New snow and gusty winds will be loading an unstable snowpack and creating dangerous conditions. Persistent slabs lie upon a base of weak faceted snow and will become increasingly sensitive to human triggers are the day progresses. Natural avalanche activity is possible, especially in association with gusty winds that are expected to accompany the passage of a cold front later in the day. Cautious route finding and a conservative approach to avalanche terrain and run out zones are essential for safe travel in the mountains today.
Persistent slabs up to two feet in depth lie upon a base of weak, faceted snow. These dangerous slabs could be triggered by the weight of a single person or by a human triggered or naturally released surface slab or loose snow slough. These slabs could release on approach on a variety of aspects and propagate across terrain boundaries.
( Discussion is generated from the previous day's afternoon forecast. )Another pulse of Pacific moisture and an associated cold front are expected to impact our forecast region overnight and through the day. Periods of heavy snowfall are likely after midnight and could continue until the cold front passes in the afternoon. Five to ten inches of new snow are possible in the mountains with the higher amounts likely to favor the Teton Range. The snowfall may mix with rain during the day at the lowest elevations before the cold front passes and the precipitation changes back to snow. Temperatures will be in the teens and 20s in the mountains and near freezing in the valleys.Winds will back from the south-southwest through the northwest to the northeast and are expected to increase to 25 to 30 with gusts to 45 miles per hour ahead and after frontal passage.The new snow will increase the load on a snowpack that has persistent instabilities. New soft surface slabs will begin to form in pockets on leeward aspects along the higher ridgelines. These slabs will become increasingly sensitive to human triggers as the day progresses. Persistent slabs with depth to three feet are a much more significant hazard and could be triggered by a single skier or rider or by a human triggered surface slab that steps down into the base layer of faceted snow. The general avalanche hazard is expected to be CONSIDERABLE and increasing with the new loading at the mid and upper elevations and LOW at the lower elevations where snow depths remain shallow.
