Northwest Coastal

Warming is coming. It is a significant change and we cannot trust the weak layers formed during the drought with the forecast warmth. Continue to reign in terrain choices and steer clear of overhead hazard.

Moderate -

A significant warm-up is happening and next week looks to be very warm with freezing level approaching 3000 m Monday. Unfortunately, very little overnight re-freeze is expected during the warm spell.SATURDAY NIGHT: Overcast, trace to 5 cm of snow, little overnight cooling with freezing level staying around 700 to 1000 m. SUNDAY: Broken cloud cover, moderate south wind, freezing level above 2000m with no overnight freeze.MONDAY: Broken cloud cover, light southeast wind, freezing level approaching 2800 m with no overnight freeze.TUESDAY:  Mix of sun and cloud, light southerly wind, continued high freezing level with no overnight freeze.

I'll continue to divide recent avalanches into two classes -- light triggers and large triggers. For light triggers there are reports of wind slabs, storm slabs, and loose avalanches up to size 2.5; however, for me the most important avalanche data is SEVERAL REMOTELY TRIGGERED AVALANCHES (some of these reports were from areas outside the forecast region but are relevant to the region's conditions). Skiers are whumpfing the snowpack, often when they group up, wiith avalanches releasing at a distance (sometimes on the slope above). Reports include this happening on previously skied terrain, include releasing several avalanches from a single whumpf, and avalanches releasing and running over normal "ski lines".Explosives are the large triggers. Continued explosive tests and explosive control released up to size 3 avalanches from big terrain in a deep snowpack area by targetting cornices.

Continued snowfall means there's 50 to 100 cm of "settled" snow since the drought ended March 10. The recent snow is settling into a slab with the warm temperatures: however, it's covering a wide variety of old snow surfaces: crusts on solar aspects, facets up high, and surface hoar in sheltered locations. Not much further below this storm snow interface is a second weak layer buried on February 19 made up of weak facets and surface hoar crystals. Recent avalanche activity was more or less equally split between these two layers. The lower snowpack is generally strong.The Avalanche Activity section below highlights remotely triggered avalanches:  the recent storm snow is settling into a cohesive slab, the old cold weak layers remain. For slightly complex reasons (snowpack creep, strain rates, viscous coupling, and similar geeky snow science stuff) warm temperatures are keeping the balance near a tipping point.