972
FXUS63 KDLH 211123
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
623 AM CDT Mon Sep 21 2026

.KEY MESSAGES...

- A Frost Advisory is in effect early this morning for the
  Borderlands

- Persistent northeasterly winds will keep the threat for rip
  currents going at Twin Port beaches today and may linger into
  mid-week as well. They will also create hazardous conditions
  on Lake Superior through Tuesday.

- Widespread frost and perhaps some areas of freeze are
  forecast for tonight into Tuesday morning. Additional chilly
  nights with the potential for frost are expected Tuesday night
  into Wednesday.

- Low chances for rainfall through the forecast period.

&&

.DISCUSSION...
Issued at 231 AM CDT Mon Sep 21 2026

Early this morning, high pressure over northwestern Ontario is
keeping our weather generally dry and cool. Between this high
pressure and lower pressure to our south there is a relatively
tight pressure gradient, which is maintaining breezy northeast
winds, particularly near Lake Superior. Drier air is filtering
into the area at low levels, but mid and high clouds have spread
across the area from the low pressure system to the south.
Temperatures dropping to overnight lows into the mid 30s
prompted a Frost Advisory through 8 AM for Koochiching, North
St. Louis, and northern Cook and Lake counties. Today, we expect
the northeast winds to slowly decrease as the gradient weakens,
and clouds will gradually clear from northwest to southeast
during the daytime.

Tonight into Tuesday morning is likely to be our coldest night
of the week. With the Canadian high settling nearly overhead,
mostly clear or clear skies and light winds will set the stage
for excellent radiational cooling. Lows are forecast to plummet
into the 30s for most inland areas, while lakeshore communities
remain slightly warmer in the 40s. A widespread frost is highly
likely across the Northland, and some locations north of the
Iron Range could see temperatures dip below freezing. Additional
frost or freeze headlines will likely be needed for tonight
into Tuesday morning.

On Tuesday, the high pressure center will begin drifting toward
the east, causing our winds to veer southeasterly. This return
flow marks the beginning of a gradual warming trend that will
carry us through the remainder of the week. Afternoon highs on
Tuesday will rebound comfortably into the 60s, though the
onshore flow will keep the North Shore a bit cooler in the upper
50s. Another chilly night is expected Tuesday night, bringing
yet another chance for patchy frost inland.

Upper level ridging will build across the Upper Midwest for the
middle and later part of the work week. A shortwave riding over
the top of the ridge brings a chance for showers Wednesday
night into Thursday, but dry low levels will limit widespread
rainfall. Otherwise, the ridging aloft will provide generally
dry and quiet weather with temperatures slowly rising into the
weekend. Highs will reach the mid 60s to lower 70s for Friday
and Saturday. Precipitation chances remain quite low and spotty
heading into the weekend even as the ridging eventually slides
eastward.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 622 AM CDT Mon Sep 21 2026

Predominantly VFR conditions are expected for this TAF period.
KDLH has some stratus this morning, and KHIB and KINL have MVFR
fog. Both sites should improve back to VFR by 14z this morning.
KDLH will have east winds around 10 knots, but all other
terminals will have winds of less than 10 kts. VFR conditions
are then expected through most of the remainder of the TAF
period. Fog is possible again tonight, especially for KHIB, and
have included some MVFR visibilities beginning around 09z.

&&

.MARINE /FOR NEARSHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 231 AM CDT Mon Sep 21 2026

Hazardous conditions will persist across western Lake Superior
through Tuesday, due to strong gusty winds caused by a tight
pressure gradient. East to northeast winds of 10 to 15 knots
with gusts reaching 25 knots are expected today, highest in the
western arm during the afternoon and early evening. Waves will
build to 2 to 4 feet. A Small Craft Advisory has been issued
for today and this evening. Winds and waves will both relax
overnight tonight. Northeast wind gusts to 25 knots will
redevelop by Tuesday afternoon, which may require an additional
Small Craft Advisory.

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

&&

.FIRE WEATHER...
Issued at 231 AM CDT Mon Sep 21 2026

Winds continue to be the main concern today and tomorrow,
especially near Lake Superior. Gusts up to 20 mph will be
possible this afternoon and early evening before diminishing
during the evening. Minimum RH values are expected to remain
above 50%. Afternoon minimum RH values of 40-55% are expected
for Tuesday and Wednesday. Values may fall into the 35-45% range
both days across the Wisconsin Pine Barrens. The next chance
for light rainfall arrives late Wednesday into Thursday, though
significant wetting rain is unlikely.

See the Fire Weather Forecast product for a more thorough
breakdown of fire weather conditions.

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...Frost Advisory until 8 AM CDT this morning for MNZ010>012.
     Beach Hazards Statement from 10 AM CDT this morning through
     this evening for MNZ037.
WI...Beach Hazards Statement from 10 AM CDT this morning through
     this evening for WIZ001.
MARINE...Small Craft Advisory from noon today to 10 PM CDT this evening
     for LSZ143>148-150.

&&

$$

DISCUSSION...LE
AVIATION...LE
MARINE...LE
FIRE WEATHER...LE