Avalanche Forecast

Issued: May 7th, 2017 4:00PM

The alpine rating is below threshold, the treeline rating is below threshold, and the below treeline rating is below threshold. Known problems include Loose Wet, Deep Persistent Slabs and Cornices.

conrad janzen, Parks Canada

Banff Yoho Kootenay.

Some good spring travel conditions exist at high elevations. Watch for clear cool nights in the forecast, then start early to complete your objective before daytime warming causes the snowpack to become weak.

Summary

Weather Forecast

The week of May 8-14 looks like a clearing and gradually warming trend.Â The first part of the week looks like the best time to get out and enjoy a good overnight freeze while the later part of the week may not have much of an overnight crust recovery. No significant precipitation is expected until late in the week.Â

Snowpack Summary

Isothermal snow exists at lower elevations. Crusts formed during clear cool nights will break down quickly with solar inputs. Expect moist surface snow to mountain top in the afternoon with the exception of high elevation North slopes. The basal facet weakness persists at treeline and above and is reactive to large triggers or warm temperatures.

Avalanche Summary

Large wet slab avalanches failing on the basal facets have been observed during recent periods of rapid heating or with large triggers such as cornices at treeline and above. These are running far with lots of destructive potential. Loose wet avalanches are being reported whenever the surface snow becomes wet with daytime heating.

Confidence

Problems

Loose Wet

Loose wet avalanches are occurring on all aspects and elevations during the warmest parts of the day, especially when the sun comes out. Some of these are also triggering wet slabs. Plan your trip to be out of any big terrain before things heat up!

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.Watch for clues, like sluffing off of cliffs, that the snowpack is warming up.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Deep Persistent Slabs

Deep persistent slab avalanche activity will taper off with cooling and increase during hot periods of the day, with large triggers like cornices or when there is no overnight refreeze. The deep facets will remain a problem through the spring season.

Travel early before the heat of the day melts surface crusts, and avoid big slopes in the afternoon.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 4

Cornices

Cornices have taken quite a hit with the recent heat. Many are cracked and slowly peeling off of ridges. These should be considered suspect as they will likely fail in the coming weeks.

Cornices become weak with daytime heating, so travel early on exposed slopes.Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

2 - 3

Valid until: May 8th, 2017 4:00PM