Snow Depth Days
of the Northeast

This page has snow depth data for the winter of 1997-1998 at sites around New England and New York.

Snow Depth Days

Traditionally, a winter's snowfall has been tracked as simply the total snow that falls during the season. While fine for several purposes, it doesn't really measure the impact of the snow on people. Suppose the total snowfall for a season is 100 inches. Near a coast where the ocean brings in warm, moist maritime air and rain, snow may not last for very long. Inland where arctic air dominates, the snow will last longer and the maximum snow depth can be much greater than near the coast.

The type of snow also has differing impacts. A foot of dry, fluffy snow will compress quickly with time (or with more snow) whereas an equal depth of wet snow presents more challenges to driving, shoveling, compression and melting.

Snow Depth Days makes a better measure of impact a winter's snows. The depth days for a whole winter are simply the sum of the snow depth on the ground for each day of the winter. Storms that start with snow and change to rain count for less than storms that are all snow.

Two major blizzards in Massachusetts show the importance of the depth day metric.  If you experienced both the Blizzard of '78 and the April Fool's Blizzard of '97, the 1978 storm wins hands down despite surprisingly similar snow distributions.  The key differences were the winds (1978 saw major coastal destruction), the weight of the snow (1997 took a heavier toll on tree limbs), and how long the snow remained. Massachusetts was shut down for a week in 1978, but the 1997 snow melted in days. 1997's storm brought far fewer depth days. WHDH has a very good account of the two storms but leaves out one important fact. A couple weeks earlier, Jan 20th, a storm left 22" of snow in Boston, a January record and 24 hour record. While a rain storm on Jan 26 melted most of the snow in Boston, snowbanks were still on the sides of the streets and sidewalks when the second storm hit on Feb 6th setting new 24 hour (23.6") and total storm records (27.5"). Boston and much of the rest of state simply had no place to put the new snow. Those were the bulk of the snow that year, it would be fun to go back to the climatic records and compute the depth days for each month in 1978 and 1997.

Persistence Quotient

After tracking depth days for a few years, Jim Corbin realized that dividing a season's depth days by the season's snowfall, you get another interesting metric. The quotient is a number that tells you how many days an average inch of snow lasts. If two sites have the same number of depth days but a very different persistence quotient, the one with the higher value was colder than the one with the lower quotient. It didn't snow as much, but what fell stayed longer. I think depth days is the more important metric, but it's easy and worthwhile to track persistence too. Maybe we can find a correlation between it and average temperature.

Daily/Monthly Data

The following table summarizes the snow fall and depth days from sites that are posting that data on the wxobs-sne mailing list. If people also prepare Web pages for daily information for their site, I'll include links to them. Cells under the "snow" column are the snowfall for the site in that month, under "SDD" are the depth days for the month.
 
Location October November December January February March April May
Snow SDD Snow SDD Snow SDD Snow SDD Snow SDD Snow SDD Snow SDD Snow SDD
S Attleboro MA 1.6 2 5.7 14 2.8 3 0.5 0.5 1.5 1
Easton MA 1.8 2 6.9 25 0.2
Fairhaven MA 0.4 0 2.0 3 5.6 6 T 0 0.4 0
Marlboro MA 6.25 22 16.5 71.5 17.0 134.5 2.0 65.5 4.25 10
Middleboro MA 7.5 10 10 31 0 0 0.5 0.5
Milton MA 4.2 6 9.2 21 8.2 39 1.1 0 3.4 5
Sterling MA 8 35 22 94 16 156 4 94 5 20
Waltham MA 4.7 10 10.4 21 16.1 45 0.8 1 4.3 3
Weston MA 4.75 15 13 89
Poland Spring ME 15.3 87 17.7 107 13.1 140 4.0 160 13.5 62
Deerfield NH 20.5 134 19.5 193
Derry NH 9.1 36.5 19.4 99 16.3 119.5 4.2 59 3.9 5
N Pelham NH 9.25? 54 17.25 109
Plymouth NH 17.5 100 17.0 205 20.0 389 6.0 505 27.3 438
Roslyn NY 0.1 0 2.1 2 1.3 0
Wilton NY 19 123 16.5 147 20.5 345 6 363 11 120
Charlestown RI T 0 8.2 16 1.7 0 0.1 0 0.5 0
Woonsocket RI 3.2 18 7.0 33 5.7 25 0.4 0 2.7 4
W Burke VT 5.8 11 18 109

1997/1998 season

The persistence quotient is lower than the ultimate value if there is still snow on the ground at the site. This data will be updated each month.

