Archived Advisory for Tue Mar 18 2008

Audio- listen online, right now

Podcast- listen on your iPod

Subscribe- to the daily Email

TUESDAY, MARCH 18

Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Tuesday, March 18th, at 7:30 a.m. A huge thanks goes out to Warren Bauder and Paul Niebauer, tireless organizers of this year’s Pinhead Classic. This advisory does not apply to operating ski areas.

MOUNTAIN WEATHER

In the last 24 hours 2-4 inches fell in the mountains, except in the Bridger Range where only an inch was recorded. Winds have been steady at 20-30 mph out of the W to SW and will get slightly stronger by this afternoon. Mountain temperatures are in the mid teens this morning and should only rise into the low 20s with cloudy skies and scattered showers. By tomorrow morning 3-5 inches of new snow could accumulate.

SNOWPACK AND AVALANCHE DISCUSSION

The Bridger Range:

The snowpack in the Bridger Range is quite stable since there are no striking weak layers. Wind-loading has not been much of an issue either which was evident as skiers punched from the top of Saddle Peak yesterday. New snow and strong westerly winds today will change this for the worse. In the Bridger Range the avalanche danger is rated MODERATE on recently wind-loaded slopes steeper than 35 degrees. All other slopes have a LOW danger.

The northern Gallatin and northern Madison Ranges:

The northern Gallatin and northern Madison Ranges received 3-4 inches of snow with strong southwest winds yesterday. Wind pillows formed and were easily ski cut by the Big Sky Ski Patrol. Over on Cedar Mountain the Patrol also saw a deep slide likely triggered by a cornice drop. In the northern mountains 2 weak layers are worth noting. The first, located 1-2 feet under the surface, is a thin layer of faceted crystals; our primary concern. Second, is a layer of larger grained sugary snow buried 1 ½ feet from the ground. This layer would take a large load to trigger, like a huge storm or cornice drop.

More snow today with stiff winds will readily form wind slabs which you could trigger. For today, on terrain steeper than 35 degrees the avalanche danger is rated CONSIDERABLE if it’s wind-loaded and MODERATE if not. On less steep slopes the danger is also MODERATE on wind-loaded terrain, but LOW everywhere else.

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

The southern mountains received 2-3 inches of new snow with blustery southwest winds. Recently wind-loaded slopes are the primary avalanche concern, especially since we have a weak layer of faceted snow buried 2 feet deep in these mountains. On Friday, and again on Sunday, skiers triggered small slides on north-facing slopes in the southern Madison range near Hebgen Lake. These broke on this faceted layer and should serve as a reminder that although many slopes are safe, a few are weaker, more unstable and ready to avalanche.

For a look at one of the slides, check out this photo: http://www.mtavalanche.com/photos/photos.php

Given the new snow and wind, for today, the avalanche danger on slopes steeper than 35 degrees is CONSIDERABLE on wind-loaded terrain and MODERATE on others. On slopes less steep but wind-loaded, the avalanche danger is MODERATE while a LOW danger exists on all other terrain.

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 email with your observations. You can reach us at 587-6984 or email us at mtavalanche@gmail.com