Avalanche Forecast
Issued: Dec 19th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs.
mconlan,
Avalanche Canada
Saturday night's snow is forecast to switch to rain early-morning, followed by a cooling trend. The forecast herein assumes the snow surface will freeze into a hard crust for Sunday. Treat the danger as CONSIDERABLE anywhere that the precipitation all fell as snow.
Summary
Confidence
Weather Forecast
SATURDAY NIGHT: Snow switching to rain, accumulation 20 cm of snow followed by 5 to 10 mm of rain, 40 to 60 km/h southwest wind, treeline temperature 3 C, freezing level 1900 m.
SUNDAY: Mix of sun and cloud, 20 to 40 km/h west wind, treeline temperature -1 C, freezing level 1000 m.
MONDAY: Snow, accumulation 20 to 30 cm, 40 to 60 km/h south wind, treeline temperature -1 C, freezing level 1100 m.
TUESDAY: Clear skies, 10 to 20 km/h north wind, treeline temperature -2 C, freezing level 800 m.
Avalanche Summary
Many small (size 1) avalanches were triggered naturally, by riders, and by explosives on Friday. This avalanche activity likely tapered Saturday, as the snow surface turned into a hard melt-freeze crust.
We have little data and a lot of uncertainty around conditions in the region, particularly in alpine terrain. If you go out in the mountains, please consider sharing your observations on the Mountain Information Network (MIN).
Snowpack Summary
Snow is forecast tonight which is expected to transition to rain by early-morning Sunday. The rain is forecast up to around 1900 m followed by a cooling trend, so I expect the snow surface to be either wet or frozen into a melt-freeze crust on Sunday. At the highest mountain tops you may just get above this freezing level and experience substantial snow accumulation that is forecast with strong southwest wind, which will likely form very touchy slabs that may sit on a melt-freeze crust formed on Friday.
The remainder of the snowpack has been reported as being well-settled. There are numerous other melt-freeze crusts buried in the snowpack, but no recent avalanches or concerning snowpack test results have been observed on them.
Terrain and Travel
- Closely monitor how the new snow is bonding to the crust.
- Remember that the snowpack will be significantly different at higher elevations than lower down.
- When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
- Cornices often break further back than expected; give them a wide berth when traveling on ridgetops.
Problems
Storm Slabs
Around 20 to 30 cm of precipitation is forecast for Saturday night, which will start as snow but is forecast to transition to rain below around 1900 m. The snow surface is expected to be wet early-morning and freeze into a hard melt-freeze crust. This snow will accumulate onto a hard crust and may not bond well to it; use particular caution in steep terrain features.
It is possible you may find dry snow at the highest mountain tops in the region. Should you find a dry snow surface up high, expect wind slabs to have formed due to strong southwest wind.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 20th, 2020 4:00PM
