Avalanche Forecast

Archived

Mar 14th, 2016–Mar 15th, 2016

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

Conservative decision making will be essential Tuesday as recent storm and wind slabs will require additional time to settle and stabilize. Avoid steep open slopes showing signs of recent wind transport. Best to confine travel to lower angled terrain away from wind effects.

Detailed Forecast

Additional showers are expected Tuesday at continued cool temperatures. Showers should generally be fewer and taper by late Tuesday.

Moderate west winds at ridge level should persist Tuesday before diminishing late Tuesday.

Recent or new wind and storm slabs will be the main avalanche problems in the Hurricane Ridge area and vicinity.

New wind slab is mostly likely to be found on NW-SE facing slopes. Firmer wind transported snow and snowpack cracking can be good signs of wind slab or storm slab instabilities.

New storm slab is likely in areas where new snow rapidly accumulates for more than several hours.

Cloudy cool conditions Tuesday may limit the development of loose wet snow but the sun is gaining power so watch for the development of loose wet snow on solar slopes if extended sun breaks occur.

The avalanche danger should gradually decrease Tuesday with less wind and slow settlement and stabilization of new snow and fairly cool temperatures.

Snowpack Discussion

Weather and Snowpack

Storms have moved across the Northwest at a nearly daily frequency the past few weeks with fluctuating but generally moderate snow levels.

Storms last week arrived with a warming trend and very strong west winds. Settled storm snow of 10 inches was reported by the park ranger at Hurricane for the 4 days ending on Saturday morning.

A front on Saturday deposited another 5 inches of snow with W-SW winds at Hurricane ending Sunday morning.

A deep surface low-pressure system moved across the Olympic Peninsula Sunday causing very stormy weather.

Cool showery weather Monday continues to deposit additional snow at lower temperatures.

New storm amounts in the Hurricane Ridge area are about 10-15 inches over the past 36 hours.

Strong winds and recent storms have created widespread wind and storm slab problems, creating dangerous avalanche conditions.

The mid and lower snowpack in the Olympics should generally be a stable mix of crusts and layers of moist and rounded snow crystals.

Recent Observations

NWAC pro-observer Matt Schonwald toured around the Hurricane Ridge area Friday. He found up to 20 cm of dense 1 F or P snow above the latest rain crust. Thin wind slab was generally not reactive except in isolated areas on N-NW lee aspects near treeline. Although cornices were large, they were generally firm and not sensitive. Matt observed evidence of a widespread natural cycle involving shallow slabs on northerly lee aspects that likely occurred Wednesday night during warming and a transition to rain. Windward slopes that had melted out a few weeks earlier had packed on a firm, and in places, icy thin cover. Overall Matt noted few current avalanche problems in the Hurricane Ridge area Friday.

Hurricane Weather Station

Internet communications to the station have been disrupted at the NWAC office. We have identified the problem and anticipate the station to return online sometime Tuesday, March 15th. We apologize for the outage and thank you for your patience. It should be back up tomorrow!

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.