Avalanche Forecast

Issued: Feb 12th, 2015 9:19AM

The alpine rating is high, the treeline rating is high, and the below treeline rating is considerable. Known problems include Storm Slabs and Persistent Slabs.

esharp, Avalanche Canada

Northwest Coastal.

There is significant variability across the region regarding forecast freezing levels and precipitation amounts. Avalanche danger ratings describe the worst case scenario where heavy rain and/or wet snow falls on a previously cold snowpack.

Summary

Confidence

Poor - Freezing levels are uncertain

Weather Forecast

By the end of Saturday a series of frontal systems will have brought up to 100mm of precipitation on the coast tapering to around 35mm further inland. Unfortunately for the southern half of the region, rising freezing levels will mean that much of this will likely fall as rain.The freezing level is forecast to remain high on Friday (1500m in the south and 600m in the north) with 5-25mm of precipitation expected Thursday night and another 5-20mm through the day Friday accompanied by moderate to strong southwest winds . Light to moderate precipitation will continue into Saturday as the freezing level falls to 1000m and winds become more westerly. By Sunday the winds are expected to be from the northwest, bringing mainly dry conditions and continued cooling with a freezing level of 750m in the south and at valley bottom in the north.

Avalanche Summary

Warming temperatures, wind, snow and rain are driving a natural avalanche cycle that started on Wednesday when we received reports of several natural and explosive controlled avalanches up to size 2 on wind loaded north-facing slopes. Avalanche control on Monday produced slab avalanches up to size 3 on virtually all aspects and elevations. It sounds like some these avalanches released on the late January crust and I wouldn't be surprised if we continue to see activity on this layer over the weekend.

Snowpack Summary

Between 10 to 40 mm of precipitation in the form of new snow and/or rain had fallen through the storm as of Thursday evening. In many places this sits on a thin layer of surface hoar that formed in the brief lull between systems on Febuary 10th. Freezing levels rose to 1500m in the southwest corner of the region on Thursday with cooler temperatures recorded further inland and to the north. Predominantly strong southwest winds are loading lee features in the alpine and at treeline. The late-January crust is down between 60 to 150cm in the south of the region and about half this depth in the north. This crust may have surface hoar on it. The mid-January rain crust and/or surface hoar layer is down over 160cm in the south and has generally become inactive although it may still be a concern in thinner snowpack areas. The November crust/facet combo near the bottom of the snowpack is still on my radar as a potential problem layer in the far north of the region.

Problems

Storm Slabs

High freezing levels means rain or wet snow will continue to load a thin layer of recently buried surface hoar. Expect very touch avalanche conditions.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

2 - 5

Persistent Slabs

Warming temperatures, snow, and/or rain will stress persistent weak layers lurking in the snowpack at and above treeline. These layers still may have the potential to produce very large and destructive avalanches.

Be aware of the potential for large, deep avalanches due to the presence of buried crusts and/or surface hoar.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

3 - 7

Valid until: Feb 13th, 2015 2:00PM