Avalanche Forecast
Regions: Olympics.
New shallow wind and storm slab layers are possible at Hurricane on Friday due to winds, some new snow and a warming trend.
Detailed Forecast
A frontal system will cross the Northwest on Friday. This will cause increasing southwest to west alpine winds, increasing rain or snow and a rise in snow levels.
Less new snow is expected at Hurricane than along the Cascade west slopes. But several inches of new snow seems likely from the upper part of the below tree line band to above treeline on Friday with a warming trend.
This weather may build shallow new upside down wind slab on lee slopes at Hurricane which should be mainly southeast to northwest slopes near and above treeline. Watch for firm wind transported or hollow sounding snow.
New shallow storm slab is also possible in areas that see rapid accumulations of new snow. The warming trend will also aid in the development of new upside down storm slab.
In most of the lower part of the below treeline band there is still insufficient snow for avalanches but watch for early season hazards such as terrain traps, rocks and creeks.
Snowpack Discussion
About 4 inches accumulated Monday at Hurricane Ridge area with generally light WNW winds recorded at the NWAC weather station.
Tuesday was a break between weather systems.
Another front passed over the Northwest on Wednesday. It has been a bit difficult to tell how much snow there was at Hurricane but the NWAC station there had about .9 inches of water ending on Thursday morning which would indicate about 9 inches. Winds on Wednesday were initially moderate southerly, shifting to more westerly and diminishing greatly by afternoon.
A bit of a break has been seen on Thursday.
A nice report was received via the NWAC website (Observations tab) for last Saturday in the Hurricane Ridge area. In summary, pit tests gave only a low quality shears or collapses and an ECT test that did not indicate any propagation. Loose dry avalanches were indicated as the main concern.
On Sunday morning the Hurricane rangers reported 7 inches of new snow. They reported that a snowboarder on Saturday triggered a small loose dry snow avalanche on the Sunrise run, a steep slope that faces northeast at about 5200 feet.
NWAC pro observer Matt Schonwald visited Hurricane on Thursday and reported lots of wind effects but a generally well bonded snow pack and snow profiles in pits that lacked a slab structure. The snow was found to be unconsolidated at lower elevations making terrain traps and creek crossings a hazard.
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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
Storm Slabs
Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. 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.
You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.
Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.
Aspects: North, North East, East, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1