Avalanche Forecast
Issued: Apr 18th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Dry, Loose Wet and Persistent Slabs.
Tim Haggarty,
A quick return to winter on Sunday has made new snow surface instabilities the main concern for the next couple of days.
Summary
Weather Forecast
A cold front dropping through Alberta has brought 10-15 cm with moderate NE winds as of Sunday afternoon. Temperatures are expected to drop as low as -15C in the alpine and just below 0C at valley bottom overnight. An unstable atmosphere seems likely Monday that should result in spotty clouds while freezing levels approach 2000m in the afternoon.
Snowpack Summary
Up to 15cm of new snow Sunday tapers with elevation and buries crusts found on solar aspects and up to 2200m on shaded aspects. Persistent layers in the mid and lower snowpack were re-activated in a few instances during the heating over the last week producing avalanches with cornice failures and explosives.
Avalanche Summary
On Friday and Saturday explosive control on the 93 S and in Yoho produced good results up to size 3 with small slabs at treeline gouging into deeper layers at lower elevations and running full path. Widespread natural loose wet avalanche activity up to size 2 was also observed at all elevations. Cooling Sunday has brought natural activity to a halt
Confidence
Problems
Loose Dry
New snow amounts will vary across the region and with elevation. Sluffing is likely in steep terrain over firm underlying surfaces and crusts. Use caution in gully features where these events could gather mass.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
Heating on Monday will depend on cloud cover, but as the winds abate in the afternoon, it will not take much sun to develop point releases in the new snow, especially around exposed rock. These may run far on the well developed crusts.
- Use extra caution on solar slopes or if the snow is moist or wet.
Aspects: South, South West, West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Cooler temperatures may decrease the likelihood of deeper layers in the mid to lower snowpack being triggered. If there is a poor freeze or one of the many large cornices fails, larger avalanches on these layers are still a possibility.
- Pay attention to overhead hazards like cornices which could trigger persistent slabs.
- Pockets of persistent slabs linger on alpine lee features.
Aspects: North, North East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Apr 19th, 2021 4:00PM
