NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 260852
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
352 AM CDT Sat Apr 26 2025

.KEY MESSAGES...

- Potential for severe thunderstorms Monday into Tuesday (risk
  level 4 out of 5 in the west, risk level 3 in the east, except
  2 along the lakeshore). Initial indications are that this
  activity will peak late Monday/Monday night, and all hazard
  types are possible.

- High temperatures near 80 degrees Fahrenheit are expected
  Monday, then cooling down toward the middle of next week.

&&

.SHORT TERM...
Issued 352 AM CDT Sat Apr 26 2025

Today through Sunday:

Low pressure over Lake Erie will continue to exit the region
today while high pressure over the Northern Plains pushes into
WI. The high will be centered over Lake Michigan by early
evening. Cyclonic flow aloft is keeping the gusty northerly
winds and low clouds around this morning. They are expected to
persist through late morning before we see clearing skies over
east central and southeast WI. Temperatures are expected to
rebound to around 60 well inland, but remain chilly in the lower
50s near Lake Michigan today.

Light winds and clear skies under the core of high pressure
tonight will allow for lows in the mid 30s. With dewpoint temps
dropping to the lower 30s this afternoon behind the lake breeze,
we cannot rule out a few pockets of 32 to 33 degree lows in the
favorable cold spots along and just west of the Kettle Moraine
tonight. There is a 30 percent chance of less than 32 degrees
for that area for one to two hours late tonight, per the HREF
Ensemble.

Southerly winds will develop on Sunday, although gusts will wait
to develop until the afternoon and should be 20 mph or less.
Temperatures will be in the mid to upper 60s inland from Lake
Michigan. Lows Sunday night will be mild, in the upper 40s to
lower 50s.

Cronce

&&

.LONG TERM...
Issued 352 AM CDT Sat Apr 26 2025

Monday through Tuesday:

Low pressure in the lee of the Wyoming Rockies will eject into the
northern Plains overnight Sunday, bringing strong WAA to
southern Wisconsin by the early morning hours on Monday. Warm
frontogenesis will lift through southern Wisconsin during the
pre-dawn hours on Monday, bringing rain and storms within a
region of approximately 500 to 750 J/kg of MUCAPE. An isolated
storm or two may produce hail, but widespread severe is not
expected.

WAA continues throughout Monday, with potential for a dry slot
developing during the afternoon. GFS keeps things a bit more moist
than the Euro, but confidence is growing in seeing at least a few
breaks in clouds and therefore enhanced instability across
southern Wisconsin. Euro/EPS and GFS/GEFS indicate timing of 00Z
to 03Z for initiation in southwestern Wisconsin, but NAM keeps
cold front hanging back until after 06Z. Currently leaning toward
Euro/GFS solutions for timing of the cold frontal passage due to
NAM nearing the end of its forecast cycle and therefore
potentially developing more errors. Timing of frontal passage will
determine how much surface CAPE is still available; however, the
system looks to remain dynamic enough to still produce isolated to
scattered severe storms through the late overnight hours. All
hazards are possible within the warm sector and along the cold
front Monday evening into Monday night, with the primary storm
mode looking to be linear along the cold front and therefore
leading to damaging winds and isolated tornadoes (CAPE 1500 to
2000 J/kg, 0 to 3 SRH 200-300 m2/s2). Hail is also possible within
a mid-level lapse rate regime of 7 to 8 degrees C/km.

The cold front will move into Lake Michigan and northern Illinois
going into Tuesday morning, with all severe weather expected to
cease by daybreak Tuesday. Wrap around showers behind the front
may continue through the day as low pressure exits into eastern
Ontario.

MH

Tuesday night through Friday:

High pressure will drift across the Upper Great Lakes Tue nt
through Wed. Temps are expected to drop into the mid 30s again.
Temps will rebound into the 60s for the latter half of the week.
An upper trough crossing the center of the country may or may
not phase (northern stream and southern stream) together.
Nevertheless, there is a chance of showers with this upper
trough, although timing and precip amount is uncertain.
Temperatures look cool for next weekend, so you may want to hold
off planting sensitive vegetation outdoors.

Cronce

&&

.AVIATION...
Issued 352 AM CDT Sat Apr 26 2025

MVFR clouds are persisting across much of east central and
southeast WI early this morning, although more holes have
developed. While Madison and westward should continue to see a
clearing trend, expect this area of clouds to persist over FLD,
UES and BUU until around noon before they can mix out
completely, although the bases should rise to VFR (above 3000
ft) before they dissipate.

Cronce

&&

.MARINE...
Issued 352 AM CDT Sat Apr 26 2025

Low pressure of 29.7 inches over Lake Erie will continue to
exit the region today. Strong high pressure around 30.4 inches
will become centered over the Upper Great Lakes by early
evening. Brisk northerly winds over Lake Michigan this morning
will gradually diminish from north to south through late
afternoon as the high builds in. Light and variable winds under
the high are expected Saturday night into Sunday morning.

Low pressure of 29.4 inches will then track from South Dakota
to the Minnesota Arrowhead on Monday while deepening to 29.3
inches, then to Quebec by mid Tuesday morning. Expect breezy
southerly winds over Lake Michigan Monday through Monday night.
Southerly gales are possible, although there will be a strong
inversion over the cooler open waters, so there is uncertainty
that the very strong winds up to 50 kt just off the surface will
be able to mix down. The associated cold front will cross Lake
Michigan on Tuesday. Winds will diminish quickly Tuesday night
as high pressure around 30.2 inches moves into the region.

For the Nearshore, the northerly winds are hanging on longer
than anticipated this morning, so I extended the Small Craft
Advisory from Sheboygan to the North Point Light until 10 AM
CDT. The S.C.A. from the North Point Light to Winthrop Harbor
remains in effect until 4 PM today.

Cronce

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643-LMZ644 until 7 AM Saturday.

     Small Craft Advisory...LMZ645-LMZ646 until 4 PM Saturday.

&&

$$

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