439
FXUS63 KDLH 211057
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
557 AM CDT Thu Aug 21 2025

.KEY MESSAGES...

- Areas of dense fog this morning will erode later this morning.

- A slow-moving cold front crosses late Thursday through Friday
  with scattered rain showers and thunderstorms. A few storms
  may be strong to severe with large hail and damaging winds
  being the primary threats.

- Behind the front expect much cooler temperatures for the
  weekend into early next week with high temperatures generally
  in the 60s and lows in the 40s. Depending on cloud cover and
  winds, frost is a concern if temperatures can cool into the
  30s at night.

- Increasing west to northwest winds Saturday through Monday
  with gusts of 25-30kts will be hazardous to small craft.

&&

.DISCUSSION...
Issued at 312 AM CDT Thu Aug 21 2025

Current Conditions/Today:

There still remains a few areas of patchy fog but those will quickly
erode shortly after sunrise. A roaring low level jet across the
Northern Plains has been supporting a thunderstorm complex over
Southern Manitoba overnight. Models are struggling with the
progression of this complex but with the low level jet weakening
through the morning hours the storms should be weakening.
However, some rain and a few rumbles of thunder across the
Borderlands this morning can`t be ruled out. The next feature to
focus on will be the cold front expected to swing in from the
Canadian Prairies this afternoon and evening. Still a rather
large spread of solutions among the CAMs which is not too
surprising given the lack of consensus on the early morning
storm complex. Convective parameters are certainly on the low
side of severe out ahead of the front with instability maxing
out around 750 J/kg of MLCAPE. A shortwave moving overhead may
provide a boost to bulk shear with values close to 45 kts.
However, a stout warm nose paired with an impressive dry slot in
the low levels will make things difficult for air parcels to
get going. The better chances for convection may be later in the
evening along the front, but by then things will be more
elevated in nature with even less instability and shear to work
with. Overall, SPC has maintained the marginal risk (threat
level 1 out of 5) over most of NE MN with the primary threats
still being large hail and damaging winds.

Friday:

The cold front continues its slow slog through the Northland and is
expected to be draped somewhere between the Brainerd Lakes Region
and up into the Arrowhead by Friday afternoon. With the models
slowing the progression of the front down SPC has expanded the
marginal risk for severe weather to include those area mentioned
above. While both today and tomorrow have a marginal risk for
severe storms to develop the Friday set up is ever so slightly
better. The forecast instability will be higher (over 1500
J/kg). A mid level jet will be crossing overhead as well
providing a much better boost to bulk shear values along the
boundary. Primary hazards still look to be large hail and
damaging winds in the afternoon and evening hours.

The weekend into Midweek:

A large upper level low will be migrating across Ontario helping to
usher in some Autumn like temperatures behind the exiting cold front
for the weekend and early next week. Highs will be in the 60s with
lows in the 40s. Cyclonic flow aloft combined with wrap around
moisture from the low will lead to scattered rain showers Saturday
and Sunday before high pressure moves in from the Northern Plains.
Not expecting severe weather with these precipitation chances, but
the steep low level lapse rates could lead to enhanced gusts at
times.

By Monday, the aforementioned high pressure will begin to nudge in
from the west and may lead to frost concerns Monday night. Rapid
radiational cooling due to lack of cloud cover may lead to
frost across portions of northern MN and NW WI. The high
pressure continues to slide east through the week with warming
temperatures back by mid week with highs returning to the 70s.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 556 AM CDT Thu Aug 21 2025

Areas of patchy fog this morning will disperse a few hours
after TAF issuance. Radar shows a thunderstorm complex in
Southern Manitoba with a few stray showers in the vicinity of
INL. Lighting trends and cloud tops show a weakening trend for
these storms. Later this afternoon and evening a cold front is
expected to move in from the west. This could generate
additional showers and storms, some of which may be strong to
severe. Timing is still very questionable with high res guidance
having a high variance in frontal placement.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 312 AM CDT Thu Aug 21 2025

A few areas of fog this morning are possible but are expected to
dissipate shortly after sunrise. Light winds out of the east today.
A slow moving cold front will cross into the Lake on Friday and may
bring some showers and storms. Northwest winds begin to increase
late Friday and into the weekend behind the cold front. Small Craft
Advisories may be needed.

For the open water discussion, refer to the NWS Marquette Area
Forecast Discussion at weather.gov/mqt.

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...Dense Fog Advisory until 8 AM CDT this morning for MNZ037.
WI...None.
MARINE...None.

&&

$$

DISCUSSION...Britt
AVIATION...Britt
MARINE...Britt