336
FXUS63 KDLH 310917
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
417 AM CDT Sun Aug 31 2025

.KEY MESSAGES...

- Warm weather with isolated to scattered showers and storms
  through Labor Day. Areas of fog overnight.

- Thunderstorms are possible with a cool front Tuesday and
  Tuesday night.

- Cooler temperatures and scattered rain showers expected
  Wednesday through the rest of the week. Frost Advisories may
  eventually be needed.

&&

.DISCUSSION...
Issued at 416 AM CDT Sun Aug 31 2025

Early this morning...

High pressure near the surface remains in place over the
western Great Lakes. Aloft there is a subtle shortwave trough
and lobe of cyclonic vorticity evident on GOES-East water vapor
imagery. The latest RAP13 forecasts continue to feature a very
subtle ripple in 700 mb heights associated with this feature.
Isentropic ascent was maximized over the Arrowhead in the
296-302K layer and was aiding ascent in that area. There appears
to be a pocket of 100 to as much as 500 J/kg of elevated
potential instability from the Arrowhead to the I-35 and US-53
corridors. A persistent cluster of showers and occasional
thunderstorms continued to percolate near the Twin Ports as of
08Z. Additional showers and occasional storms developed farther
north into the Arrowhead and northwest Ontario over the past few
hours. The showers/storms were moving toward the south-
southwest at 15 to 20 mph. The latest KDLH radar estimates
suggest rainfall amounts of a few hundredths up to around a
quarter inch of rain per hour with the precipitation. Storm
total accumulation revealed a few swaths of 0.5 to over 2 inches
where the heaviest showers were located. Expect the showers to
continue to bubble with occasional lightning discharges through
late this morning.

Elsewhere the story is similar to yesterday morning. We
continue to watch and wait for fog to develop under mainly clear
skies and light winds. Brainerd saw variable visibility between
unlimited and 1 mile so far. Aitkin, Bigfork, Longville, and
Hinckley each had reduced visibility as well. It appears the
pressure gradient is slightly tighter than last night which is
contributing to low, but not calm winds. Will continue to
monitor. A Dense Fog Advisory is not out of the question, though
there would need to be a rapid and more widespread decease in
visibility to warrant a headline.

Rest of today through Monday night...

Not much change from yesterday expected with today`s
conditions. Temperatures will climb into the middle 70s to low
80s with mostly sunny to partly cloudy skies initially. By this
afternoon diurnal heating will contribute to MLCAPE of 500 to
1500 J/kg with the greatest values forecast over the Arrowhead.
Convergence over the Arrowhead near the Lake Superior shore
should contribute to isolated to scattered showers and a few
thunderstorms. Effective shear is forecast to be quite anemic at
around 10 to 20 knots therefore pulse type convection is most
likely and severe weather is not expected. Slow storm motions
toward the southwest may produce brief periods of locally heavy
rain. Isolated rainfall amounts of 2 to 4 inches are possible
wherever the heaviest showers occur, although most locations
will see far less precipitation and much of the Northland will
be dry.

Small chances of showers and occasional thunderstorms persist
overnight. Overall trend PoPs downward a bit due to uncertainty
in location and coverage. Patchy fog will be possible once again
where skies are clear and winds calm.

Labor Day Monday will see weak southerly return flow will
develop in the low levels. Afternoon isolated to scattered
showers and a few thunderstorms appear likely, although coverage
is uncertain and warranted slight chance and chance PoPs in the
forecast. MLCAPE of 500 to 1500 J/kg is forecast again with
weak effective shear. Slow storm motions will provide a few
narrow and localized areas of heavy rain. Temperatures will be
in the middle 70s to low 80s.

The diurnal convection will persist into Monday night and may
increase in coverage in response to isentropic ascent over
northern Minnesota.

Tuesday through next weekend...

A cold front will sag southward across the Northland on
Tuesday. Showers and storms are likely to accompany the front.
Modest potential instability and limited shear will set the
stage for isolated non-severe storms. A closed upper-level low
will follow the front on Wednesday and will take up residence
over the western Great Lakes for the remainder of the week. Look
for autumnal temperatures with highs in the 50s to low 60s
Wednesday through Saturday and mainly cloudy skies. With cold
air advection and cyclonic flow aloft expect scattered showers
through the period. Anyone over northern Minnesota and awake
during the overnight hours may see the season`s first
"conversational" snowflakes Wednesday night and Thursday night.
The colder temperatures may also warrant Frost Advisories if
skies can clear and winds become calm.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1245 AM CDT Sun Aug 31 2025

A cluster of showers and occasional thunderstorms stretched
from near EVM to TWM to ASX as of 0515Z and were moving south-
southwest at around 15 mph. They will move through the DLH, HIB,
and HYR terminals before 09Z. Winds will veer easterly or
northeasterly as the showers pass by. Outside of the
showers/storms we still anticipate fog to develop at most of the
terminals overnight. BRD saw visibility as low as 1 mile so
far. Expect BRD, HIB, and HYR to see LIFR conditions later this
morning. Conditions should improve by 14Z as surface wind speeds
increase and daytime heating begins. Fog is possible again
after 01.06Z.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 416 AM CDT Sun Aug 31 2025

High pressure will remain in place over the region for the next
few days. This will keep winds generally less than 10 knots
from the southwest. Isolated showers and storms are likely today
and tonight. Occasional cloud-to-water lightning will be the
main threat from the storms.

A cold front is forecast to move southeastward across western
Lake Superior on Tuesday. Showers and thunderstorms are expected
with the front and winds will veer northwesterly and increase
in speed behind the front. Conditions will become hazardous for
small craft. Cool air will continue to pour into the area
through the end next week. Seasonably warm water temps will
contribute to persistent stronger winds and conditions hazardous
for smaller vessels.

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...Huyck
MARINE...Huyck