947
FXUS63 KDLH 021128
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
628 AM CDT Wed Jul 2 2025

.KEY MESSAGES...

- Widely scattered thunderstorms are expected across much of the
  Northland today into this evening. Storms may be strong to
  severe along and south of a Walker to Hibbing to Silver Bay to
  Ontonagon MI line. This includes central Minnesota, the I-35
  corridor, and all of northwest Wisconsin.

- Very warm and humid conditions are expected Friday. A Heat
  Advisory may be needed.

- Strong to severe thunderstorms are possible Friday afternoon
  through Saturday. Storms may also produce heavy rainfall
  which could lead to flash flooding.

&&

.DISCUSSION...
Issued at 316 AM CDT Wed Jul 2 2025

Today - This Evening:

Showers with some embedded thunderstorms ongoing over northwest
MN as of 230 AM CDT this morning are occurring in a region of
low- level convergence and warm-air advection south of a surface
cold front that is located in southern Manitoba and northwest
Ontario and under very subtle 500 mb troughing aloft. As the
front slowly sags south into the Northland today, these
scattered showers and storms will continue to track southeast
into northeast MN and northwest WI this morning into this
evening. The storms should remain sub-severe into the morning
hours. However, some redevelopment/reinvigoration in their
intensity is expected this afternoon into mid to late evening as
a pool of 1000-1700 J/kg of MLCAPE develops. Low-level shear
will be weak, but deeper shear should be ample enough for some
discrete to small clusters of storm organization with 0-6km bulk
shear of 30-40 kt and 0-10km shear (essentially storm depth
shear) of around 50 kt. The cap looks to break by mid-afternoon
as the weak inhibition mixes out. There isn`t much in the way of
mid/upper-level forcing for these storms, so coverage is
expected to be on the more widely scattered basis this
afternoon and evening. Initial storm threat appears to be hail
up to 1" (the size of quarters), with increasing downdraft CAPE
during the later afternoon into evening increasing the potential
for a few damaging wind gusts to 60 mph, as well. Given the
relatively limited coverage of storms, brief, localized rainfall
amounts in excess of 0.5" could occur, but flooding is not
expected and most locations should see 0.1-0.25" or less. The
best potential for afternoon/evening strong to severe storms
would be along and south of a Walker to Hibbing to Silver Bay to Ontonagon
MI line. This includes central Minnesota, the I-35 corridor,
and all of northwest Wisconsin. Storms should dissipate by late
evening.

Outside of storms, expect widespread upper 70s to mid 80s for
high temperatures today and similar heat indices for areas away
from Lake Superior.

Thursday - Thursday Night:

The cold front should stall out over southern portions of the
Northland tonight/Thursday morning and then push back northward
as a warm front on Thursday into Thursday night. Aloft, an
upper-level ridge will be building over the Northern Plains and
Upper Midwest for Thursday into Friday, which should bring an
increase to both temperatures and moisture/PWATs both days, with
PWAT values in the 1.5-2" range, on the higher end of
climatology for this time of year. There appears to be some
subtle mid-level shortwave trough energy that rounds the top of
the ridge and moves through the Northland Thursday afternoon
into night that could kick off some showers and storms along
and north of the warm front (20-40% chance), though very weak
shear in place should keep these from becoming severe.

Temperatures and heat indices in the upper 70s to mid 80s are in
store for Wednesday, and slightly cooler near Lake Superior and
at the head of the Lake. Onshore winds at the head of the Lake
around 10-15 mph with gusts to 20-25 mph could lead to rip
currents. We will continue to watch this rip current threat
closely, as a Beach Hazard Statement may be needed Thursday for
Minnesota and Wisconsin Point beaches.

Friday - This Weekend:

A few concerns pop up for this timeframe: 1) Heat and humidity
for Friday, 2) Strong to severe thunderstorm potential Friday
into Saturday, and 3) Heavy rainfall and flooding potential
Friday into Saturday.

Independence Day (Friday) will be a hot and muggy affair
underneath the apex of the upper-level ridge with surface
dewpoints in the upper 60s to low 70s and high temperatures away
from Lake Superior in the upper 80s to low 90s and mid-70s to
mid 80s from the Twin Ports up the North Shore. This will lead
to widespread heat indices in the low to upper 90s away from
Lake Superior, with the potential for Heat Advisories for most
of the Northland looking increasingly likely.

