Avalanche Forecast
Regions: Olympics.
There is GREAT UNCERTAINTY in the avalanche forecasts at this time. Dangerous avalanche conditions are expected in this area on Tuesday. Careful snowpack evaluation and conservative decision making will be essential.
Detailed Forecast
A low pressure system is expected to move across the Washington Oregon border area on Tuesday. This is expected to cause the strongest winds, the most snow and possibly the most fluctuation in temperatures in the south Cascades.
With this next unusual and hard to predict incoming storm, so much recent snow, lack of knowledge of stabilizing of recent snow, and lack of knowledge of bonds to the Valentines Day crust, there is GREAT UNCERTAINTY in the avalanche forecasts at this time. This is a time to plan travel on lower angled terrain well away from avalanche paths or run out zones. Avoid large steep open slopes or terrain of consequence. Change your plans if weather and snow conditions are different than expected.
More than the usual zones are in this forecast due to the expected differences from south to north on Tuesday.
Alpine winds have recently been SW to W, with further mostly SW to W winds expected on Tuesday. Hence wind slab should be most likely on northwest to southeast aspects. But watch for firmer wind transported snow on other aspects especially in areas of complex terrain.
Most areas have experienced rapidly accumulating snowfall and temperature fluctuation the past couple days. Storm slab from this weather may not have stabilized. More areas of rapidly accumulating snowfall with fluctuating temperatures are expected on Tuesday.
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 2-3 feet or more in the Hurricane Ridge area.
Strong southwest flow carried a strong front across the Northwest on Friday evening. This caused strong southwest alpine winds and heavy, moist, dense new snow above about 3-4000 feet.
Between the NWAC station at Hurricane and the ranger reports it looks like there has been about 2-3 feet of snow the past 3Â days at Hurricane.
A region wide avalanche cycle was seen late Friday and Saturday, with some more avalanches on Sunday.
Recent Observations
NWAC observer, Matt Schonwald was at Hurricane on Friday and found that ski tests were showing rapidly increasing propagation and increasing sensitivity of the deepening storm slab. Previous winds had loaded various slope aspects while south winds on Friday were loading N aspects.
Reports by NPS rangers early Sunday and a report listed on the NWAC Observations page indicate 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
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: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1
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: Likely
Expected Size: 1 - 1