Sunny skies with inversion conditions Saturday: watch heating inputs closely.
Recent warming has created a skiable crust on most slopes and west winds have created widespread wind effect above treeline.
The Jan 3 surface hoar layer is a concern in some locations; forecasters are keeping ratings BTL and at TL elevated.
20-40 cm of snow fell Monday with moderate to strong SW-W winds. Continued W winds and mild temperatures have consolidated the slab in the upper snowpack and created widespread wind effect. Cornices have new and fragile growth.
The January 3 surface hoar now sits 30–80 cm deep. In some areas, this layer has a firm slab over it and is at a prime depth for skier triggering. There have also been some recent reports of small avalanches on this layer and tests showing sudden planar shears. Dig frequently and test for sensitivity.
Basal facets remain near the ground. The recent storm and heating generated a few cornice-triggered and alpine slabs - mainly in shallow features. The remaining concern centers on the eastern side of the forecast area, particularly in thin to thick snowpack transitions.
A field trip to Little Yoho today found further evidence of this week's natural cylce to sz 2.5 +. Deep slabs on E-facing alpine terrain that likely triggered by cornice failures or wind-induced sluffs out of extreme terrain.
A flight on Thursday to the Wapta also found widespread evidence of wind slabs & cornice failures to size 2 - only a few deep releases were observed.
An sz 2 slab on the basal facets triggered by a cornice fall was reported on Jimmy Junior peak Thursday.
A thin, skiable, temperature crust now caps the snowpack in most locations that was created by above-freezing layers early in the week. This will vary with each valley...
Widespread wind effect is found in the alpine and down into treeline elevations.
In several locations through the region, the January 3rd surface hoar layer is reactive down 30-100 cm.
The November facet/crust interfaces sit 20 - 40 cm up from the ground.
Treeline snowpack depths range from 100 to 200cm +.
The region is under the influence of an upper ridge maintaining warm and dry conditions through the middle of next week.
An above-freezing layer between 2500-3000m will lead to inversion conditions Saturday. Treeline temperatures will also approach 0C. Ridgetop winds will be light to moderate from the NW through the day.
Cooling with a decrease in windspeed looks to be on track for Sunday.