In addition to the heat, a return of shower and thunderstorm
potential is forecast for Friday into Friday night, as well. The
Northland should be pretty well nestled into the warm sector of
a low pressure system approaching from the Northern
Plains/Canadian Prairies. A capping inversion should hold across
much of the Northland with a relative lack of synoptic forcing
for ascent much of the day, which should likely stave off
precipitation until the evening. Farther to our west along and
ahead of the cold front, storms should begin developing in a
region of falling heights aloft and lower-level convergence over
North Dakota, northwestern MN and northwestern Ontario in the
late afternoon/evening where the capping inversion will be
weaker. Then, during the evening (starting around 6-8PM CDT)
storms will begin to work into northwestern portions of the
Northland and gradually spread east through the remainder of the
evening and overnight hours on a more widespread basis. Some of
these storms should be strong to severe with 0-6km bulk shear
values of 35-45 kt and 1500-2500 J/kg of MUCAPE to initially
work with, though instability does drop off with time later in
the evening and overnight. The primary hazard would be damaging
wind gusts given plenty of downdraft CAPE, with large hail as a
secondary threat. There is also a period of time until the late
evening where storms could be surface based and have access to
just enough low-level helicity for a non-zero tornado threat.
However, with surface winds forecast to be out of the south-
southwest, this tornado threat remains very low.

A more pressing concern in addition to the severe potential
would be a deep layer of southwest winds aloft being parallel to
the surface warm and cold fronts. When combined with PWATs
increasing to around 2" and the surface to freezing level depth being
around 13,000 feet, the threat for training storms with
efficient, heavy rainfall rates becomes a real concern and could
even lead to localized flash flooding. Still have to refine some
details as to where exactly this heavy rainfall threat would be
highest Friday evening into Saturday depending on where the
surface fronts set up, but right now the best potential for 2"+
of rainfall (40% chance) is for central and north-central MN.
NBM probabilities for >1" for this same timeframe are 60-80% in
north-central and northeast MN and 30-60% in northwest WI.

As the cold front slowly sweeps east across the Northland on
Saturday, more mild temperatures return with highs in the upper
70s to low/mid 80s. There is a shorter window of time Saturday
afternoon and evening where a few strong to severe storms will
be possible once again, primarily in northwest WI. However, this
Saturday severe threat will depend on how morning showers/storms
progress through the Northland.

Looking cooler and drier for Sunday behind the cold front with
highs in the 70s and more comfortable dewpoints in the 50s to
low 60s.

Early Next Week:

We see a more zonal upper-level pattern set up for early next
week, with occasional shortwave energy traversing the flow,
keeping more transient shower/thunderstorm chances going (20-40%
chance) on Monday and Tuesday. Temperatures should be more
seasonal in the 70s for highs. A more robust shortwave/low
pressure around the middle of next week could bring more showers
and thunderstorms to the Upper Midwest, keeping this active
weather pattern going.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 628 AM CDT Wed Jul 2 2025

Showers this morning in central and north-central Minnesota have
weakened and become widely scattered, with thunderstorm chances
remaining low (less than 20%). Therefore, expect VFR conditions
to prevail as these showers persist through much of the morning
and also push into parts of northwest Wisconsin. With that said,
additional widely scattered showers and storms develop south of
a cold front mid to late afternoon into evening, mainly south
of a KGPZ to KTWM line in central and eastern Minnesota and for
all of northwest Wisconsin. This includes KDLH/KBRD/KHYR. Exact
locations of storms and coverage is still a little uncertain
given weak forcing for these storms, but can`t rule out some
gusty and erratic wind as well as small hail and brief MVFR
conditions should a storm move over a terminal.

Behind the cold front, smoke from Canadian wildfires moves
through aloft, as well as possibly at KINL/KHIB towards the end
of the period. Have included SCT high cloud mention for the
smoke aloft and a 6SM FU for KINL where confidence is higher in
seeing some surface smoke in the current TAF period. There is
also a signal for some fog development tonight, particularly in
NW WI. Included MVFR to IFR visibility in fog to HYR tonight for
now, but this may need to be lowered in subsequent updates if
the increasing fog forecast trend persists.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 316 AM CDT Wed Jul 2 2025

West to southwest winds of 5 to 15 knots are in store for today,
veering northeasterly for Thursday with sustained winds
increasing in the SW arm of Lake Superior to 10-15 mph with
gusts to around 20 knots, then turning back southerly on Friday
with gusts to around 20 knots at the head of the Lake near the
Twin Ports. Several rounds of showers and storms are expected
for today through Saturday. Storms this afternoon could produce
small hail and wind gusts to 30 to 40 knots. Storms on Friday
evening into Friday night and Saturday afternoon and evening
could become strong to severe.

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...Rothstein
AVIATION...Rothstein
MARINE...Rothstein