641
FXUS63 KDLH 021146
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
646 AM CDT Tue Sep 2 2025

.KEY MESSAGES...

- Rain and thunderstorms this morning. Then storms redevelop
  this afternoon ahead of a cool front. A few storms may be
  strong to severe. Locally heavy rain may lead to localized
  minor flooding.

- In the wake of the cold front Wednesday through Saturday,
  expect colder temperatures. Skies will be mostly cloudy until
  Saturday. There will be rain showers off and on through the
  end of the week. A few snowflakes may mix in with the rain
  during the overnight periods. No accumulation expected.

- Starting Wednesday night, there will be the potential for
  frost with overnight lows dropping into the 30s for areas in
  northern Minnesota.

&&

.UPDATE...
Issued at 646 AM CDT Tue Sep 2 2025

MCV over Koochiching and Itasca counties will continue to
propagate southeastward this morning. The best instability and
forcing for additional storms continues to be south of the meso-
low over central Minnesota into northwest Wisconsin. The cluster
of showers and storms was moving toward the southeast at around
25 mph. Radar estimated rainfall in portions of northern Cass
County were 1.5 to nearly 2 inches. Flash flood guidance is
about 4 inches this morning so we have little concern for
flooding for the moment. The storms will move through northwest
Wisconsin through late this morning. Current expectations are
that the weakening trend will continue. The main question after
that is how quickly skies clear. GOES-East satellite imagery
reveals mostly clear skies already in Lake of the Woods, Roseau,
and Kittson counties. If skies are able to clear by late
morning over much of central and northern Minnesota, the heating
and moisture flux from the morning rainfall may give a boost to
instability and severe storm potential later today.

&&

.DISCUSSION...
Issued at 426 AM CDT Tue Sep 2 2025

Early this morning...

A well-developed MCV was evident on region radar mosaics over
Lake of the Woods and Koochiching counties as of 0830Z. RAP
mesoanalysis revealed this feature was located within a
shortwave trough which was propagating eastward over northern
Minnesota. A broadening cluster of showers and thunderstorms
extended from near the center of the MCV east into northern St.
Louis County and south into the Brainerd Lakes before arcing
back toward the northwest to near Mayville, ND. Instability is
weaker than the last update around 06Z and was in the 500 to
around 1300 J/kg range per RAP analysis with the maxima located
south of the existing storms in central Minnesota. Effective
shear remained meager in the 15 to 25 knot range. Storms pulsed
up and down over the past few hours which appears to limit the
risk of hail and damaging winds. Rainfall has not been
particularly high either due to the variable intensity of the
storms.

The MCV is forecast to propagate southeastward toward the Twin
Ports this morning. Look for rain and storms to gradually weaken
with time as they advance south and southeastward into
northwest Wisconsin by 16-18Z.

Later today and tonight...

Cold front is still poised to run southeastward across the
Northland this afternoon and tonight. Skies are expected to
become partly cloudy in the wake of the morning storms which
should allow ample destabilization by late afternoon. RAP MUCAPE
along the front is forecast between 1500 in northern St. Louis
County to around 2500 J/kg in the Brainerd Lakes. Effective
shear along the front should be in the 15 to 25 knot range which
suggests mainly upright pulse storms and a limited severe
weather risk. Shear improves over central Minnesota into
northwest Wisconsin this evening to 20 to 30 knots which may
support better storm-scale organization and a slightly greater
risk of severe storms. Hail to ping pong ball size and wind
gusts of 40 to 60 mph are the main concern with storms that
develop along the front later today. Highs today will reach the
low to upper 70s, which will be very pleasant compared to the
remainder of the week.

Storms will propagate southeastward with time tonight and
gradually weaken overnight as they move out of our area.
Elongating moisture transport vectors from the I-35 corridor
into northwest Wisconsin in the presence of PWATs around 1.3
inches and very moist vertical profiles suggest storms will be
efficient rain producers. Locally heavy rainfall is a
possibility with training storms both this afternoon and tonight
which could lead to localized minor flooding.

Wednesday and beyond...

A very broad closed upper-level low pressure system will take
up residence over northeast Ontario Wednesday through Saturday
morning. This will keep the Northland under cold air advection
and cyclonic flow aloft. Temperatures will fall well below
normal for the remainder of the week with highs in the upper 40s
in the Arrowhead to the upper 50s to low 60s elsewhere. Lake-
effect rain showers are likely for portions of the South Shore.
Widespread rain showers are expected for Wednesday and should
become scattered on Thursday and Friday. Profiles remain cold
enough for a few snowflakes or snow showers overnight. No
accumulation is expected from any snow that falls. The upper low
gradually migrates toward the Canadian Maritimes over the
weekend which will allow warmer temperatures to return. Highs on
Sunday are expected to be in the 60s and a few 70s are possible
next Monday.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 646 AM CDT Tue Sep 2 2025

An area of rain and storms over central and east-central
Minnesota will continue to move southeast at 25 mph this
morning. This will bring the storms into HYR around 14Z. Rain
and storms will move out of the terminals this morning. The main
concern is whether and when storms redevelop this afternoon
ahead of an approaching cold front. Continued the earlier trend
of PROB30s for the most likely times for additional storms.
Behind the cold front expect MVFR ceilings.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 426 AM CDT Tue Sep 2 2025

Showers and a few thunderstorms are expected over the southwest
arm later this morning and the South Shore early this
afternoon. A cold front will advance eastward across the water
this afternoon and tonight. Another round of showers and
thunderstorms are forecast. Storms may be strong with wind gusts
of 35 to 50 knots possible and hail up to quarter size. Winds
will veer northwesterly behind the front. Wind speeds and gusts
will increase overnight and Wednesday morning and will become
hazardous to smaller vessels. A Small Craft Advisory has been
issued. Strong and gusty winds will persist through the end of
the week as cold air continues to pour into the region.
Additional Small Craft Advisories will be needed.

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...Small Craft Advisory from 4 AM Wednesday to 4 AM CDT Thursday
     for LSZ121-140>148-150.

&&

$$

UPDATE...Huyck
DISCUSSION...Huyck
AVIATION...Huyck
MARINE...Huyck