Avalanche Forecast
Sea To Sky
A winter storm system is expected Sunday night into Tuesday. Significant snow is expected, however amounts are uncertain. If snowfall amounts reach or exceed the highest forecasted values, avalanche hazard will be HIGH. See "Details".
Avalanche Problem 1: Storm Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- Whumpfing, shooting cracks and recent avalanches are all strong indicators of unstable snowpack.
- Avoid freshly wind loaded features and leeward slopes.
- Give cornices a wide berth when travelling on or below ridges.
Avalanche Summary
On Sunday there was a report of a skier-triggered cornice failure (size 2) on a northwest aspect at 2100 m. Explosive control work also produced cornice failures to size 3 with little effect on the slopes below.
Saturday we received reports of a natural avalanche cycle from size 2-3 that occurred during the storm in wind loaded and cross-loaded alpine terrain, as well as numerous reports of large (size 2) skier and sled triggered storm slabs including several size 1-2.5's remotely triggered from a distance. These avalanches are suspected to have failed on the recently buried (March 21st) surface hoar/crust layer. Read details of a personal account here.
On Friday explosive control work and ski cutting produced numerous storm slab results from size 1.5-2, as well as size 2 cornice results and few remote/sympathetically triggered size 1.5 releases. Crown depths generally ranged from 20-40 cm deep, although up to 60 cm in loaded alpine areas.
There was also a report of a skier triggered size 1.5 on Friday that surprised a group on a convex feature at treeline. Read MIN report
Snowpack Summary
Thursday and Friday's storm snow delivered 20 to 50 cm of snow accompanied by strong to extreme wind out of the southwest, south and southeast. Storm slabs on immediate lee features at ridgeline may be up to 60 cm in depth. These slabs rest on a mix of moist grains at low elevations, crusts on solar aspects at all elevations and surface hoar/facets on north/east facing features at treeline and alpine elevations. Some west facing features may have surface hoar on top of a crust which would be particularity problematic. The storms transition from warm to cold should be good for our snowpack in the long term.
A crust from mid-March is now down 40 to 60 cm below the surface. This crust is prevalent everywhere with the exception of high elevation north aspects.
80 to 140 cm below the surface is a combination of facets, surface hoar, and/or crust known as the mid-February layer. This interface has not been active recently, but it does continue to produce resistant planar results in snowpack tests.
The mid and lower snowpack are strong and well settled.
Weather Forecast
Snowfall amounts for Monday/Tuesdays storm are uncertain. Higher amounts are for southern areas near Squamish.
TONIGHT: Snow. Accumulation 10-20 cm. Ridge wind moderate to strong, southwest. Alpine temperature near -8. Freezing level 600 m.
MONDAY: Flurries. Accumulation 5-20 cm. Ridge wind moderate to strong, west. Alpine temperature near -5. Freezing level 1200 m.
TUESDAY: Cloudy, flurries. Accumulation 5-15 cm. Ridge wind moderate, west. Alpine temperature near 0. Freezing level 1800 m.
WEDNESDAY: Mostly sunny. Ridge wind moderate, west. Alpine temperature near -5. Freezing level 1500 m.
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New snow and strong winds will form fresh storm slabs at all elevations. This will add to the recent storm snow which sits above a weak layer consisting of crusts, surface hoar and facets that has been most reactive at treeline and above.