Over a foot of snow has fallen in the Tetons and more is expected today. Strong west winds have accompanied this snowfall and have formed wind slabs at the mid and high elevations. Backcountry riders and skiers could easily trigger these slabs and have an increasing potential to trigger older and harder slabs that lie upon buried weaknesses. At the low elevations caution is also advised as new snow has fallen on a weak faceted snowpack. Areas that previously had inadequate coverage could now see loose snow sluffs or pockets of soft slabs in steep terrain. Yesterday there were multiple skier triggered avalanches and one skier had a close call when he was partially buried to his waist. An avalanche watch is being issued for the weekend as a potent storm system approaches and dangerous avalanche conditions are expected.
Strong winds that have blown from the west-southwest to the northwest have formed wind slabs on steep leeward slopes. These slabs could be easily triggered by backcountry travelers today with depths to two feet this morning. These slabs are expected to increase in size and sensitivity as snowfall and continued winds continue to load them throughout the day.
Persistent layers of faceted snow lie in the snowpack. Rapid loading since yesterday has increased the chances to trigger these older hard slabs that could reach depths to as much as four feet. These older dangerous hard slabs could be triggered after initiation of a wind slab, by a single person hitting a weak spot, or by larger loads such as snow machines.
A potent storm system is on track to bring snow to the area starting around sunrise on Saturday. This storm will increase in intensity throughout the day with the heaviest snowfall expected on Saturday evening. Winds are to be very strong and westerly with gusts exceeding 60 miles per hour.The general avalanche hazard above 7,500 feet is expected to be CONSIDERABLE and may increase to HIGH in the afternoon as heavy snowfall and wind add additional loads to the snowpack. Wind slabs with depths that could reach three feet by the afternoon are expected to be very sensitive to human triggers. Older weaknesses in the snowpack could also fail with slab depths to an additional four feet possible. Deeper, persistent slabs have had limited activity in recent weeks however rapid loading tomorrow will increase the chance that these denser slabs could be triggered by moving wind slabs or by the weight of a single rider or skier. At lower elevations the general avalanche hazard is expected to be MODERATE. New snow and warming temperatures will be increasing the hazard and the potential to trigger pockets of soft slab and loose snow sluffs in areas where weak faceted snow is prevalent. An Avalanche Watch is in effect for the area. This may be elevated to an Avalanche Warning tomorrow depending on the strength and timing of the storm.
