719
FZUS63 KMQT 180801
GLFLS

Open Lake Forecast for Lake Superior
National Weather Service Marquette MI
401 AM EDT Mon Aug 18 2025

For waters beyond 5 nautical miles of shore on Lake Superior.

Waves are the significant wave height - the average of the
highest 1/3 of the wave spectrum. Occasional wave height is the
average of the highest 1/10 of the wave spectrum.

.SYNOPSIS...

A 30.3 inch high is south of James Bay this morning while broad 29.9
inch troughing extends through the Great Plains. Throughout today
into tonight, the trough will weaken slightly while the high shifts
fully into Quebec. As weak low pressure near 30.0 inches skirts
south of the lake, 30.1 inch high presssure builds over northern
Minnesota/northern Ontario/southern Manitoba Tuesday. This high
builds further to 30.2 inches over the lake Wednesday afternoon. By
late Thursday, a 29.7 inch low over northern Manitoba and far-
northern Ontario will erode the high pressure over the Upper Great
Lakes to 30.0 inches. For Friday and into the weekend, the low will
pass along the shores of Hudson Bay at around 29.6 inches, passing a
29.8 inch trough over Lake Superior.


LSZ162-182000-
Lake Superior west of a line from Saxon Harbor WI to Grand
Portage MN beyond 5NM-
401 AM EDT Mon Aug 18 2025 /301 AM CDT Mon Aug 18 2025/

.EARLY THIS MORNING...Southeast winds 10 to 20 knots. A chance of
showers and a slight chance of thunderstorms. Waves 3 to 5 feet
occasionally to 7 feet subsiding to 2 to 4 feet.
.TODAY...Southeast winds 10 to 20 knots backing east in the
afternoon, then diminishing to 5 to 15 knots late. Showers likely
through early afternoon. A chance of thunderstorms. A chance of
showers by mid afternoon. Waves subsiding to calm to 2 feet.
.TONIGHT...Northeast winds 5 to 15 knots backing north after
midnight. A slight chance of showers through midnight. Waves calm
to 2 feet.
.TUESDAY...North winds 10 to 20 knots diminishing to 5 to
15 knots in the afternoon, then veering east late. Waves calm to
2 feet.
.TUESDAY NIGHT...East winds 5 to 15 knots backing north after
midnight. Waves calm to 2 feet.
.WEDNESDAY...North winds 5 to 15 knots veering south by mid
afternoon. Waves calm to 2 feet.
.WEDNESDAY NIGHT...Southeast winds 5 to 15 knots veering south
after midnight. Waves calm to 2 feet.
.THURSDAY...South winds 5 to 15 knots becoming southwest 10 to
20 knots. A chance of showers. Waves calm to 2 feet.
.FRIDAY...West winds 10 to 20 knots. Waves building to 1 to
3 feet.

$$

LSZ263-182000-
Lake Superior from Saxon Harbor WI to Upper Entrance to Portage
Canal MI 5NM off shore to the US/Canadian border including Isle
Royale National Park-
401 AM EDT Mon Aug 18 2025

.EARLY THIS MORNING...Southeast winds 10 to 20 knots. A chance of
showers and a slight chance of thunderstorms. Waves 2 to 4 feet.
.TODAY...Southeast winds 10 to 20 knots. Showers likely through
early afternoon. A chance of thunderstorms. A chance of showers
by mid afternoon. Waves subsiding to 1 to 3 feet, then building
to 3 to 5 feet occasionally to 7 feet.
.TONIGHT...Southeast winds 10 to 20 knots becoming south 5 to
15 knots after midnight, then backing north late. A slight chance
of thunderstorms through midnight. A chance of showers. Waves
subsiding to 1 to 3 feet.
.TUESDAY...North winds 10 to 20 knots diminishing to 5 to
15 knots late. Waves subsiding to calm to 2 feet.
.TUESDAY NIGHT...North winds 5 to 15 knots diminishing to less
than 10 knots after midnight. Waves calm to 2 feet.
.WEDNESDAY...North winds less than 10 knots becoming south 5 to
15 knots by mid afternoon. Waves calm to 2 feet.
.WEDNESDAY NIGHT...South winds 5 to 15 knots. Waves calm to
2 feet.
.THURSDAY...South winds 5 to 15 knots becoming southwest 10 to
20 knots. A chance of showers. Waves building to 1 to 3 feet.
.FRIDAY...West winds 10 to 20 knots. Waves building to 2 to
4 feet.

$$

LSZ264-182000-
Lake Superior from Upper Entrance to Portage Canal to Manitou
Island MI 5NM off shore to the US/Canadian Border-
401 AM EDT Mon Aug 18 2025

.EARLY THIS MORNING...Southeast winds 10 to 20 knots. Waves 1 to
3 feet building to 2 to 4 feet.
.TODAY...Southeast winds 10 to 20 knots increasing to 15 to
25 knots in the afternoon. A chance of showers through early
afternoon, then showers likely and a slight chance of
thunderstorms by mid afternoon. Waves building to 3 to 6 feet
occasionally to 8 feet.
.TONIGHT...Southeast winds 10 to 20 knots diminishing to 5 to
15 knots late. A slight chance of thunderstorms through midnight.
A chance of showers. Waves subsiding to 2 to 4 feet.
.TUESDAY...North winds 10 to 20 knots. Waves subsiding to calm to
2 feet.
.TUESDAY NIGHT...North winds 5 to 15 knots. Waves calm to 2 feet.
.WEDNESDAY...North winds less than 10 knots backing southwest by
mid afternoon. Waves calm to 2 feet.
.WEDNESDAY NIGHT...Southwest winds less than 10 knots becoming
south 5 to 15 knots after midnight. Waves calm to 2 feet.
.THURSDAY...South winds 5 to 15 knots becoming southwest 10 to
20 knots. Waves building to 1 to 3 feet.
.FRIDAY...West winds 10 to 20 knots. Waves building to 2 to
4 feet.

