187
FXUS63 KDLH 021941
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
241 PM CDT Tue Sep 2 2025

.KEY MESSAGES...

- Showers and thunderstorms this afternoon and evening. A storm or
two could become strong to severe.

- Fall weather moves in on Wednesday, bringing cool temperatures and
persistent light rain shower chances. Some frost is possible
Wednesday and Thursday nights. A few snowflakes can`t be ruled out
overnight.

- Slightly warmer weather late-weekend into early next week.

&&

.DISCUSSION...
Issued at 241 PM CDT Tue Sep 2 2025

This afternoon and evening:

An unstable air mass is in place this afternoon ahead of a cold
front, which will pass through this evening. Skies have
partially cleared over north-central Minnesota following an MCV
that passed through earlier this morning. There won`t be a lot
of shear to tap into until the cold front passes through later
this evening, so chances for severe weather remain quite
marginal. A few cells that have already popped off in
Koochiching county are low-topped and nearly vertical. Mixed
layer shear is between 500 and 1000 J/kg, which is supportive
for the non-severe storms that they are. There is going to be a
few hours of opportunity for instability to build yet this
afternoon as these storms continue to expand in coverage and
move southeast. A storm or two could potentially become strong
to severe with large hail and damaging winds being the main
threats. As the cold front continues southeast, there could be a
brief window in northwest Wisconsin this evening where
lingering instability and better shear could combine to keep the
marginal severe threat going into the evening.

The rest of tonight:

The storms ahead of and along the cold front are expected to get
out of here by or just a bit after midnight. After they depart,
we will be in the post-frontal cold air advection northwest
flow, which will combine with a potent upper-level trough aloft
and some lingering moisture to keep some sprinkles or scattered
showers going.

Wednesday into Friday morning:

The temperatures will be noticeably cooler Wednesday with highs
staying in the 50s for most places. Widespread lows in the 30s
are expected Wednesday night into Thursday morning. Some of the
first snowflakes of the season could happen in inland portions
of the Arrowhead early Thursday morning as cyclonic flow aloft
and more moisture closer to the upper-level low in Ontario will
keep shower chances going through the night. Snow accumulations
are not expected, but a mix or brief changeover to wet snow is
certainly possible come Thursday morning. The other question for
Thursday is frost potential, and with so many clouds and showers
across the Arrowhead, chances for frost will be reduced there,
even with the potential for snowflakes. Much of the rest of the
region may have a slightly better chance for some frost if
enough of the clouds can clear.

Cyclonic flow aloft continues Thursday, and another trough is
likely to move overhead Thursday afternoon and evening. This
should bring another round of rain to much of the region. This
will be a light, cold rain with amounts perhaps reaching a
quarter inch on the high end (most places less). Any snowflakes
from this would again be confined to the inland Arrowhead areas,
but it will be much less likely Friday morning with slightly
warmer air.

Friday into this weekend:

Lingering cool cyclonic flow will keep scattered showers around
with highs still topping out in the 50s for most. Going into
Saturday, the broad upper trough will finally start moving east
and a broad ridge to our west will bring a very slow moderation
to temperatures as warm air advection starts to move in from the
west. We may still hang on to a few showers even into Saturday,
but Sunday should be dry with southerly winds developing. Early
next week is looking warmer with highs returning to the 60s and
perhaps some rain and storm chances returning.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1249 PM CDT Tue Sep 2 2025

The first wave of showers is making its way through right now,
just about to exit DLH and HYR. A brief period of MVFR ceilings
is possible at HYR in the next hour or two, then VFR at most
other terminals for the next few hours. Ceilings are already
starting to fall to MVFR at INL in advance of a cold front.
Additional showers and storms are expected to develop along and
ahead of the front through this afternoon and should either
directly affect each terminal or at least pass by in the
vicinity. These showers and storms should be at least somewhat
scattered in coverage, which leads to uncertainty in timing and
proximity to terminals, which is why they were handled with
tempo groups. After that, winds become gradually northwesterly
and breezy. Widespread MVFR ceilings are expected to persist
through the period with occasional passing light rain showers.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 241 PM CDT Tue Sep 2 2025

A cold front will pass through this evening, bringing scattered
showers and thunderstorms with it. There is a low chance (5%)
for a stray strong to severe storm which could produce large
hail to quarter size or gusty winds to 30-40 kt. After the front
passes, winds from the northwest will pick up with gusts to
around 25 kt across all nearshore waters. The Small Craft
Advisory has been bumped back to a start time at midnight as
stronger wind gusts may arrive a bit earlier. The gusty
northwest winds are expected to persist with slight ups and
downs through Friday. The Small Craft Advisory currently in
effect through Wednesday night will likely need an extension
into Thursday, and slightly stronger winds gusting up to 25-30
kt on Friday will also likely require a Small Craft Advisory.
Some breezy conditions may persist into Saturday. From Wednesday
through Friday, there will also be scattered showers at times.

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 midnight tonight to 4 AM CDT
     Thursday for LSZ121-140>148-150.

&&

$$

DISCUSSION...JDS
AVIATION...JDS
MARINE...JDS