Snow Depth Days
of the Northeast

This page has snow depth data for the winter of 2005-2006 at sites around New England and New York. Data for previous years are available:

A summary of several years is on the homepage.

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. On, Jan 20, 1978 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.

The season in review

This season got off to a "promising" start with some snow in November bringing a white Thanksgiving and a big storm in early December guaranteed Penacook with a white Christmas, but the weather pattern underwent a major change in January. Only five days had a subfreezing high temperature, no days went below zero, two days had highs above freezing and on the 21st the high was 68! February continued the pattern, but was not as extreme. The February high temperature was "only" 59. The second half of the month became more seasonable. March was fairly seasonable in terms of temperature, the only days above 59 were in a warm spell at the very end of the month. March was extremely dry and snow-free at several stations. This brought an early end to snowcover for the season. April continued the dry pattern. (On the other hand, May featured record rainfall and flooding, primarily from a single event, an oceanic feed that would have made things very interesting had it set up in January.)

Some stations reported more depth days in December than in the rest of the season, especially those stations that missed a southern New England blizzard. Fluffy snow from the blizzard and warm weather afterwards meant some stations had more snow in January than December but fewer depth days.

Daily/Monthly Data

The following table summarizes the snow fall and depth days from sites that are posting that data on the WHDH weather observations mail list and a couple others. 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
Collinsville CT 4.8 11 16.5 116 25 170 14.5 38 5 17.0 1.2
Ashland MA 0.5 2.6 5 13.5 112 16.2 54 15.2 28 0 0.0
N Berlin MA
Fairhaven MA 0.4 1 1 8.4 15 2.1 3 10.8 26 8.3 24.0 0
Groveland MA 2 3 20.4 19 18.2 115 13.4 60.9 0.1 6.4 0.1 0.1
Manchester MA 2.6 2.2 0.3 0 13.4 79.6
Marlboro MA 3.3 6 16.5 90.5 17.2 74.5 17.1 34 0 0.0 0.5
Milton-BHO MA
Monson MA 2.1 2 13.65 136 15.7 80 20.75 55
Newburyport MA
Pepperell MA 5.9 19 18.1 151 18.7 121 22.5 54 0.4 3.0
Poland Spring ME 5.6 22 15.7 142 13.7 87 4.6 29 2 2.0 2 2
Bow NH 5.2 15 26.6 164 18.4 159 11.9 64 0.4 26.0
Deerfield NH 19 214
Penacook NH 4.9 14 20.2 182.0 14.2 140 9.5 26 0 6.0
Peterborough NH
Charlestown RI 0 0 8.6 25 4.3 26 7.7 19 6.6 21.0 0
Woonsocket RI 0.3 2 13 96.1 10.2 42 16.2 40 3.6 8.0 0
Mt. Mansfield VT 21.8 111 41.5 158 44 830 34.8 1236 26.1 1583 32.8 2125.0 13.5 1621 6.5 415

2005-2006 season to end of last month

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.

Location Snowfall Depth Days Persistence
Quotient
Collinsville CT 67 352 5.3
Ashland MA 48 199 4.1
N Berlin MA 0 0 ...
Fairhaven MA 31 69 2.2
Groveland MA 54.2 204.4 3.8
Manchester MA 16.3 81.8 5.0
Marlboro MA 54.6 205 3.8
Milton-BHO MA 0 0 ...
Monson MA 52.2 273 5.2
Newburyport MA 0 0 ...
Pepperell MA 65.6 348 5.3
Poland Spring ME 43.6 284 6.5
Bow NH 62.5 428 6.8
Deerfield NH 0 233 ...
Penacook NH 48.8 368 7.5
Peterborough NH 0 0 ...
Charlestown RI 27.2 91 3.3
Woonsocket RI 45.3 186.1 4.1
Mt. Mansfield VT 221 8079 36.6

Contributors

Name Location
Dennis Bollea Fairhaven MA
A Cadoret Woonsocket RI
Wayne Cotterly Poland Spring ME
Matthew Douglas Milton-BHO MA
Tim Fisher Peterborough NH
Todd Gross N Berlin MA
Paul Hansen Marlboro MA
Jim Hilt Bow NH
Christopher McCray Monson MA
Andrew Plona Collinsville CT
Jot Ross Ashland MA
Chris Seeber Charlestown RI
Jim Spillane Deerfield NH
Don Towle Manchester MA
Rick Tracy Groveland MA
Paul Venditti Pepperell MA
Ric Werme Penacook NH
Ray Whitley Newburyport MA

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 NE Weather Spotters 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.) The University of Vermont has graphs of snow depths at Stowe through many seasons.

Last update: 2006 June 4
Ric Werme

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