Monday January 21, 2019
Cornice Fall, Loose Wet
Travel & Terrain Advice
Rising freezing levels and rain below treeline and at treeline on Tuesday will cause the upper snow pack to lose strength. Be aware of changing conditions with elevation changes. Cornices will be more fragile as temperature rises and with added precipitation load. Do not travel above or below consequential overhangs or the slopes below them that may be affected.
Very little activity observed/reported. A few small isolated size 1 wind slab avalanches were triggered with ski cuts on north aspects at 1500 m. These avalanches were initiated in the recent storm snow and were not very deep.
Cornices that have grown throughout the season will continue to weaken and become more fragile with rising temperatures and added precipitation load. These cornices may be easily triggered with a light load and could have the potential to be large in size (1-2). NW through NE aspects in the alpine and upper treeline will be the areas of highest hazard.
Spiking freezing levels with the addition of rain will almost certainly produce loose wet avalanches, especially below treeline and lower treeline elevations on all aspects. Expect these avalanches to be small in size, but combined with terrain traps may have larger consequences.
Clear and calm nights have produced surface hoar development on all aspects and elevations. These weak feathery crystals have formed on top of 20-50 cm of our most recent storm snow which sits on top of an old strong melt freeze crust. This snow is bonding well and showing little to no signs of instability at that interface. Below this crust the mid and lower snow pack is well settled and dense.
|Surface||Weak feathery surface hoar has grown on all aspects and elevations.|
|Upper||Dry loose storm snow with several weak layers. Bonding well to old crust surface.|
Friday and Saturday brought 20-50 cm of accumulation with highest totals above treeline and in the southern region. Strong winds associated with this precipitation created highly wind affected surfaces. Cool temperatures have prevailed and maintained snow quality with dry snow on all aspects above 1200 m. Recent clear calm nights in the wake of low pressure have created surface hoar and a drying of the upper snow pack.
MONDAY - Minimal precipitation, with light winds from the NW veering to strong SE in the afternoon. Freezing levels around 900 m.
TUESDAY - 20-35 mm of precipitation with freezing levels spiking up to 2100 m in the afternoon. Winds strong to extreme from the south.
WEDNESDAY - 5-10 cm with freezing levels dropping from their height on Tuesday to around 800 m. Winds moderate from the NW.
Posted on Monday January 21, 2019 by Dan Goodwin