Avalanche Forecast

Issued: Mar 15th, 2014 11:09AM

The alpine rating is high, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs, Wet Slabs and Deep Persistent Slabs.

jlammers, Avalanche Canada

South Rockies.

Incoming weather combined with a complex snowpack means this is no time to be pushing into steep terrain. Conservative slope selection is critical to safe mountain travel.

Summary

Confidence

Poor - Intensity of incoming weather systems is uncertain on Sunday

Weather Forecast

Overview: A pacific frontal system will push inland on Saturday bringing moisture to the interior until early Monday morning. Expect a ridge of high pressure to develop for Monday and Tuesday. Due to significant weather model disagreement for Sunday, I have limited confidence in forecast snowfall amounts and freezing levels.Sunday: Moderate snowfall with the greatest amounts falling in the south / Moderate westerly winds with extreme gusts / Freezing level between 1700m and 2000mMonday: A mix of sun and cloud / Moderate westerly winds becoming northwesterly with strong gusts / Freezing level at 1500mTuesday: Mainly sunny skies / Light northwest winds / Freezing level at about 1200m

Avalanche Summary

A recent natural cornice triggered Size 2.5 avalanche was observed Smith Basin area north of Elkford. I expect a new round of storm slab activity with forecast weather. Rain at lower elevations may activate wet slab avalanches.

Snowpack Summary

Light to moderate amounts of new snow overlie crusts on previously sun-exposed slopes. The bond between the new snow and the freshly buried crusts is expected to be quite weak. With more snow and wind on the way, the size and reactivity of the developing storm slab will increase. Forecast rain at lower elevations may also reactivate potent wet slabs.The deep facet/crust persistent weakness buried at the beginning of February, now down up to 150cm, is still producing sudden results in snowpack tests. I would be very leery of any slopes that have not already avalanches as any avalanches at this interface would be large and destructive. Triggering will become more likely if forecast precipitation falls as rain.Cornices have also become large and potentially unstable.

Problems

Storm Slabs

Steady snowfall and wind will add to a developing storm slab problem. Expect touchy conditions, especially in wind exposed terrain or in places where the new slab overlies buried crusts.

Choose conservative lines and watch for clues of instability.>Be alert to conditions that change with elevation.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Wet Slabs

Forecast precipitation is expected to fall as rain at lower elevations with the potential to trigger deep and pushy wet slab avalanches. Be cautious of slopes that did not avalanche during the last big cycle.

Avoid steep unsupported terrain below treeline especially if the snow is moist or wet.>Avoid paths that have not avalanched recently.>Be alert to conditions that change with elevation.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Deep Persistent Slabs

In some areas the deeply buried weak layers that formed in early February are still showing significant reactivity in snowpack tests. Avalanches at this interface would be large and destructive and are possible at all elevation bands.

Consider the consequences of the terrain if an avalanche steps down to a persistent weakness.>Use conservative route selection, resist venturing out into complex terrain even if you observe no obvious signs of unstable snow.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Mar 16th, 2014 2:00PM