If the upper values of forecast precipitation amounts and freezing levels ring true, stay home!
A rain on snow event could put us into another destructive cycle at lower elevations, alongside a winter storm cycle up high.
Up to 50cm of storm snow (and counting!) overlies a hard crust at treeline elevations and above, with more on the way! More snow has fallen on the west end of the park than in the east.
The likelihood of wet, loose avalanches increases with daytime warming, especially if it rains. The heavy, wet mass of these avalanches has the potential to trigger deep persistent wet slabs.
This deep weak layer may wake up again with another rain event at lower elevations. Last week, loose wet avalanches were triggering this rain soaked layer and resulted in very lrge, destructive avalanches that broke mature trees as they ran full path
Another weather system arrives late tonight and will bring rain and snow with very strong gusty winds. Forecasts are quite uncertain!
Tonight: Snow, 14cm + convective cells. Fzl 1400-1700m. Wind S- 30km/h gusting to 60.
Monday: Snow, 10cm. Fzl 1500m. Wind SW- 15km/h gusting to 70.
Tuesday: Flurries, 6cm. Fzl 1300. Wind W- 20 km/h gusting to 50.
30-50cm of storm snow has accumulated at Treeline and above (drainage dependant due to convection) burying a variety of surfaces including wind slabs, solar crusts to mountain top, and a melt/freeze crust to 2200m. Northerly slopes in the Alpine hold cold, wintery snow. The December 1st crust is down 1.5-2m. Late season cornices are LARGE!
No new avalanches observed since Wednesday with the cooler temps. The widespread natural avalanche cycle from Mon/Tues was driven primarily by strong solar input and rain, especially at lower elevations. Wet slabs, deep persistent slabs, glides, and loose wets were gouging to ground, breaking trees, and running full path.
