446
FXUS63 KMKX 160858
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
358 AM CDT Fri May 16 2025

.KEY MESSAGES...

- Gusty non-thunderstorm winds are expected across southern Wisconsin
  today. Be sure to secure any loose outdoor objects &
  furniture before heading out this morning.

- Scattered showers and thunderstorms are expected this
  afternoon, with peak potential (~30-60% chances) being
  between 3-8 PM. Widespread severe weather is unlikely, though
  a few storms could produce large hail and strong wind gusts.

- Much cooler conditions this weekend through the beginning of
  next week, with below-normal high temps forecast each day.

- Next shower and thunderstorm chances (~30-60%) return Monday through
  Tuesday.

- Temperatures return to near-normal late next week.

&&

.SHORT TERM...
Issued 358 AM CDT Fri May 16 2025

Today through Tonight:

Synopsis/Mesoanalysis: GOES water vapor imagery places an upper
trough over the ND-MN border vicinity early this morning. Positioned
beneath the wave, surface low pressure is apparent just to the south
of Fargo, ND. An occluded front---the same boundary responsible for
yesterday afternoon`s severe convection---branches out from the
surface low, with 3 AM observations showing the front extending
across Lake Superior toward Lake Huron. A surface ridge trails the
occluded front, which has allowed winds to temporarily lighten
across southern Wisconsin. Surface pressures fall once more moving
west toward the Missouri River vicinity, where a secondary cold
front is positioned. Both this front and the aforementioned upper
trough will cross southern Wisconsin today, resulting in increasing
southeasterly winds from late morning into the afternoon. Said winds
will be gusty at times, with the highest gusts expected during the
12-6 PM time frame. Lift from the passing surface front & upper
trough will also support scattered showers and thundershowers this
afternoon, with potential peaking during the 3-8 PM time period.
This activity won`t be nearly as intense as the storms occurring
yesterday, though a few storms could produce large hail and strong
wind gusts. Shower/thundershower chances will gradually taper as the
upper trough & surface front move east of the area tonight.

Today: South-southwest, non-thunderstorm winds will become gusty
ahead of an approaching front by early this afternoon. Have carried
gusts of 35-40 MPH range in the current forecast, with the highest
readings favored during the 12-6 PM time frame. Locally higher gusts
in the 40-45 MPH range are possible during this time period.
Whether/not more widespread 45 MPH gusts can materialize will depend
on the depth of boundary mixing that occurs through this afternoon,
with forecast soundings from different meso models depicting
slightly different boundary depths & momentum transfer. In
coordination with surrounding offices, thus elected to hold off on
any Wind Advisories in the overnight forecast, though trends will be
closely monitored. Also anticipate scattered shower & thundershower
development during the afternoon hours, with potential peaking
during the 3-8 PM time frame. While widespread severe weather is
unlikely, a combination of cold air aloft/steep mid-level lapse
rates, strong synoptic wind fields, & deeply mixed boundary
layers/efficient momentum transfer will support some potential for
large hail and damaging wind gusts in the strongest cells. Expect
this potential to be maximized to the east of I-39, where surface-
based instability is progged to be greatest. Cloud to ground
lightning will also be a concern in/around the strongest cells. Stay
weather aware if planning to be outdoors this afternoon/early
evening, and move indoors if a storm approaches your area.

Quigley

&&

.LONG TERM...
Issued 358 AM CDT Fri May 16 2025

Saturday through Thursday:

The upper level trough over the central Great Lake Region will
continue northeast out of the area toward the New England States.
Breezy west winds are expected to continue through the early morning
hours as the pressure gradient will remain tight until the low pulls
out of the region. Cooler air will be ushered into southern
Wisconsin with these breezy winds leading to highs in the mid 60s
across the forecast area. As the low pressure pulls out, there could
be some lingering showers in the early morning hours. Not expecting
much more than some light rain as there will be dry air moving in
with the westerly flow.

Strong high pressure will build in across Manitoba and Ontario
Canada Sunday. Dry weather and lighter winds are expected for
Wisconsin as this ridge moves through the region. Under the weaker
winds, a backdoor cold front/aggressive lake breeze should move
inland and drop temperatures across east central and lake shore
counties. These areas can expect highs in the 50s with inland areas
in the mid to upper 60s.

