Avalanche Forecast
Regions: Mt Hood.
Strong E-NE winds and snow showers will form fresh wind slabs Thursday. Wind slabs may be sensitive to triggering, especially where bonding to old snow is weak. Wind slabs should be very likely near and above treeline, especially on westerly facing terrain, but watch for firmer wind transported snow in all terrain.
Detailed Forecast
Strong E-NE winds should persist Thursday along with light snow showers. The winds and snow showers will continue to build sensitive wind slabs on a variety of aspects, but mainly near and above treeline. Primary aspects for wind slabs should be any slopes facing west, but may form on a variety of slopes.Â
Fresh wind slabs may be particularly touchy in areas where poorly bonded poorly to an underlying crust or firm old layer. Watch for firmer wind transported snow in all elevation bands, especially in open terrain in the upper elevations of the below treeline band. All aspects are listed for wind slabs to account for the strength of the winds and for any lingering older wind slabs formed over the weekend. Â
Snowpack Discussion
Weather and Snowpack
An atmospheric river arrived Tuesday 1/17 with rain up to about 7000 feet on Mt. Hood. From Thursday 1/19 through Sunday 1/22, generally 15-20 inches of snow accumulated at NWAC Mt Hood stations.
A large upper ridge and warm air mass built over the Northwest last Thursday to Saturday. By Saturday temperatures had reached the 40's.
A front crossed the Northwest Sunday afternoon causing moderate southwest winds, slight cooling and no measurable precipitation through Monday morning. Westerly winds above treeline were strong Monday night through Tuesday morning with occasional periods of light snow.Â
Very strong NE-SE winds developed Wednesday with very cold temperatures. The winds have likely built touchy wind slabs in a variety of terrain, especially westerly facing.
Recent Observations
The Mt. Hood Meadows pro-patrol reported little in the way of avalanche activity over the last few days, but did not a thin melt-freeze crust up to 6600 feet Monday morning along with some wind transport of previous snow that had occurred above 6500 feet Sunday.Â
Avalanche Problems
Wind Slabs
Release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..
Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.
Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Very Likely
Expected Size: 1 - 1