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Saint Lawrence Freeze Up Date Outlook

National Weather Service Buffalo NY

1023 AM EST Fri Dec 1 2023



...FREEZE-UP DATE OUTLOOK FOR THE SAINT LAWRENCE RIVER...



The date of the first freeze-up on the Saint Lawrence River near 

Massena, NY is forecast to be January 5, 2024.



WATER TEMPERATURES...



Water temperatures started the month of November near average, but

only slowly fell through the middle of the month. A colder

pattern evolved in late November, allowing water temperatures to

drop to near average at the start of December. 



Water Temperatures December 1st:



Alexandria Bay, NY   45F (normal 45F) 



LAKE ONTARIO OUTFLOW...



The outflow from Lake Ontario has averaged about 258,000 CFS through 

the last week of November, which is above the long term average. 

Above average outflow from Lake Ontario is expected to continue 

through much of December.



Above average outflow from Lake Ontario results in faster current in 

the Saint Lawrence River, which can delay the onset of shore to 

shore ice.



AIR TEMPERATURES...



Temperatures through the month of November averaged slightly below

normal. Temperatures had a much more typical range through the 

month than the big temperature swings of October, with just a few 

brief periods of well above or well below normal temperatures. 



November Average Air Temperatures through November 30th: 



Watertown, NY   37.0F (1.0F below normal) 

Massena, NY     34.5F (1.3F below normal)



FORECAST FOR DECEMBER...



Air temperatures are forecast to be above normal much of the time

through the first half of December, with the pattern across

North America favoring frequent periods of west to east flow

and mild Pacific air spreading east across the US/Canadian border.

There are early signs that this mild pattern may relax for the

second half of December, with a trend towards more normal early

winter temperatures, or even a period of below normal 

temperatures as we move closer to the holidays.



A moderate to strong El Nino pattern will continue through the 

winter, which favors increased odds of above normal temperatures 

on average in the eastern Great Lakes and Saint Lawrence Valley as 

we move into the winter months.



Given the above factors, and the overall trend in later onset of

ice cover over the past 15 years, the first freeze-up on the Saint 

Lawrence River near Massena, NY is forecast to be January 5, 2024. 

This date is almost two weeks later than the long term average. 



NOTE: Once the water temperature drops to the mid 30s, ice cover can 

develop in just one very cold, calm night.



NOTE: This forecast is for the first shore to shore freeze-up of the 

Saint Lawrence River near Massena, NY. The first permanent shore to 

shore ice often occurs several weeks later.



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HITCHCOCK