The new snowfall will increase the hazard as the day progresses. Humans who venture onto steep slopes and into avalanche terrain could trigger soft surface slabs or deep hard slabs with severe consequences. Safe travel procedures and conservative terrain choices are essential for safe travel in avalanche terrain today.
Soft surface slabs will increase in depth and volume as the day progresses and become increasingly sensitive to human triggers. These slabs could build to depths of one to three feet and could step down to buried layers of faceted snow deep in the snowpack.
In some areas weak layers of faceted snow persist deep within the snowpack. Failure of these layers will produce very large avalanches with depths up to six feet. The additional load from the new snowfall will increase the sensitivity of these dangerous slabs to humans triggers.
( Discussion is generated from the previous day's afternoon forecast. )A deep low pressure system is spinning off of the California Coast and will pump warm moist air into the region overnight. The center of this low is forecast to move into South Central Idaho and draw very cold arctic air in from the north. If this scenario verifies abundant moisture is likely to fall as a mix of rain and snow on the south side of the interface between these clashing air masses and as heavy snowfall on the north side of that boundary. A winter storm warning has been issued by the National Weather Service. Significant snowfall is expected overnight and through Saturday with a decrease likely by Saturday evening. Strong southwest winds with speeds of 20 to 30 and gusts to 40 will accompany the snowfall. Accumulations of up to two feet in the mountains and up to a foot in the valleys are possible in the next 24 hours. Temperatures are forecast to be in the 20s. Heavy snowfall and high winds will increase the avalanche hazard in all areas. New wind slabs with depths of one to three feet are likely to form and be easily triggered by humans on steep slopes. Natural avalanche activity is possible and wet slides are possible in areas that receive rain. Large, dangerous avalanches are possible in areas with poor snowpack structure. The general avalanche hazard is likely to increase to HIGH and travel in avalanche terrain will not be recommended if this weather forecast verifies.
