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Avalanche Forecast

Mar 11th, 2013–Mar 12th, 2013
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: South Rockies.

Forecasted precipitation quantity vary spatially for the region. This forecast takes into account where most amounts should occur, most likely the S part of the region.

Confidence

Poor - Forecast snowfall amounts are uncertain for the entire period

Weather Forecast

Monday Night and Tuesday: The first of a series of systems approaching the interior is expected to start spreading precipitation over the region early Tuesday. Light to moderate precipitation amounts (around 15 mm water equivalent in areas in the SW part of the region) are expected with strong SW winds. Freezing level will start rising to reach around 1700 m. and will stay high for the rest of the period.Wednesday: Precipitation easing off but still some moisture available. Winds are forecasted to be strong to extreme from the W. Temperatures staying warm and freezing rising near 2000 m.Thursday:Light precipitation is expected with similar freezing levels and lighter winds switching from the SW.

Avalanche Summary

There was report of a size 3 skier remote triggered on an East facing slope in the region. The avalanche is suspected to be a recent windslab sliding on an old surface. Otherwise, no other avalanches were reported.

Snowpack Summary

A trace of new snow overlies a variety of surfaces; hard wind slabs lee of N, SW and W winds in alpine and treeline features, a well developed surface hoar in shaded areas above 1700 m., a melt-freeze crust below that elevation and a 3 cm sun crust on solar aspects at all elevations. The forecasted precipitation and warm temperatures will add a good load to the snowpack (fair bit of uncertainty about quantities, but right now looking like 20 mm in water equivalent until Thursday). I suspect that the variety of surfaces described previously will become gradually more reactive as the load add up starting tomorrow. This could also make the 30 cm deep surface hoar layer that has been reactive to skier traffic (see avalanche observation section) even touchier, creating a potential for even larger avalanches.

Avalanche Problems

Storm Slabs

  Precipitation and warm temps are expected in the days to come creating new storm slabs at all elevations, new wind slabs lee of strong SW winds in the alpine and treeline.
Make conservative terrain choices during periods of heavy loading from new snow, wind, or rain.>Watch for clues of instability like whumphing and cracking in the snow.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 5