Avalanche Forecast

Issued: Mar 8th, 2014 8:33AM

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

Avalanche Canada jcoulter, Avalanche Canada

More snow/rain=More Danger!Forecasted snowfall/rain will be higher in the south of the region. Danger ratings reflect the zones with higher precipitation amounts.South Rockies Blog

Summary

Weather Forecast

The large moist pacific system is poised to reach the South Rockies by Saturday evening bringing increased winds from the south and moderate to heavy precipitation overnight. The southern areas of the forecast region (Elk Valley South and Flathead) will see more precipitation than the north as the system is sticking close to the US/Canada border. Sunday will see continued rain and snow, with a possible dip in the freezing levels as the frontal system passes later in the day. Quieter, spring like weather should prevail for Monday, Tuesday.Ovn Sat: 2-5mm north/15-20mm in the south, with strong south winds as the system arrives. Freezing levels 1600-1800mSunday: 5-20mm with moderate west winds with strong gusts and freezing levels up to 2100m.Monday: No significant precipitation, sunny breaks with light west winds and freezing levels 1700-1800m

Avalanche Summary

Avalanches in clearcuts, road banks, lower angle terrain and non obvious avalanche paths continue to surprise backcountry enthusiasts throughout the region, so consider them carefully in your travel plans as danger ratings rise on Sunday. Avalanches in the region have the potential to run full path. As an example we got a report of an avalanche hitting the road during the day on Friday on Hartley Lake Road.Two recent avalanches on east aspects, size 2.5-3 were noted by the field team and other observers in the Crowsnest pass on Friday.In the Harvey Pass area there was a widespread natural cycle on Thursday with some avalanches up to size 3. Most avalanches are failing at the storm snow interface, but some are initiating or stepping down to the February 10th persistent weak layer, even in surprisingly low angle and gladed terrain.There was a report of a large avalanche in Thursday's cycle hitting the grooming about 4km before the Rolling Hills cabin near Fernie.On Thursday the South Rockies team reported a size 2.5 avalanche out of a north facing chute near Grave Lake that left 6 meters of debris on a logging road, blocking their return to the trucks.

Snowpack Summary

Some areas of the South Rockies (Elk Valley South and Flathead) received Thurday's precipitation as significant rain event below 1500m-1700m, while other areas like the Crowsnest, had dry snow below treeline under the influence of colder air. In areas above 1600m there is approximately 40-70cm of new storm snow sitting on top of the March 2 interface consisting of surface hoar, facets or a crust depending on your aspect and elevation . Forecasted new snow and rain, combined with warm temperatures, will likely create another storm slab avalanche cycle by Sunday. Moderate to strong SW winds will continue to create windslabs in alpine lee features and contribute to the already significant cornice growth..The mid pack still contains a layer of facets and/or surface hoar that is now down between 70-180cm depending on your location in the South Rockies. It is still showing good fracture character on snowpack tests, suggesting that it may be possible for storm slabs to step down to this persistent weakness. Check the South Rockies Blog for the latest snowpack discussion.

Problems

Storm Slabs

An icon showing Storm Slabs
New snow and rain will add to the storm slab sitting on a weak layer buried in early March. Windslabs and cornice growth continue to build in the alpine due to recent SW winds.
The new snow will require several days to settle and stabilize.>Avoid freshly wind loaded features.>Caution required around loaded road banks, cutblocks and other non obvious avalanche terrain>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Wet Slabs

An icon showing Wet Slabs
Slopes that are becoming rain soaked for the first time will be a particular concern. Loose wet slides are also possible in areas where rain soaked snow has lost its cohesion.
Avoid steep unsupported terrain below treeline especially if the snow is moist or wet.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
Large loads like cornices and storm slabs in motion have the potential trigger a persistent weak layer that is now buried between 100-170cm deep.
Use conservative route selection, resist venturing out into complex terrain even if you observe no obvious signs of unstable snow.>Consider the consequences of the terrain if an avalanche steps down to a persistent weakness.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

3 - 6

Valid until: Mar 9th, 2014 3:00PM

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