Avalanche Forecast
Regions: Olympics.
Lowering snow levels and winds on Tuesday will develop shallow wind slabs above treeline. Mitigate hazard by approaching lee slopes with caution and observing new snow amounts and snow transport, which may extend into the near treeline zone in areas that see more snowfall than anticipated.
Detailed Forecast
Moderate rainbands are approaching Hurricane Ridge Thursday evening and will bring rain to the Olympics overnight. The cold front will pass in the early morning hours and the snow line will slowly work its way down the hill during the day Tuesday with light to moderate SSW winds expected to re-distribute the small amounts of snow that do accumulate on a re-freezing old snow surface.
Watch for the development of shallow wind slabs, particularly on NW through SE aspects above treeline. Monitor new snow and wind transport diligently throughout the day and avoid wind-loaded slopes.
Note that while it's not listed as a problem here, wet snow exists in the upper snowpack and before a crust has fully formed at lower elevations it may still be possible to trigger a loose wet slide during the morning hours. Where boot penetration is deep, adjust your plans accordingly.
Despite the recent snow, early season hazards still exist. Many creek beds have still not filled in for the winter.
Snowpack Discussion
The upper snowpack has gone through three days of melt-freeze during the recent high pressure cycle. Warm temperatures and sunshine Saturday-Monday has allowed wind slabs formed during Thursday's storm to stabilize.
About of foot of storm snow from Thursday is bonding to the most recent rain crust. Below this rain crust, no notable layers of concern have been identified within the snowpack.
The height of snow across the terrain is quite variable with little snow in many areas below treeline. Numerous obstacles still exist at all elevations.
Observations
NPS rangers reported a skier triggered avalanche from the Hurricane Ridge area Saturday morning. The avalanche occurred as the skier was traversing across a steep convex rollover locally known as Avalanche Run near Poma Bowl (SW aspect around 5300 feet). The avalanche was estimated to be 12 inches deep, about 100 feet wide, and ran down slope for 300-400 feet. The skier was caught and carried but did not sustain any injuries.
Skier triggered wet snow avalanche 1/13, releasing on traverse (upper right). photo: NPS ranger
A separate natural, loose-wet avalanche occurred on Saturday in a known avalanche path named 20th of June. The avalanche occurred around 10am and ran for 300-400’.
Rangers also noted several glide cracks on steep smooth rock slabs.
NWAC pro-observer, Matt Schonwald was at Hurricane Ridge on Thursday 1/11. Matt found despite the significant storm snow, below the treeline elevation band had quite variable snow cover. Winds actively transported new snow near and especially above treeline, but the loading pattern was variable.
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: All aspects.
Elevations: Alpine.
Likelihood: Possible
Expected Size: 1 - 1