630
FZUS63 KMQT 182001
GLFLS

Open Lake Forecast for Lake Superior
National Weather Service Marquette MI
401 PM 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 resides over Quebec through tonight while 29.9 inch
troughing dissipates over the Northern Plains. A weak low pressure
at 29.9 inches skirts south of the lake on Tuesday while 30.1 inch
high pressure builds over northern Minnesota, northern Ontario and
southern Manitoba. 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, sending a 29.8 inch trough over Lake Superior.


LSZ162-190800-
Lake Superior west of a line from Saxon Harbor WI to Grand
Portage MN beyond 5NM-
401 PM EDT Mon Aug 18 2025 /301 PM CDT Mon Aug 18 2025/

.LATE THIS AFTERNOON...Northeast winds 5 to 15 knots. A slight
chance of showers and thunderstorms. Waves calm to 2 feet.
.TONIGHT...Northeast winds 5 to 15 knots backing north late. A
slight chance of showers through midnight. Waves calm to 2 feet.
.TUESDAY...North winds 10 to 20 knots becoming northwest 5 to
15 knots in the afternoon, then backing south late. Waves calm to
2 feet.
.TUESDAY NIGHT...East winds 5 to 15 knots backing north late.
Waves calm to 2 feet.
.WEDNESDAY...Northeast winds 5 to 15 knots veering southeast by
mid afternoon. Waves calm to 2 feet.
.WEDNESDAY NIGHT...East winds less than 10 knots veering south
after midnight. Waves calm to 2 feet.
.THURSDAY...Southwest winds 5 to 15 knots backing south by mid
afternoon. Waves calm to 2 feet.
.THURSDAY NIGHT...Southwest winds 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.
.SATURDAY...West winds 15 to 25 knots veering northwest. Waves
building to 2 to 4 feet, then subsiding to 1 to 3 feet.

$$

LSZ263-190800-
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 PM EDT Mon Aug 18 2025

.LATE THIS AFTERNOON...Southeast winds 15 to 25 knots. A chance
of showers and a slight chance of thunderstorms. Waves 2 to
4 feet.
.TONIGHT...Southeast winds 10 to 20 knots diminishing to 5 to
15 knots after midnight, then backing northeast late. A slight
chance of showers through midnight. Waves subsiding to calm to
2 feet.
.TUESDAY...North winds 5 to 15 knots. Waves calm to 2 feet.
.TUESDAY NIGHT...North winds 5 to 15 knots becoming northwest
less than 10 knots after midnight, then veering north late. Waves
calm to 2 feet.
.WEDNESDAY...Northeast winds 5 to 15 knots veering south by mid
afternoon. Waves calm to 2 feet.
.WEDNESDAY NIGHT...East winds 5 to 15 knots becoming south less
than 10 knots after midnight. Waves calm to 2 feet.
.THURSDAY...South winds 5 to 15 knots. Waves calm to 2 feet.
.THURSDAY NIGHT...South winds 5 to 15 knots becoming southwest
10 to 20 knots after midnight. A chance of showers. Waves
building to 1 to 3 feet.
.FRIDAY...West winds 10 to 20 knots increasing to 15 to 25 knots.
Waves building to 2 to 4 feet.
.SATURDAY...West winds 20 to 30 knots becoming northwest 15 to
25 knots. Waves building to 3 to 5 feet occasionally to 7 feet,
then subsiding to 2 to 4 feet.

$$

LSZ264-190800-
Lake Superior from Upper Entrance to Portage Canal to Manitou
Island MI 5NM off shore to the US/Canadian Border-
401 PM EDT Mon Aug 18 2025

.LATE THIS AFTERNOON...Southeast winds 20 to 30 knots. A chance
of showers. Waves 3 to 5 feet occasionally to 7 feet.
.TONIGHT...Southeast winds 15 to 25 knots diminishing to 5 to
15 knots. A slight chance of showers. Waves subsiding to 1 to
3 feet.
.TUESDAY...North winds 5 to 15 knots. Waves subsiding to calm to
2 feet.
.TUESDAY NIGHT...Northwest winds 5 to 15 knots becoming north
less than 10 knots after midnight. 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 backing
south after midnight. Waves calm to 2 feet.
.THURSDAY...South winds 5 to 15 knots. Waves calm to 2 feet.
.THURSDAY NIGHT...South winds 5 to 15 knots becoming southwest
10 to 20 knots after midnight. 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.
.SATURDAY...West winds 20 to 30 knots becoming northwest 15 to
25 knots. Waves building to 3 to 6 feet occasionally to 8 feet,
then subsiding to 2 to 4 feet.

