Avalanche Forecast

Issued: Apr 12th, 2017 4:33PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Storm Slabs and Cornices.

Ruari Macfarlane, Parks Canada

Waterton Lakes.

Keep an eye on Thursday's weather - forecast freezing levels and precipitation vary between forecasts. Avalanche danger will depend on new snow amounts. Watch for temporarily elevated danger if rain falls on fresh snow in the lower Alpine.

Summary

Weather Forecast

Thursday: Rain (snow at Alpine elevations), 10-15mm forecast. Ridge wind: Moderate Southerly. Freezing Level 2200- 2500m. Treeline low 0.5, High 2.Friday: A mix of sun and cloud, the odd flurry. Ridge wind Strong SW. Freezing Level 1700m. Treeline Low -6, High -4.Saturday: Mostly cloudy, isolated flurries possible. Ridge wind: Moderate SW.

Snowpack Summary

A generally well settled spring snowpack, with thick supportive crusts at/near the surface. Rain at/below Treeline may soften these crusts. New snow in the Alpine will be redistributed by wind, building slabs on lee slopes.Well preserved, loose facets make up the lower snowpack in isolated Alpine areas. These have been unreactive for several weeks.

Avalanche Summary

On Tuesday, forecasters observed several small (Size 1) Loose Dry avalanches on NE - SE aspects, in extreme (unskiable) Alpine terrain. These happened as strong April sun hit cold new snow for the first time.

Confidence

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

Problems

Storm Slabs

New snow arrives in the alpine on Thursday. Rising winds Thursday into Friday will create storm slabs on lee slopes, which may be reactive where they overlie hard crusts.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Cornices

Cornices remain impressively large, and will increase in size and sensitivity with forecast snow, warmth and wind on Thursday.

Do not travel on slopes that are exposed to cornices overhead.Give cornices a wide berth when traveling on ridges.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Apr 15th, 2017 4:00PM