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Avalanche Forecast

Archived

Mar 26th, 2016–Mar 27th, 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.

A mix of likely dangerous winter and spring avalanche conditions is likely at Hurricane on Sunday. The sun is getting much stronger and new snow may be very reactive to solar effects. The greatest danger should be in the afternoon and to the end of the daylight hours.

Detailed Forecast

Southwest flow should carry an energetic front and shortwave to the Northwest Saturday evening and night. Moderate west flow should carry a 2nd short wave, an upper low and a cool unstable air mass to the Northwest Sunday. This should cause southwest to west winds, rain or snow changing to snow showers and lowering snow levels on Sunday. Snow and snow showers should cause about to about 6 inches of snow at Hurricane by the end of the daylight hours on Sunday. There is a chance of thunderstorms in the forecast Sunday afternoon and evening.

A mix of likely dangerous winter and spring avalanche conditions is likely at Hurricane on Sunday. The sun is getting much stronger and new snow may be very reactive to solar effects. The greatest danger should be in the afternoon to the end of the daylight hours.

New wind slab of up to a foot seems likely near Hurricane on lee slopes on Sunday. This is most likely on north to east slopes. Watch cracking and firmer or chalky wind transported snow. Snow pits may not be helpful due to variability in the snowpack.

New storm slab layers will be likely in areas where there is rapidly accumulating snow for more than a few hours. Warming daytime temperatures may contribute to upside down layers and instability. Pay special attention to slope convexities where storm slab is mostly likely to be triggered.

 Loose wet avalanches may be possible on steep solar slopes on Sunday. Don't overstay your welcome if you start seeing pinwheels or small initial natural loose wet avalanches. Be aware of terrain traps where even a small loose avalanche could have unintended consequences if you venture out on Sunday.

Cornices have grown large recently. Cornices can break much further back on ridges than expected and releases can be unpredictable during the spring.

Snowpack Discussion

Weather and Snowpack

Snow accumulations Wednesday to Friday following the last front were about 4-6 inches at Hurricane with new snow of over a foot on wind loaded slopes near treeline. The new snow since Monday should be well-bonded to a moist crust buried March 22nd.  ?

Frequent March storms have built large cornices along some ridges in the Hurricane Ridge area.

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 professional observer Matt Schonwald toured in the Hurricane Ridge area Friday 3/25.  Matt generally found the new storm snow unreactive in snowpit tests and with ski cuts on test slopes. No recent avalanches were observed in the Hurricane Ridge area. Wind effects were limited to directly below ridgelines, with generally settled powder and good skiing found on non-solar aspects with less wind effect. Area cornices were firm and unlikely to trigger. 

Hurricane Weather Station

Internet communications were restored to the station on 3/23!  Thank you for your patience. 

Problems

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.

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.

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.