600 FZUS63 KMQT 202001 GLFLS Open Lake Forecast for Lake Superior National Weather Service Marquette MI 400 PM EDT Wed May 20 2026 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 over the Upper Great Lakes rises to 30.4 inches tonight. The high pressure then shifts east through Friday to New England and Quebec, but ridging of at least 30.3 inches remains over Lake Superior. Meanwhile, a 29.7 inch low develops over the Southern Plains and lifts toward the Great Lakes. The low gradually weakens to 30.0 inches as it lifts over Lower Michigan and Lake Huron Saturday into Sunday. Weak troughing of 29.9 to 30.0 inches passes northward over Lake Superior Saturday night into Sunday before high pressure around 30.0 inches returns on Monday. LSZ162-210800- Lake Superior west of a line from Saxon Harbor WI to Grand Portage MN beyond 5NM- 400 PM EDT Wed May 20 2026 /300 PM CDT Wed May 20 2026/ .LATE THIS AFTERNOON...South winds 5 to 15 knots. Waves calm to 2 feet. .TONIGHT...Southeast winds 5 to 15 knots backing east after midnight. Waves calm to 2 feet. .THURSDAY...Southeast winds 5 to 15 knots backing east in the afternoon. Waves calm to 2 feet. .THURSDAY NIGHT...Northeast winds 5 to 15 knots veering east late. Waves calm to 2 feet. .FRIDAY...East winds 10 to 20 knots becoming northeast 15 to 25 knots by mid afternoon. Waves building to 2 to 4 feet. .FRIDAY NIGHT...Northeast winds 15 to 25 knots diminishing to 10 to 20 knots after midnight. A chance of rain showers after midnight. Waves building to 3 to 5 feet occasionally to 7 feet, then subsiding to 2 to 4 feet. .SATURDAY...Northeast winds 10 to 20 knots. Rain showers likely through early afternoon, then a chance of rain showers by mid afternoon. Waves 2 to 4 feet. .SATURDAY NIGHT...Northeast winds 5 to 15 knots backing north after midnight. A chance of rain showers. Waves subsiding to calm to 2 feet. .SUNDAY...Southwest winds 5 to 15 knots. Waves calm to 2 feet. .MONDAY...East winds 5 to 15 knots. Waves calm to 2 feet. $$ LSZ263-210800- Lake Superior from Saxon Harbor WI to Upper Entrance to Portage Canal MI 5NM off shore to the US/Canadian border including Isle Royale National Park- 400 PM EDT Wed May 20 2026 .LATE THIS AFTERNOON...South winds 5 to 15 knots. Waves calm to 2 feet. .TONIGHT...Southeast winds 5 to 15 knots diminishing to less than 10 knots after midnight, then becoming south 5 to 15 knots late. Waves calm to 2 feet. .THURSDAY...South winds 5 to 15 knots backing northeast in the afternoon, then veering east late. Waves calm to 2 feet. .THURSDAY NIGHT...East winds 5 to 15 knots veering southeast after midnight. Waves calm to 2 feet. .FRIDAY...East winds 5 to 15 knots increasing to 10 to 20 knots by mid afternoon. Waves building to 2 to 4 feet. .FRIDAY NIGHT...East winds 10 to 20 knots diminishing to 5 to 15 knots after midnight. Waves subsiding to 1 to 3 feet. .SATURDAY...East winds 10 to 20 knots. Rain showers likely. Waves building to 3 to 5 feet occasionally to 7 feet. .SATURDAY NIGHT...East winds 5 to 15 knots veering southwest after midnight. A chance of rain showers. Waves subsiding to 1 to 3 feet. .SUNDAY...Southwest winds 5 to 15 knots. Waves subsiding to calm to 2 feet. .MONDAY...Southwest winds 5 to 15 knots. Waves calm to 2 feet. $$ LSZ264-210800- Lake Superior from Upper Entrance to Portage Canal to Manitou Island MI 5NM off shore to the US/Canadian Border- 400 PM EDT Wed May 20 2026 .LATE THIS AFTERNOON...Southwest winds 5 to 15 knots. Waves calm to 2 feet. .TONIGHT...Southwest winds 5 to 15 knots diminishing to less than10 knots after midnight, then becoming south 5 to 15 knots late. Waves calm to 2 feet. .THURSDAY...South winds 5 to 15 knots backing southeast late. Waves calm to 2 feet. .THURSDAY NIGHT...Southeast winds 5 to 15 knots veering south late. Waves calm to 2 feet. .FRIDAY...Southeast winds 5 to 15 knots becoming east 10 to 20 knots by mid afternoon. Waves calm to 2 feet. .FRIDAY NIGHT...East winds 10 to 20 knots. Waves building to 2 to 4 feet. .SATURDAY...East winds 15 to 25 knots. A chance of rain showers. Waves building to 3 to 6 feet occasionally