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Avalanche Forecast

Archived

Feb 2nd, 2017–Feb 3rd, 2017

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Olympics.

A pattern change will begin to take place over the Northwest on Friday. You will need to pay lots of attention to conditions and forecasts during the transition Friday and Saturday if you decide to venture into the back country.

Detailed Forecast

A pattern change will begin to take place over the Northwest on Friday. Dry weather and strong cold E-NE winds seen Wednesday and Thursday will gradually get replaced by increasing southwest flow aloft, increasing rain or snow and milder temperatures Friday and Saturday. You will need to pay lots of attention to conditions and forecasts during the transition Friday and Saturday if you decide to venture into the back country.

Wind slab formed by strong E-NE winds on Wednesday and Thursday will linger on Friday. The primary aspects for these wind slabs should be any W facing slopes but could be found on other aspects.

New sensitive wind slab is likely to begin forming as shower bands of snow begin to move across the Olympics and Cascades on Friday with a slight warming trend. The primary aspects for these wind slabs should be NW to SE facing slopes except for W facing slopes in the Cascade Passes.

Wind slab may be more 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 recent winds and for any lingering older wind slabs formed over the weekend.  

New storm slab is also likely to begin forming on Friday on more sheltered slopes in areas that see more than a few inches of rapidly accumulating snow. The warming trend will help build upside down layers and promote storm slab formation.

Snowpack Discussion

Weather and Snowpack

An atmospheric river arrived over the Northwest Tuesday 1/17 with heavy rain seen up to at least 6000 feet in the Hurricane Ridge area. A storm cycle from Thursday 1/19 through Sunday, 1/22 deposited about 2 feet of snow at Hurricane Ridge.

A large upper ridge and warm air mass built over the Northwest Thursday through Saturday 1/26-1/28. Temperatures warmed into the 40s at Hurricane Ridge with south winds in the 20 mph range on Saturday. 

A weak front crossed the Northwest Sunday afternoon and night, depositing 1 inch of new snow at Hurricane Ridge through Monday morning after starting as light rain Sunday afternoon.

Strong NE-E winds have been seen Wednesday and Thursday with very cold temperatures. Fresh, touchy wind slabs formed with large plumes of snow visibly transporting loose snow from exposed terrain. 

Recent Observations

A skier was caught and carried by a wind slab avalanche on the back side of Maggies Saturday. A report with a well done video is available on the NWAC Observations page.

Another report received on Saturday from the Obstruction Point road area via the NWAC Observations page indicated windy and warm conditions, with pinwheels, roller balls and surface crusts on W-SW slopes.

Problems

Wind Slabs

Wind Slab avalanches are the 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.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.