Avalanche Forecast

Issued: Apr 17th, 2014 4:00PM

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

tim haggarty, Parks Canada

Waterton Lakes.

The snowpack will be under stress this weekend as temperatures increase. Remember, even small amounts of solar heating or rain can weaken snow quickly to cause an increase in the avalanche hazard beyond the posted danger ratings.

Summary

Weather Forecast

Continued precip through Friday with the freezing level dropping to about 1800m. Winds will pick up to strong. Clearing Friday night should allow for a light freeze but Saturday will bring sunny skies and a 3000m freezing level. A poor recovery is likely into Sunday with clouds and some light precip forecast. Conditions will be even warmer on Mon.

Snowpack Summary

10 to 20 cm of snow now lies on the April 11 crust that is found on N aspects to 2300m and to ridgelines on solar aspects. This is becoming soaked by rain as of late Thursday evening. The deeply buried February Facets and early season Basal Facets remain weak and will likely wake up with significant and sustained heating.

Avalanche Summary

Widespread Loose Wet activity is occurring as the falling rain soaks the fresh snow. These events have been up to size 1.5 running 10 to 15 cm deep over the April 11 crust on all aspects below about 2200m.

Confidence

Due to the number of field observations

Problems

Loose Wet

Even short bursts of solar heating can rapidly affect the snow this time of the year. With mild temperatures in the forecast, watch for rain to affect the snow at lower elevations.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Wind Slabs

Isolated and thin windslabs have been built in open features and can be found poorly bonded to crusts. Watch for these to grow or to become hidden with incoming snow and weakened with incoming rain.

The recent snow may now be hiding windslabs that were easily visible before the snow fell.Be cautious as you transition into wind affected terrain.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

Strong solar heating and rain will start to weaken the upper snowpack. A skier traveling through a thin spot or a large load hitting a slope such as a cornice fall or smaller avalanche could potentially trigger these serious slabs.

Pay attention to overhead hazards like cornices.Be aware of the potential for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Apr 20th, 2014 4:00PM