to 8 feet. .SATURDAY NIGHT...Southeast winds 10 to 20 knots becoming south 5 to 15 knots after midnight. A chance of rain showers. Waves subsiding to 1 to 3 feet. .SUNDAY...Southwest winds 5 to 15 knots. Waves subsiding to calm to 2 feet. .MONDAY...Southwest winds 5 to 15 knots backing south. Waves calm to 2 feet. $$ LSZ265-210800- Lake Superior West of Line from Manitou Island to Marquette MI Beyond 5NM from shore- 400 PM EDT Wed May 20 2026 .LATE THIS AFTERNOON...Southeast winds 5 to 15 knots. Waves calm to 2 feet. .TONIGHT...South winds 5 to 15 knots. Waves calm to 2 feet. .THURSDAY...South winds 5 to 15 knots becoming east 10 to 20 knots in the afternoon, then increasing to 15 to 25 knots late. Waves building to 1 to 3 feet. .THURSDAY NIGHT...Southeast winds 10 to 20 knots diminishing to 5 to 15 knots after midnight. Waves subsiding to calm to 2 feet. .FRIDAY...East winds 10 to 20 knots increasing to 15 to 25 knots by mid afternoon. Waves building to 2 to 4 feet. .FRIDAY NIGHT...East winds 15 to 25 knots. Waves 2 to 4 feet. .SATURDAY...East winds 15 to 25 knots. A chance of rain showers. Waves building to 4 to 7 feet occasionally to 9 feet, then subsiding to 3 to 6 feet occasionally to 8 feet. .SATURDAY NIGHT...Southeast winds 10 to 20 knots veering south after midnight. Waves subsiding to 1 to 3 feet. .SUNDAY...West winds 10 to 20 knots backing southwest. Waves subsiding to calm to 2 feet. .MONDAY...Southeast winds 10 to 20 knots veering south. Waves calm to 2 feet. $$ LSZ266-210800- 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- 400 PM EDT Wed May 20 2026 .LATE THIS AFTERNOON...Northwest winds 5 to 15 knots. Waves 1 to 3 feet subsiding to calm to 2 feet. .TONIGHT...West winds 5 to 15 knots backing south late. Waves calm to 2 feet. .THURSDAY...South winds 5 to 15 knots backing east late. Waves calm to 2 feet. .THURSDAY NIGHT...Southeast winds 10 to 20 knots. Waves building to 1 to 3 feet, then subsiding to calm to 2 feet. .FRIDAY...Southeast winds 10 to 20 knots becoming east 15 to 25 knots by mid afternoon. Waves building to 1 to 3 feet. .FRIDAY NIGHT...East winds 15 to 25 knots. Waves building to 2 to 4 feet. .SATURDAY...East winds 15 to 25 knots. A chance of rain showers. Waves building to 4 to 7 feet occasionally to 9 feet, then subsiding to 3 to 6 feet occasionally to 8 feet. .SATURDAY NIGHT...Southeast winds 15 to 25 knots diminishing to 10 to 20 knots after midnight. Waves subsiding to 1 to 3 feet. .SUNDAY...South winds 5 to 15 knots veering southwest. Waves subsiding to calm to 2 feet. .MONDAY...South winds 5 to 15 knots increasing to 10 to 20 knots. Waves calm to 2 feet. $$ LSZ267-210800- Lake Superior from Grand Marais MI to Whitefish Point MI 5NM off shore to the US/Canadian border- 400 PM EDT Wed May 20 2026 .LATE THIS AFTERNOON...Northwest winds 10 to 20 knots. Waves 2 to 4 feet subsiding to 1 to 3 feet. .TONIGHT...Northwest winds 5 to 15 knots becoming south less than 10 knots late. Waves subsiding to calm to 2 feet. .THURSDAY...South winds less than 10 knots becoming northeast 5 to 15 knots in the afternoon, then veering east late. Waves calm to 2 feet. .THURSDAY NIGHT...East winds 5 to 15 knots veering southeast after midnight. Waves calm to 2 feet. .FRIDAY...East winds 10 to 20 knots. Waves calm to 2 feet. .FRIDAY NIGHT...East winds 10 to 20 knots increasing to 15 to 25 knots after midnight. Waves building to 2 to 4 feet. .SATURDAY...East winds 20 to 30 knots. A chance of rain showers. Waves building to 4 to 7 feet occasionally to 9 feet, then subsiding to 3 to 6 feet occasionally to 8 feet. .SATURDAY NIGHT...Southeast winds 15 to 25 knots diminishing to 10 to 20 knots after midnight. Waves subsiding to calm to 2 feet. .SUNDAY...South winds 5 to 15 knots veering west. Waves calm to 2 feet. .MONDAY...Southeast winds 5 to 15 knots veering south. Waves calm to 2 feet. $$ LSZ261-210200- MAFOR 2021/ Superior West 11400 15300 11210. Waves 1 foot or less. Superior North Central 11510 13500 13400 11310. Waves 1 foot or less. Superior South Central 11800 12500 13400 11310 11220. Waves 2 feet or less. Superior