Avalanche Forecast
Regions: Cascades - North East.
Cooling by Thursday will help to lower the wet snow avalanche problem. Glide and wet slab avalanches will be unlikely, but are difficult to predict and remain a threat while water in the snowpack drains after recent melting and rain. Avoid travel on or below steep, unsupported terrain. Shallow fresh wind slabs are possible near ridges in higher terrain.
Detailed Forecast
Gradual cooling is underway as of Wednesday afternoon as a cooler trough approaches. Light showers at further lowering snow levels are expected Wednesday night and early Thursday with moderate crest level winds.
Cool air should be over the area by Thursday with only scattered light showers expected as high pressure rebuilds over the area.
This weather will allow the previously wet snow pack to begin re-freezing and strengthening, causing an overall decreasing trend in the avalanche danger.Â
The cooling trend through Thursday will lower the overall danger as surface snow begins to form a crust and liquid water continues to drain.  Realize, however, that wet snow avalanches, specifically wet slab avalanches, are very hard to predict and demand an extra amount of caution when engaging with avalanche terrain.Â
With that said, there remains a possibility of further wet slab avalanches, especially on unsupported slopes with a rock face bed surface.  These types of avalanches are highly unpredictable and not necessarily tied to peak warming or rainfall. Besides their huge destructive potential, wet slab avalanches often surprise backcountry travelers when they run further than expected. Watch for evidence of large cracks forming in the snow due to glide of the snowpack, especially on terrain with smooth rocky bed surfaces.
Cornices have been weakened and prone to failure due to rain and mild temperatures. Very large cornices have been reported in many areas and have been involved in recent accidents and close calls. A cornice failure could trigger a large and destructive wet slab avalanche.
If you manage to venture into the above treeline zone Thursday, expect new or previous wind slabs mainly on NW-SE aspects due to recent SW-W winds. Continue to watch for firmer wind transported snow on all aspects, especially in areas of complex terrain.
The persistent slab problem previously listed in the NE zone has taken a temporary hiatus from the avalanche problem set until further snowpack investigation post-storm cycle. However, be aware that avalanches stepping down to the Valentine's Day or 2/17 crust would be large and very dangerous.
Snowpack Discussion
Weather and Snowpack
The first week or so of March was very cool and snowy. NWAC and NRCS stations indicate about 2 feet of snow in the northeast Cascades with less elsewhere along the Cascade east slopes.Â
A strong frontal system brought increasing precipitation and winds along with a warming trend to the Cascades on Thursday 3/9. On Thursday night rain may have pushed up to about 4000 feet in the northeast Cascades and about 5000 feet in the southeast Cascades. By Friday morning 3/10 NWAC stations along the Cascade east slopes had about 0.35- 0.90 inches of WE (water equivalent) with only 0-5 inches of snow.
Moist W-SW flow and a stalled frontal boundary have produced periods of light to moderate rain and snow along the east slopes of the Cascades Monday through Wednesday. There was a strong downslope drying effect with much less precipitation east of the crest during this time. Precipitation amounts ranged from less than 0.5 inches to about 1.5 inches of water equivalent over the past three days.  Snow levels pushed above 6500 feet Tuesday afternoon with the summit stations at Mission Ridge, Washington Pass, Harts Pass and Dirty Face Peak all above freezing. Â
Recent Observations
North
On Saturday 3/11 a report for Delancy Ridge via the NWAC Observations page indicated many natural large loose wet avalanches on solar slopes.
The NCH on Saturday 3/11 reported significant recent warming and settlement. Recent natural size D1.5 - D2 wind and storm slab were seen in the Silver Star area. Pits in the upper Willow drainage had generally right side up layers with the Valentine's Day crust seen at 100-128Â cm.
The NCH were in the Varden and Silver Star areas on Sunday 3/12 and reported many natural size D1-2 storm slabs on steep north slopes in the 5200-8400 ft range. Some cracking and propagation was observed. Shallow storm slabs were reactive about 10 cm down.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.
Likelihood: Possible
Expected Size: 1 - 1
Wet Slabs
Release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slab avalanches can be very destructive.
Avoid terrain where and when you suspect Wet Slab avalanche activity. Give yourself a wide safety buffer to handle the uncertainty
A Wet Slab avalanche. In this avalanche, the meltwater pooled above a dusty layer of snow. Note all the smaller wet loose avalanches to either side.
Wet slabs occur when there is liquid water in the snowpack, and can release during the first few days of a warming period. Travel early in the day and avoiding avalanche paths when you see pinwheels, roller balls, loose wet avalanches, and during rain-on-snow events.
Elevations: Treeline, Below Treeline.
Likelihood: Possible
Expected Size: 1 - 1