Avalanche Forecast
Issued: Jan 4th, 2020 1:00AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Cornices, Wet Slabs, Loose Wet and Storm Slabs.
Ryan Shelly,
VIAC
Limited field observations, however we are expecting major storm snow and extreme winds over the weekend. Watch for precipitation amounts and storm snow loading in excess of 30cm and monitor wind speeds as snow transport and redistribution will be very important in determining where avalanches will occur. Natural avalanches are likely this weekend at Alpine and Treeline elevation bands if the forecasted wind speeds and snow volume arrives.
Summary
Past Weather
Several moderate snowfall events earlier in the week have bonded due to warm winter air temperatures and rain (including rain in Alpine) which has helped facilitate bonding.
Weather Forecast
A large storm cycle of extreme precipitation, wind and freezing level fluctuations is expected over the next 48 HRS. Saturday - warm temps from Friday will subside and rain will transition to snow (10cm-60cm), Extreme Winds will relocate snow to Easterly Aspects, Temps O degrees - minus 7, Freezing Level 700M Sunday - Another 20cm - 50 cm of snow is expected, Extreme Winds will lessen throughout the day but expect more snow transport to multiple aspects as wind direction varies widely during the storm cycle on Sunday, Temps -1 to -7 degrees, Freezing Level 800M dropping to 400M later in the day. Monday - More "Classic West Coast Weather" - Forecast models approximate between 10cm -15 cm of snow and later in the day a transition to 10mm - 30mm of rain as the air temperature goes from minus 6 degrees to +2 at 1500M of elevation
Terrain Advice
Very dangerous avalanche conditions. Travel in avalanche terrain is not recommended at Alpine and Treeline Elevation bands.
Snowpack Summary
The snowpack was generally well settled will very little information regarding avalanches occurring. The major warming trend, coupled with 50+mm of rain and up to another 50+cm of new storm snow over the next 24 HRS we could expect major volatility within the snowpack.
Snowpack Details
- Surface: 50+ MM of Rain and another 50MM of snow is forecast in the next 24-36 HRS leaving the upper snowpack and Storm Snow highly unstable
- Upper: Generally well settled however new rain and major warming events may lessen consolidation, particularly on storm snow interfaces from earlier in the week and overnight into the weekend
- Mid: Well bonded midpack that does include two weaker layers (Facet layer and Surface Hoar layer)
- Lower: Well Settled except on exposed rocky cliffs and rocky outcroppings where basal facets are lingering in Alpine
Confidence
Moderate - Weather models in agreement, moderate field weather and snowpack observations, limited weather station data
Problems
Cornices
Fridays overnight Rains into the early hours of Saturday will hasten potential for cornice fall however with extreme winds and up to 50cm of additional snow, cornices will also likely fail due to the extreme nature of the current weather cycle.
Likelihood
Expected Size
Wet Slabs
Monday's forecast of rain changing to snow (up to 50cm) will also exacerbate stability and further stress the snowpack. New snow and rain fall Monday could create dense moisture laden upper snowpack.
Likelihood
Expected Size
Loose Wet
Saturday Below Treeline Hazard Friday Night Rain of 50+mm of rain and freezing level above 2,500M of elevation will undoubtedly cause major instability in the upper and mid snowpack.
Likelihood
Expected Size
Storm Slabs
Major precipitation in the form of snow and wind will cause major instabilities in the snowpack. Expect all Alpine and Treeline environments to be very likely areas to trigger an avalanche.
Likelihood
Expected Size
Valid until: Jan 5th, 2020 1:00AM
