Avalanche Forecast
Sea To Sky
A strong winter storm system is expected Monday night into Tuesday. Significant snow is expected, however amounts are uncertain. If snowfall amounts exceed forecasted values, avalanche hazard will increase.
Avalanche Problem 1: Storm Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- Avoid freshly wind loaded features and leeward slopes.
- Whumpfing, shooting cracks and recent avalanches are all strong indicators of unstable snowpack.
- 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, as well as skier and sledder triggered storm slabs (size 1.5) on east and north aspects in the alpine. Explosive control work also produced cornice failures, size 2-3 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
Another 5-10 cm of storm snow with strong southerly wind Sunday night adds to last week's storm which delivered 20 to 50 cm of snow accompanied by strong to extreme wind out of the southwest, south and southeast. This storm snow rests on the March 21st interface, 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.
Deeper in the snowpack, 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
Forecasted snowfall amounts are uncertain for Monday night & Tuesday. Higher amounts are expected for areas near Squamish.
TONIGHT: Snow. Accumulation 10-20 cm. Ridge wind strong to extreme, southwest. Alpine temperature near -4. Freezing level 1500 m.
TUESDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind strong to extreme, west. Alpine temperature near -3. Freezing level 1600 m.
WEDNESDAY: Mix of sun and cloud. Ridge wind moderate, northwest. Alpine temperature near -5. Freezing level 1400 m.
THURSDAY: Cloudy, flurries. Accumulation about 5 cm. Ridge wind moderate, west. Alpine temperature near -5. Freezing level 1200 m.
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New snow and strong winds will form storm slabs at all elevations. This adds to 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.