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Valid until Wednesday March 07th 2012.
Confidence: Fair as snowfall amounts vary widely. Must much more snow on West side and perhaps Northern areas up to 50 cm increasing hazard to high for all elevations in those areas.
Main Concerns: (Avalanche problems)
Wind Slab - Wind slabs are forming with West winds over night Sunday loading N E aspects and higher wind cross loaded and exposed terrain. Human triggering is Likely or possible in specific terrain features: steeper or unsupported wind loaded terrain. New slabs could be formed by fresher North West North winds Monday Tuesday redistributing snow and loading Southern SE aspects with new slabs. All of these wind slabs are a problem that will be found at tree line and in the alpine and will produce avalanches from small to just large enough to bury, injure or kill a person. Note if any of these wind slabs once triggered steps down to the wet storm slab it could be bigger..
Storm Slab - New snow forecast for Sunday may come in sufficient quantity depending on where you are on the island, to make for instability in the storm snow at higher elevations and on most aspects. These could produce avalanches from small to just large enough to bury, injure or kill a person. Triggering could be probable in steeper or previously avalanche areas. Note: If started the storm slab could trigger a deeper wet slab or step down avalanche.
The island Alps received variable weather over the weekend. Light snowfall Friday at warm temperatures gave way to snow over night giving 15 to 30 cm snow, winds were only a factor at the higher elevations. Rain and above freezing temps developed Saturday until the evening when things cooled of and the snow showers started again. Winds have not been a factor due to wet snow and light speeds. Light snow and cooler temps prevailed for Sunday. The Outlook is:
Sunday/Monday: Snow starting later in the day Sunday and finishing Monday AM. with 20 to 30 cm possible. Winds increasing to moderate W. Freezing level around 600m and dropping.
Tuesday: clearing and cooling. Winds rising to moderate and strong from the W NW . Freezing level around Surface to 400m cooler in outflow affected areas EG: East coast.
Wednesday: Clear and cool give way to light snow in late day, more on the West and North. Winds continue North and switch when the precipitation starts to West to SW and a bit on the light side. The freezing levels rise to 900m or lower.
New snow is falling on buried crusts or a wet layer near surface. Wet storm snow from Saturday was shearing pretty easily down 25 on a rime/temperature crust from late Friday. The snow from late February sits in three layers above the Feb 14 crusts. A storm shear sits 60 down and weak faceted crust is below that and then the strong crust below that nearly 80 to 120 down. All layers are bonding well except where shallower than 50 cm. Steeper starting zone have shed most of the snow down to the mid Feb crusts and are repeating with each snow fall.
Saturday SC triggering of wind slabs and wet storm slabs on challenging terrain was producing numerous size 1.5 perhaps size 2 slides 30cm to with wind slab 60 deep. Mostly steeper slopes all aspects. Big mess and en training more loose wet storm snow on way down. Natural loose wet and pinwheels were observed below 1600 m.
- Enter the wind zone at tree line and above with caution during the forecast period. Monday with West winds loading NE E and SE aspects. Expected cross loaded and redeposited wind slabs on Southerly aspects. Note that hazard will increase as the wind shifts Monday with cool temperatures to NNW N.
- Wind slabs are often stiffer and may have pattern, watch for unusual distribution in the forecast period.
- Avoid steeper slopes and larger terrain.
- Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.
- Gradually increase your exposure to avalanche terrain as your information and repeated testing suggest. .
- Steep terrain may have crusts exposed that do not bond as well to the new or wind loaded snow.
- Crusts may not be supportive making travel and skiing difficult.
Prepared by Niko Weis