Danger ratings are based on higher snowfall accumulations expected for the Southern part of the Region.
Confidence
Fair - Forecast snowfall amounts are uncertain
Weather Forecast
Monday: A low pressure system over Gulf of Alaska will move onto the North Coast, sliding south. Snow amounts near 10 cm accompanied by strong ridgetop winds from the NW. Alpine temperatures rising to -3.0 and freezing levels near valley bottom. Tuesday: An intense warm front will continue to bring light-moderate snow amounts 10-25 cm. Ridgetop winds will switch and blow strong from the SE. Alpine temperatures near -1 and freezing levels rise to 1300 m. Wednesday: An upper ridge continues to build generally bringing dryer conditions during the day. Alpine temperatures near -2.0. Ridgetop winds blowing form the West in the light ranges.
Avalanche Summary
No new avalanche observations reported.
Snowpack Summary
Over the next two days new storm snow will blanket the region. This will continue to bury a variety of surfaces including hard old wind slabs, thin and thick crusts and large surface hoar crystals which can be found in sheltered terrain below treeline. Winds will likely transport the new snow and build winds slabs in the lee of terrain features, possibly burying old wind slabs. A surface hoar layer buried down 40-80 cm seems to be gaining strength, but still exhibits moderate, sudden results in isolated snowpack tests. The new load from snow and wind will test this layer and its reactivity. Near the base of the snowpack, a crust/facet layer exists, which is now unlikely to be triggered, except perhaps by heavy triggers in unsupported, shallow, rocky terrain where more faceting has taken place.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.