Avalanche Forecast
Regions: Mt Hood.
Watch mainly for lingering local wind slab from early in the week.
Detailed Forecast
An upper ridge will reassert itself over the US coastal waters on Saturday. Northwest flow and moisture should decrease a bit over the Olympics and Cascades. Clouds should decrease a bit during the day and lead to some partly sunny weather especially in the south and east of the crest.
Watch for lingering wind slab from early in the week where the northeast winds redistributed snow mainly near and above treeline.
Sun crusts, while not an avalanche danger on Saturday, are likely on steep south slopes where the sun warmed the snow on Wednesday and Thursday.
Right side up stable powder may also still be found on shaded sheltered slopes on Saturday.
Heads up in advance for Sunday when moderate to heavy snow with warming should bring a significantly increasing avalanche danger.
Snowpack Discussion
A storm system hit the Northwest last weekend with strong west to northwest winds. NWAC sites at Mt Hood picked up about 28 inches of storm snow with a good cooling trend. Strong northeast winds hit at the tail end of the storm Monday and Tuesday. This transported snow and formed some local wind slab on exposed slopes and near ridges. But in most areas this layer bonded well and lacked underlying weak layers.
NWAC observer CJ Svela reported on Tuesday that the main problem at Mt Hood is lingering wind slab near ridgetops. A report via the NWAC Recent Observations also indicated easy compression tests at 25-30 cm due to areas of small wind slab near ridges.
An upper ridge over the coastal waters tilted inland Wednesday and Thursday producing sunny weather and warm temperatures at higher elevations. This may have caused some snowballing and wet loose avalanches on steep slopes facing the sun at Mt Hood.
A weak front is crossing the Northwest on Friday. But little if any snow will make it to the south such as Mt Hood but there will be cooling.
A generally strong mid and lower snowpack is expected at Mt Hood.
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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: South East, South, South West, West, North West.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 1