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Avalanche Forecast

Archived

Dec 24th, 2017–Dec 25th, 2017

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

Regions

Olympics.

Recent wind slab and storm snow should continue to stabilize. Avoid steeper terrain features with firmer wind transported snow. Be prepared to step back from your plans if the system Sunday afternoon and night is stronger than expected.

Detailed Forecast

A weakening front and a weak surface low will move across the Northwest Sunday afternoon and night. The main snow should be seen in the south Cascades and mainly at Mt Hood. Light amounts of new snow if any are expected at Hurricane. Watch for a change Monday to light to moderate W-NW alpine winds. Temperature fluctuations could be a little problematic.

So not a lot of change is expected on Monday. This should mainly continue to allow recent storm snow to stabilize.

But keep an eye out for previous wind slab on Monday. Winds will have potentially loaded various non-traditional aspects.

Be prepared to step back from your plans if the system Sunday afternoon and night is stronger than expected.

Early season hazards still exist at lower elevations and especially around creek beds that are not filled in.

Snowpack Discussion

Little if any new snow fell at Hurricane in the 24 hours ending Saturday morning.

But about 18 inches fell there early in the week. Cool and fair weather allowed this snow to mostly stabilize Wednesday and Thursday resulting in a decrease in the avalanche danger.

Winds mainly Tuesday redistributed some snow near ridge crests and in exposed terrain.

In general about two feet of snow now sits on the old snow surface from a week ago.

Observations

NWAC pro observer Matt Schonwald was at Hurricane on Saturday and reported evidence of north to east winds but no wind slab or significant shear in the upper snowpack. The structure was generally F over 4F with good bonds to the Thanksgiving crust.

A nice observations for Friday via the NWAC Observations page indicated 70-85 cm of recent storm snow. Tests gave stubborn results for storm slab and there were no natural or triggered avalanches noted.

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.