$$

LSZ265-182000-
Lake Superior West of Line from Manitou Island to Marquette MI
Beyond 5NM from shore-
401 AM EDT Mon Aug 18 2025

.EARLY THIS MORNING...Southeast winds 15 to 25 knots. Waves 1 to
3 feet building to 2 to 4 feet.
.TODAY...Southeast winds 15 to 25 knots. A chance of showers
through early afternoon, then showers likely and a chance of
thunderstorms by mid afternoon. Waves building to 3 to 5 feet
occasionally to 7 feet, then subsiding to 2 to 4 feet.
.TONIGHT...Southeast winds 10 to 20 knots. A chance of
thunderstorms through midnight. A chance of showers. Waves
subsiding to 1 to 3 feet.
.TUESDAY...Northwest winds 10 to 20 knots becoming north 15 to
25 knots in the afternoon. Waves subsiding to calm to 2 feet.
.TUESDAY NIGHT...North winds 10 to 20 knots diminishing to 5 to
15 knots after midnight. Waves calm to 2 feet.
.WEDNESDAY...North winds 10 to 20 knots diminishing to 5 to
15 knots by mid afternoon. Waves calm to 2 feet.
.WEDNESDAY NIGHT...South winds 5 to 15 knots. Waves calm to
2 feet.
.THURSDAY...Southeast winds 5 to 15 knots becoming southwest
10 to 20 knots. Waves calm to 2 feet.
.FRIDAY...West winds 10 to 20 knots. Waves calm to 2 feet.

$$

LSZ266-182000-
Lake Superior East of a line from Manitou Island to Marquette MI
and West of a line from Grand Marais MI to the US/Canadian Border
Beyond 5NM from shore-
401 AM EDT Mon Aug 18 2025

.EARLY THIS MORNING...Southeast winds 15 to 25 knots. Waves 2 to
4 feet.
.TODAY...Southeast winds 15 to 25 knots. A chance of showers
through early afternoon, then showers likely and a slight chance
of thunderstorms by mid afternoon. Waves building to 3 to 5 feet
occasionally to 7 feet.
.TONIGHT...Southeast winds 15 to 25 knots diminishing to 10 to
20 knots after midnight. A chance of showers and thunderstorms.
Waves subsiding to 2 to 4 feet.
.TUESDAY...Southeast winds 10 to 20 knots becoming north 15 to
25 knots in the afternoon, then diminishing to 10 to 20 knots
late. A slight chance of showers through early afternoon. Waves
subsiding to 1 to 3 feet.
.TUESDAY NIGHT...North winds 10 to 20 knots. Waves subsiding to
calm to 2 feet.
.WEDNESDAY...North winds 5 to 15 knots. Waves calm to 2 feet.
.WEDNESDAY NIGHT...Northwest winds 5 to 15 knots backing south
after midnight. Waves calm to 2 feet.
.THURSDAY...South winds 5 to 15 knots increasing to 10 to
20 knots. Waves calm to 2 feet.
.FRIDAY...Southwest winds 10 to 20 knots becoming west 5 to
15 knots. Waves building to 1 to 3 feet.

$$

LSZ267-182000-
Lake Superior from Grand Marais MI to Whitefish Point MI 5NM off
shore to the US/Canadian border-
401 AM EDT Mon Aug 18 2025

.EARLY THIS MORNING...Southeast winds 15 to 25 knots. Waves 2 to
4 feet.
.TODAY...Southeast winds 15 to 25 knots. A chance of showers and
a slight chance of thunderstorms by mid afternoon. Waves building
to 3 to 5 feet occasionally to 7 feet, then subsiding to 2 to
4 feet.
.TONIGHT...Southeast winds 15 to 25 knots. A chance of showers
and thunderstorms. Waves subsiding to 1 to 3 feet.
.TUESDAY...Southeast winds 10 to 20 knots backing north late. A
chance of showers. Waves subsiding to calm to 2 feet, then
building to 1 to 3 feet.
.TUESDAY NIGHT...North winds 10 to 20 knots. Waves subsiding to
calm to 2 feet.
.WEDNESDAY...North winds 10 to 20 knots backing northwest by mid
afternoon. Waves calm to 2 feet.
.WEDNESDAY NIGHT...North winds 5 to 15 knots. Waves calm to
2 feet.
.THURSDAY...South winds 5 to 15 knots. Waves calm to 2 feet.
.FRIDAY...Southwest winds 10 to 20 knots veering west. Waves
building to 1 to 3 feet, then subsiding to calm to 2 feet.

$$

LSZ261-181400-
MAFOR 1809/
Superior West 11320 11326 11316 14210 11800. A chance of
thunderstorms today and this evening. Waves 3 to 5 feet subsiding
to 1 to 3 feet today. Waves 2 feet or less tonight.

Superior North Central 11320 12330 12336 11330 12320. Waves 2 to
4 feet building to 3 to 6 feet today. Waves 3 to 6 feet subsiding
to 2 to 4 feet tonight.

Superior South Central 11320 12330 12336 13320. A chance of
thunderstorms this afternoon and tonight. Waves 2 to 4 feet.

Superior East 11320 11330 11320 12330 11336 12330. A chance of
thunderstorms tonight. Waves 2 to 4 feet building to 3 to 5 feet
today. Waves 2 to 4 feet tonight.

$$

WFO MQT

Experimental modernized open lake forecast is available online at
weather.gov/mqt/glftable

Graphical marine forecasts are available online at:
weather.gov/greatlakes