Avalanche Forecast

Issued: Dec 2nd, 2015 10:05AM

The alpine rating is below threshold, the treeline rating is below threshold, and the below treeline rating is below threshold. Known problems include Storm Slabs and Wind Slabs.

ghelgeson, Avalanche Canada

Purcells.

Storm snow is falling on a variety of nasty weak layers. As new snow, wind and potential warming combine over the next few days an avalanche cycle is expected to ensue. Pay attention out there, conditions could get real this weekend.

Summary

Confidence

Poor - Due to the number of field observations

Weather Forecast

A series of rather warm systems are stacked up off the Coast of BC. These storms are expected to pummel the coast bringing significant precipitation and wind. Its expected that some of this energy will spill over into the Purcells, but its impossible to say just how much. Thursday should deliver a few centimeters of snow during the day and winds are expected to be strong out of the SW as the freezing level climbs towards 1700m. Thursday night should usher in a 2 to 5cm as the freezing level hovers around 1600m. Just a trace of snow is expected Friday with the freezing level around 1400m. Saturday and Saturday night may offer more juicy systems, but its too far out to say what the impact will be, the pattern is just too dynamic to even provide a reliable guess. For detailed mountain weather information visit avalanche.ca/weather.

Avalanche Summary

No new avalanche activity reported.

Snowpack Summary

Our relatively young snowpack is already quite complicated. Tuesday night's storm brought 1 to 5 cm that is likely being formed into small storm slabs. Previous to this, northerly winds associated with last weeks outbreak of Arctic air stripped many south facing features down to rock near ridge crest. As a result, wind slabs that have now grown old and tired were reported on north facing features at and above treeline. The cold air and associated inversion created surface facets and the well reported trophy sized surface hoar that averages 20mm in size and can be found from creek bottom up to around 1800m. Sun and above freezing alpine temperatures were also part of the last week of wonky November weather, so you'll find a suncrust at and above treeline just under the new storm snow on solar aspects. The three different November surface hoar interfaces that we were previously concerned about seem to be a thing of the past. It's thought that there is also a crust/facet interface on or just above the ground on high elevation north facing features, but this interface is likely very isolated and is probably inactive at this time.

Problems

Storm Slabs

A few nasty weak layers are being buried by the new snow. Storm slabs should not be much of a problem yet, but this problem is expected to become very touchy as the new snow combines with wind and potential warming this weekend.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.> Pay close attention to the amount of new snow, when the total nears 20cm and begins to take on just a touch of cohesion, (slab) things will get VERY touchy in a HURRY.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Wind Slabs

Previously strong north winds formed wind slabs that extend from treeline to just below ridge crest. Most of these wind slabs are probably old, tired and hard to trigger, but there may be a few that remain sensitive to human triggering.

Be cautious as you transition out of wind sheltered terrain and avoid features that are actively being wind loaded.> It's best practice to use ridges or ribs to avoid pockets of wind loaded snow at this time.>

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Dec 3rd, 2015 2:00PM