Avalanche Forecast
Regions: Cascades - East.
The avalanche danger should slowly improve Sunday, however, give additional time for the significant recent storm snow to stabilize. Avoid steep slopes recently loaded with wind transported snow. Evaluate the snow and terrain carefully.
Detailed Forecast
Given the recent active avalanche conditions, the main emphasis is to step back and give this significant storm snow additional time to heal and stabilize.Â
Dangerous avalanche conditions are expected to gradually improve, however Careful snowpack evaluation and cautious routefinding will be essential Sunday.
Light to moderate snow showers at cool temperatures are expected overnight and early Sunday before tapering through the day. Winds should be light, except light to moderate in the alpine.
Only light accumulations of new snow are expected and with cold temperatures and light winds this should not affect the current avalanche danger significantly.
Recent moderate to strong S-SWÂ winds will make wind slab most likely on northwest to southeast slopes, but keep an eye out on all aspects in areas of more complex terrain. Watch for firmer wind transported snow from Friday and possible deeper wind transported layers. Older wind slabs may be masked by the recent fresh snow.
Cornices won't be listed as an avalanche problem in this area, but avoid travel on ridges, where recent cornices may have formed and avoid slopes below cornices.
Snowpack Discussion
Weather and Snowpack
The most recent wet warm storm arrived on Valentines Day 2/14 and formed the uppermost strong rain crust in our snowpack in the Central East and Southeast Cascades while only a thin freezing rain crust was observed in the Washington Pass area.
A series of disturbances in cool, NW flow aloft from Saturday 2/25 through Tuesday 2/28 deposited 2-16 inches snow along the east slopes of the Cascades. Very strong alpine west winds were seen in most of the Olympics and Cascades on Tuesday.
Southwest flow aloft began to ramp up again on Thursday as the first in a new series of fronts crossed the Northwest. Strong southwest flow carried a second stronger front across the Northwest on Friday evening. Along the Cascade east slopes this caused strong southwest alpine winds and heavier moist or denser new snow above about 3-4000 ft and wet snow or rain below about 3-4000 ft.
Greater recent storm snow has accumulated nearer the crest, with up to 2 feet or more in the latest storm cycle.
Recent Observations
North
AÂ report from the NC Heli Guides indicates a cycle of natural and ski triggered wind slab avalanches during the wind event on Tuesday and Wednesday 2/28-3/1. About 50-80 cm of storm snow was found with a good bond to the Valentine's Day crust. About 20-30 cm of recent snow was covering about 10 cm of wind slab in some areas.
A party of four skiing at Washington Pass near the highway hairpin on the east side of the pass was hit by a natural cornice released avalanche on Tuesday afternoon. Four people were caught and carried up to 1000 ft downslope. Fortunately, there were no fatalities and no full burials but there were apparently some injuries. The release occurred on a very steep slope at the top of a northeast facing bowl at about 6600 ft.
Windy conditions prevented the North Cascades Heli Guides from flying on Wednesday.
Another recent and large cornice failure was observed by the NCH on Thursday in the Cutthroat drainage. Plenty of other unreleased large cornices were noted.
A NC Mountain Guides report for Friday for the Delancey area indicates heavy snow in the near and below treeline and 35-60 cm of storm snow on the Valentine's Day crust. Moderate planar shears were found in recent storm snow layers. New storm slabs were forming and ski tests were producing storm slab and loose dry releases. Whumpfing and cracking was seen above 6600 ft.
There was a skier triggered storm slab avalanche involvement Saturday, resulting in a full burial and beacon recovery. The full details are not known at this time, but the party member is expected to be fine, another fortunate outcome. This avalanche involved a storm slab well below ridgeline at about 6600 feet on a north aspect, in the Cedar Ck drainage, east of Washington Pass.  Â
Central
No recent observations. Â
South
No recent observations.Â
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: Possible
Expected Size: 1 - 1