1. Long-term trends in snowpack in the Pacific Northwest Philip Mote, Alan Hamlet, and Dennis Lettenmaier

5. 20th century decline in NH snow cover R.D. Brown, J. Climate, 2000

6. Elevation (m) Areas with December temperatures near freezing Topography of the Pacific Northwest

7. Trends in snowpack Use VIC and met data to evaluate trends, roles of temperature and precipitation

8. Outline Snow course results VIC results Wild speculation

22. Trends in April 1 snow water equivalent, 1940-1992

23. Precipitation trend (%) Temperature trend (C)

24. Attributing proportion of trend T = r(S,T) where = trend in T T = proportion of trend in S attributable to trend in T r(S,T) = regression of S on T, interannual

33. Outline Snow course results VIC results Wild speculation

35. VIC simulation 1/8° long x 1/8° lat 47°N to 49°N, coast to Continental Divide Daily weather data, 1/1/1915 - 9/30/98 interpolated to VIC grid points from USHCN stations

37. +: observed o: nearest VIC grid point

42. Outline Snow course results VIC results Wild speculation

45. Conclusions Observations show substantial declines in Northwest snowpack; corroboration with VIC suggests they are real Trends in temperature are partly responsible A foretaste of things to come?