Avalanche Forecast
Regions: Olympics.
The main avalanche problem in the Olympics should be possible wind slab formed over the weekend mainly on northwest to southeast slopes near and above treeline.
Detailed Forecast
A weak upper trough should begin to linger over BC and the Northwest on Monday. Winds should generally decrease in the Olympics and Cascades by Monday. The trough will cause decreasing clouds in the Olympics and north Cascades but more clouds and some light rain or snow in the south Cascades mainly at Mt Hood Monday afternoon and night with further cooling.
The main avalanche problem in the Olympics should be possible wind slab formed over the weekend mainly on northwest to southeast slopes near and above treeline. But watch for firmer wind transported snow on other aspects. Note the skier triggered wind slab avalanche reported on the backside of Maggies on Sunday.
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.
The NPS rangers reported a storm total of 15 inches of snow at the Hurricane Ridge manual snow plot Thursday morning 1/19. Showers continued during the day but our precipitation gage didn't record any precipitation after 9 am due to equipment problems. About a foot of snow fell at the Waterhole NRCS Snotel over a 24 hour period ending Friday morning 1/20.Â
Showers late Saturday 1/21 and another band Sunday 1/22 deposited about 4-6 inches of new snow as of Sunday afternoon at Hurricane with strong S-SE winds.
A large upper ridge and warm air mass built over the Northwest Thursday to Saturday. Temperatures warmed into the 40s at Hurricane with south winds in the 20 mph range on Saturday.
A front crossed the Olympics on Sunday afternoon causing more south winds in the 20 mph range, light rain or snow and further cooling.
Recent Observations
NWAC pro-observer, Matt Schonwald, was at Hurricane Ridge Friday 1/20. Matt found 10 inches of settled recent storm snow generally well bonded to the 1/17 crust and not reactive.
A skier triggered and was carried by a wind slab avalanche on the back side of Maggies on Saturday and a report with a well done video is available on the NWAC Observations page.
Another report for Saturday for the Obstruction Point road area via the NWAC Observations page indicated wind warm conditions with pinwheels, roller balls and crust snow on W-SW slopes.
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: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1