651
FXUS63 KDLH 061954
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
254 PM CDT Sat Sep 6 2025

.KEY MESSAGES...

- Frost is likely for interior portions of northeast Minnesota
  tonight and northwest Wisconsin tonight. Freezing
  temperatures are likely for many places in Koochiching and
  north/central St. Louis counties. Frost and freeze headlines
  are in effect.

- Temperatures return to around seasonal normals for next week.

- There is a small chance (~20%) for a few strong to severe
  storms Monday afternoon and evening.

&&

.DISCUSSION...
Issued at 253 PM CDT Sat Sep 6 2025

This afternoon:
There`s just enough instability out there combined
with a passing short wave aloft to promote scattered showers, which
are expected to persist through the afternoon and early evening. A
few rumbles of thunder can`t be ruled out this afternoon, but for
the most part, instability less than 500 J/kg should keep most of
the showers lightning free.

Tonight:
Surface high pressure will pass through with the Northland just
on the northern side of the center. As such, winds are expected
to become very light tonight, and there should be some large-
scale clearing of clouds after the convective showers end this
evening and the upper-level trough moves east. That said, there
will probably be some clouds that linger, including some lake-
effect cloud streamers coming off the larger inland Minnesota
lakes and also affecting the South Shore. This will help
moderate things a little bit, but otherwise, it`s looking like a
pretty good radiational cooling night. Much like last night,
there will probably be a few localized locations that fall to or
just a degree or two below freezing, though most places should
be a bit above freezing. Frost should be pretty widespread
across the interior Arrowhead areas, much like last night.
Northwest Wisconsin is a little less certain with a bit more
lingering clouds possible as the upper-level trough slowly moves
out, combined with the aforementioned lake-effect clouds along
the South Shore. Despite some uncertainties, ensemble
probabilities for temperatures below 36 degrees for most areas
is ~90% and there are 40-60% probabilities for freezing
temperatures in areas where a Freeze Warning has been issued for
Koochiching and north/central St. Louis Counties. Cover up your
plants!

There may be a bit of fog tonight as well, with 20-50%
probabilities for visibilities down to half a mile or so for a
brief period tonight for mainly inland areas.

Sunday and Sunday night:
High pressure at the surface will move east
and winds will become west to southwesterly as 850 hPa ridging moves
in. Highs are expected to rise into the low 60s for most places with
dry weather expected. There could be a stray shower in the tip of
the Arrowhead as a weak wave passes by in Ontario, but this should
be pretty insignificant. Sunshine should be quite prevalent during
the day, and as winds become southerly Sunday night with warm air
advection, low temperatures will be warmer and frost is not expected.

Monday and Tuesday:
Southwesterly warm air and moisture advection aloft will
combine with potential for some weak synoptic lift with some
passing shortwaves to bring about some chances for showers and
thunderstorms during the afternoon and evening. There hasn`t
been much change with this update for expected conditions. It
still looks like shear should be pretty modest at around 25 kt
and instability will be on the low end of favorable for any
strong to severe storms at around 500 to just over 1000 J/kg.
Another potential issue may be capping that could prevent some
storms initially, though that could also lead to a bit of a
"loaded gun" scenario where, once the cap does bust, a few
discrete storms could go a little wild for a bit and produce
some large hail or damaging winds. So, it`s worth keeping an eye
on, but right now it`s looking like the Northland will see some
general showers and thunderstorms (40-60% chance) and a ~20%
chance for any of those to become strong to severe (hail to
around quarter size and wind gusts up to 60 mph).

With the warm air advection persisting into the night, showers and
storms could persist into Tuesday, though severe potential should
disappear sometime Monday evening. We`ll have to keep a casual eye
on a very small potential for training of showers/storms with PWATs
in the ~1.0-1.5" range. Some localized rainfall amounts exceeding an
inch could be possible (~10-20% chance). Outside of storm
chances, expect more mild weather with highs reaching the lower
70s come Tuesday with at least some sunshine likely.

Wednesday through Saturday:
There`s high confidence that we will stay within a general
southerly flow warm air advection pattern during this period
which will keep temperatures on the mild side. The broad ridge
is looking like it could be a bit dirty with the potential for
some passing shortwaves that could bring some rain chances at
times. Deterministic and ensemble models are not in good
agreement for any specific timeframes, but overall suggest on-
and- off opportunities for passing waves that could bring brief
bouts of rain. Thunder can`t be ruled out either. Diurnal
instability may also contribute to some afternoon popcorn-style
showers at times in the absence of a broader synoptic feature.
In general, this period shouldn`t be a total washout, and
certainly some sunshine can be expected at times as well.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1241 PM CDT Sat Sep 6 2025

The main concern for this afternoon is scattered showers and the
stray possibility for a brief thunderstorm. Confidence is low
enough not to include a thunder mention in the TAFs. The
showers are ongoing, and despite a little gap between INL/HIB,
their coverage is scattered to numerous such that the best way
to handle them is with PROB30 in the TAFs through this
afternoon. Right around sunset, the showers are expected to
decrease in coverage and intensity before coming to an end this
evening. Occasional wind gusts to 15-20 kt can be expected in
and around any of these showers.

Tonight, largely VFR conditions, though some fog is possible in
the usual low-lying areas (mainly HIB/BRD/HYR) with clearing
skies and light winds. A period of MVFR/IFR visibility is
possible in the early morning hours.

Northwesterly winds this afternoon become light tonight, then
westerly Saturday morning.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 205 PM CDT Sat Sep 6 2025

With winds gusting up to 18-23 kt from Port Wing to Devils
Island to La Pointe, the Small Craft Advisory will remain in
effect through the early evening. If winds lessen earlier, the
Small Craft Advisory may be allowed to expire early. Winds are
expected to remain southwesterly through the rest of the weekend
with gusts often from 15-20 kt. Winds become southerly going
into Monday. There will be some scattered showers out there
through this evening, dry on Sunday, then shower and storm
chances return Monday afternoon.

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

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...Freeze Warning from 2 AM to 8 AM CDT Sunday for MNZ010-011-019.
     Frost Advisory from 2 AM to 8 AM CDT Sunday for MNZ012-018-025-
     026-035>038.
WI...Frost Advisory from 2 AM to 8 AM CDT Sunday for WIZ001>003-
     006>008.
MARINE...Small Craft Advisory until 10 PM CDT this evening for LSZ146-
     147-150.

&&

$$

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