Archived Advisory for Tue Dec 30 2008

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TUESDAY, DECEMBER 30

Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Tuesday, December 30th at 7:30 a.m. Island Park Adventures and Yamaha, in cooperation with the Friends of the Avalanche Center, sponsor today’s advisory. This advisory does not apply to operating ski areas.

AVALANCHE WARNING

A Backcountry Avalanche Warning continues for the southern Gallatin and southern Madison Ranges, the Lionhead area near West Yellowstone, the mountains around Cooke City and the Washburn Range in Yellowstone National Park. Seven days of snow and strong winds have loaded an extremely weak snowpack. Today the avalanche danger remains HIGH on all slopes. Areas of unstable snow are common. Natural and human triggered avalanches are likely. Avalanche terrain including runout zones should be avoided.

MOUNTAIN WEATHER

Snows pummeled Cooke City with 16-20 inches falling since yesterday morning. The southern Gallatin and Madison Ranges received 6-8 inches while 5-7 inches fell in the northern Madison and Gallatins and 3 inches in the Bridger Range. Westerly winds are averaging 25-30 mph with gusts hitting the 60s. Today will become mostly cloudy, mountain temperatures will rise from the single digits to the high teens and winds will lessen and shift to the southwest at 15-25 mph. Another storm moves in overnight. I’m expecting an inch or two of new snow by dawn, but the meat of the disturbance it will hit later Wednesday.

SNOWPACK AND AVALANCHE DISCUSSION

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

Cooke City is getting snow like bankers are getting bailout money. It’s dumped for the last 8 days dropping 4.4 inches of Snow Water Equivalency (SWE) or almost 5 feet of snow. Over half that amount fell in the last 48 hours which I experienced in all its fury during my field visit. Sunday and Monday were a blizzard with typhoon winds loading slopes at all elevations and aspects. Evidence of instability was everywhere, even with poor visibility. Yesterday, a natural avalanche in Miller drainage hit the road with 4 foot piles of debris. On Sunday I triggered a large avalanche from flat terrain on Henderson Ridge. It slid on faceted snow 1.5 feet off the ground on a low angled, 33-degree slope. Be sure to check out the video and pictures.

http://www.youtube.com/watch?v=HxL7byezJvE

http://www.mtavalanche.com/photos/photos.php

Other activity included snowmobilers triggering a slide from low on the slope near Windy Pass in the southern Gallatin Range; collapsing, cracking, natural and human avalanche activity in the Taylor Fork area; and a skier triggered slide on a 33-degree slope near Lionhead.

I believe that the only reason riders and skiers have not been caught in an avalanche is that the snow’s too deep and weather has been too stormy to get around. Today will be a reprieve from the unsettled weather but not from avalanches. There’s lots of new snow and winds are loading slopes at a dangerous clip. Avalanches are likely and the danger is rated HIGH.

The Bridger, northern Madison and northern Gallatin Ranges:

Last night the northern mountains got slammed with high winds and snow which will keep the avalanche danger elevated. Since Friday, strong winds created wind slabs which released naturally in the Bridger Range. Faceted snow near the ground is also breaking clean in stability tests throughout the northern areas. In summation, we’ve gotten reports of natural and human triggered avalanches in the Bridger Range, poor stability in the northern Gallatins and human triggered slides near Buck Ridge in the northern Madison Range. For today, a HIGH avalanche danger exists on all wind-loaded slopes. Areas untouched by the wind will have a CONSIDERABLE danger.

AVALANCHE NEWS

Eight snowmobilers were buried and killed in an avalanche in British Columbia near Fernie Sunday afternoon. (story here: http://www.reuters.com/article/latestCrisis/idUSN29314337 ).

Seven were buried in the initial slide and a rescuer was caught and buried by a subsequent avalanche. This is a tragic incident. So far Montana has been spared avalanche fatalities even though we have a very unstable snowpack. Avoid all slopes steeper than 30 degrees as well as runout zones. And if you do venture into avalanche terrain, only put one person at a time on the slope.

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