$$

LSZ265-190800-
Lake Superior West of Line from Manitou Island to Marquette MI
Beyond 5NM from shore-
401 PM EDT Mon Aug 18 2025

.LATE THIS AFTERNOON...Southeast winds 20 to 30 knots. A chance
of showers. Waves 2 to 4 feet.
.TONIGHT...Southeast winds 15 to 25 knots diminishing to 5 to
15 knots. A chance of showers. Waves subsiding to calm to 2 feet.
.TUESDAY...West winds 10 to 20 knots veering north late. Waves
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...Southeast winds less than 10 knots veering
south after midnight. Waves calm to 2 feet.
.THURSDAY...South winds 5 to 15 knots becoming southeast 10 to
20 knots by mid afternoon. Waves calm to 2 feet.
.THURSDAY NIGHT...South winds 10 to 20 knots veering southwest
after midnight. Waves calm to 2 feet.
.FRIDAY...West winds 10 to 20 knots. A chance of showers. Waves
calm to 2 feet.
.SATURDAY...West winds 15 to 25 knots veering northwest. Waves
calm to 2 feet.

$$

LSZ266-190800-
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 PM EDT Mon Aug 18 2025

.LATE THIS AFTERNOON...Southeast winds 15 to 25 knots. A chance
of showers. Waves 3 to 5 feet occasionally to 7 feet.
.TONIGHT...Southeast winds 15 to 25 knots diminishing to 5 to
15 knots. A chance of showers. Waves subsiding to 1 to 3 feet.
.TUESDAY...Southeast winds 10 to 20 knots backing north in the
afternoon. A slight chance of showers through early afternoon.
Waves subsiding to calm to 2 feet.
.TUESDAY NIGHT...North winds 10 to 20 knots. Waves calm to
2 feet.
.WEDNESDAY...North winds 5 to 15 knots. Waves calm to 2 feet.
.WEDNESDAY NIGHT...North winds 5 to 15 knots becoming south less
than 10 knots after midnight. Waves calm to 2 feet.
.THURSDAY...South winds 5 to 15 knots backing southeast by mid
afternoon. Waves calm to 2 feet.
.THURSDAY NIGHT...South winds 10 to 20 knots veering southwest
after midnight. Waves calm to 2 feet.
.FRIDAY...Southwest winds 10 to 20 knots veering west. A chance
of showers. Waves building to 1 to 3 feet.
.SATURDAY...West winds 15 to 25 knots veering northwest. Waves
building to 3 to 5 feet occasionally to 7 feet, then subsiding to
2 to 4 feet.

$$

LSZ267-190800-
Lake Superior from Grand Marais MI to Whitefish Point MI 5NM off
shore to the US/Canadian border-
401 PM EDT Mon Aug 18 2025

.LATE THIS AFTERNOON...Southeast winds 15 to 25 knots. A chance
of showers. Waves 2 to 4 feet subsiding to 1 to 3 feet.
.TONIGHT...Southeast winds 15 to 25 knots. A chance of showers.
Waves building to 2 to 4 feet, then subsiding to 1 to 3 feet.
.TUESDAY...Southeast winds 10 to 20 knots backing north late. A
slight chance of showers. Waves subsiding to calm to 2 feet.
.TUESDAY NIGHT...North winds 10 to 20 knots. Waves 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 veering northeast
after midnight. Waves calm to 2 feet.
.THURSDAY...Southeast winds 5 to 15 knots backing east by mid
afternoon. Waves calm to 2 feet.
.THURSDAY NIGHT...South winds 5 to 15 knots increasing to 10 to
20 knots after midnight. Waves calm to 2 feet.
.FRIDAY...Southwest winds 10 to 20 knots veering west. A chance
of showers. Waves building to 1 to 3 feet.
.SATURDAY...West winds 15 to 25 knots. Waves building to 3 to
5 feet occasionally to 7 feet.

$$

LSZ261-190200-
MAFOR 1821/
Superior West 12210 11200 11100 11800 12810 11800. Waves 2 feet
or less.

Superior North Central 11340 11330 12320 11310 11110 12810. A
chance of showers this evening. Waves 3 to 5 feet subsiding to 2
to 4 feet tonight. Waves 1 to 3 feet Tuesday.

Superior South Central 12330 12320 11410 11510 11710 11810. A
chance of showers this evening. Waves 2 to 4 feet subsiding to 1
to 3 feet tonight. Waves 1 to 2 feet Tuesday.

Superior East 13330 12320 12310 11110. A chance of showers
tonight and Tuesday morning. Waves 2 to 4 feet tonight. Waves 1
to 3 feet Tuesday.

$$

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