Although the storm did not bring the anticipated moisture, several inches of new snow and strong west winds have formed new wind slabs on the surface of a snowpack that contains deeper instabilities. Above 8000 feet, new slabs will be sensitive to skiers and riders in steep wind loaded areas. The potential also exists to trigger deeper persistent slabs if a particularly weak spot in the snowpack is impacted or if larger loads such as groups of people or snow machines are present. Make travel decisions by carefully evaluating the snowpack relative to specific terrain. Avalanches below 8000 feet are not expected today except for in shallow isolated pockets.
New wind slabs with depths to a foot could be triggered in steep wind loaded avalanche terrain at the higher elevations. These slabs will become more sensitive today as temperatures increase and they are affected by periods of direct sunlight.
In steep wind loaded terrain, the chance continues for a single person to trigger slabs that formed last Wednesday and Thursday with slab depths to eighteen inches. The slight chance also continues for deeper slabs involving snow that was buried in November. These larger slabs will require significant loading to cause failure and could have depths of three feet.
( Discussion is generated from the previous day's afternoon forecast. )A winter weather advisory has been issued by the National Weather Service for the Teton and Gros Ventre Mountains. The incoming storm is to bring significant snowfall tonight and into Wednesday. The storm is start on the warmer side for this time of year and cool through the night. Winds will be a significant factor with this storm event. West wind average speeds are to increase into the forties with gusts in the sixties. By sunrise nearly a foot of snow is predicted in the higher elevations, especially in the Tetons, while valleys are to see two to six inches. Winds are to be on the decrease during the day but are likely to be a challenge to visibility during the morning. Temperatures near twenty degrees are expected on Wednesday. The general avalanche hazard is expected to increase to Considerable above 7500 and to Moderate below that elevation. New wind slabs will quickly form on a variety of snow surfaces overnight. Given the rapid loading, these slabs will be sensitive to skiers and riders in steep leeward avalanche terrain. If the storm produces as expected, these new slabs could have depths to over two feet at the higher elevations and to depths of a foot at lower elevations. The existing persistent slab problems will also become more likely to trigger as they are stressed by the new snow load creating the possibility for large avalanches. Below 7500 feet, strong winds will form pockets of new surface slabs in very steep terrain. These slabs will form on a snowpack with poor structure, particularly on north aspects. Conservative decision making is essential to manage these dangerous avalanche conditions.
