Avalanche Forecast
Regions: Cascades - North East.
Sunshine Saturday may lead to shallow wet snow conditions on steep solar aspects during the late morning to afternoon. Watch for snow rollerballs, snow falling from trees, and for wet surface snow more than the top few inches. Watch for cornice hazard as well.
Detailed Forecast
A brief period of high pressure should build over the area Saturday. This will allow for clearing and plenty of sunshine Saturday. Winds should remain light with very cool temperatures.Â
Old wind slabs should continue to heal, becoming very isolated to specific terrain features, and very stubborn to human triggering Saturday.Â
More sunshine is expected Saturday than previously this week. Direct sunshine and some daytime warming should gradually increase the potential for loose wet avalanches Saturday, mainly confined to steep solar aspects during the warmest part of the day. Watch for wet surface snow deeper than a few inches if you find yourself on sun exposed slopes during any extended sun breaks.
Loose dry avalanches have been triggered this week, but will not be indicated as an avalanche problem. You can do tests for loose dry avalanches by pushing snow onto small safe test slopes.
Avoid areas along ridges where there may be a cornice and slopes below cornices, since cornices can fail at any time.
Snowpack Discussion
Weather and Snowpack
The latest of several warm, wet SW streams of moisture this season arrived Valentine's Day 2/14 through Thursday 2/16 along the Cascade east slopes. An avalanche cycle occurred Wednesday night to Thursday east of the Cascade crest.
In the northeast zone the NWAC station at Washington Pass received about 10-14 inches of moist snow over a thin freezing-rain crust formed early in the storm cycle.  In the central-east and southeast zones, light rain likely reached up about 5-6000 feet in the central-east and up to about 7000 feet in the southeast zone.
A short period of fair weather on Friday, 2/17 caused another surface crust, especially on solar aspects.
Light amounts of new snow accumulated last weekend.
A slightly unstable weather pattern this week caused a mix of sun and light snow showers with cold temperatures and light winds from Tuesday through Friday. The weather this week helped to freshen the surface with a few inches of snow. This weather has all tended towards increased snowpack stability through the week, while maintaining some excellent touring conditions, especially on shaded terrain.Â
Recent Observations
North
The NCMG were out near Washington Pass on Sunday 2/19 and reported that ski tests on steep features gave no results and that wind slab was generally unreactive. A size 2.5 slab, 1 m x 200 m crown was seen on a north aspect at 7200 feet that probably released after cornice fall on 2/15.
On Monday 2/20, the NCMG observed a fresh and large storm slab that was triggered by cornice fall mid-day above treeline in the Hairpin Valley on a NNE aspect near 7000 feet. No other avalanche activity was observed. The slab averaged around 40 cm to the most recent crust.
The NC Heli Guides report on Tuesday 2/21 recent snow is settling nicely with no test results and good ski conditions.
Another report via the NC Mountain Guides on Tuesday for N-E slopes on Mt Burgett north of Mazama indicates older wind slab on some alpine features giving some results at about 40 and 80 cm due to flattened surface hoar layers. They avoided steep unsupported terrain features and the wind slab was not seen below ridges.
A report via the NWAC Observation page for the Washington Pass area for Tuesday indicates 12" powder well bonded to the likely 2/14 crust.
More reports around the Washington Pass area the past few days, including Friday, 2/24, continue to indicate excellent quality snow conditions with no signs of avalanches under cold temperatures and light winds. Not much more you can ask for, enjoy!Â
Central
NWAC observer Tom Curtis was at Jove Peak on Monday 2/20 and found the recent snow generally bonding well to the Valentine's Day crust. Some previous wind slab was apparent below ridgelines near treeline. The possibility for skier triggered, loose wet avalanches increased around midday during a slight warming trend.
Tom Curtis was in the Blewett Pass area Wednesday 2/22 and found the recent wind slabs were confined to very isolated terrain features on mostly easterly facing terrain at higher elevations. These slabs remained sensitive to ski trigger, but were very isolated in extent, ranging from 2-8 inches.
Very similar conditions were reported from Mission Ridge Wednesday 2/23, with isolated wind slabs of 6-8 inches confined to specific steep terrain features below ridges. Â
South
No recent observations.Â
Avalanche Problems
Loose Wet
Release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.
Several loose wet avalanches, and lots of pinwheels and roller balls.
Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.
Aspects: South East, South, South West.
Elevations: All elevations.
Likelihood: Possible
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: North, North East, East, South East, North West.
Elevations: Alpine.
Likelihood: Unlikely
Expected Size: 1 - 1