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 6:58 AM by Brian McCall

Highlights

Over a foot of new snow fell in some areas of the Aspen zone in the last 24 hours. Near and above treeline, winds shifted from a Westerly direction to Northeast around sunset. Some areas of the zone may have seen East winds as well. These winds were strong enough to transport the new snow at times so look for slabs to have formed on many aspects near and above treeline. This combination of wind and some heavy snowfall will bump our danger up to for the weekend.

danger. Over a foot of new snow and stronger winds at higher elevations. Forecast is here

Avalanche danger in the Aspen zone has increased for Saturday with the combination of new snow and stronger winds during the last 24 hours.

You will find danger on all slopes above treeline today.

At treeline you will find pockets of danger on steep wind loaded slopes on all aspects. Danger is on all slopes below treeline today.

Snow & Avalanche Discussion

Winter has returned to the Aspen zone during the last two days after a period of warm and dry weather. During the last 24 hours, weather stations are showing 5-7" of new snow at Aspen Mountain, Independence Pass, and Sunlight. Periods of heavier snow fell yesterday at McClure Pass, Marble, and Schofield bringing upwards of 1 to 1.3" of water equivalent at the Snotel stations there and likely 12 to 15" of new snow. Snowmass also picked up higher totals with around 10" in the last 24 hours. Storm totals for the last two day are 12 inches or more for most areas in the zone. Access to wind data is somewhat limited this morning, but it looks like those upper level winds did shift from the West, to North and Northeast throughout the day yesterday. We may have seen some stronger East winds in some locations around the zone as well. Expect to find new wind slabs that have formed on most aspects above treeline today. At treeline, keep an eye out for pockets of new winds slabs in steeper terrain. A period of stronger Northerly wind is in the forecast for later today as well, so the loading may not be over just yet.

The warm weather of the past week generated some isolated wet slide activity, especially on the sunnier Southeast, South, Southwest, and West aspects. Cooler weather yesterday and some single digit temperatures this morning will lock up that old snowpack and end any wet slide threat. The primary concern for this weekend will be new snow and the new wind slabs sliding on the old snow surface. Carefully evaluate that interface in the upper snowpack and see how well the new snow has bonded. Where wind loading occurred, slabs up be 2-3 feet thick and easily triggered in steep terrain. At lower elevations out of the effects of stronger wind speeds, new snow may sluff easily in steeper terrain as well. With many persistent weak layers buried in the middle and lower snowpack, areas of the Aspen zone with a shallower snowpack may see the isolated avalanche today that fails in these old snowpack layers. If this does occur, expect large avalanches to be the result.

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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