Archived Advisory for Thu Mar 20 2008

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20 March 2008

Good morning. This is Ron Johnson with the Gallatin National Forest Avalanche Advisory issued on Thursday, March 20, at 7:30 a.m. The Moonlight Basin Ski Patrol, in partnership with the Friends of the Avalanche Center, sponsor today’s advisory. This advisory does not apply to operating ski areas.

MOUNTAIN WEATHER

Wintry weather prevails on the first day of spring. Overnight 2-4 inches of snow accumulated in the mountains around Bozeman and Big Sky. The mountains around West Yellowstone and Cooke City got 6-10 inches. This morning at 4:00 a.m., mountain temperatures were in the low 20’s F and westerly ridgetop winds were 15-25 mph. More snow will accumulate today. The mountains around Bozeman and Big Sky will get 2-4 inches, while 4-6 inches falls on the mountains around West Yellowstone and Cooke City. Mountain temperatures will reach the upper 20’s F and ridgetop winds will remain westerly at 15-25 mph.

SNOWPACK AND AVALANCHE DISCUSSION

The Bridger Range:

Yesterday ski patrollers at Bridger Bowl found the six inches of snow that fell Tuesday wasn’t readily blown around and subsequently no avalanches were reported. Today the addition of 2-4 inches of new snow and westerly ridgetop winds blowing 15-25 mph will likely produce wind slabs on the lee side of ridges and gullies. The slabs will be 6-12 inches thick and on steep slopes will fracture under skis and snowmobiles. Today a CONSIDERABLE avalanche danger exists on wind-loaded slopes steeper than 35 degrees. Less steep wind-loaded slopes have a MODERATE danger. A LOW avalanche danger exists on slopes without recent deposits of wind blown snow.

The northern Gallatin and northern Madison Ranges:

During the past 48 hours 6-12 inches of snow accumulated in the northern Gallatin and northern Madison Ranges. Yesterday ski patrollers at Big Sky got a few wind slabs to fracture a few inches deep. Today recently formed wind slabs will once again pose avalanche problems as will a thin, weak layer of faceted crystals buried 2-3 feet deep. Today all wind-loaded slopes have a CONSIDERABLE avalanche danger. A MODERATE danger exists on non-wind loaded slopes.

The southern Madison and southern Gallatin Ranges, the Lionhead area near West Yellowstone, the mountains around Cooke City, and the Washburn Range:

Since Tuesday 1-2 feet of new snow accumulated in the mountains around West Yellowstone and Cooke City. A weak layer of faceted snow buried 2-4 feet deep, which produced human triggered avalanches last weekend near West Yellowstone, now has enough of a load that avalanches will likely occur on steep wind-loaded slopes. In fact, yesterday near Cooke City, Doug and Mark found recently released avalanches on this type of slope. The weak layer that produce the avalanches is similar to the one that exists in the mountains near West Yellowstone. They posted a photo on our website. http://www.mtavalanche.com/photos/photos.php

They also wrote, produced, filmed, starred in, and directed a video clip.

http://www.youtube.com/watch?v=KYlXtVLR_4Y

Today a HIGH avalanche danger exists on wind-loaded slopes steeper than 35 degrees. Less steep wind loaded slopes have a CONSIDERABLE avalanche danger. A MODERATE danger exists on non wind-loaded slopes.

Mark Staples will issue the next advisory tomorrow morning at 7:30 a.m. If you get out in the backcountry give us a call or email with your observations. You can reach us at 587-6984 or email us at mtavalanche@gmail.com