Snow Depth Days
of the Northeast

This page has snow depth data for the winter of 2003-2004 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

The first snow of the 03/04 season fell on October 23th over much of the area, one year to the day of the first measurable snow of the previous year. That was about it until early December.

December featured two large storms in the first half of the month, but then warm weather and rain melted nearly all of it, but the piles of shoveled and plowed snow provided a reminder of the storms.

January started out well above average, but then the bottom fell off the thermometer. Three cold snaps set new records throughout the region. Several places broke the old record by over 5 degrees. Mt. Washington reached -45F, two degrees from its all-time low. Here in Penacook our low for the month was -14F. We had eleven days with sub-zero readings and two days with a high a fraction of a degree above zero. Once the cold hit, only one day made it above freezing.

Blue Hill recorded two record low minima and four record low maxima during the month. The average temperature tied for third coldest January in their 119 year record.

Cold air is dry air. It's also heavy air and creates "cold air damming" that forces storms to the south. Penacook had only 6" of snow, but we ended the month with more snow on the ground than at the start.

February brought warmer temperatures, but one cold snap returned the area to sub-zero mornings. However, the storm track stayed south and Penacook had only slightly more snow than in January. Cape Cod and even North Carolina had more. Only a few days were above freezing, and those were dry, so the snow pack showed little melting until the last few days of the month.

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 0.9 0 0 0 16.6 54 15.1 72 7 214 12.5 41.0
N Berlin MA 2 1 0 0 20 85 7.8 58 5.7 99 11.5 30.0
Fairhaven MA 0 0 0 0 19.5 66 10.1 33 5.8 20 8.9 20.0
Marlboro MA 0 0 0 0 22.1 64 9.3 44 4 70 11.2 33.0
Pepperell MA 0.7 0 0 0 21.8 111 10 107 7.1 178 12.6 34.0 0.1 0
Poland Spring ME 0.3 0 0 0 31.6 133 2.2 23 14.4 111 6 21.0 1.4 2
Derry NH 0 0 0 0 23.2 108 8.6 95 5 131 10.8 25.0
Penacook NH 0.7 1 0.5 0.0 28.5 157 6.1 108 7.2 213 7.6 25.0
Charlestown RI 0 0 0 0 19.6 56 16.1 62 4.1 36 9.6 23.0
Woonsocket RI 0 0 0 0 21.1 85 8.7 34 2.4 11 10 24.8
Mt. Mansfield VT 4.2 19 18.5 249 61 1241 33.5 1880 36.3 2324 32.7 2795.0 13.8 2303 10.5 461

2003/2004 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 52.1 381 7.3
N Berlin MA 47 273 5.8
Fairhaven MA 44.3 139 3.1
Marlboro MA 46.6 211 4.5
Pepperell MA 52.3 430 8.2
Poland Spring ME 55.9 290 5.2
Derry NH 47.6 359 7.5
Penacook NH 50.6 504 10.0
Charlestown RI 49.4 177 3.6
Woonsocket RI 42.2 154.8 3.7
Mt. Mansfield VT 210.5 11272 53.5

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 tgross whdh.com
Watoquadoc Hill MA
Paul Hansen Marlboro MA paulh01 comcast.net
Jim Hilt Derry NH jimhilt yahoo.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 ric werme.8m.net

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: 2005 April 2
Ric Werme

Back to home page.