The next chance for rain looks to be Tuesday into Wednesday as a low
pressure system tracks east from the central plains. Guidance has
this area of low pressure tracking just the south of the state,
which should provide southern Wisconsin with some nice wetting rain.
Not anticipating anything severe as we should be on the northern
edge of the low and dealing with more or a stratiform rain set up.
Still a bit of uncertainty in how far south this low may travel and
just how much rain we might see, but overall a very solid set up.
Mild and comfortable temperatures are expected through mid week with
highs in the 60s for inland areas and slightly cooler temperatures
near the lake shore in the 50s.

Patterson

&&

.AVIATION...
Issued 358 AM CDT Fri May 16 2025

VFR flight categories prevail at all southern Wisconsin terminals
late this evening. Responding to a departed frontal boundary,
generally westerly winds remain elevated near Lake Michigan, with
several sites continuing to report gusts. Gusts will taper moving
into the predawn hours. Can`t rule out a brief period of LLWS near
FL020 near sunrise at western fields, with potential being accounted
for in the 06Z update. Gusty conditions are anticipated once more
late this morning into the early evening hours as second frontal
boundary moves across southern Wisconsin. Isolated to widely
scattered -SHRA/-TSRA are possible along/ahead of the approaching
boundary, with gusty winds and hail possible in the strongest cells.
Have continued to account for this potential at all fields with
PROB30 groups in the 06Z update, and will assess the need for
prevailing and/or TEMPO groups in subsequent forecasts. Precip
potential will conclude during the early evening hours. Anticipate
lowering cloud bases through the second half of the Friday evening &
overnight hours, with categorical reductions approaching KMSN and
KJVL near the end of the period. Expect categorical reductions to
reach KMKE nearing the end of the 30 hour period. Will account for
categorical reductions at other sites in later forecasts.

Quigley

&&

.MARINE...
Issued 358 AM CDT Fri May 16 2025

A cold front is in the process of crossing the northern third of
Lake Michigan this morning, with a narrow line of showers and
thundershowers in progress from Manistique to Traverse City. The
boundary has cleared the southern two-thirds of Lake Michigan,
resulting in a gusty west wind shift. Said gusty west wind shift
will overspread the northern third of the open waters as the surface
front pushes east through dawn. Patchy fog is possible over the
northern third of Lake Michigan through daybreak, and will quickly
dissipate after sunrise. Dense fog is not anticipated.

Currently situated along the North Dakota-Minnesota border, low
pressure near 990 mb will progress into northwestern Wisconsin
today, ultimately crossing northern Lake Michigan tonight. Southerly
winds will increase ahead of the approaching today, becoming gusty
from late morning through the afternoon hours. Widespread gusts
between 25-30 knots are forecast across all of the open waters
during this time frame. A few gusts could briefly approach gale
thresholds, though widespread gale potential is low. Have thus held
off on gale headlines in the overnight forecast. The approaching
surface low will be accompanied by scattered showers and
thunderstorms. Widespread severe storms are unlikely, though some
storms could produce small hail. Winds will shift out of the west on
Saturday as 994 mb low pressure moves into Ontario. Rain chances
will continue, particularly across the northern half the open waters.
Thunderstorms are not anticipated. Winds will turn out of the
northwest Saturday night, when 1016 mb high pressure will build into
the Upper Mississippi River Valley.

Gusty south to southeasterly winds and elevated wave heights will
result in Small Craft Advisory conditions today in all nearshore
zones. A few gusts could briefly approach gale thresholds,
particularly from North Point to Sheboygan. Gusts could occasionally
approach gale thresholds this afternoon, particularly from North
Point to Sheboygan, though any such conditions would be brief. Have
thus replaced the previous Gale Watch with a Small Craft Advisory in
the overnight forecast update. Scattered showers and storms are
expected this afternoon. Widespread severe storms aren`t expected,
though a few storms could produce hail. Winds and waves will briefly
dip below advisory thresholds after midnight, prior to increasing to
Small Craft Advisory levels once more Saturday morning. Have thus
maintained the Small Craft Advisory through 7 PM CDT Saturday
evening, when conditions will begin to steadily improve.

Quigley

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646...10 AM
     Friday to 7 PM Saturday.

&&

$$

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