343
FXUS63 KDLH 201147
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
647 AM CDT Sun Sep 20 2026

.KEY MESSAGES...

- Dangerous swimming conditions expected for the beaches of the
  Twin Ports today and Monday.

- Frost is forecast beginning tonight and continuing through
  Wednesday night. The coldest night will be Monday night into
  Tuesday morning, when sub-freezing temperatures are forecast.

&&

.DISCUSSION...
Issued at 305 AM CDT Sun Sep 20 2026

Early this morning, a weak cold front continues to push south
across the Northland, We will see lingering low clouds and fog
which dissipate after sunrise. Today, gusty northeast winds are
expected to develop, as the cold front sags to our south and
high pressure moving in from the north tightens the pressure
gradient. Wind gusts of up to 35 mph are possible for the Twin
Ports and South Shore areas during the daytime, with wind gusts
of 20 to 25 mph farther inland. These winds will lead to another
day of High Risk for rip currents for the Twin Ports beaches. A
Beach Hazards Statement will again be needed for Sunday and
also likely again Monday. This surge will also bring cooler and
drier air into the region, with high temperatures near Lake
Superior only in the upper 50s, with 60s elsewhere.

We have been seeing signals for isolated lake effect showers in
the CAMs for today, but I suspect we do not yet have enough
temperature difference between the surface and 850mb for true
lake effects. Later today, the drier air moving in from the
northeast will shut off this potential completely.

Clouds will clear from northwest to southeast tonight into
Monday. Together with the high pressure building in with lighter
winds and the cooler airmass, means a small area of frost is
possible for the Minnesota Borderlands and interior Arrowhead by
early Monday morning. Frost headlines may be needed for these
limited areas pending the exact sky cover trends today and this
evening. Monday will feature mostly sunny skies but cool
conditions with a repeat of 50s near Lake Superior and low-mid
60s elsewhere. The northeast winds will likely give us another
day with elevated rip current risk along the beaches of the Twin
Ports.

The coldest night this week will be Monday night into Tuesday
morning, with mostly clear skies, and light winds with the
surface high pressure ridge overhead. This will lead to
excellent radiational cooling overnight, which should produce
widespread frost over much of the region, with even some sub-
freezing temperatures in our local cold spots. Frost and Freeze
headlines will likely be needed. Tuesday will remain sunny and
cool with with high temperatures moderating slightly but still
on the cool side. Another round of frost is possible Tuesday
night into Wednesday morning with continued dry, calm and clear
conditions.

A gradual warming trends begins on Wednesday as the surface
high pressure ridge slides east of the area, allowing warmer air
and more moisture to move back into the area. A shortwave may
bring some precipitation chances back into the area on Thursday,
but otherwise the forecast is generally dry for the rest of the
work week, with high temperatures rising into the 60s and low
70s by Friday and Saturday. Next weekend there are some
indications we may have some precipitation chances, but
confidence remains low with an upper level ridge in place and
generally weak features.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 647 AM CDT Sun Sep 20 2026

A weak cold front has sagged south into northwest Wisconsin as
of early this morning. Along the front, there is an area of MVFR
to VFR ceilings which are being dragged south along with it.
Away from the front where there are few to no clouds, we are
getting some fog development, with visibilities ranging from
LIFR to IFR. Another area of stratus with IFR to MVFR ceilings
has sagged into far northern MN, affecting KINL and is
approaching KHIB. The fog should gradually dissipate this
morning, but the stratus may take longer and have not returned
INL to VFR until 18z. Once this stratus lifts or sags south of
the area, I expect the remainder of the TAF period to have VFR
conditions. Winds will increase out of the northeast today, and
will be strongest at DLH with gusts around 20 kts. Winds to
diminish around 00z to 10kts or less.

&&

.MARINE /FOR NEARSHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 305 AM CDT Sun Sep 20 2026

Winds will increase significantly this morning for most of
western Lake Superior. Northeast winds of 15 to 25 knots are
forecast, with gusts reaching 25 to 30 knots in the southwest
arm and along the South Shore. Waves will build to 4 to 7 feet.
Small Craft Advisories are in effect. A short period of gales to
35 knots is possible but not likely from Silver Bay to Duluth
and along the South Shore. Winds decrease Sunday evening, but
expect lingering swell into Monday from 1 to 3 feet under
continued northeast winds of 10 to 20 knots and gusts of 20 to
25 knots for the South Shore and southwest arm during the day on
Monday. Additional Small Craft Advisories may be needed. The
northeast winds continue on Tuesday, but speeds will be lighter.

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

&&

.FIRE WEATHER...
Issued at 305 AM CDT Sun Sep 20 2026

Fire weather concerns remain low through the forecast period.
Minimum relative humidity values today will remain above 50
percent, even as winds increase out of the northeast and become
gusty. The strongest winds will be found near Lake Superior,
where winds of 10 to 15 mph may gusts as high as 25 mph.
Elsewhere, winds will be 5 to 15 mph with gusts up to 20 mph.
The generally cooler conditions will continue into Monday with
highs only in the 60s and with minimum RH values generally
between 40 and 50 percent. Otherwise, we have a period of no
precipitation through Wednesday, with gradually lowering minimum
RH values, moderating temperatures and lighter wind speeds.

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

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...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 until 10 PM CDT this evening for LSZ121-
     143>148-150.
     Small Craft Advisory until 4 PM CDT this afternoon for LSZ140.

&&

$$

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