991  
FZUS81 KCLE 041448  
ICEGL  
 
GREAT LAKES FREEZE-UP OUTLOOK  
NATIONAL WEATHER SERVICE CLEVELAND OH  
1050 AM EDT SAT NOV 4 2017  
 
GREAT LAKES ICE SEASON FOR 2017-2018 IS EXPECTED TO BE SIMILAR  
TO THE 2016-2017 ICE SEASON AS A LA NINA WATCH CONTINUES.  
 
A LA NINA WATCH REMAINS IN EFFECT AS WATER TEMPERATURES AND  
ATMOSPHERIC CONDITIONS HAVE BEEN TRENDING TOWARD A LA NINA  
OVER THE LAST SEVERAL WEEKS.  
 
THE LATEST LONG RANGE OUTLOOK IS CALLING FOR TEMPERATURES TO BE  
ABOVE NORMAL ACROSS THE ENTIRE GREAT LAKES DURING THE WINTER  
MONTHS. THE LONG RANGE PRECIPITATION OUTLOOK IS NOW CALLING FOR  
EQUAL CHANCES OF ABOVE...NEAR...OR BELOW NORMAL. THIS MEANS THAT  
THERE IS NO STRONG INDICATION THAT WOULD SUGGEST ABOVE...NEAR...OR  
BELOW NORMAL CONDITIONS WILL OCCUR. THESE FORECASTS ARE  
DETERMINED THROUGH THE USE OF SEVERAL COMPUTER MODELS. IF A  
SIGNIFICANT NUMBER OF THE MODELS INDICATE ONE OF THE OUTCOMES  
OF ABOVE OR BELOW NORMAL...THAT AREA IS HIGHLIGHTED.  
OTHERWISE...IF THERE IS NO CONSENSUS...THEN EQUAL CHANCES IS  
FORECAST.  
 
EVEN THOUGH A LA NINA IS EXPECTED TO DEVELOP ACROSS THE AREA...  
A WEAK LA NINA IS FORECAST TO OCCUR DURING THE WINTER MONTHS OF  
DECEMBER...JANUARY...AND FEBRUARY.  
 
LA NINAS WILL DEVELOP A BLOCKING HIGH PRESSURE CENTER OVER THE  
GULF OF ALASKA FORCING THE JET STREAM TO TRACK EAST ACROSS  
CENTRAL ALASKA AND THEN SOUTHEAST THROUGH ALBERTA CANADA INTO  
THE OHIO VALLEY. THIS TRACK IS VARIABLE THROUGH THE WINTER  
BUT CAN FAVOR COLDER AIR ACROSS THE WESTERN GREAT LAKES REGION.  
THIS TRACK ALSO FAVORS THE INTERACTION OF THE COLD ARCTIC AIR  
FROM CANADA WITH THE WARM MOIST AIR FROM THE GULF OF MEXICO.  
HENCE...THIS SCENARIO FAVORS GREATER CHANCES FOR PRECIPITATION  
ACROSS THE LOWER GREAT LAKES REGION. HOWEVER...SINCE THE  
FORECAST FOR LA NINA IS TO BE WEAK...THE POTENTIAL EXISTS THAT  
OTHER FACTORS SUCH AS THE ARCTIC OSCILLATION AND NORTH ATLANTIC  
OSCILLATION CAN PLAY A MAJOR ROLE IN SHAPING THE WINTER SEASON  
FOR THE GREAT LAKES.  
 
LAST WINTERS WEAK LA NINA PRODUCED VERY LITTLE ICE ON THE ENTIRE  
GREAT LAKES. ANY ICE THAT DID FORM WAS CONFINED TO THE NORTHERN  
SHORES OF THE LAKES AND VERY THIN ICE OVER THE WESTERN BASIN OF  
LAKE ERIE THAT LASTED ONLY A FEW DAYS. IF SIMILAR  
TEMPERATURES EXIST AS EXPECTED THROUGH THIS WINTER SEASON...  
ICE ON THE LAKES WILL ONCE AGAIN BE VERY MINIMAL AND HAVE  
LITTLE IMPACT ON SHIPPING THIS SEASON.  
 
RELATIVELY LOW ICE FORMATION ON THE GREAT LAKES WILL LEAD TO  
THE POTENTIAL FOR THE COMBINATION OF INCREASED STORM ACTIVITY  
AND SIGNIFICANT LAKE EFFECT SNOW ACCUMULATION DURING THE COLD  
AIR OUTBREAKS.  
 
