3/24/2010
Warmer weather can actually increase avalanche threat
BOISE
- When the snow turns to rain, and warmer temperatures replace frigid
winter cold, it may be a wonderful thing for drivers and residents in the lower
elevations. But those warmer conditions may actually create a rising avalanche
hazard, according to ITD Lead Avalanche Forecaster Bill Nicholson.
Warmer temperatures, and increased water content in the snow caused by melting
or rain, can combine to create a considerable avalanche hazard, especially
if the snow pack is weak and unstable to begin with.
Colder temperatures can actually help stabilize the existing snow pack.
Click
here to see a picture of a warm-weather avalanche. Click here to see a picture of ITD checking
snow temperature.
The first picture is of a small spring slide that hit the road even as the warmer
temperatures have
melted the snow from the surrounding hills. The other photo
is Mick Riffie of the ITD Avalanche
Forecast Office taking the snow temperature
in an obviously thin snowpack in Canyon Creek on
a warm day in early March.
Riffie
noted that while the amount of remaining snow is certainly of note, the more
important indicator in warm-weather conditions is the temperature of the snow
at different depths.
"As spring weather gets warmer, the snow becomes more like
slush during the hot part of the day and usually refreezes at night," Riffie
explained.
"The
temperatures help us get a picture of how deeply the warmth is penetrating the
snowpack and can give us clues about how soon we could see avalanches due to
heating."