Eastern Sierra Avalanche Bulletin

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Eastern Sierra Avalanche Center Report

These bulletins are now issued by the Inyo National Forest in conjunction with the Eastern Sierra Avalanche Center. The CSAC Avalanche Center (avalanche-center.org) takes absolutely no responsibility whatsoever for the content or technical accuracy of this information.

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Good morning, this is Sue Burak with the Inyo National Forests Eastern Sierra Avalanche Centers advisory posted for the week of May 27 to May 30, 2008.

This is the final avalanche advisory for the season.

Mountain Weather

The unusually cool to cold windy weather will continue until the end of this week. A massive low pressure system continues to rotate over California, sending out shortwaves that keep the weather unsettled and wet. Another upper shortwave rotates around the low over Mono County this morning, with storms beginning by 11AM.

The upper low is moving slowly east but the emphasis is on the word slow. Today will be a repeat of Tuesdays weather with early morning clear skies followed by rain showers by late morning. Freezing levels will be 9500 to 10,000 ft with possible snowfall in isolated areas near convection cells. The unsettled weather continues Thursday with a brief break on Friday.

Temperatures will be in the upper 30s at the 9,000 ft elevation and mid 30s at 10,000 ft. Higher elevations will see highs in the low to mid 30s for the next few days with lows in the 20s. Winds will be gusty around the storms with south and southwest winds gusting to 25 mph. The Owens Valley will have another windy day with gusty southerly winds in the 20 to 30 mph range.

The long range forecast is for thunderstorms and rain/snow showers for the weekend.

Snowpack and Avalanche Discussion

The downhill slide of snowpack loss has been temporarily and delightfully postponed by the cold wintery weather of the last week. The higher elevations of the eastern Sierra picked up 10 to 12 inches of new snow. The Sonora Pass area picked up a foot of new with over an inch of water. Bishop Pass picked up over an inch of water as did Mammoth Pass and the high elevation Gem Pass. Calm to light winds and cold temperatures made for a great day of skiing on Monday.

Wet slide activity increased yesterday with clear morning skies and late May radiation. Not much new snow accumulated yesterday and not much is expected for today. With the cold nights, the spring corn cycle is renewed and there is enough snow to slow the progress of sunup growth. The new snow is sluffing readily so position yourself and others to avoid getting caught in large spring slides. Any new snow will be more sensitive to the suns heating than older snow. Spring temperatures and sunshine are intense and will initially decrease the stability of any new snowfall on steeper slopes. Pay close attention to how deep the overnight freezes penetrate the snowpack.

Avalanche danger during this period of cool and unsettled weather is except on very isolated steep slopes with accumulations of fresh snow. Late spring radiation will rapidly transform winter pow to turn to sticky glop. After the new snow is melting, it doesnt take much time for wet snow sluffs to occur. The avalanche danger can be in these areas.

Bottom Line

Avalanche danger during this period of cool and unsettled weather is except on very isolated steep slopes with accumulations of fresh snow. Late spring radiation will rapidly transform winter pow to turn to sticky glop. After the new snow is melting, it doesnt take much time for wet snow sluffs to occur. The avalanche danger can be in these areas.

Please note that the avalanche danger rating in this advisory expires in 24 hours. This advisory is our best interpretation of snow pack conditions and NWS forecasts issued today. Backcountry travelers should be aware that elevation and geographic distinctions are approximate and that a transition zone exists between upper and lower elevations.

Avalanches do not happen by accident and most human involvement is a matter of choice not chance. Most avalanche accidents are caused by slab avalanches that are triggered by the victim of member of the victim's party. Even small slides can be dangerous. Always practice route finding skills and carry avalanche rescue gear. Remember that avalanche danger ratings are only general guidelines. Distinctions between geographic areas, elevations, slope aspects and slope angles should be made.

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