A new normal for snow


Idaho hydrologist Phil Morrisey has been fielding some complaints lately. Although the Natural Resources Conservation Service -- the federal agency he works for -- reports normal snowpack, skiers say they're schussing through thin powder. And they have a point, Morrissey says: The agency just started using a new standard for measuring average snowfall -- and it's drier than the old one.

"Normal" climate is often measured in 30-year increments, adapted every decade by many weather-watching organizations. Until recently, Morrisey's NRCS, whose SNOTEL sites track Western snowpack, used 1971-2000 as its standard. Now, however, it uses 1981-2010, meaning precipitation averages exclude the 1970s' wet years. Instead, the dry 2000s have replaced them, so this year's Western snowpack conditions may sound better than they are. This affects far more than peeved powder hounds; irrigators and rafters hoping to avoid parched crops and rocky rivers will have to adjust their notions about what a normal snowpack is.

Robert Laybourn
Robert Laybourn Subscriber
Mar 16, 2013 07:02 AM
Streamflow graphs are showing similar adjustments, plus the melt is coming sooner and ending more quickly. This results in effectively hotter summers at higher elevations.