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 Center with an advisory posted on Sunday, May 11, 2008.

This is the last call for letters of support. For those of you from out of the area who use this service; let me know if you find it valuable for your trip planning. For locals and some of our business supporters and employees who use the advisories, a few minutes of your time will go a long way in keeping this service going.

Mountain Weather

For today, the main weather story will be the winds. A dry cold front will push through our area by late afternoon with warm air ahead of the front possibly bringing a few degrees of warming. Winds at the top of Mammoth are steady at about 45 mph this morning. Later today the winds will pick up along the 395 corridor with gusts to 30 mph. Above 10,000 ft, moderate west winds in the 20 to 30 mph range will be accompanied with gusts over 55 mph.

High temperatures at the 10,000 ft elevations in the Tioga Pass and Virginia Lakes areas will be in the low to mid 50s, while the southern Sierra around South Lake will be in the low 40s with cooler night time temperatures in the mid 20s.

By Monday, temperatures will drop 6-10 degrees as the front passes over the eastern Sierra. By Wednesday, a large ridge of high pressure both at the surface and aloft will build into northern California.

Snowpack and Avalanche Discussion

Over the last few days, lows have been creeping up into the mid 30s. This morning, the low was 39 at the 9,600 ft elevation at Leavitt Lake, 31 F at 10,000 ft on Tioga Pass and 32 on the 10,700 ft elevation at Gem Pass. These are the warmest low temperatures for the year at the higher elevations.

With lousy overnight refreezing, the safe window of skiing and riding is narrow today. The daily melt freeze cycle is strongly affected by cloud cover and warm air masses that do not allow the snowpack to refreeze. Freezing allows strength recovery with surface crust formation. The competing forces swing back & forth like a pendulum: frozen solid to slushy & mushy, bomb proof to natural wet avalanches.

With Sonora Pass open, many people are enjoying skiing, riding and snowmobiling. Wet slides are triggered by solar energy and skiers, but high marking snowmobiles make great triggers also. 13 out of 32 US avalanche fatalities this season were riding snowmobiles when they died.

Before this morning, the snow in higher elevation terrain around Tioga Pass, South Lake, Bishop Pass and Charlotte Lake was freezing hard at night. Though the snow was soft by 1 -2 PM, there were only a couple of small sluffs yesterday in the South Lake area around Mt Thompson. There is more sluff activity in the Tioga Pass area. After one observer reported firm snow on the east side of Gaylor Peak and good skiing around 10AM, later in the day a party triggered a slide on a long traverse after entering a steep gully.

For today, the avalanche danger rating is in the morning, increasing to on steep slopes above 35 degrees. There have been numerous smaller wet sluffs observed over the last week.

Bottom Line

For today, the avalanche danger rating is in the morning, increasing to on steep slopes above 35 degrees. There have been numerous smaller wet sluffs observed over the last week.

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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