Snow Depth Days
of the Northeast

This page has snow depth data for the winter of 2002-2003 at sites around New England and New York. Data for other years are available from the SDD home page.

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.

The season in review

The first snow of the 02/03 season fell on October 6th over much of the area. Given that the last snow of the previous season amazed everyone on May 18th, we had a remarkably short period between seasons.

The winter started out with some small storms, but several storms on and after Christmas gave the region decent snow cover. The second half of January was very cold and that carried into February. The cold was due in part to the storm track being pushed southward, and that left several southern New England stations getting more snow than the north. Woonsocket RI and Mt. Mansfield each recorded 27.5"! The cold and dry stretched into March, and some stations saw more snow in April than in March.

A snowstorm on February 16th brought 27.5" of snow to observers at Logan airport, establishing new records for 24 hour snowfall and storm total. However, there were disputes about the actual amount of snow, the frequency the snow board was cleared, etc. It appears Logan was in a band of low density "ocean effect" snow that brought a lot of fluffy snow. One estimate of the the density came out to 70:1. At any rate, the snow on the ground packed sown pretty quickly and snow depths were quite a bit less. The snowfall Logan saw was more than the general area and less water than several other storms.

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
Collinsville CT 14.3 29 17.1 100 16.3 287 30.3 385 12.7 304 3.9 4
N Berlin MA 1.25 0 8 15 23.25 105 20.25 435 32.25 507 8.25 315.0 5.25 9
Fairhaven MA 3.4 6 9.8 28 5.4 10 27.5 178 11.2 45.0 2.8 3
Marlboro MA 1.2 0 6.3 12.5 20.4 80.5 18.4 298 28.4 346 8.2 145.0 4.4 6
Milton MA 0.3 0 7.3 15 13.3 54 7.8 45 45.2 203
Milton-BHO MA 1.3 0 8.2 21 21.8 90 12.7 189 51.3 382
Newburyport MA 5.5 15 18.7 78 22 520
Pepperell MA 2.3 0 7.1 15.8 23.2 146 23.1 455 27.9 485 9.0 258.0 6.4 19
Sudbury MA 1 0 8.75 17 19.25 115 19 397 32.75 502 8.75 329.0 5.75 9
Poland Spring ME 6.3 31 18.5 88 24.6 647 13.2 627 3.5 414.0 2.3 4
Derry NH 7.4 12 25.4 122 21.8 450 30.8 468 7.6 279.0 5.8 13
Penacook NH 1 1 8.6 26.5 14.9 72 25.6 500 16.1 488 5.4 372.5 12.4 51
Charlestown RI 3.8 7 10.4 33 5.6 9 28.5 165 9.3 40.0 2.2 1
Woonsocket RI 5.9 16 13.9 61 10.9 109 31.3 269 10.7 121.0 1.8 0
Mt. Mansfield VT 7.25 28 46.1 429 40.1 1209 26.9 1936 27.5 2148 22.8 2485.0 9.8 2017 0 688
Mt. Snow VT 8 16 40.5 119 41.25 540.5 46 1068 22.25 1037 12.0 978.5 8.0 137.5

2002/2003 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 94.6 1109 11.7
N Berlin MA 98.5 1386 14.1
Fairhaven MA 60.1 270 4.5
Marlboro MA 87.3 888 10.2
Milton MA 73.9 317 4.3
Milton-BHO MA 95.3 682 7.2
Newburyport MA 46.2 613 13.3
Pepperell MA 99 1379 13.9
Sudbury MA 95.25 1369 14.4
Poland Spring 68.4 1811 26.5
Derry NH 98.8 1344 13.6
Penacook NH 84 1511 18.0
Charlestown RI 59.8 255 4.3
Woonsocket RI 74.5 576 7.7
Mt. Mansfield VT 180.45 11628 64.4
Mt. Snow VT 178 3894 21.9

Contributors

Name Location Email name Email domain
Dennis Bollea Fairhaven MA 76624.2745 compuserve.com
A Cadoret Woonsocket RI cumulus att.net
Wayne Cotterly Poland Spring ME cotterly pivot.net
Matthew Douglas Milton MA mdouglas attbi.com
Milton-BHO MA
Todd Gross N Berlin MA toddwx rcn.com
Sudbury MA
Paul Hansen Marlboro MA paulh01 attbi.com
Jim Hilt Derry NH jimhilt attbi.com
Charles M. Kozierok Mt. Snow VT ixl fearn.pair.com
Andrew Plona Collinsville CT nwconnecticut comcast.net
Chris Seeber Charlestown RI cseeber cox.net
Paul Venditti Pepperell MA paulvenditti prodigy.net
Ric Werme Penacook NH ewerme attbi.com

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

Last update: 2004 March 1
Ric Werme

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