Avalanche Forecast

Issued: Apr 20th, 2014 4:11PM

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

tim haggarty, Parks Canada

Waterton Lakes.

Watch for warm temperatures and potentially some heavy precip this week. 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

Watch for moderate warming on Monday with a freezing level to 2700m and a few showers in the forecast. A poor recovery into Tuesday will allow further shower activity to weaken the snowpack further at lower elevations. Models are conflicted so far for Wednesday but we may see heavy precip. Watch freezing levels and precip amounts carefully.

Snowpack Summary

10 to 40 cm of snow now lies on the April 11 crust that is found on N aspects to 2300m and to ridgelines on solar aspects. Moist snow below 1800m on all aspects. 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 has been seen with rain soaked snow below 2000m. These events have been up to size 1.5 running 10 to 20 cm deep over the April 11 crust on all aspects below about 2200m.

Confidence

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

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.Travel early on frozen crusts before the heat of the day.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Wind Slabs

Isolated windslabs have developed in open features. These are becoming old however significant transport is still occurring. These may grow or become hidden with incoming snow or weakened with incoming rain.

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Deep Persistent Slabs

Solar heating and rain has weakened the upper snowpack BTL. With continued warming, 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.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Apr 23rd, 2014 4:00PM