Avalanche Forecast
Regions: Olympics.
Yet another storm will impact the Olympics on Thursday with increasing rain and snow, wind and rising snow levels beginning in the afternoon and continuing Thursday night. Travel in avalanche terrain is not recommended on Thursday due to the increasing hazard in the afternoon.
Detailed Forecast
A weak low pressure system should produce up to 6 inches of snow for the Olympics Wednesday afternoon and night.Â
However the main event will be the storm system forecast Thursday afternoon through Friday morning. A low pressure system tracking north across Washington State will bring increasing precipitation Thursday afternoon to the Olympics. This will be accompanied by a warming trend that peaks Thursday night with a shot of strong SW winds through Friday morning. Â
All of these weather factors will stress the upper snowpack still struggling to settle and stabilize. The warming trend and increasing snowfall will increase the likelihood of new storm slab layers.
Wind slab should be watched for on all aspects but should be found mainly on NW to SE aspects due to recent SW to W winds. Watch for firmer wind transported snow on varied aspects especially in areas of complex terrain.
Loose wet avalanches will not be listed for the Olympics but with rainfall possible below 3500 feet in the afternoon, loose wet avalanches are possible on steeper slopes below treeline and they may entrain a significant amount of recent snow.Â
There is still higher than normal uncertainty due to the fewer than normal backcountry field reports and the recent heavy snowfall. Add all of these factors together and err on the side of caution by avoiding avalanche terrain on Thursday and by making sure that if you are in the backcountry you have exit routes that do not cross avalanche paths.Â
Cornices won't be listed as an avalanche problem but avoid travel on ridges near where cornices may have formed and avoid steep slopes below cornices that may fail at any time.
Snowpack Discussion
Weather and Snowpack
The most recent warm, wet storm arrived on Valentines Day 2/14 forming a strong rain crust, now buried 3 feet or more in the Hurricane Ridge area.
Strong southwest flow carried a strong front across the Northwest on Friday evening March 3rd. This caused strong southwest alpine winds and heavy, moist, dense new snow above about 3-4000 feet. A region wide avalanche cycle was seen late Friday March 3rd and Saturday March 4th.
Between the NWAC station at Hurricane Ridge and the ranger reports it looks like there has been about 3 feet of snow the past 6Â days at Hurricane.
Recent Observations
Reports by NPS rangers early Sunday 3/5 and a report listed on the NWAC Observations page indicates there were at least three and possibly four separate triggered avalanches in the Hurricane Ridge area Saturday 3/4, including the areas known as Maggies, Hurricane Hill and Sunrise Face.
Avalanche Problems
Storm Slabs
Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. 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.
You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.
Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Very Likely
Expected Size: 1 - 1
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, Treeline.
Likelihood: Very Likely
Expected Size: 1 - 1