Avalanche Forecast

Sea To Sky

Date issued

Feb 3, 2018 - 5:07 PM

Valid until

Feb 4, 2018 - 2:00 PM

Prepared by

mgrist

New snow totals are uncertain in this weather pattern. Danger ratings are based on 5-15 cm of new snow. If snowfall amounts are greater than 20 cm, the danger is CONSIDERABLE and time to dial back your terrain use while avoiding overhead hazard.

Regular season
Saturday - February 3, 2018
Alpine

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Below Treeline

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

Sunday - February 4, 2018
Alpine

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Below Treeline

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

Monday - February 5, 2018
Alpine

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Treeline

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

Below Treeline

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

Avalanche Problem 1: Storm Slabs

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

Areas with high amounts of new snow could be primed for storm slabs whereas areas that see less snow may be more susceptible to wind slabs. Wet loose avalanches are possible below tree line if precipitation falls as heavy rain.

Travel and Terrain Advice
  • Stay off recent wind loaded areas until the slope has had a chance to stabilize.
  • Be alert to conditions that change with elevation.
  • Be cautious as you transition into wind affected terrain.

Avalanche Problem 2: Cornices

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

Recent heavy snowfall and high winds have formed fragile new cornices. These monsters may surprise with nasty consequences. Use extra caution around ridge crests.

Travel and Terrain Advice
  • Falling cornices may trigger large avalanches on the slopes below.
  • Give cornices a wide berth when travelling on or below ridges.

Avalanche Summary

On Saturday we received reports of a skier triggered size 1.5 avalanche near Whistler on a north west aspect around 2100m.

On Friday ski cutting produced several size 1 soft slabs on immediate down wind (lee) features.

Explosives control on Thursday and Friday triggered cornices at ridge crests, mostly size 1.5 - 2.

Snowpack Summary

Over the past two days 7-12 cm of new snow has fallen as temperatures warmed up to +2 at tree line on Saturday afternoon. Winds, however, were strong to extreme from the south, creating fresh wind slabs in exposed downwind (lee) terrain. At lower treeline and below, generally light amounts of snow or rain now overlie a melt-freeze crust which formed during last Monday's warm storm.

The new snow adds to the 170cm of snow that fell during the last few weeks of January. These series of storms were accompanied by strong to extreme winds which resulted in extensive scouring and impressive cornice growth in upper elevation terrain. These accumulations sit on a crust from mid-January which generally shows signs of bonding to the overlying snow; however, it has the potential to "wake-up" with a large trigger such as a cornice fall.

Below this, the snowpack is thought to be generally strong and well-settled.

Weather Forecast

Sunday: 5-10cm of snow Saturday overnight to Sunday with another 5-10 cm possible during the day / Moderate gusting strong west winds / Freezing level at 1500m

Monday: Mainly cloudy with isolated flurries / Light north westerly winds / Freezing level at 1200m

Tuesday: Isolated flurries (5cm possible) / Light to moderate south westerly winds / Freezing level 1000m.

Danger Ratings Explained

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

Natural avalanches possible; human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

4 - High

Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

Natural avalanches likely; human-triggered avalanches very likely.

Large avalanches in many areas; or very large avalanches in specific areas.

5 - Extreme

Avoid all avalanche terrain.

Natural and human-triggered avalanches certain.

Large to very large avalanches in many areas.

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