Wednesday January 1, 2020
Loose Wet, Storm Slab
Travel & Terrain Advice
Study the bond of the new snow arriving Wednesday and Thursday to the old snow surface left after Tuesdays rain event and factor that into your decisions.
Stay out of all avalanche terrain when the hazard rating is at high, during the forecast substantial rain event Thursday night into Friday
Low avalanche hazard at below treeline, but many shallow snowpack hazards exist to keep an eye out for (open creeks, rocks, stumps..). Like the 5 year old girl said when she was skiing on the hill in a smear of mud, rock and snow the other day “Daddy its like skiing in brown sugar”. It might be a very thin start to the season but hey at least we are getting outside to play.. Smile!
Limited observations due to poor visibility (fog past few days) including during Tuesdays rain storm. One can, with a high level of certainly, expect widespread loose wet avalanche activity has occurred. When travelling in the hills keep a eye out for recent activity and factor that into your decisions.
Thursday night into early Friday significant amounts of rain will soak the new snow that is forecast to fall in the next two days. This rain (along with warm temps and a high freezing level) will almost certainly result in loose wet avalanche activity. We can expect that these loose wet slides will almost certainly trigger with human activity, and will very likely trigger naturally up to size 2 to 2.5 on all aspects in the treeline and alpine.
With the potential for up to approximately 20 cm of new snow Wed-Thurs there is the possibility of storm slab avalanche activity. We can expect these avalanches will be up to size 2, will exist in the treeline and alpine and will be on all aspects (esp the Norths). Human triggering will be possible to likely and natural will be possible.
Rain Tuesday saturated the upper snowpack. This moist snow will freeze (into a crust) as temps drop Wednesday and Thursday, reducing concerns around the weak layers found in the mid and lower snowpack.
|Surface||Rain saturated from Tuesdays storm all the way to the top of the alpine|
|Upper||Moist warm rain soaked snow (with the forecast cooling temps Wed and Thurs, this layer should freeze up)|
|Mid||Mainly settled with two suspect weak layers.|
|Lower||Mainly settled and bridged, but a weakness near the ground from early season still exists.|
Tuesday saw significant rain all the way to the top of the alpine with warm (positive temps) and high freezing levels 2500 to 3000 m
Get it while its… good (ish) because it won’t last long… Some new snow Wednesday Thursday and then another big rain event Thursday night into Friday.
Wednesday - Things cool off and some new snow arrives. 2 to 11 cm of new snow, winds strong SW drop to moderate SW, temps 0 dropping to -7, freezing levels 1200 down to 500 m.
Thursday - More new snow early in the day. approx 10 more cm, winds light SW rising to strong S as the next warm wet storm approaches, temps -7 rising in the evening to +3, freezing level 500 up to 2000 m.
Friday - Significant rain. approx 50 mm of rain forecast, winds moderate to strong SE, temps +2 to +1, freezing level 2000 dropping to 1300 m, so we might see the rain tapering into snow after the soaking. Potentially very high summits will see all snow vs rain.
Posted on Wednesday January 1, 2020 by Bill Phipps