Avalanche Forecast

Issued: Feb 21st, 2021 4:00PM

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

Snow Safety,

Little Yoho.

Warm temperatures, strong wind and snow will combine to start an avalanche cycle overnight Sunday through until end of day on Monday. A good time to step back.

Summary

Weather Forecast

Warm temperatures (zero at the valley) will persist into Monday. Snow will start in earnest Sunday night and will deposit up to 25cm near Emerald Lake by the end of Monday. Wind will remain in the strong to extreme range until late Monday night. The weather forecast has all of the ingredients for an avalanche cycle.

Snowpack Summary

Extensive wind effect and isolated, thin wind-slabs throughout the alpine from extreme wind on Sunday. Approximately 40cm of recent storm snow is present at tree line tapering down to 15cm below tree line. A facet and sun crust layer buried Jan 27 persists at treeline down 30-40 cm.

Avalanche Summary

Loose dry avalanches up to size 1.5 out steep cliffy terrain in Little Yoho today. Despite strong to extreme wind few wind slabs were observed. Additionally, loose dry avalanches to size one were running over many of the steep ice climbs on Mt. Dennis.

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Sunday

Problems

Wind Slabs

Strong to extreme wind on Sunday has created fresh wind-slabs in the alpine. Snow fall and more wind is expected to continue over night Sunday, so expect the wind slab problem to drastically increase in the near term.

Use caution in lee areas. Recent wind loading has created wind slabs.
Pay attention to overhead hazards like cornices which could trigger slabs.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Very Likely

Expected Size

1 - 2.5

Loose Dry

Loose dry avalanches were running today on Mt. Field and Mt. Dennis in steep terrain. Storm conditions overnight Sunday will accentuate this problem on Monday, especially in gully features.

Be very cautious with gully features.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely - Certain

Expected Size

1 - 2

Storm Slabs

There is approximately 40cm of storm snow currently at treeline which has not quite yet settled into a slab. However, it is expected that further snow load and warming temperatures will settle the storm snow into a slab overnight Sunday.

Use caution in the alpine and treeline. Storm snow is forming reactive slabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Valid until: Feb 22nd, 2021 4:00PM