258
FXUS63 KDLH 220145
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
845 PM CDT Thu Aug 21 2025

.KEY MESSAGES...

- A slow moving cold front creates scattered rain showers and
  isolated thunderstorms tonight and a period of strong
  thunderstorms are possible Friday.

- A secondary front brings much cooler temperatures for the
  weekend into early next week with high temperatures generally
  in the upper 50s and 60s with lows in the upper 30s and 40s.
  Depending on cloud cover and winds, frost is a concern as
  temperatures cool into the 30s Tuesday morning.

- Increasing west to northwest winds Friday night through
  Sunday night with gusts of 25-30kts will be hazardous to small
  craft.

&&

.DISCUSSION...
Issued at 152 PM CDT Thu Aug 21 2025
Updated at 835 PM

UPDATE 835 PM - The more primed severe weather environment has
remained into western Minnesota and is largely expected to
linger there into the early overnight hours tonight. The chances
of severe weather tonight has largely diminished as of now for
the Northland. An isolated strong thunderstorm still cannot be
ruled out for the Borderlands of far northern Minnesota though
as a second weak ripple in the mid-levels keeps scattered rain
showers and isolated thunderstorm chances in place.

PREVIOUS DISCUSSION

A nearly stacked low pressure system is pushing east across
southern Canada today, with an initial cold front stretching
south from Manitoba through the Dakotas. Ahead of that front, a
band of light rainfall has been pushed eastward along the
International Border most of today. Stronger mid level winds
have helped sustain a couple clusters of thunderstorms moving
through Lake of the Woods southward to near INL.

The front will slowly push eastward into the Northland later
today and help kick off scattered showers and storms. There is
40-50kts of shear along with an increase in CAPE values with
daytime heating. Strong to severe chances will be limited given
a cap at 850mb and the lack of significant forcing. If an
updraft can sustain itself this afternoon, large hail and
damaging winds will be the main threats. With loss of heating
through the evening, severe chances diminish. The front
continues through the area tomorrow, and the focus for strong to
severe storms will shift eastward, more focused along and south
of a line from the Arrowhead to Brainerd. Lapse rates are not
as supportive tomorrow, with the better wind shear removed from
the best instabilities. Best chances for a strong to severe
storm would be along the front as wind profiles increase near
the instability gradient.

A secondary cold front arrives Friday night as the upper level
system shifts eastward into Ontario. Northwesterly winds will
usher in cooler and briefly drier air, as surface high pressure
slides southward into the northern Plains. The large upper low
system will spin across southeast Canada through early next
week, leaving the Northland in deep layer northwesterly flow
into Tuesday. Moisture advects back into the area, and could see
scattered showers under the low across the Arrowhead Saturday
and Sunday. This could also promote some lake effect showers on
the south shore Monday and Tuesday.

Highs on Saturday will be in the 60s, with lows Saturday night
in the 40s. Coolest air arrives for Sunday, keeping highs in the
mid to upper 50s across the Arrowhead and 60 elsewhere. Surface
high pressure slides over the area Monday night into Tuesday.
With lows falling into the mid 30s to lower 40s, patchy frost is
possible Tuesday morning, but locations and extent will depend
on how much the wind fields relax. A gradual warming trend is
expected through the rest of the week.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 637 PM CDT Thu Aug 21 2025

Southerly winds are ongoing this evening out ahead of a slow
moving cold front that drops southeastward into the region
tonight. Expect widely scattered rain showers and thunderstorms
this evening and early overnight, with a second round after 12Z
Friday morning for east-central Minnesota and most of northwest
Wisconsin. Winds shift westerly around 12Z and increases in
speed around 18Z for north-central Minnesota. Expect gusty
westerly winds lasting into Friday night and much of the
weekend.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 835 PM CDT Thu Aug 21 2025

Southwest winds persist Friday daytime ahead of a slow-moving
initial cold front that crosses over the lake. Behind that
front, westerly winds begin to increase early Friday night. A
Small Craft Advisory was issued for all nearshore zones in
western Lake Superior covering Friday night through Saturday
evening. While the end time of this headline is currently
Saturday evening at 10 PM CT, maybe all or at least many zones
are likely to be needed extensions in time into Sunday. A
secondary reinforcing cold front drops southward Saturday and
further shifts winds to northwesterly. These gusty northwesterly
winds slowly decrease Monday daytime as high pressure sets up.

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 10 PM Friday to 10 PM CDT Saturday
     for LSZ121-140>148-150.

&&

$$

DISCUSSION...NLy/HA
AVIATION...NLy
MARINE...NLy