East 12710 11700 11600 13400 11200. Waves 1 to 3 feet subsiding to 1 foot or less tonight. Waves 1 foot or less Thursday. $$ 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  777 FZUS61 KBUF 202003 GLFLO Open Lake Forecast for Lake Ontario National Weather Service Buffalo NY 403 PM EDT Wed May 20 2026 For waters beyond five nautical miles of shore on Lake Ontario 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 large 30.4 inch area of surface high pressure will build across the entire Great Lakes region through Thursday, before sliding east off the New England coast late Friday. This surface high will then strengthen to 30.6 inches as it anchors over Atlantic Canada through Sunday. A 29.9 inch low and attendant warm front will then slowly approach the Lake late Friday night and Saturday, before weakening and sliding eastward Sunday. A 30.1 inch high will settle across the region Monday through Tuesday. LOZ062-210300- Lake Ontario open waters from the Niagara River to Hamlin Beach- 403 PM EDT Wed May 20 2026 .TONIGHT...Northwest winds 10 to 15 knots becoming northeast 15 to 20 knots. Waves 1 to 3 feet. .THURSDAY...Northeast winds 15 to 20 knots becoming southeast 5 to 15 knots. Waves 2 to 4 feet subsiding to 1 to 2 feet. .THURSDAY NIGHT...East winds 10 knots or less. Waves 1 foot or less. .FRIDAY...East winds 5 to 10 knots increasing to 15 to 20 knots. Waves 1 to 3 feet building to 2 to 4 feet. .FRIDAY NIGHT...East winds 15 to 20 knots. A chance of showers overnight. Waves 2 to 4 feet. .SATURDAY...East winds 15 to 25 knots. Showers. Waves 5 to 8 feet subsiding to 3 to 6 feet. Waves occasionally around 10 feet. .SUNDAY...Southeast winds 5 to 15 knots becoming south. Showers likely during the day, then a chance of showers Sunday night. Waves 2 to 4 feet subsiding to 2 feet or less. .MONDAY...Southwest winds 10 knots or less becoming west. A chance of showers during the day. Waves 1 foot or less. $$ LOZ063>065-210300- Lake Ontario open waters from Hamlin Beach to the Saint Lawrence River- 403 PM EDT Wed May 20 2026 .TONIGHT...West winds 15 to 25 knots becoming northeast. Waves 3 to 6 feet. .THURSDAY...Northeast winds 15 to 20 knots becoming west 5 to 15 knots. Waves 3 to 6 feet subsiding to 1 to 3 feet. .THURSDAY NIGHT...Northwest winds 10 knots or less becoming northeast. Waves 1 foot or less. .FRIDAY...East winds 5 to 15 knots becoming northeast. Waves 2 feet or less. .FRIDAY NIGHT...Northeast winds 10 to 15 knots becoming east. A chance of showers overnight. Waves 1 to 3 feet. .SATURDAY...East winds 15 to 25 knots becoming southeast. Showers. Waves 2 to 4 feet building to 3 to 6 feet. .SUNDAY...Southeast winds 15 to 25 knots becoming south and diminishing to 10 to 15 knots. Showers. Waves 3 to 6 feet subsiding to 1 to 3 feet. .MONDAY...South winds 5 to 15 knots becoming west. Showers likely during the day. Waves 2 feet or less. $$ LOZ061-210300- MAFOR 2021/ ONTARIO WEST 1/2 11610 11710 11810 11110 11120 11110 11210 11300. Waves 1 to 3 feet building to 2 to 4 feet tonight. Waves 2 to 4 feet subsiding to 1 to 2 feet Thursday. ONTARIO EAST 1/2 12620 11820 12130 11110 11100 11800. Waves 3 to 6 feet tonight. Waves 3 to 6 feet subsiding to 1 to 3 feet Thursday. $$  827 FZUS61 KBUF 202004 GLFSL Forecast for the Saint Lawrence River including the Thousand Islands Region National Weather Service Buffalo NY 404 PM EDT Wed May 20 2026 SLZ022-024-210300- Saint Lawrence River from Cape Vincent to Saint Regis 404 PM EDT Wed May 20 2026 .TONIGHT...Northwest winds 10 to 15 knots becoming north 15 to 20 knots. Partly cloudy. .THURSDAY...North winds 5 to 15 knots diminishing to less than 10 knots. Sunny. .THURSDAY NIGHT...North winds less than 10 knots. Mainly clear. .FRIDAY...Light and variable winds. Sunny. .FRIDAY NIGHT...Northeast winds less than 10 knots becoming east. Partly to mostly cloudy. .SATURDAY...East winds 10 knots or less becoming southeast. Showers likely. .SUNDAY...Southeast winds 5 to 10 knots becoming south. Showers likely. .MONDAY...South winds 10 knots or less becoming southwest. Showers likely during the day. $$