Tetons

The General Avalanche Hazard is MODERATE at the Mid and Upper elevations. There are two avalanche concerns: Surface slabs one to three feet in depth, which rest on suncrusts and buried surface hoar, remain susceptible to human triggers. These slides may may be triggered by the second or later person or multiple people at the same time on a slope. Slides were easily released by skiers last weekend but there are no reports of more recent slides. The second concern is the possibility of deep, hard slab avalanches in steep areas that have a shallow snow cover such as thinly covered cliff bands. Weak faceted snow lies beneath a supportable upper snowpack and can give backcountry travelers a false sense of security. The possibility of releasing this type of avalanche in the Tetons is low, but the consequences could be severe. The General Avalanche Hazard at Low elevations is LOW.

An upper level disturbance and colder air aloft will move south down the Continental Divide and across Western Montana. This system will bring a quick shot of new snow to the western mountains tonight. In general 2 to 4 inches of new snow is expected, however convective snow showers may bring up to six inches of new snow to some locations. This snowfall will be accompanied by northwest winds at 10 to 20 miles per hour. A high pressure ridge will quickly build in behind this disturbance. Expect skies to rapidly clear Thursday morning. Early morning temperatures at all elevations are expected to be near minus 10 and to rise to near 10 above during the day. Ridgecrest winds will back to the west and diminish to 10 to 15 miles per hour.The general avalanche hazard is expected to be MODERATE. In the TETON area unstable surface slabs one to three feet in depth persist. These slabs lie upon buried suncrust and surface hoar. These slabs continue to be a hazard to skiers and snowmobliers who venture into steep wind loaded terrain. The new snow and wind overnight is expected to create new isolated pockets of very shallow windslab along the leeward side of the highest ridgelines. These isolated pockets will lie upon excellent sliding surfaces and in very steep cliffy terrain could knock over or sweep skiers who venture onto them over cliffs.In the CONTINENTAL DIVIDE/TOGWOTEE PASS and SOUTHWEST TRAILS/GREYS RIVER areas the surface slab hazards discussed above exist. These areas also have dangerous persistent deep slab instabilities. Weak well developed faceted snow in the base of the snowpack has resulted in numerous human triggered full depth slab avalanches. This weak basal layer lies beneath a supportable upper layer that can provide a false sense of stability. The potential for skiers, snowboarders and snowmobilers to trigger dangerous full depth slab avalanches on steep snow covered slopes persist. These surface and deep slab instabilities have proven to be unpredictable and problematic. During the past several weeks there are numerous instances where a steep slope did not slide when it was first crossed and then later failed after having been crossed multiple times. In addition many steep avalanche prone slopes have been skied or ridden without instance while other similar slopes have failed on approach. CAUTION IS ADVISED.