929
FXUS63 KDLH 011040
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
540 AM CDT Tue Jul 1 2025

.KEY MESSAGES...

- Widely scattered thunderstorms are expected Wednesday across
  all of the Northland. Storms may be strong along and south of
  US Hwy 2, with an isolated severe in eastern Minnesota to all
  of northwest Wisconsin.

- Very warm and muggy conditions are expected Friday and a Heat
  Advisory may be needed in time.

- Friday PM and Saturday is a likely period for heavy rainfall
  and lower-end chances for strong thunderstorms. A few of
  these strong storms may be severe.

&&

.DISCUSSION...
Issued at 230 AM CDT Tue Jul 1 2025

Mean westerly flow aloft persists over the north-central United
States with a few weak waves dropping east-southeastward over
the next few days. The first of these waves passes through far
northern Ontario today and brings a very slight chance (15-30%)
for widely scattered high-based rain showers and an isolated
thunderstorm late morning to sunset today. The most likely
locations for any shower or storm would be along and east of US
Hwy 53 in far northeast Minnesota. Strong to severe storms are
not expected if an isolated thunderstorm does even form. The
upper-end forecast rainfall would be 0.25 inches. As the wave
pushes further eastward later today, expect a 10-15% chance of a
rain shower as well east of US Hwy 53 in northwest
Wisconsin...best chances though southeast of US Hwy 63. For the
time being, mentionable weather was not placed in the forecast
this afternoon and early evening for northwest Wisconsin areas
due to the fair uncertainty on if any showers can even form with
a bit better cap aloft. Future forecast updates may need short-
term increases in these chances of precipitation and mentionable
weather if these showers become a bit more likely.

As the next vorticity maxima pushes into the region Tuesday
night into Wednesday, a more moist Gulf tap will occur into
eastern Minnesota and central Wisconsin. The combination of this
increased moisture, a bit better mid-level lapse rates around 7
C/km, a CAPE gradient right along and south of US Hwy 2 and
limited shear to 35 knots create a more favorable environment
for strong to maybe an isolated severe storm Wednesday. The most
likely areas for these widely scattered strong to isolated
severe storms would be a line from the Brainerd Lakes to Grand
Rapids to Twin Ports and southward in northern Minnesota and
across all of northwest Wisconsin from late afternoon to late
evening. The marginal severe environment though keeps hazards
limited largely to hail the size of a penny up to a quarter and
winds 40 to 60 mph. If the better shear environment can setup
further northward into east-central Minnesota and inland
northwest Wisconsin and the CAPE gradient just a bit further
northward then the chances for isolated severe storms would
increase. Either way, a mean storm motion to the southeast is
favored so any storms that do form could then move out of the
Northland into central Minnesota and western/central Wisconsin.

Thursday daytime will see a wind shift over the western waters
of Lake Superior to aid in funneling a northeast wind into the
Twin Ports. These conditions may create a Moderate Swim Risk day
due to possible rip currents forming right along Lake Superior
beaches such as Canal Park, Minnesota Point and Wisconsin Point
beaches. Check back on the latest Surf Forecasts over the next
couple of days for those beaches to keep up to date on this
possible Moderate Swim Risk hazard Thursday. Expect a notable
lake breeze formation to help moderate daytime temperatures
Thursday for the head of the lake locations and along the North
and South Shores.

Thursday afternoon, a warm front begins to lift northward
Thursday afternoon as low pressure deepens over Manitoba. Expect
scattered rain shower and isolated general thunderstorms chances
(30-50%) Thursday night along and trailing the warm front.

Lingering sky cover behind the warm front will be a large factor
in just how much the air temperatures can warm Friday daytime to
aid in the very warm and muggy conditions that are currently
forecast. Right now the forecast calls for a middle of the road
forecast from a range of probabilistic solutions in medium range
global ensembles favoring Max Temps Friday daytime in the mid
to upper-80s, except along the North Shore. Beyond these 7-10
degrees above normal temperatures for early July, the dewpoint
temperatures in the upper-60s to low-70s will really add to the
potential for heat impacts Friday. When factoring in the
bordering criteria conditions and many outdoor events and
recreation that will be going on, a widespread Heat Advisory may
be needed in future forecast issuances for Friday.

For the Friday severe weather potential (remaining fairly low
and conditional), at this point looks to be mainly favored
towards north-central and northeast Minnesota. These corridors
have the highest likelihood of lining up a narrow corridor of
Shear to 40 knots in the late afternoon and early evening with
instability approaching 2000 J/kg...all with the available
moisture plume ranging somewhere from 1.5 to 2 inches of
precipitable water. The lacking mechanism though is a greater
synoptic or even mesoscale forcing mechanism to help allow for
sustained storms given the weakly sheared environment and only
modest amounts of instability. Right now if the conditional
environment were to come together Friday in northern Minnesota,
damaging winds from unorganized clusters of strong to maybe
severe storms seems most likely.

As the low pressure moves eastward a deep and very moist
southerly advection persists into Friday night. This quickly
turns over the chances of severe weather as the primary hazard
to more of a heavy rainfall setup with erratic wind gusts as a
secondary hazard. The reinforcing mechanism for potentially
widespread and prolonged heavy rainfall Friday night into
Saturday morning would be a trough deepening over the U.S. Central
Plains lifting northeastward in this time period. There is a 75%
chance of at least 0.5 to 1 inches of rainfall areawide by
Saturday night...with upper-ends (10% chance of occurring) approaching
at least a few inches over much of the region pending how the
track of the second low sets up.

Saturday afternoon and evening could also be a period of strong
thunderstorms in eastern Minnesota and northwest Wisconsin as
the reinforcing cold front and upper-level trough finally move
through the Upper Midwest and east of the region. Temperatures
are likely to cool back towards normal from Sunday into early
next week with lingering isolated 10-30% chance of scattered
rain showers and thunderstorms each day.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 537 AM CDT Tue Jul 1 2025

VFR conditions prevail this morning and early afternoon today.
While most places remain VFR this TAF period, the Arrowhead will
see localized reductions to MVFR under widely scattered rain
showers and thunderstorms 19-02Z. Another area of rain showers
and isolated storms drops into far north-central Minnesota after
06Z and moves southeastward to the Twin Ports towards 12Z, MVFR
conditions are also possible at these terminals in this late
night time period. Expect continued light westerly winds to
increase and gust 20 knots after 16Z. Diurnal cumulus build in
coverage 15-17Z and lingering through sunset Tuesday.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 151 AM CDT Tue Jul 1 2025

West to southwest winds prevail the next two days, all around
or under 20 knots. These conditions keep wave heights highest
from 2 to 3 feet along the North Shore, lesser into the Twin
Ports and along the South Shore. Expect a wind shift Thursday to
easterly and building waves into Twin Ports. Wednesday mid-
afternoon to mid-evening has the highest chances of a strong
thunderstorms near or over the waters of the next few days.

For the open water discussion, refer to the NWS Marquette Area
Forecast Discussion at weather.gov/mqt.

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
MARINE...None.

&&

$$

DISCUSSION...NLy
AVIATION...NLy
MARINE...NLy