DURING THE NEXT TWO WEEKS...THE NORTH ATLANTIC OSCILLATION AND  
THE ARCTIC OSCILLATION ARE EXPECTED TO BE IN THE STRONG  
POSITIVE PHASE. THIS TREND USUALLY RESULTS IN ABOVE NORMAL  
TEMPERATURES ACROSS THE GREAT LAKES REGION. THESE OSCILLATION  
FORECASTS ARE ONLY GOOD OUT TO TWO WEEKS.  
 
THE NEXT 6 TO 10 DAYS...TEMPERATURES ARE EXPECTED TO BE NEAR  
NORMAL ACROSS THE SOUTHERN LAKES...BELOW NORMAL IN THE  
NORTHWEST...AND ABOVE NORMAL AROUND LAKE MICHIGAN. THE 8 TO  
14 DAY FORECAST IS IN LINE WITH THE ARCTIC AND NORTH ATLANTIC  
OSCILLATION FORECASTS CALLING FOR ABOVE NORMAL TEMPERATURES.  
 
THE WATER TEMPERATURES ON THE GREAT LAKES ARE RUNNING ABOVE  
NORMAL IN THE NORTHWEST AND NEAR NORMAL OVER THE REST OF  
THE LAKES. A MILD OCTOBER HELPED KEEP WATER TEMPERATURES  
ELEVATED THROUGH MUCH OF THE MONTH. RECENT STORMINESS AND  
EXTENSIVE CLOUD COVER CAUSED WATER TEMPERATURES TO DROP  
SEVERAL DEGREES OVER THE LAST COUPLE WEEKS.  
 
KEEP IN MIND THAT ICE COULD DEVELOP EARLIER OR LATER SINCE ICE  
DEVELOPMENT IS HIGHLY DEPENDENT ON THE OCCURRENCE OF COLD AIR  
OUTBREAKS AND WARM PERIODS ACROSS THE GREAT LAKES DURING THE NEXT  
TWO MONTHS.  
 
ICE FORMATION IS DETERMINED BY TWO FACTORS--THE AMOUNT OF HEAT  
STORED IN THE WATER FROM THE SUMMER AND HOW FAST THAT HEAT CAN BE  
REMOVED BY ARCTIC OUTBREAKS OF POLAR AIR AND HIGH WINDS. LONG RANGE  
OUTLOOKS DO NOT CONSIDER THE "STORMINESS" FACTOR WHICH CAN  
SIGNIFICANTLY ALTER THE LAKES THERMAL STRUCTURE OVER SHORT PERIODS  
OF TIME.  
 
THE LATEST HARBOR WATER TEMPERATURES COMPARED TO PREVIOUS YEARS:  
 
2017 2016 2015 2014 2013 2012 2011 2010 2009 NORMAL  
 
DULUTH 55 52 53 44 48 43 50 48 50 44  
SAULT STE MARIE 55 58 53 46 50 52 54 47 48 47  
CHICAGO 55 60 55 48 54 57 54 54 50 53  
ALPENA 52 58 53 50 50 52 53 45 52 48  
DETROIT 55 56 53 49 48 58 53 47 51 52  
CLEVELAND 58 62 58 53 57 51 55 51 53 56  
BUFFALO 54 60 54 52 55 52 55 51 53 54  
 
WATER TEMPERATURES FROM THE MID-LAKE BUOYS COMPARED TO PREVIOUS  
YEARS:  
 
LAKE SUPERIOR  
WEST 52 49 43 43 46 41 47 44 45 47  
CENTRAL 52 47 45 42 44 44 46 46 43 47  
EAST 52 52 45 42 MM 41 44 47 44 48  
 
LAKE MICHIGAN  
NORTH 56 59 51 47 53 45 MM 50 47 54  
SOUTH 58 61 54 46 54 48 55 48 48 56  
 
LAKE HURON  
NORTH 51 56 53 48 49 48 46 49 46 53  
SOUTH 59 57 54 49 56 48 54 53 51 55  
 
LAKE ERIE  
WEST 56 61 51 51 54 45 54 49 53 56  
CENTRAL 63 62 58 53 57 46 55 53 53 58  
EAST 62 59 56 52 54 48 55 52 53 57  
 
THE NEXT FREEZE UP OUTLOOK WILL BE ISSUED IN APPROXIMATELY TWO WEEKS.  
 

 
 
LOMBARDY  
 
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