763  
FZUS63 KMKX 210808  
GLFLM  
 
OPEN LAKE FORECAST FOR LAKE MICHIGAN  
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI  
308 AM CDT THU OCT 21 2021  
 
FOR WATERS BEYOND FIVE NAUTICAL MILES OF SHORE ON LAKE MICHIGAN.  
 
WAVES ARE PROVIDED AS A RANGE OF SIGNIFICANT WAVE HEIGHTS, WHICH  
IS THE AVERAGE OF THE HIGHEST 1/3 OF THE WAVE, ALONG WITH THE  
AVERAGE HEIGHT OF THE HIGHEST 10% OF THE WAVES WHICH WILL  
OCCASIONALLY BE ENCOUNTERED.  
   
SYNOPSIS
 
 
 
LOW PRESSURE OF 29.7 INCHES WILL CONTINUE EASTWARD TONIGHT OVER  
THE MIDDLE SECTION OF LAKE MICHIGAN, SUPPORTING WESTERLY TO  
SOUTHWESTERLY WIND OVER THE SOUTHERN HALF OF THE LAKE AND  
NORTHEAST WINDS OVER THE NORTHERN HALF OF THE LAKE. AS THIS LOW  
EXITS EASTWARD OVER THE STATE OF MICHIGAN, NORTHEASTERLY WINDS  
WILL INTENSIFY AND SURGE DOWN THE LAKE FROM NORTH TO SOUTH AS  
COLD AIR ADVECTION INCREASES. ABOUT A 2 TO 5 HOUR WINDOW IS  
EXPECTED FOR GALE FORCE GUSTS TO 35 KNOTS THIS MORNING INTO THE  
AFTERNOON. HENCE A GALE WARNING HAS BEEN POSTED FOR THE LAKE  
MICHIGAN OPEN WATERS FROM LATE TONIGHT THROUGH THURSDAY. THE WINDS  
WILL GRADUALLY DIMINISH THURSDAY NIGHT AND FRIDAY.  
 
MORE NORTHWESTERLY WINDS WILL TAKE HOLD ON FRIDAY LEADING TO SOME  
LAKE EFFECT SHOWER ACTIVITY OVER THE EASTERN HALF OF THE LAKE.  
SOME LOW LEVEL INSTABILITY WILL BE PRESENT SUPPORTING SOME  
WATERSPOUT THREAT WITH THIS LAKE EFFECT SHOWER ACTIVITY,  
ESPECIALLY OVER THE SOUTHERN END OF THE LAKE.  
 
LMZ261-362-364-366-563-565-567-868-211530-  
LAKE MICHIGAN FROM SEUL CHOIX POINT TO ROCK ISLAND PASSAGE 5 NM  
OFFSHORE TO MID LAKE-  
LAKE MICHIGAN SOUTH OF A LINE FROM SEUL CHOIX POINT TO THE  
MACKINAC BRIDGE AND NORTH OF A LINE FROM CHARLEVOIX MI TO SOUTH  
FOX ISLAND 5 NM OFFSHORE-  
LAKE MICHIGAN FROM CHARLEVOIX TO POINT BETSIE MI 5 NM OFFSHORE TO  
MID LAKE-  
LAKE MICHIGAN FROM POINT BETSIE TO MANISTEE MI 5 NM OFFSHORE TO  
MID LAKE-  
LAKE MICHIGAN FROM ROCK ISLAND PASSAGE TO STURGEON BAY WI-  
LAKE MICHIGAN FROM STURGEON BAY TO TWO RIVERS WI 5 NM OFFSHORE TO  
MID LAKE-  
LAKE MICHIGAN FROM TWO RIVERS TO SHEBOYGAN WI 5 NM OFFSHORE TO  
MID LAKE-  
LAKE MICHIGAN FROM PENTWATER TO MANISTEE MI 5 NM OFFSHORE TO MID  
LAKE-  
308 AM CDT THU OCT 21 2021  
 
SHEBOYGAN WI TO PENTWATER MI NORTH...  
   
..GALE WARNING IN EFFECT THROUGH THIS AFTERNOON
 
 
   
TODAY
 
NORTHEAST WINDS TO 30 KT BECOMING NORTH GALES TO 40 KT,  
THEN DIMINISHING TO GALES TO 35 KT LATE. CHANCE OF SHOWERS. WAVES  
4 TO 7 FT OCCASIONALLY TO 9 FT BUILDING TO 10 TO 14 FT  
OCCASIONALLY TO 18 FT.    
TONIGHT
 
NORTH WINDS TO 30 KT DIMINISHING TO 10 TO 20 KT.  
SLIGHT CHANCE OF RAIN SHOWERS. WAVES 8 TO 12 FT OCCASIONALLY TO  
16 FT SUBSIDING TO 4 TO 6 FT OCCASIONALLY TO 8 FT.    
FRIDAY
 
NORTHWEST WINDS 10 TO 15 KT DIMINISHING TO 5 TO 10 KT.  
WAVES 3 TO 5 FT SUBSIDING TO 1 TO 2 FT.    
FRIDAY NIGHT
 
NORTH WINDS 10 TO 15 KT BECOMING NORTHWEST.  
CHANCE OF RAIN SHOWERS. WAVES 1 TO 3 FT.    
SATURDAY
 
NORTHWEST WINDS 10 TO 15 KT. WAVES 1 TO 3 FT.    
SATURDAY NIGHT
 
NORTHWEST WINDS 10 TO 15 KT. WAVES 1 TO 3 FT.    
SUNDAY
 
NORTH WINDS 10 TO 15 KT BECOMING NORTHEAST 10 TO 20 KT.  
WAVES 1 TO 2 FT BUILDING TO 2 TO 4 FT.    
MONDAY
 
EAST WINDS TO 30 KT BECOMING NORTHEAST 15 TO 25 KT.  
CHANCE OF RAIN SHOWERS. WAVES 4 TO 7 FT OCCASIONALLY TO 9 FT.  
 

