Avalanche Forecast

Southwest flow will carry the first in a parade of mild wet fronts across the Northwest on Thursday. This will cause increasing winds and increasing moderate to heavy rain or snow Thursday morning with rising snow levels. Snow levels east of the crest should be lower than west of the crest some or much of Thursday.

New storm slab and wind slab should build east of the crest above treeline in the morning hours. The trend of rising temperature will help build upside down higher density snow over lower density snow above the snow level. New storm or wind slab of up to several inches seems possible above the snow level. Any surviving buried surface hoar from late January could act as a weak layer.

Increasing loose wet snow avalanches involving snow from so far in February should be seen mainly near and below treeline. The late January crust should make a good bed surface on many slopes. Small natural or triggered loose wet avalanches should be likely in many areas. This problem may work its way into the above treeline by the end of the day due to rising snow levels.

Dangerous avalanche conditions are expected on Thursday especially above treeline. Back country travel in avalanche terrain above treeline is not recommended on Thursday.

Mild weather with sunny days or minor rain or snow was seen in the Cascades from about January 26th to about January 31st. East of the crest this should have caused some consolidation and stabilizing. A surface crust will have formed on solar slopes but less so on shaded slopes or at higher elevations. Surface hoar formed on shaded and north slopes in some areas in fair weather during this time.

Slightly wet weather from about February 1 through today produced about 2-5 inches of snow at NWAC sites east of the crest with more at higher elevations in the northeast and central east zones.

NWAC pro-obs and North Cascade Guides reports last week in the northeast and central east zones have the January 15th facet/crust layers at 40 cm-1 m below the surface with the facets starting to turn to rounded grains and not reactive or not releasing in pit tests. So the January 15th facet/crust layers appear to be strengthening and stabilizing by late January. This problem will be removed from the central east zone but retained in the northeast zone until more information becomes available there.

NWAC pro-observer Tom Curtis was at 7500 ft on Mt Cashmere in the Wenatchee Mountains on January 28th and found a local facet/crust combo buried on a lee slope next to a ridge crest under 35 cm of thick, surface crust and 1F-P snow. This sort of slab could be very hard for a skier to trigger, but could be possible with a large sudden load, such as a snowmobile.

Other private groups in the Washington Pass area on February 2 and 3 report some upside down densities in the recent snow and natural and ski cut avalanches although the types of avalanches were not noted.