Eastern Sierra - Sun Mar 14 2010
Eastern Sierra avalanche advisory |
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The avalanche danger is MODERATE on any slope approaching 35 degrees or steeper with recent deposits of wind drifted snow. Cross-loading may have created unstable slabs on southeast and northwest facing slopes as well. Watch for sluffing as daytime solar energy bombardment on mid to upper elevation west to south to east aspects creates surface wet snow instability. |
After a windy and cold Saturday, there will be a noticeable change today. Temperatures will warm up considerably from the cold temperatures yesterday. The strong, northwest winds from yesterday have diminished to reasonable levels As the day heats up, the snow closest to the surface could start to lose cohesion. This loss of cohesion facilitates unstable conditions and can result in wet snow avalanches. While it might be too early to see much surface instability today, by tomorrow, expect to see an increase in point release wet snow avalanches.
After the windloading that occurred yesterday, there will be some touchy slabs along exposed ridgelines, as well as some crossloading on open bowls and in gullies. Yesterday’s winds varied from northwest to northeast, so west-, south- and east-facing slopes have been loaded. During the storm two days ago, wind directions were from the southwest to west. This means be suspicious of all steep slopes just off the ridges and the top sections of gullies. In cross loaded gullies avoid the loaded side. Yesterday in the Rock Creek area, northwest winds loaded slopes just below the tops of the ridges. Observers reported similar wind loading patterns just below the ridges in Bishop Creek yesterday.
Safe travel requires making good observations of obvious clues like whumpfing and cracking and recent avalanche activity. Choose terrain that gives you many options to reduce risk and avoid terrain traps like narrow gullies or skiing below avalanche paths. Look for small slopes, avoid cross loaded slopes, and trees, and avoid the big convex slopes and gullies.
After a cold night, sunny skies will grace the eastern Sierra today and Monday. The upper low is east of us, leaving lingering northerly winds blowing this morning from 15-25 mph with gusts to 45 mph over the higher terrain. High temperatures will be 10-15 degrees warmer today than yesterday with highs around 40 at the 8,000 to 9,000 ft elevations. Higher terrain will warm up from the mid 20’s of yesterday to the mid and upper 30’s today.
A gradual warming trend over the next three days will bring highs up to around 50 by Tuesday at the 8,000 ft elevations and the low 40’s in the higher terrain.
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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