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Archived

Avalanche Forecast

Mar 27th, 2013–Mar 28th, 2013
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Glacier.

Cornices and daytime heating are the two big concerns today.  Watch for changing conditions throughout the day, and with changes in elevation and aspect.

Weather Forecast

A weak ridge will remain over the area today bringing mostly sunny skies.  The sun is expected to "pack a punch" today - i.e. strong solar radiation and heating.  We had little overnight recovery in temperatures, so the snow can be expected to get moist earlier in the day.  Another small disturbance will move through on Thursday.

Snowpack Summary

The generally well settled snowpack is being affected by strong solar radiation.  North aspects are remaining cool, but sunny aspects and all lower elevations are warming up substantially during the day.  Thin snowpack areas will be most susceptible, specifically on S and W aspects.  Several PWLs (mostly buried sun crusts with SH) are still active.

Avalanche Summary

More very large avalanches were observed in the Selkirks yesterday.  Most of these were triggered by cornice failures.  Near Glacier Park, a size 4.5 slab was reported, triggered by a cornice fall.  Cornice triggered avalanches have increased throughout the area, with warm daytime temperatures.  Moist avalanches were noted at lower elevations.

Confidence

Avalanche Problems

Cornices

Cornices are large and unsupported. Wide fluctuations in diurnal temperatures are increasing their fragility.  If the cornice doesn't get you, the resulting avalanche may.  Reports of cornice triggered slides to size 4.5 have been reported!
Cornices become weak with daytime heating, so travel early on exposed slopes.Give cornices a wide berth when travelling on or below ridges.

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

Elevations: Alpine.

Likelihood: Likely

Expected Size: 2 - 4

Persistent Slabs

PWL's are becoming stubborn, but should not be discounted.  Slopes receiving direct sun become more reactive during the day with warming. This is most likely on steep solar aspects where buried crusts exist, but northerly aspects are not immune.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.

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

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Loose Wet

The sun will be strong today.  Avoid terrain traps where moist slides could pile up deeply.  Solar triggered avalanches are most likely around exposed rocks and may trigger deeper slabs.
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: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2