Avalanche Forecast

Issued: Nov 23rd, 2017 4:01PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Persistent Slabs and Loose Wet.

jfloyer, Avalanche Canada

South Rockies.

If the rain-soaked snow freezes as expected through Friday and Saturday, avalanche hazard will follow a decreasing trend until the next storm on Sunday. Please treat this forecast as an initial assessment, as we have little information at this time.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

Harmer (1870m):Temps between 2 and 4.5C over last 24 hours. HS decreased from 57 to 43cm. Winds 30-45 SE (prev SW)Crowsnest Ck (1450m):H96W: 18mm; H24W: 12mm; TMax 9; TMin 4S Racehorse Ck(1950m): H96W: 52mm; H24W: 32mm; TMax 7; TMin 3Castle Mtn (1420m): H24W: 14.4mm rain; H48W: 40mm rain. TMin 6; TMax 8; Mod SW winds

Avalanche Summary

There are few observers right now, but avalanches almost certainly ran during the onset of the rain on Wednesday. I suspect this activity will taper off with cooling temperatures on Friday and Saturday.

Snowpack Summary

Rain and warm weather have resulted in a widespread wet upper snowpack. The freezing level rose to approximately 2700 m on Wednesday and Thursday meaning very few places, if any, will have escaped the melt. The last 48 hours have seen the snowpack diminish by approximately 10 cm. Expect treeline snow depths of around 45 cm in the Elk Valley and more like 80 cm further south in the Flathead in sheltered areas. A crust that formed around Halloween has been reported within the snowpack that may lie around 40 cm below the surface.

Problems

Persistent Slabs

We know there's a crust buried approx. 40cm below the surface, but don't know much about how likely avalanches are on it. Once there's a new thick crust on the surface, this lower layer may become less of a problem. Until then, assume it's a player.

Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.Start cautiously on small slopes before gradually working up to larger objectives.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Loose Wet

Recent rain and warm temperatures may lead to ongoing loose wet avalanches, particularly if the snow surface has not hardened into a crust.

Start with lower angle slopes before gradually working up to steeper objectives.A crust on the surface will help bind the snow together, but may make for tough travel conditions.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Nov 24th, 2017 2:00PM