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RegisterJan 31st, 2015–Feb 1st, 2015
Snoqualmie Pass.
Shallow storm slabs are possible Sunday afternoon. Watch for new snow that bonds poorly to existing surface crusts or in areas of preserved surface hoar.
Generally very light precipitation is expected Sunday morning, with light to moderate rain and snow in the afternoon along the west slopes. The Cascade Passes will locally stay cooler through Sunday afternoon thanks to cool easterly flow. A frontal passage is expected later Sunday afternoon, switching the Pass winds to westerly and popping snow levels up to free-air levels of 5000 ft.
New snow may bond poorly to surface crusts, allowing shallow storm slabs to develop Sunday afternoon especially on lee aspects near and above treeline. New storm slabs may also fail on surface hoar that survives on shaded aspects generally below treeline.
A fair amount of uncertainty surrounds a potentially stronger frontal system Monday but generally expect increasing avalanche danger Monday.
Last weekend (Jan 24-25th) a warm and wet weather system caused high snow levels and rain. Most NWAC sites west of the crest had about 1-3 inches of rain. This caused loose wet avalanches, some possible wet slab avalanches and consolidation.
This week, high pressure aloft has caused abundant sunshine and mild temperatures, generally well into the 40's and at times lower 50's.
The snowpack is therefore dominated by strong surface crusts, limiting the avalanche potential. There has been some surface hoar growth over the past few clear nights and this may be preserved on shaded terrain and mainly found below about 5000 feet, and especially at lower elevations where more fog or low clouds have formed. See Jeff's video from the Steven's Pass area below.
The snowpack west of the crest should mainly consist of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.