1935-2006 Duration of Snowcover and Growing Degree Trends from the Summit and Base of Mount Washington, NH

Start and end dates of continuous snowcover, growing degree days and thawing degree days were calculated using the 71-year climate record from the summit of Mount Washington (1914m ASL), NH. Preliminary results show the start of continuous snowcover (defined as ≥ 2.54cm of snow on ground) on the summit of Mount Washington occurs later in the autumn by 2.1 days decade -1 and ends slightly later in the spring by 0.3 days decade -1, a net decrease in continuous snowcover of 1.8 days decade -1. The trend of a shorter snow season is more pronounced for the date of first and last observed snow on the ground; the first snow occurring 6.7 days decade -1 later in the autumn and last snow 3.3 days decade -1 earlier in the spring. Similarly, using hourly values, cumulative thawing degree days (>0° C) and growing degree days (>5° C) exhibit spring warming; for example the date at which the cumulative thawing degree days = 50 is occurring earlier by 1.1 days decade -1. There is a slight discrepancy between the later continuous snowcover persistence in the spring and the other metrics that we are examining. The above metrics will also be presented from for the eastern base of the mountain, Pinkham Notch, New Hampshire (619m ASL), and compared with these summit data. These results provide insight into how the remnant islands of Arctic flora surviving on the Northeast's higher peaks are now and will be challenged in the future.