Archived Advisory for Sat Dec 8 2007

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Saturday, December 8th, 2007

Good Morning. This is Scott Schmidt with the Gallatin National Forest Avalanche Advisory issued on Saturday, December 8th at 7:30 a.m. The Gallatin Valley Snowmobile Association, in cooperation with the Friends of the Avalanche Center, sponsor today’s advisory. This advisory doesn’t apply to operating ski areas.

MOUNTAIN WEATHER

Scattered flurries produced a trace of snow throughout the mountains of southwest Montana yesterday. Ridge winds have been from the east at 10 – 25 mph, and mountain temperatures are in the single digits this morning.

Today will be partly cloudy with a few lingering snow showers but no significant accumulation. Winds will be 10 – 25 mph from the northeast, with mountain temperatures in the low teens at 9000 feet.

SNOWPACK AND AVALANCHE DISCUSSION

The Bridger Range and northern Gallatin Range:

The Bridger Bowl ski patrol found very stable conditions on their control routes yesterday. They reported wind slabs that formed in unusual place due to east winds but these recent wind deposits did not release with ski cuts or explosives. As always, steep wind-loaded slopes should be approached with caution. Today, the avalanche danger in the Bridger and Northern Gallatin Ranges is MODERATE on all recently wind-loaded slopes. On non-wind-loaded slopes, the avalanche danger is LOW.

The northern Madison Range:

Mark and I spent yesterday digging snowpits with the Yellowstone Club ski patrol. A weak layer of faceted snow, approximatly12 inches above the ground, has adjusted to last week’s new snow load and our stability test indicate stable conditions on non-wind-loaded slope. Karl Birkeland found similar conditions on non-wind-loaded slopes in Middle Basin just north of Big Sky, and the Big Sky ski patrol tested several steep non-wind-loaded slopes with explosives and got no results. Wind-loaded slopes in the mountains around Big Sky continue to be unstable as illustrated by a massive avalanche released by the Big Sky patrol with explosives. Mark and I got to watch this avalanche first hand. For avalanche guys, it was a thing of beauty. You can see a picture of the debris field at

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

Today, for the northern Madison Range, the avalanche danger is CONSIDERABLE on all wind-loaded slopes. Non-wind-loaded slopes in these mountains have a MODERATE danger

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

The combination of significant snowfall being deposited on a very weak snowpack produced many natural and human triggered avalanches last week in the southern mountains. Doug and I saw evidence of widespread natural avalanche activity in the Lionhead area on Tuesday, and experienced lots of snowpack collapsing and cracking as we went about our travels.

A snowmobiler was injured in an avalanche in the mountains north of Cooke City last Tuesday. He was riding near the bottom of the slope when he initiated a fracture that propagated up and across the slope above him. Doug and Mark investigated this avalanche on Wednesday and found the avalanche had run on faceted crystals just under last week’s new snow.

Today, the avalanche danger remains CONSIDERABLE on all slopes in the southern Gallatin, southern Madison, and Washburn Ranges, the Lionhead area near West Yellowstone, and the mountains around Cooke City.

AVALANCHE EDUCATION AND EVENTS

An Avalanche Awareness for Snowmobilers class is being held in West Yellowstone, Thursday and Friday, December 13th and 14th. Lectures on Thursday are being held at the West Yellowstone Conference Hotel from 12-5 pm with an all day field session on Friday. Call 597-6984 for more information.

Ron 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 through our website www.mtavalanche.com.