Colorado Avalanche Bulletins

This bulletin is from the CAIC, which is an agency of the State of Colorado.

Colorado Avalanche Information Center (CAIC) Advisory

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Issued 03/20/2010 7:10 AM by Brad Sawtell

Highlights

Colder temperatures have locked up the pre-existing snowpack. The primary concern is the storm snow sliding on the old snow surface.

Choose your terrain carefully by avoiding terrain traps and slopes where slides could carry you into trees, rocks, or over cliffs. Slabs have formed in unusual places because the wind direction has changed several times in the last 36 hours.

Be alert on all slopes when travelling through the near treeline elevation band to above treeline areas. Slab formation will be inconsistent.

Winter is back and is still here.

The avalanche danger for the Sawatch zone is on all aspects near and above treeline. New snow and wind has formed triggerable slabs on a variety of aspects. Inspect the new snow, old snow interface for bonding. Below treeline the danger is .

Snow & Avalanche Discussion

Winter is back...for the weekend. Temperatures have plummeted, winds were breezy at the higher elevations and we received some snow around the zone. Remote weather stations indicate a consistent five to seven inches over the last 24 hours...Ski Cooper reporting seven. Wind directions came from the South, then northeast and east. Today they have shifted again to the Northwest. The only avalanche to report came in from the Chaffee County Road and Bridge Department. Details are not clear but workers reported yesterday a large sized natural avalanche that crossed County Road 162, which is on the way up to the town site of St. Elmo, West of Nathrop. Debris covered 150 yards of roadway. I assume the avalanche occurred on the north side of Boulder Mountain.

Today, the avalanche problem will mostly involve the new snow. Wind directions have changed drastically over the last 36 hours, so do not expect much in the way of consistency with loading and slab formation.

Although the snowpack has received a good freeze, do not rule out the possibility of triggering a deeper avalanche. Once the temperatures come back to normal and the surface layers settle, we still will have a deep slab instability problem.

If you venture into the backcountry today, expect tender fresh slabs growing like weeds on a variety of aspects near and above treeline.

Slabs will thicken through the day, especially on lee aspects facing East through South. Cross loaded areas will be a concern as well on Northeast and Southwest aspects. Cracking and natural avalanche activity will be the two frequent natural signs of instability. Inspect the new snow, old snow interface on each slope. Bonding will likely vary greatly across each slope. Because the new snow fell on a warm surface, expect to find small facets formed at the interface. New snow and clearing skies allow for some interesting decision making. Do not let your guard down.

Weather Discussion

A trough of low pressure is moving southeast out of Colorado this morning. Associated moisture was stubborn to leave some mountain locations, such as the Northern San Juans, but any remaining clouds will dissipate by mid-morning. Sunny skies will give way to scattered afternoon clouds. Northerly flow will keep temperatures seasonably cool. Clear skies tonight contribute to a cold start on Sunday. High pressure approaching from the west and mostly sunny skies allow temperatures to rebound nicely with high temperatures about 15 degrees warmer. Winds back to westerly on Monday, temperatures remain mild, and afternoon clouds increase in advance of the next storm system.

Unsettled weather is likely for Tuesday and Wednesday with more mountain snow.

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