Snow Depth Days
of the Northeast

This page has snow depth data for the winter of 2007-2008 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 measurable snowfall was 2" a couple of days before Thanksgiving. A pretty average start, overall. December was not! Except for one rain event, measurable snow fell every three or four days. A "Norlun Trough Event" on the 19th and 20th made us the bullseye with 15" and left my snowstake nearly covered. Fortunately I have a 48" yard stick. (It is a "yard" stick, as I use it to measure snow in the yard. Sorry.) On the last day of the month snow bands from a more conventional storm also made Penacook the bullseye with 14" and brought the snow back up to the top of the snow stake. All told, the 52.5" of snow was by far the most I've recorded in 10 years of records, see the table below. It was more snow than I saw in five seasons. December had 361 Snow Depth Days, more than two entire seasons.

Concord NWS data reports from the last storm just 10.1" and a total December snowfall of 44.5" which breaks the old record of 43.0" set back in 1876. While Concord is close by and another storm had an equally sizable difference with Penacook, I think both data points are right and the differences are due mainly to location!

January did not keep up the consistant storminess, though it did have several snowfalls. The biggest were 6" and 13". Between the reduced activity and a welcome thaw, the month felt like a break. However, it did have 24.8" total, making it the 5th snowiest month in my record. Despite the thaw, the lowest snow depth was 12" and the 587 SDDs made it the 2nd most snowbound month behind the 630 SDDs from March 2001.

February had neither the big snows of December nor the January thaw. The biggest storm was only 9.4", and the high for the month was 48. However, we did have 12 days with snow and enough cold rain or sleet to make the month very wet. We also broke just about every snowfall and snow depth record of the ten years I've lived here, including seasonal records for most snowfall and snow depth days. Concord is on the brink of exceeding the all-time record of 122 inches in the 1873-74 season.

We kind of coasted through March. Snowfall was a very ordinary and average 15", temperatures were unremarkable. Half the snow fell on the 1st which brought us our peak snow depth of 40.5". By the end of the month we were down to 17", but broke the monthly SDD record set the month before. Concord did not break the all-time record, but surpassed the 100 year record.

New records include:
Name New record Old record Old 2nd place Average Last place
 
Snowfall		  
Dec 2007: 52.5" 2003: 28.5" 2005: 20.2" 17.5" 1999: 0.0"
Feb 2007: 34.0" 2005: 26.2" 2003: 25.6" 15.5" 2000: 0.0"
Monthly Dec 2007: 52.5"
Feb 2007: 34.0"		 Mar 2001: 38.1" Dec 2003: 28.5" N/A Mar 2006: 0.0"
Season 2007/2008: 129.5" 2000/2001: 97.6" 2002/2003: 84.0" 74.0" 1998/1999: 43.0"
 
Snow Depth Days		  
Dec 2007: 361 2005: 182 2003: 157 97 1999: 0
Jan 2008: 587 2003: 500 2001: 234 236 2007: 19
Feb 2008: 710 2003: 488 2001: 470 319 2006: 26
Mar 2008: 812 2001: 630 2003: 373 277 2006: 6
Monthly Mar 2008: 812
Feb 2008: 710		 Mar 2001: 630 Jan 2003: 500 N/A Dec 1999: 0
Season 2007/2008: 2565 2002/2003: 1511 2000/2001: 1501 956 2006/2007: 354
 
Deepest snow		  
Dec 2007: 27" 2003: 15" 2005: 13" 9.1" 1999: 0"
Jan 2008: 28" 2003: 21" 2005: 14" 13.0" 2007: 1"
Feb 2008: 35" 2001: 27" 2003: 23" 17.2" 2006: 6"
Mar 2008: 39" 2001: 33" Two: 19" 17.2" 2006: 2"
Monthly Mar 2008: 39"
Feb 2008: 35"		 Mar 2001: 33" Feb 2001: 27" N/A Two: 0.5"
Season 2007/2008: 39" 2000/2001: 33" 2002/2003: 23" N/A 2001/2002: 8"
 
Continuous
snow cover		  
Season 2007/2008: 130 days 2000/2001: 100 2003/2004: 93 86.4 2001/2002: 40

Daily/Monthly Data

The following table summarizes the snow fall and depth days from sites that are posting that data on local weather observations mail lists 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 1.3 1 18.3 161 12.2 192 16.3 113
Ashland MA 24 183 11.5 80 17 49
Fairhaven MA 12 57 9.2 27 5.3 13 0.3 0
Groveland MA 0.6 0.6 32.1 304.8 13.2 276.2 24.5 195.6 7 55.6
Marlboro MA 0.5 0 26.8 218.5 14.9 141.5 21.9 63 1.9 9
Pepperell MA 1 1 41.6 331 20.4 497 24.1 475 12.2 280 0.3 0
Poland Spring ME 1 1 36.9 285 28.7 327 40.9 478 15.8 609
Bow NH 2 2 53.2 379 27.2 629 37.6 742 18.6 884 0.6 198
Penacook NH 2 2 52.5 361 24.8 587 34 710 15 812 1.2 93
Charlestown RI 5 30 1.4 5 6.4 15 1.1 0
Woonsocket RI 19 140 8.4 53 10.6 24 3.8 4
Mt. Mansfield VT 36.5 348 79.5 1407 29.5 1668 39.1 2270 56.6 3069

2007-2008 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 48.1 467 9.7
Ashland MA 52.5 312 5.9
Fairhaven MA 26.8 97 3.6
Groveland MA 77.4 832.8 10.8
Marlboro MA 66 432 6.5
Pepperell MA 99.6 1584 15.9
Poland Spring ME 123.3 1700 13.8
Bow NH 139.2 2834 20.4
Penacook NH 129.5 2565 19.8
Charlestown RI 13.9 50 3.6
Woonsocket RI 41.8 221 5.3
Mt. Mansfield VT 241.2 8762 36.3

Contributors

Name Location
Dennis Bollea Fairhaven MA
A Cadoret Woonsocket RI
Wayne Cotterly Poland Spring ME
Paul Hansen Marlboro MA
Jim Hilt Bow NH
Andrew Plona Collinsville CT
Jot Ross Ashland MA
Chris Seeber Charlestown RI
Rick Tracy Groveland MA
Paul Venditti Pepperell MA
Ric Werme Penacook 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 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: 2008 May 3
Ric Werme

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