NWS-Milwaukee/Sullivan Forecast Discussion
FXUS63 KMKX 280023 AAA
AFDMKX
Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
723 PM CDT Mon Apr 27 2026
.KEY MESSAGES...
- Scattered thunderstorms are expected to shift eastward through
the area this evening, exiting to the east around midnight.
These storms will pose a risk of hail and strong winds mainly
along and west of I-39 into this evening.
- Cooler temperatures are expected Tuesday through the end of
the week. There is a less than 20 percent chance of a freeze
Thursday night and a 20 to 40 percent chance of a freeze
Friday night.
&&
.UPDATE...
Issued 723 PM CDT Mon Apr 27 2026
A scattered area of storms in southwest Wisconsin is expected
to shift eastward into south central Wisconsin, along the
advancing cold front. These storms should still pose a risk for
hail up to one inch in diameter and strong winds into this
evening, mainly west of I-39. There is still northeast 0 to 3 km
shear vectors of 35 to 40 knots into this evening, with up to
1000 J/kg of MLCAPE.
So, any northeastward surge in any of these storms could pose a
strong wind risk. As daytime heating is lost and instability
weakens later this evening, the storms may also gradually weaken
as they shift into east central and southeast Wisconsin. Will
still watch these storms closely through the evening hours. This
activity should shift east of the area around midnight.
There should be some low clouds that develop later this evening
and overnight, as gusty west winds develop behind the cold
front. Also, some fog may develop over Lake Michigan, but
should remain east of Sheboygan, Milwaukee and Kenosha. They
may linger into Tuesday morning, before scattering out in the
afternoon with west northwest winds. Lows tonight should drop
into the middle to upper 40s, with highs Tuesday around 60
degrees.
Wood
&&
.SHORT TERM...
Issued 140 PM CDT Mon Apr 27 2026
Rest of the This Afternoon and Tonight:
Warm advection band of rain and embedded thunder continues to
move to the northeast. On the back edge of this rain, winds are
still gusting to between 40 and 50 mph. Latest observations are
closer to 40 mph. The back edge of this area of rain should exit
to the east/northeast between 2 and 230 PM.
Attention then focuses to the west where some clearing has
occurred over Iowa and a cumulus field has developed. A narrow
band of scattered storms is starting to develop across portions
of central to north central Iowa in an axis of increasing CAPE.
Other narrow low level convergence zones exist across eastern
Iowa, which should provide focus for additional development.
With some daytime heating to the west, surface based CAPE will
approach 1500 J/kg, mixed layer a bit lower at 1000 J/kg. This
nose of instability will enter southwestern WI during the
mid/late afternoon as the aforementioned boundaries and
convergent zones approach.
Scattered storms will pose a marginally severe hail threat and a
localized downburst wind threat. The tornado threat hinges on
maintaining some sort of backed, southeasterly flow. Guidance
indicates as the afternoon progresses, low level winds veer more
to the southwest, so the overall tornado risk has decreased, but
if a cell can latch on to the southeasterly winds, it has a
chance for a brief tornado. The area of main concern with this
would be Iowa/Lafayette/Green/southwestern Dane counties.
As the surface low moves steadily to the northeast into this
evening, the associated surface boundary will be progressive.
Scattered storms will move steadily to the east, exiting over
Lake Michigan after 10 PM.
Gagan
&&
.LONG TERM...
Issued 140 PM CDT Mon Apr 27 2026
Tuesday through Monday:
Cooler, drier conditions will build into the region Tuesday,
though low clouds will hang on for at least the morning.
Northwest flow aloft begins to take hold and will send a few
embedded shortwaves our way. Timing these waves will be the
trick, but blurring ones eyes there is a chance for showers
Wednesday evening into Thursday morning.
Surface high pressure builds in the region for the end of the
week and at least the first portion of the weekend. Will need to
keep a close eye on frost/freeze potential Thursday and Friday
nights. Right now, the better opportunity for a freeze looks to
be Friday night.
Northwest flow aloft will remain in control this weekend into
early next week. Another shortwave passage is progged for the
latter half of the weekend, with the next chance for rain slated
for late Sunday into Monday morning.
Overall, this is a cooler and drier pattern for the next week or
so. The GEFS CIPS analogs maintain a cooler than average pattern
and temperatures will be at or below average for the next week
or so. Rainfall chances will be there every 2-3 days, but should
be quick hitters in this fast flow.
Gagan
&&
.AVIATION...
Issued 723 PM CDT Mon Apr 27 2026
A scattered area of storms in southwest Wisconsin is expected
to shift eastward into south central Wisconsin, along the
advancing cold front. These storms should still pose a risk for
hail up to one inch in diameter and strong winds into this
evening, mainly west of I-39. These may affect Madison and
Janesville at times through 03Z Tuesday. May see locally reduced
ceilings and visibility values with any storms.
As daytime heating is lost and instability weakens later this
evening, the storms may also gradually weaken as they shift into
east central and southeast Wisconsin. Thus, this activity may
affect Sheboygan, Waukesha, Milwaukee and Kenosha at times later
this evening. This activity should shift east of the area
around midnight.
There should be some low clouds with ceilings of 700 to 1500
feet AGL that develop by later this evening and linger
overnight, as gusty west winds develop behind the cold front.
Also, some fog may develop over Lake Michigan, but should remain
east of Sheboygan, Milwaukee and Kenosha. They may linger into
Tuesday morning, before scattering out in the afternoon with
west northwest winds.
Wood
&&
.MARINE...
Issued 723 PM CDT Mon Apr 27 2026
The south to southeast gales look to have ended across the
southern half of the open waters of Lake Michigan. Thus, the
Gale Warning has been allowed to expire for the open waters and
nearshore waters of Lake Michigan. A Small Craft Advisory is in
effect for the nearshore waters through 1 PM CDT Tuesday for
gusty winds and waves between 5 and 8 feet.
High pressure will gradually build into the region Tuesday, and
will result in gradually decreasing winds and waves. Light
winds and waves between 1 to 2 feet are expected for the rest
of the week.
Wood
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until
1 PM Tuesday.
&&
$$
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