Full winter:


 
Location Snowfall Depth Days Persistence Quotient
S Attleboro MA 11.6 21 1.8
Fairhaven MA 8.4 9 1.1
Marlboro MA 41.75 293.5 7.0
Middleboro MA 18 41.5 2.3
Milton MA 26.1 71 2.7
Sterling MA 55 399 7.3
Waltham MA 36.3 80 2.2
Poland Spring ME 63.9 556 8.7
Deerfield NH 76 1189 15.6
Derry NH 52.9 319.5 6.0
N Pelham NH 47 405+ 8.6?
Plymouth NH 87.8 1737 19.8
Wilton NY 73 1115 15.3
Charlestown RI 10.5 16 1.5
Woonsocket RI 19.0 80 4.2

Partial season:

Location Snowfall Depth Days Persistence Quotient
Easton MA 8.7** 27 3.1
Weston MA 17.75** 104 5.9
Roslyn NY 3.5* 2 0.6
W Burke VT 23.8*** 120 5.0

*: Data for February not included
**: Data for January, February not included
***: Data for December, January, February not included

Contributors

Name Location
Dennis Bollea Fairhaven MA
Bear Burnes Weston MA
A Cadoret Woonsocket RI
Karen Connolly Middleboro MA
Justin Consor Roslyn, NY
Jim Corbin S Attleboro MA
Wayne Cotterly Poland Spring ME
Bob Davitt Deerfield NH
North Pelham NH
Matthew Douglas Milton MA
Paul Hansen Marlboro MA
Jim Hilt Derry NH
Paul Himottu Sterling MA
Scott Kaplan Waltham MA
Josh Nichols Easton MA
W Burke VT
Chris Seeber Charlestown RI
Tom Ventre Wilton NY
Ric Werme Plymouth NH

Credits

Jim Corbin, a meteorologist from Rhode Island, proposed the concept of both snow depth days and the persistence quotient, but he didn't have good names for them.  After a bouncing around various ideas, I came up with Depth Days.  It seems to fit into colloquial speech well, e.g. "When mired in the Depth Days of February, she thought fondly of the Dog Days of August." Of course, none of us snow lovers would ever think that. I picked Persistence Quotient while putting this page together, we'll see how it wears with time.

Musings

I think depth days is a great statistic, and I'm surprised that it is catching on slowly outside of the wxobs-sne mail list. I never expected that the NWS would embrace it quickly, but I had hoped that TV meteorologists would start using it, in monthly summaries, if nothing else. It would be nice if ski areas would use it, but they may not wish to if they are not likely to be #1 consistantly. (And if only one area reports depth days, it would not be a good comparative statistic.) I see that UVM has has graphs of snow depths at Stowe through many seasons.

Comments on this winter

Well, in February I thought I'd save some quotes here. However, I started too late, and just have this one. Maybe I can dig up a Jim Corbin "Saving $$$$$$!" post.

From: "Brian Monahan, Clarksboro, NJ"
Date: Wed, 25 Feb 1998 22:47:04 -0500

By the way... with just three days remaining in meteorological winter, it's becoming clear that this winter will certainly go down into the books as one of the least "wintry" ever... ZERO SNOW DEPTH DAYS since December 1st, and for that matter, in one year... That's unbelievable for a spot this far in the northeastern United States.. For the season... 0.4 INCHES OF SNOWFALL since December 1st... 13.8" behind last year's final tally... Also, lowest temp this season was just a mere 18F, coming back on the 1st of the month... also the date of the coolest high; 32F... So clearly a winter to remember here, not for snow like 95-96, but for the lack thereof... Also, Philadelphia with just 0.7" of snowfall is just 72 hours away from only the 2nd season there below 1" in 124 years of continuous records (last occurence being the dreaded TRACE year of 72-73)... Also, since 1874, only 5 seasons have featured snowfall below 6", and barring a miracle, #6 is certainly on the way...

Last update: 1998 April 3
Ric Werme

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