A powerful cold front produced strong to severe thunderstorms over Lake Superior on the evening of the 12th.

Marine Thunderstorm Wind in UPPER ENTRANCE OF PORTAGE CANAL TO EAGLE RIVER MI, LAKE SUPERIOR
From 12-SEP-11 19:00:00 to 12-SEP-11 19:05:00 (EST-5)
Location: MCCLAIN STATE PARK
Magnitude: 42.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Buoy

Wind gusts between 45 and 48 mph were measured at buoy 45023 and the Portage Canal GLOS station.

Marine Thunderstorm Wind in EAGLE RIVER TO MANITOU ISLAND MI, LAKE SUPERIOR
From 12-SEP-11 19:04:00 to 12-SEP-11 19:15:00 (EST-5)
Location: COPPER HARBOR
Magnitude: 40.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Wind gusts of 45 mph or greater were measured by the Copper Harbor ASOS.

Marine Thunderstorm Wind in MANITOU ISLAND TO POINT ISABELLE MI, LAKE SUPERIOR
From 12-SEP-11 19:04:00 to 12-SEP-11 19:15:00 (EST-5)
Location: BETE GRISE LIGHT
Magnitude: 40.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Wind gusts of 45 mph or greater were measured by the Copper Harbor ASOS.

Marine Thunderstorm Wind in POINT ISABELLE TO LOWER ENTRANCE OF PORTAGE CANAL MI, LAKE SUPERIOR
From 12-SEP-11 19:20:00 to 12-SEP-11 19:24:00 (EST-5)
Location: TRAVERSE BAY
Magnitude: 42.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Wind gust measured by the Grand Traverse Bay GLOS.

Marine Thunderstorm Wind in POINT ISABELLE TO LOWER ENTRANCE OF PORTAGE CANAL MI, LAKE SUPERIOR
From 12-SEP-11 19:30:00 to 12-SEP-11 19:50:00 (EST-5)
Location: KEWEENAW LOWER ENTRANCE LIGHT
Magnitude: 36.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Buoy

Measured wind gusts of 40 mph or greater were recorded over a 20-minute period at buoy 45025 in Keweenaw Bay.

Marine Thunderstorm Wind in PORTAGE LAKE TO HURON IS MI TO LOWER ENTRANCE OF PORTAGE CANAL TO HURON IS INC KEWEENAW AND HURON BAYS, LAKE SUPERIOR
From 12-SEP-11 19:30:00 to 12-SEP-11 19:50:00 (EST-5)
Location: KEWEENAW LOWER ENTRANCE LIGHT
Magnitude: 36.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Buoy

Measured wind gusts of 40 mph or greater were recorded over a 20-minute period at buoy 45025 in Keweenaw Bay.

Marine Thunderstorm Wind in HURON ISLANDS TO MARQUETTE MI, LAKE SUPERIOR
From 12-SEP-11 20:10:00 to 12-SEP-11 20:22:00 (EST-5)
Location: BIG BAY POINT LIGHT
Magnitude: 40.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Wind gusts measured by the Big Bay GLOS station.

Marine Thunderstorm Wind in MANITOU ISLAND TO MARQUETTE MI AND W OF GRAND MARAIS MI TO US/CANADIAN BORDER BEYOND 5NM OF SHORE, LAKE SUPERIOR
From 12-SEP-11 19:57:00 to 12-SEP-11 20:00:00 (EST-5)
Location: STANNARD ROCK LIGHT
Magnitude: 46.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: C-MAN Station

Measured wind gust at the Stannard Rock C-Man station.

Marine Thunderstorm Wind in MARQUETTE TO MUNISING MI, LAKE SUPERIOR
From 12-SEP-11 21:35:00 to 12-SEP-11 21:38:00 (EST-5)
Location: MUNISING
Magnitude: 36.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Measured wind gust at the Munising ASOS.

Marine Thunderstorm Wind in MUNISING TO GRAND MARAIS MI, LAKE SUPERIOR
From 12-SEP-11 21:35:00 to 12-SEP-11 21:38:00 (EST-5)
Location: GRAND ISLAND HARBOR LIGHT
Magnitude: 36.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Measured wind gust at the Munising ASOS.

Marine Hail in ONTONAGON TO UPPER ENTRANCE OF PORTAGE CANAL MI, LAKE SUPERIOR
From 12-SEP-11 18:52:00 to 12-SEP-11 18:57:00 (EST-5)
Location: ONTONAGON LIGHT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Quarter and dime-sized hail were reported.  Thunderstorms wind gusts estimated up to 65 mph also brought down several large branches.

Marine Thunderstorm Wind in ONTONAGON TO UPPER ENTRANCE OF PORTAGE CANAL MI, LAKE SUPERIOR
From 12-SEP-11 18:44:00 to 12-SEP-11 19:04:00 (EST-5)
Location: BEACON HILL
Magnitude: 64.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Wind gusts of greater than 50 mph were reported for 20 minutes by the spotter at Freda.  A peak wind gust of 74 mph was measured at 1904 EST.  Quarter-sized hail was also reported.

Marine Thunderstorm Wind in PORTAGE LAKE TO HURON IS MI TO LOWER ENTRANCE OF PORTAGE CANAL TO HURON IS INC KEWEENAW AND HURON BAYS, LAKE SUPERIOR
From 12-SEP-11 19:30:00 to 12-SEP-11 19:34:00 (EST-5)
Location: KEWEENAW LOWER ENTRANCE LIGHT
Magnitude: 36.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Buoy

Wind gust measured by buoy 45025 in the Keweenaw Bay.

Marine Thunderstorm Wind in GRAND MARAIS TO WHITEFISH POINT MI, LAKE SUPERIOR
From 12-SEP-11 21:40:00 to 12-SEP-11 21:43:00 (EST-5)
Location: GRAND MARAIS LIGHT
Magnitude: 35.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Measured wind gust at the Grand Marais GLOS station.