Rain and positive temperatures high into the alpine are creating very dangerous avalanche conditions.
Large natural avalanches are likely & human triggered avalanches are very likely.
A persistent weak layer (PWL), buried March 5th, is down 60-120cm. Depending on aspect and elevation, this layer may be suncrust, facets &/or surface hoar. Wet loose or wet-slab avalanches may step down to this layer resulting in large avalanches.
Natural wet loose avalanches will be likely as freezing levels stay elevated. These avalanches may be large enough to trigger our March 5 persistent weak layer.
30mm of unexpected rain fell on 60cm of old storm snow creating a widespread heavy layer in the upper snowpack. These slabs are expected to become very reactive as temperatures rise with accompanied rain and wet snow.
A widespread natural avalanche cycle is underway at the time of writing this bulletin. Naturals up to size 4 are running to valley bottom.
Natural activity is expected to continue with the forecasted rain and overnight temps remaining above zero in the alpine.
Neighboring regions have reported serious incidents and large avalanches. Similar conditions are expected in Rogers pass as we see the same warming trend with rain.
30mm of rain/wet snow has destabilized the upper snowpack.
60cm of recent snow sits on-top of the March 5th persistent weak layer (PWL).
The March 5 PWL consists of a crust &/or surface hoar and is down 60-120cm. There is concern that wet avalanches will step down to this PWL and may entrain more snow at lower elevations.
Additional PWL's from Jan/Feb are now buried 140-190cm deep.
Freezing levels continue to stay near mountain top overnight through Thursday.
Tonight: 11mm of rain. Alpine low 3°C. Wind SE 15-25km/hr. Freezing Level (FZL) 2500m
Thurs: Cloudy w/ scattered flurries. 4cm. Wind SW 10-45km/hr. FZL 2800m
Friday: Snow, 15cm. Alpine High -1°C. SW wind 10-30km/hr. FZL 1900m
Sat: Cloudy w/ sunny periods. Trace precip. Alpine high of -2°C. SW wind 10-30km/hr. FZL 1800m