 
 
LMZ080-669-671-673-675-777-779-870-872-874-876-878-211530-  
LAKE MICHIGAN FROM MICHIGAN CITY IN TO ST. JOSEPH MI 5 NM  
OFFSHORE TO MID LAKE-  
LAKE MICHIGAN FROM SHEBOYGAN TO PORT WASHINGTON WI 5 NM OFFSHORE  
TO MID LAKE-  
LAKE MICHIGAN FROM PORT WASHINGTON TO NORTH POINT LIGHT WI 5 NM  
OFFSHORE TO MID LAKE-  
LAKE MICHIGAN FROM NORTH POINT LIGHT TO WIND POINT WI 5 NM  
OFFSHORE TO MID LAKE-  
LAKE MICHIGAN FROM WIND POINT WI TO WINTHROP HARBOR IL 5 NM  
OFFSHORE TO MID LAKE-  
LAKE MICHIGAN FROM WINTHROP HARBOR TO WILMETTE HARBOR IL 5 NM  
OFFSHORE TO MID LAKE-  
LAKE MICHIGAN FROM WILMETTE HARBOR IL TO MICHIGAN CITY IN 5 NM  
OFFSHORE TO MID LAKE-  
LAKE MICHIGAN FROM WHITEHALL TO PENTWATER MI 5 NM OFFSHORE TO MID  
LAKE-  
LAKE MICHIGAN FROM GRAND HAVEN TO WHITEHALL MI 5 NM OFFSHORE TO  
MID LAKE-  
LAKE MICHIGAN FROM HOLLAND TO GRAND HAVEN MI 5 NM OFFSHORE TO MID  
LAKE-  
LAKE MICHIGAN FROM SOUTH HAVEN TO HOLLAND MI 5 NM OFFSHORE TO MID  
LAKE-  
LAKE MICHIGAN FROM ST. JOSEPH TO SOUTH HAVEN MI 5 NM OFFSHORE TO  
MID LAKE-  
308 AM CDT THU OCT 21 2021  
 
SHEBOYGAN WI TO PENTWATER MI SOUTH...  
 
...GALE WARNING IN EFFECT FROM 10 AM CDT THIS MORNING THROUGH  
THIS EVENING...  
   
TODAY
 
WEST WINDS 15 TO 25 KT INCREASING TO GALES TO 40 KT LATE  
THIS MORNING, THEN BECOMING NORTHWEST EARLY THIS AFTERNOON  
BECOMING NORTH GALES TO 35 KT LATE. CHANCE OF SHOWERS. WAVES 4 TO  
6 FT OCCASIONALLY TO 8 FT BUILDING TO 10 TO 14 FT OCCASIONALLY TO  
18 FT.    
TONIGHT
 
NORTH WINDS TO 30 KT DIMINISHING TO 10 TO 20 KT.  
SLIGHT CHANCE OF RAIN SHOWERS. WAVES 10 TO 14 FT OCCASIONALLY TO  
18 FT SUBSIDING TO 5 TO 8 FT OCCASIONALLY TO 10 FT.    
FRIDAY
 
NORTH WINDS 10 TO 15 KT BECOMING NORTHWEST 5 TO 10 KT.  
WAVES 4 TO 6 FT OCCASIONALLY TO 8 FT SUBSIDING TO 2 TO 4 FT.    
FRIDAY NIGHT
 
NORTHWEST WINDS 5 TO 10 KT INCREASING TO 10 TO  
15 KT. WAVES 1 TO 3 FT.    
SATURDAY
 
NORTHWEST WINDS 10 TO 15 KT. WAVES 1 TO 3 FT.    
SATURDAY NIGHT
 
NORTH WINDS 5 TO 10 KT BECOMING EAST 10 TO  
15 KT. WAVES 1 TO 3 FT.    
SUNDAY
 
EAST WINDS 10 TO 20 KT INCREASING TO 15 TO 25 KT.  
CHANCE OF SHOWERS. WAVES 2 TO 4 FT BUILDING TO 3 TO 5 FT.    
MONDAY
 
EAST WINDS TO 30 KT BECOMING NORTHEAST. CHANCE OF  
SHOWERS. WAVES 5 TO 8 FT OCCASIONALLY TO 10 FT.  
 

 
 
LMZ761-211530-  
MAFOR 2109/  
MICHIGAN NORTH...GALE WARNING IN EFFECT...11130 11146 12850 12840  
11830 11820. CHANCE OF SHOWERS EARLY THIS MORNING. CHANCE OF  
SHOWERS THIS AFTERNOON. WAVES 2 TO 4 FEET BUILDING TO 10 TO 13  
FEET TODAY. WAVES 7 TO 11 FEET SUBSIDING TO 3 TO 6 FEET THE REST  
OF TONIGHT.  
 
MICHIGAN SOUTH...GALE WARNING IN EFFECT...11530 11630 11650 11750  
11850 11840 11830 11820. CHANCE OF SHOWERS TODAY. WAVES 2 TO 4  
FEET BUILDING TO 10 TO 14 FEET TODAY. WAVES 10 TO 14 FEET  
SUBSIDING TO 4 TO 7 FEET THE REST OF TONIGHT.  
 

 
 
CMILLER  
 
EXPERIMENTAL MODERNIZED OPEN LAKE FORECAST IS AVAILABLE ONLINE AT  
WEATHER.GOV/MKX/GLFTABLE  
 
GRAPHICAL MARINE FORECASTS ARE AVAILABLE ONLINE AT:  
WEATHER.GOV/GREATLAKES  
 
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