Confidence
Fair - Timing or intensity of solar radiation is uncertain on Wednesday
Weather Forecast
A weak Pacific system is expected to run into the ridge of high pressure on Monday that should cause some light flurries. Clearing skies are expected by the afternoon or early evening. The wind should change to north by Tuesday morning as more high pressure moves across the interior. Valley fog is forecast to develop overnight for the Columbia Basin. Clear skies and strong solar radiation is expected during the day on Tuesday, however northwest winds should help to keep alpine maximum temperatures close to -7.0 on shaded aspects. Temperatures should drop down to about -12.0 in the alpine by Wednesday morning. The ridge of high pressure is expected to continue to bring clear skies and light winds during the day Wednesday. Alpine temperatures may rise above freezing on solar aspects, but should remain slightly below freezing on shaded aspects.
Avalanche Summary
Some minor sloughing in steep terrain on northerly aspects continues to be reported.
Snowpack Summary
A couple of cm fell overnight and Sunday morning during a period of calm to light westerly winds. Most areas have a thin layer of new snow above buried surface hoar. Some areas have reported a very light freezing drizzle that has mixed with some rimed stellars to form a thin soft crust above the recently buried surface hoar layer(120208 SH). Warm alpine temperatures and solar radiation have developed a melt-freeze crust on southerly aspects in the alpine and on all aspects below about 1300 metres. There are a couple of layers that are buried between 25-35 cm that give resistant planar results from tests when hard forces are applied. Recent facetting in the top 20 cm appears to be rounding and bonding. The mid pack is generally well settled and well bonded. Deeper weaknesses in the snowpack are less of a concern; however, in the southern end of the region there is still talk of basal facets as some operators are avoiding thin and rocky alpine features. This represents a very low probability-high consequence scenario. Large cornices are also widespread in the alpine.
Problems
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.