Expect a spike in avalanche activity on Friday with rapidly warming temperatures (read more in this Forecasters' Blog). Wind slabs may also remain reactive to human triggering.
Wind slabs above a crust layer have been reactive to human triggering over the past week. Looking forward they may still be possible to trigger in steep open terrain.
Spiking freezing levels will destabilize surface snow and result in natural wet loose avalanches, especially on Friday.
Warming could also possibly initiate slab activity in shallow snowpack areas like the Wheaton Valley.
WEDNESDAY NIGHT: Partial clearing overnight, south wind 40-60 km/h easing to 30 km/h, treeline temperatures drop to -5 C.
THURSDAY: Partly cloudy, 20 km/h south wind, freezing level climbing to 1500 m in the afternoon.
FRIDAY: Mix of sun and cloud, light south wind, freezing level climbing from 1500 to 2200 m.
SATURDAY: Mix of sun and cloud with some isolated flurries, light northeast wind, freezing level around 1500 m.
With the incoming warming trend expect avalanche activity to transition from wind slab to wet loose activity. Weather forecasts suggest the greatest warming impacts will be on Friday. Keep in mind periods of rapid warming can increase the likelihood of large natural avalanches.
There were a few reports of small wet loose avalanches at low elevations on Tuesday and numerous reports of reactive wind slab avalanches between Friday and Monday (with multiple size 1-2 avalanches running on a 30-70 cm deep crust layer).
Warming temperatures over the next few days will form moist surfaces at lower elevations and on sun-exposed slopes (if the clouds break up). 15-30 cm of wind-affected snow overlies a hard crust found up to 1300 m. The wind effect is particularly widespread along the highway corridor at White Pass but may be less so as you push into the side valleys.
While there have not been many weak layers of concern this season, there is some uncertainty about whether the big warm up on Friday will increase the reactivity of any deeper layers. This will more likely be an issue in shallow snowpack areas like the Wheaton compared to the thicker and stronger snowpack around White Pass.
