Understanding mountain weather: Avalanches and winter weather
year dozens of people around the globe are killed on mountains and in the backcountry
by avalanches -- sliding masses, often slabs, of snow (snowslides) and ice that
can let loose on moderatley steep slopes with little warning, reaching speeds
over 100 mph and carrying rocks, trees, debris and people with them. Many avalanches
are triggered by skiers, snowboarders, hikers and snowmobilers. The links below
take you to more detailed information on avalanches. Or visit USA TODAY's online
winter weather page for links to graphics
and stories on cold-season weather and its effects in the USA.
The Northwest Weather and Avalanche Center
has avalanche forecasts and information
for Washington and Oregon, and mountain weather forecasts, including links to
avalanche forecasts & information
from other areas of the USA.
The Cyberspace Snow and Avalanche Center
offers inks to current conditions, avalanche education, and incident reports.
The Westwide Avalanche Network
is a repository of mountain weather and avalanche data with dozens of links
to avalanche information.
Winds that blow down the mountains are called downslope
winds and often bring sunny, warm weather.
Extreme weather on U.S. mountains
The world record wind speed of 231 mph was measured in New Hampshire on 6,288-foot
Mount Washington on April 12, 1934. Find out more about its extreme weather
on the Mount Washington
Observatory Web site. Its main
page has information on weather research and educational outreach programs.
Washington state’s 14,410-foot Mount Rainier is well known for its extreme
snowfall, which averages nearly 700 inches a year at the 5,400-foot Paradise
Ranger Station. Information on Mount Rainier weather, including the annual climate
at Paradise Ranger Station, can be found here.
General information about the park is available from the Mount
Rainier National Park Service.
How topography affects weather
Narrow mountain canyons in the Southwest can quickly become the scenes of a
raging flood. Find out how narrow canyons help spawn dangerous
Seattle's rainfall gets a boost from a local topographic effect known as the
"Puget Sound convergence zone."
Often, the heaviest snow falls over the highest elevations of mountain ranges.
A graphic compares the snowfall at two locations
in Utah, which are very close together, but are at different elevations.
A graphic shows why rainy weather often causes mud
slides in hilly areas.
Topography is often a key factor in the
daily weather of mountain ranges.
Mountain streams can become raging torrents when heavy rain falls. A graphic
and text tells why flood waters
are so dangerous. Another graphic shows how warm air flowing up the side
of a mountain can spawn massive
flooding in the Pacific Northwest.
Winds that blow uphill are called upslope winds
and can bring fog, rain and snow.
By Chad Palmer, USA TODAY Weather team