How Important is December Snow?

The amount of snowfall Connecticut receives in December correlates pretty well to what we’ll see in the rest of winter. In particular Decembers that feature below average snowfall are followed by below normal snow for the rest of the winter most of the time.

Part of this is intuitive. Since 8″ of snow in December is average if we only pick up 3″ you’d expect the seasonal total to be about 5″ shy of average all other things being equal. However the numbers show that if December is below average snow-wise there’s a fairly large probability the rest of the season will under perform as well.

For the greater Hartford area here is how the numbers break down.

  • Average December Snow – 8.4″
  • Average Seasonal Snow – 45.3″

Decembers with less than 6″ of snow

  • Happened in 37 out of 93 winters
  • Of those winters 7 of 37 had above normal seasonal snow
  • 30 of 37 (81%) had below normal seasonal snow
  • Of those 37 winters the average seasonal snow was 32.7″

Decembers with less than 1″ of snow

  • Happened in 10 of 93 winters
  • Of those winters NONE had above normal seasonal snowfall
  • Of those 10 winters the average seasonal snow was 24.4″

Of course the obvious is true here. When you get a month with little snowfall of course your seasonal snow is likely to be below average. These numbers also tell us, however, that a December with little snow is frequently followed by below normal snow in the months of January, February, and March. The seasonal snowfall deficit grows larger beyond December.

It turns out that a relatively snowless December is a reasonable predictor for the rest of the winter.

What will we see this December? Too early to say but the pattern does appears favorable for snow particularly the week around Christmas with the potential for a light event before that.

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4 thoughts on “How Important is December Snow?

  1. As of right now…this morning (Sunday) the power of the subtropical Atlantic Ocean south of 40 latitude is quite apparent: The surface temps have surged into the 40’s, New Haven is 43 F, Groton 43 F, NYC 49 F, Atlantic City is now 55 F!. I think a big factor in WHY these winter lows seem to head for the Great Lakes is the strong Atlantic ridge. We must remember that low pressure moving south of Tri-State (or out to sea) is really more a rare event, compared to what is known as “inside runners” (meaning the low goes through the Great Lakes). Of course with the American subtropics so close (Koppen starts this zone around southeast Virginia), warm air advection is always in the cards.

    The power of the warm Atlantic is often the saving grace for the East Coast and contributes to the relatively mild winters in places like Connecticut, NYC, NJ, MD, …etc (compared to the interior USA). Its mornings like this I’m glad I live on the East Coast and not up in the Midwest !

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