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Avalanche Forecast

Archived

Mar 13th, 2016–Mar 14th, 2016

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

Regions

Olympics.

Conditions are a bit hard to predict following the low pressure system on Monday. Conservative decision making will be a good plan until the avalanche forecasts get refined after new information becomes available on Monday.

Detailed Forecast

Another 5-10 inches of new snow seems likely at Hurricane by Monday morning.

West winds aloft and a cool slightly unstable air mass should be seen over the Northwest on Monday. This should cause snow showers and up to a few more inches of snow seems likely at Hurricane by the end of the day.

New wind and storm slab seem likely to be the main avalanche problems at Hurricane.

New wind slab is mostly likely to be found on northwest to southeast slopes. Firmer wind transported snow and snowpack cracking can be good signs of wind slab.

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

Cloudy cool conditions on Monday 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.

Conditions are a bit hard to predict following the low pressure system and front on Monday. The avalanche danger may decrease a little on Monday due to a little less wind, some stabilizing of new snow and fairly cool temperatures. This forecast will take a conservative approach to the danger levels and the avalanche forecasts will get refined after new information becomes available on Monday.

 

 

Snowpack Discussion

Weather and Snowpack

Storms have moved across the Northwest almost every day or two the past couple weeks with fluctuating but generally moderate snow levels.

A storm last Wednesday and Thursday caused a warming trend that peaked Wednesday night with very strong west winds. About 10 inches of new snow was reported by the Hurricane ranger for the 4 days ending on Saturday morning.

A front on Saturday caused west-southwest winds and likely up to another 5 inches or so of snow at Hurricane ending Sunday morning.

A deep surface low pressure system is moving across the Olympic Peninsula and causing stormy weather at Hurricane on Sunday.

The mid and lower snow pack 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 but unfortunately our hardware will not be repaired until early next week. We apologize for the outage and are working to get the station back up ASAP. 

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.