Avalanche Forecast South Columbia
Tuesday 12th February 2019
New wind slabs, older wind slabs, and a few troublesome buried persistent weak layers. These are what we are dealing with, which can be tricky to manage. For further info on the conditions, check out the Forecaster Blog here.
TUESDAY Night: Mainly cloudy with flurries, light southwest wind, alpine temperature -14 CWEDNESDAY: Cloudy with sunny breaks, light west wind, alpine temperature -13 C.THURSDAY: Mix of sun and cloud, light to moderate southeast wind, alpine temperature -10 C.FRIDAY: Flurries, accumulation 5-10 cm , light southwest wind, alpine temperature -7 C
Many small and large wind slab avalanches were triggered on Monday and Sunday. They were triggered naturally and by skiers. Most of the avalanches were on west and north aspects, but there were reports of avalanches on all aspects. They occurred at all elevation bands.The mid-January persistent weak layer described in the Snowpack Summary has recently been reactive to human triggers, although activity has decreased in the past few days. The most recent activity was on Friday, as skiers triggered small avalanches on north and northeast slopes between 1650 and 1900 m.The most recent deep persistent slab was reported on Saturday, which was very large (size 3.5) and triggered naturally on a northeast aspect at 2950 m. The slab was 400 cm thick and 150 m wide.
The top 10 to 20 cm of snow has been affected by recent strong wind from variable directions. Expect to find wind slabs in lee terrain features in exposed terrain. This snow may be particularly touchy where it sits on a weak layer of feathery surface hoar crystals, as seen here. Beneath this lies two weak layers of surface hoar, which have produced large avalanches in the region. The layer that was buried at the end of January is around 30 cm deep and the layer buried mid-January is between 40 and 90 cm deep. The mid-January layer may also be associated with a melt-freeze crust on southerly aspects. These layers are most prominent at treeline and below treeline elevations. Recent avalanches on the mid-January layer have been mostly in the northern half of the region.The remainder of the snowpack is generally well-settled. However, there have been sporadic reports of very large avalanches that have released near the base of the snowpack, suggesting that instability exists in isolated locations. Most of the avalanches have been in the high alpine. There has been about one report a week for the past month, suggesting it is a low probability but very high consequence problem.
1 - 2.5
Recent newly formed wind slabs and previously formed wind slabs from the weekend may still be reactive. They are particularly reactive where they overly a weak layer of surface hoar. Use added caution on all aspects in exposed terrain.
Travel in low-consequence terrain and avoid terrain traps.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Use caution in freshly wind-loaded features, especially near ridge crests and in steep terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
1.5 - 2.5
Two weak layers of surface hoar crystals are buried between 30 and 90 cm in the snowpack. The layers are most prominent at treeline and below. Skiers have recently triggered large avalanches, mostly in the north half of the region.
Avoid steep, open and/or sparsely treed slopes at and below treeline.Be aware of the potential for wide propagation.Any steep opening in the trees should be treated as suspect.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.