Avalanche Forecast
Issued: Jan 23rd, 2021 1:00AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs, Wind Slabs and Storm Slabs.
Ryan Shelly,
VIAC
It's been boiler plate hard pack out there, no new avalanches to report. Expect this to change sharply with the arrival of new snow and strong winds on Sunday jan 24th.
Summary
Past Weather
Cool, clear and calm weather has contributed to a stiffening of the snowpack however it has also allowed for the growth of surface hoar at the snowpack surface.
Weather Forecast
There is a discrepancy in terms of extent of precipitation and wind for Vancouver Island on Sunday. The southernmost reach of the avalanche forecast region shows Light to Moderate winds throughout the Storm event on Sunday with 15cm of snowfall. The northern reach of the forecast region shows Strong to Extreme wind gusts during the storm and slightly less precipitation. All regions agree on a Below Treeline Freezing level which is positive but it the Southern region may have slightly safer avalanche conditions this Sunday into Monday based primarily on the less aggressive wind speeds forecasted for the Southern region. Saturday: No precipitation expected, Winds Light from the NW, Freezing level will reach a high of 600 meters south island and 1,100M on the North Island.Sunday: Moderate precipitation expected (10-15cm Snow), Winds Strong from the NW (particularly from mid-day onward to evening), Freezing level will reach a high of 750 meters.Monday: Very light precipitation expected (less than 1 cm Snow), Winds Strong from the North shifting to Moderate North winds in afternoon, Freezing level 650M elevation
Terrain Advice
Beginning Sunday January 24th, dangerous avalanche conditions will exist. Cautious route-finding and conservative decision-making will be essential Sunday into Monday. The avalanche hazard will increase with incoming precipitation amounts and strong winds. Be aware as the storm arrives to your area and be vigilant of signs of instability such as snow cracking underfoot/under your sled. AS precipitation volumes and winds increase by mid-day the possibility of triggering an avalanche will become a "very likely" scenario. Be aware of changing snow/avalanche conditions on Sunday and into Monday. Careful and cautious route finding when transitioning from scoured areas into areas of wind loaded snow.Avoid traveling below and above cornice features as they are large and touchy.Avoid open and steep slopes during periods of warming and rain; even small loose wet avalanches will have enough mass to push a mountain traveler into gullies and over cliffs. From the Mid island to the North, the seasoned backcountry veteran will seek out "Simple Avalanche Terrain" where slope angle is generally under 30 degrees.
Snowpack Summary
A series of fluctuating air temperatures have created an array of upper snowpack melt freeze and rain crusts all within the upper 40-50cm of the snowpack. Within 5-10 cm of the upper surface, a relatively supportive crust exists and at the Below Treeline elevation band this crust is exceptionally dense and firm and provides challenging ski/snowmobile conditions until it softens (particularly at lower elevations (BTL)) with day time heating. Expect this crust to remain in place and firm/supportive as a result of generally cool air temperatures over the next several days.
Snowpack Details
- Surface: Widespread surface hoar (PWL)
- Upper: 5-10 cm below the surface exists a reactive facet layer sitting on top of a firm melt freeze crust (as of Friday Jan 22)
- Mid: generally well settled with several melt freeze crust layers
- Lower: well settled and well bridged and includes a 10cm thick layer of large facets
Confidence
Moderate - Confidence is Moderate based on conclusive weather modelling, the North of the island is set to receive stronger winds while the southern portion (Lake Cowichan/5040) are set to receive moderate snowfall and moderate winds.
Problems
Persistent Slabs
There exists 2 (persistent weak layer = PWL) within the upper snowpack which will be further compromised by the arrival of new snow in the form of precipitation and wind loading.
The positive point of this Persistent slab problem is that it is a very shallow problem (at least on Saturday). On Sunday into Monday with the arrival of additional precipitation and strong winds, the two PWL's contained within the upper snowpack will become more avalanche prone.
Location: Found at all elevation bands and on multiple aspects
Possibility: Triggering of this avalanche problem is "possible" to "likely" from light loads such as skiers and snowmobilers. Natural avalanches are unlikely.
Size: If triggered expect these avalanches to be large enough to bury a person (size 2).
Likelihood
Expected Size
Wind Slabs
Found on predominantly South aspects, this avalanche problem overlies a variety of surfaces including a thick ice crust as well as a surface hoar layer within the upper snowpack. Expect that this problem will reveal itself Sunday mid-day as new snow and excessive wind speeds begin to transport and overload down wind areas creating prime zones for human triggering Sunday afternoon and into Monday.
**Location:** South aspects in down wind areas at all elevation bands Sunday into Monday.
**Possibility:** Triggering of this avalanche problem is "likely to very likely" from light loads such as skiers. Natural avalanches are "possible" to "likely" depending on elevation band.
**Size:** If triggered expect these avalanches to be large enough to bury a person, size 2.
Likelihood
Expected Size
Storm Slabs
On the south island, where winds are forecasted to arrive without enough "punch" to redistribute snow, there is a possibility that storm slabs could exist on all aspects and elevations.
**Location:** All aspects and at all elevation bands Sunday into Monday.
**Possibility:** Triggering of this avalanche problem is "possible" from light loads such as skiers. Natural avalanches are "possible" to "unlikely" depending on elevation band.
**Size:** If triggered expect these avalanches to be small and in areas that receive closer to 30cm of new snow an avalanche could have the ability to bury a person, size 2.
Likelihood
Expected Size
Valid until: Jan 24th, 2021 1:00AM
