advection should bring
in cooler but more seasonable temperatures, with highs
Wednesday in the lower to middle 60s.

Wood

&&

.SHORT TERM...
Issued 1106 PM CDT Mon May 11 2026

Today through Wednesday night:

Low pressure will approach from the northeast tonight, dragging
a warm front over southern WI around daybreak. WAA on the
leading edge of the warm advection will drive showers around
dawn and through the morning hours. All of these showers will
be elevated with negligible MUCAPE, so thunder is not expected.
Shower activity will then grow more scattered heading into the
afternoon as the main push of mid level WAA moves
east/northeast, with strong surface WAA on gusty southwest winds
advecting a warm surface airmass in the mid 70s into southern
WI. A cold front is then expected to move through the area
during the mid to late afternoon. Shower and storm coverage and
strength along the front will be highly contingent upon air mass
recovery during the late morning into the mid afternoon. At
this time, CAMs depict just enough instability along the front
(~400 J/kg CAPE) to drive scattered storm development. However,
the skinny nature of the modeled CAPE profiles will limit storm
strength and severity. A few rumbles of thunder are most likely
with activity along the front, while small hail and gusty winds
will remain isolated and only occur with storms that manage to
become well established in Far SE WI before moving over Lake
Michigan.

Following the cold front, sfc CAA will usher in a cooler air
mass for Wednesday. Highs will be in the low to mid 60s amid
breezy northwest winds. Light frost may occur Wednesday night
into Thursday.

CMiller

&&

.LONG TERM...
Issued 1144 PM CDT Mon May 11 2026

Thursday through Tuesday:

A gradual warming trend will take hold on Thursday as upper
level ridging from the Plains leans east into the Great Lakes
region. Highs are projected to rise into the 80s on Saturday.
The warming will be spurred on by multiple waves of WAA, most
notably Thursday night into Friday, then Saturday into Sunday.
With these waves of WAA, expected shower and storm chances and
modest increases in humidity. Beyond, models vary a bit
regarding how showers and storms will evolve along a passing
cold front on Sunday and how much rain will linger into Monday,
with the ECMWF favoring a drier solution, while the GFS favors
storms Sunday night and lingering showers Monday. In either
case, warmth sticks around for the end of the extended period.

CMiller

&&

.AVIATION...
Issued 548 AM CDT Tue May 12 2026

An area of showers will move east through the area during the
morning hours, with mainly VFR conditions expected. This
activity may exit the area by midday, or linger in southeast
Wisconsin later this morning into early or perhaps middle
afternoon. There is uncertainty with how much additional showers
and some storms develop from middle to late afternoon across
the area with the cold frontal passage.

The main thing to watch will be how long the showers and
associated VFR clouds linger into this afternoon, and if we can
get any sunshine and instability to develop. If so, some storms
may develop and produce gusty winds and small hail. Less
development would occur with less sunshine. This activity should
exit to the east by early this evening.

There may be brief low level wind shear conditions for the next
few hours, until surface winds pick up, but will keep out of
TAFs for now due to borderline conditions.

Gusty south to southwest winds are expected today, with gusts
of 30 to 35 knots at times. There could be a gust or two to 40
knots. Gusty winds will shift west to northwest behind the cold
front this evening, with gusty northwest winds later tonight
into Wednesday. Scattered to broken, or perhaps more overcast,
stratocumulus clouds around 3500 to 4000 feet AGL should linger
as well.

Wood

&&

.MARINE...
Issued 548 AM CDT Tue May 12 2026

Winds will become south southeast early this morning and
quickly become south and gusty through the morning hours, as low
pressure around 29.6 inches approaches from the northwest.

Despite the cold lake surface temperatures, showers over the
lake will mix down gales from middle morning through middle
afternoon. A Gale Warning is in effect for this time period,
over roughly the middle third of the lake, as well as for the
nearshore waters from Sheboygan to Port Washington. Building
waves are expected today into this evening.

Gusty winds then ease a bit during the early evening hours, as a
cold front passes and winds become northwesterly. Gusty northwest
winds then return later tonight into Wednesday. A Small Craft
Advisory is in effect today into Wednesday for the nearshore
waters of Lake Michigan. Building waves are expected today into
this evening in this area.

North to northwest winds then ease Wednesday night into Thursday,
as high pressure around 30.1 inches moves over Lake Michigan.
South to southwest winds should then become gusty Friday into
Saturday. A Small Craft Advisory may be needed for the nearshore
waters during this period.

CMiller/Wood

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Gale Warning...LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-LMZ643-
     LMZ669-LMZ671-LMZ868-LMZ870-LMZ872...9 AM Tuesday to 5 PM
     Tuesday.

     Small Craft Advisory...LMZ643...5 PM Tuesday to 4 PM Wednesday.

     Small Craft Advisory...LMZ644-LMZ645-LMZ646...9 AM Tuesday to
     4 PM Wednesday.

&&

$$

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