Updated Thursday at 6:40 AM: A sustained period of heavy precipitation and extreme wind Wednesday night through Friday means the avalanche danger will be HIGH in alpine terrain. Minimize your exposure to avalanche terrain during periods of heavy rain.
A crust that formed in early January has been bonding poorly to the overlying snow. With the recent new snow load, this crust is now buried about 100 cm deep, a prime depth for human-triggering as well as large, consequential avalanches.
30-50 cm of snow may accumulate at upper elevation overnight Wednesday and through Thursday. Expect deep deposits in lee terrain with extreme southerly winds.
Rising freezing level through the day will bring heavy rain at lower elevations and saturate and weaken the new snow that fell in the overnight period Wednesday.
No recent avalanches have been reported, however heavy precipitation and extreme winds over the next 48 hours will likely trigger a natural avalanche cycle at upper elevations.
Up to 30cm of new snow may be sitting on a crust that formed Tuesday night.
There is likely 90-130cm sitting over a thin crust layer above 1000 m. This crust has been highlighted as a critical avalanche layer in recent snowpack tests. Frequent rain has been eroding the already thin snowpack below this elevation.
Snowpack depths at treeline are around 120 cm, tapering quickly with elevation. Although the snowpack in most forested areas below treeline remains below threshold depths for avalanches, many steep bluffs, cutbanks, and alpine features in the upper below treeline band are capable of producing avalanches.
Wednesday Night
Heavy precipitation overnight bringing 20-30 cm of new snow to upper elevations. Strong to extreme southerly wind. Treeline high temperatures around -2°C with a freezing level around 1000m.
Thursday
Heavy precipitation falling as snow above 1000m until mid-morning. Accumulations of 20-40cm through the day at upper elevations. Snowfall will shift to rain by midday below 1600m. Extreme south winds. Treeline high temperatures reaching +2 as the freezing level climbs from 1000 to 1800 m throughout the day.
Friday
Cloudy with continuing heavy rain at all but highest alpine elevations. Extreme south winds. Treeline high temperatures around +4 with freezing levels between 1800 to 2000m.
Saturday
Cloudy with flurries at upper elevations. Moderate south winds. Treeline high temperature around -1.
More details can be found in the Mountain Weather Forecast.
