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Saint Lawrence Freeze Up Date Outlook

National Weather Service Buffalo NY

420 AM EST Fri Dec 15 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 7, 2024.



WATER TEMPERATURES...



Water temperatures have been running near average for the month of 

December so far, beginning the month in the mid 40s and falling a 

few degrees over the first two weeks of the month. 



Water Temperatures December 15th:



Alexandria Bay, NY   42F (normal 42F) 



LAKE ONTARIO OUTFLOW...



The outflow from Lake Ontario has averaged about 257,000 CFS through 

the first half of December, which is above the long term average. 

Above average outflow from Lake Ontario is expected to continue 

through the rest 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.



Temperatures through the first half of December have been well above

average most of the time, with just one short period from the 5th

through the 8th featuring below normal temperatures.  



December Average Air Temperatures through December 14th: 



Watertown, NY   36.2F (6.3F above normal) 

Massena, NY     29.8F (2.9F above normal)



FORECAST FOR THE REST OF DECEMBER...



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

through the rest of December, with no sustained cold in the

foreseeable future for the Saint Lawrence Valley. The sustained

above normal air temperatures through the rest of the month will

likely allow water temperatures to become increasingly above

normal, with the lack of cold weather only supporting very slowly

dropping water temperatures. 



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 continue through 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 7, 2024. 

This date is around 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