513
FXUS63 KDLH 020551
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1251 AM CDT Wed Jul 2 2025

.KEY MESSAGES...

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

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

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

&&

.DISCUSSION...
Issued at 342 PM CDT Tue Jul 1 2025

Showers were hard to come by so far this afternoon. There`s a
narrow zone of 500-700 J/kg of MLCAPE over north-central
Minnesota per the 20Z SPC RAP mesoanalysis. That area
corresponds to the axis of some TCu which stretched from Lake of
the Woods County southeast to near Hibbing and Virginia per the
GOES-East Day Cloud Phase RGB product. KDLH WSR-88D was unable
to find showers either near the surface or aloft from those
taller clouds. A few other pockets of TCu were found from the
I-35 corridor east into northwest Wisconsin. No indication of
showers from those clouds, either. As such I downgraded most of
the PoPs for this afternoon into the evening to "sprinkles".
It`s not impossible for a storm or two to develop although the
best convergence was located north of the Canadian border north
of Lake Superior.

Frontogenesis is forecast over northwest Ontario and southern
Manitoba this evening as a surface trough propagates southward.
The resultant cold front will sag southward across northern
Minnesota and northwest Wisconsin late tonight and Wednesday.
Showers and a few storms are forecast to develop over southern
Manitoba and adjacent areas of northwest Ontario tonight in
response to surface to 850 mb convergence. Those showers and
storms should then propagate southeastward with time ahead of
the front spreading across northern Minnesota and into northwest
Wisconsin from 06Z through Wednesday evening. There is a
limited risk of a few severe storms. Low-level wind shear will
be lacking, though hodographs are long and relatively straight
between 2km and 10km. Forecast MLCAPE of 1000-1500 J/kg and
modest mid-level lapse rates should support a risk of large
hail. Splitting supercells are a possibility in which case the
left-moving storm could produce hail up to 2 inches in diameter.
Limited inhibition may lead to numerous sub-severe storms
instead of several strong to severe storms. Later in the
afternoon and evening expect downdraft CAPE to increase which
may give rise to a few damaging wind gusts.

The cold front will eventually stall out Wednesday night and
Thursday morning before returning northward as a warm front. A
building upper-level ridge over the northern Plains will bring
southerly return flow and warmer temperatures into the region
for Thursday and Friday. A shortwave trough and accompanying
ribbon of vorticity will round the crest of the ridge and
propagate southeastward over northern Minnesota and northwest
Wisconsin Thursday afternoon and evening. Another round of
showers and storms is forecast, although severe weather is not
anticipated at this time.

Attention then shifts to Independence Day Friday and the
holiday weekend. Warm and muggy conditions will raise the
potential for heat-related illness just in time for folks to
head outside to celebrate with friends and family. High
temperatures on Friday will reach the upper 80s and low 90s
(except middle 70s to middle 80s along the North Shore). Heat
indices will be in the 90s. Heat Advisories may eventually be
needed.

It wouldn`t be Independence Day weekend in the Northland
without the atmosphere attempting it`s own fireworks show. The
heat and humidity will build underneath an ample capping
inversion during the afternoon. A cold front will approach from
the Canadian Prairies and northern Plains Friday evening.
Increasing convergence along the front along with falling
heights west of the ridge axis and a strengthening southwesterly
low-level jet should initiate thunderstorms over North Dakota
into northwest Ontario by late afternoon. The storms will
propagate southeastward with time and should move into the
Northland after 8 PM. Some storms will likely be strong to
severe. Large hail and damaging wind gusts are the main threat.
There is a chance of a few tornadoes, too, although that is a
secondary hazard compared to the hail and wind. Winds aloft
ahead of the front will be parallel to the boundary which raises
the potential for training storms and localized flash flooding.
If you have outdoor plans Friday night and Saturday, keep up
with the latest forecast as details are refined. Make sure you
have a place to shelter indoors in case storms threaten.

The cold front will usher in cooler temps for Saturday. The
slow southeastward progression of the front will continue the
risk of training storms and flash flooding on Saturday. A few
storms may be strong to severe once again. Sunday appears drier
and cooler with highs in the 70s. Another round of showers and
storms is possible Monday and Tuesday.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1251 AM CDT Wed Jul 2 2025

VFR conditions are expected ahead of an approaching cluster of
storms ahead of a cold front from northwest Minnesota that will
push southeastward through northern Minnesota into portion of
northwest Wisconsin through the current overnight hours into
this morning. Expect brief deterioration in conditions as they
move through, with MVFR visibility possible. The storms remain
scattered, so have primarily highlighted them with VCTS and
PROB30 groups, but will likely make amendments if thunderstorm
threats to a terminal become more prevalent. Expect diurnal
cumulus to develop today, with widely scattered thunderstorm
development expected along and south of the cold front this
afternoon into early evening, mainly a potential for terminals
south of a KGPZ to KTWM line in central and eastern Minnesota
and for all of northwest Wisconsin. This includes
KDLH/KBRD/KHYR. Behind the cold front, smoke from Canadian
wildfires moves through aloft, though there is uncertainty as to
how much mixes down to the surface. Have included SCT150 to
SCT200 sky mention for the smoke. Also included FU mention at
KINL where confidence is higher in seeing some surface smoke in
the current TAF period.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 342 PM CDT Tue Jul 1 2025

West to southwest winds of 5 to 15 knots with a few gusts to 20
knots are forecast over the next several days. There are
additional chances of thunderstorms Wednesday through Saturday.
Storms Wednesday afternoon and again Friday and Saturday may be
strong to severe. Aside from the thunderstorm chances, hazardous
conditions are not expected this week.

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