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Parks Canada lisa paulson, Parks Canada

Little Yoho Avalanche Forecast

May 3rd, 2019 4:00PM

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

Localized snow amount may very at higher elevations. Deeper areas could develop larger then expected wind slabs.

Summary

Weather Forecast

Mixed sun and cloud with isolated convective flurries or rain at lower elevations is forecasted through the weekend with light to moderate SW wind.

Snowpack Summary

5 to 30 cm of new snow and recent winds have created soft slabs in immediate lees in the alpine. Moist snow observed on solar aspects, but alpine north aspects are staying dry. Concern still exists for a facet layer down 30-50 cm which is producing clean shears with snow-pit tests and has been reactive to skier triggering.

Avalanche Summary

Small wet loose avalanches have been observed on solar aspects. Tuesday our field team observed several natural and skier triggered avalanches in the Observation Peak area. These avalanches were triggered on the persistent problem down 40 cm.

Confidence

Problems

Persistent Slabs

Though not widespread, where this layer does exist ,expect it to be most reactive in areas where a slab sits over previously formed crusts. On Tuesday we observed several large skier triggered and natural avalanches fail on this layer.

  • Dig down to find and test weak layers before committing to a line.

Aspects:

All aspects.

Elevations:

Alpine.

Likelihood

Likely - Possible

Expected Size

1 - 2.5

Wind Slabs

Continued precipitation and moderate winds have formed small pockets of wind slab in immediate lee features at higher elevations. Though in many areas these slabs will be small, localized areas of heaver accumulations may have formed larger slabs.

  • Use caution in lee areas. Wind loading could create slabs.
  • The new snow will require several days to settle and stabilize.

Aspects:

North, North East, East, South East.

Elevations:

Alpine.

Likelihood

Possible - Unlikely

Expected Size

1 - 2

Loose Wet

If the sun comes out for any length of time expect loose wet avalanches out of steep sun exposed terrain.

Aspects:

South East, South, South West, West.

Elevations:

Alpine, Treeline.

Likelihood

Likely - Possible

Expected Size

1 - 1.5

Valid until: May 4th, 2019 4:00PM