Eastern Sierra - Sat Feb 13 2010

Today the avalanche danger is estimated to be mostly LOW. Recent dry weather has resulted in a relatively stable snowpack. Generally safe avalanche conditions exist, but continue to watch for isolated shallow wind slabs along upper elevation ridgelines and in alpine terrain. Use extra caution on slopes steeper than 35 degrees in shallow, rocky areas or steep rollovers. This information does not apply to developed ski areas or highways. This advisory describes general avalanche conditions and local variations always occur.

 

The dry weather and gradual warming trend of the past few days has left us with generally stable avalanche conditions on most slopes throughout our advisory area. If you look hard enough, you may find two exceptions: hard slabs leftover from Tuesday’s moderate to strong winds and wet loose avalanches. The wind slabs are found in isolated, pockety areas along and right below ridgetops on northwest to east facing slopes.

Wet snow instabilities are becoming more common on east to southeast facing slopes around rock ridges and outcrops. Reports of sunballs and small wet point releases came in yesterday from the Pine Creek and Convict Canyon area. If you are traveling below cliffs, ridges and in narrow depressions and gullies surrounded by rocks, wet snow avalanches can start with little or no disturbance from humans to slide. Wet snow instability can sometimes be assessed by pushing snow onto test slopes with no one below.

With a dry and warm weather forecast, there will be more wet snow instability. North slopes above 9,000 ft are receiving more of the sun’s energy than a month ago, but the snowpack remains colder than more sun exposed and wet snow instability is likely a month or more away. By mid week, there is a possibility the avalanche danger from wet snow avalanches could increasee on east to south facing slopes while the north, shaded slopes remain generally stable.

I visited the Rock Creek area yesterday and found a shallow snowpack with rounding facets at the bottom. Instability tests were inconclusive with ragged shears and moderate to hard results. While I need more data to form a conclusion in other areas, it seems reasonable to assume the bottom layer of weak faceted snow is becoming stronger.

The prospect for stormy weather is pretty bleak right now as high pressure has found a home above the West Coast. Storms are hitting the ridge and moving north into eastern Oregon and Washington. The Sierra Crest could see a couple of snow showers on Tuesday, otherwise, it will be dry, clear and warm for the week.

Temperatures at the 8,000 to 9500 ft elevations will be in the mid to upper 40’s today. Higher elevations will reach the upper 30’s and low 40’s. Night time lows will be in the single digits and teens in narrow confined valleys at high elevation locations, otherwise lows will be in the mid to upper 20’s. Winds will be light through Monday.

There is a chance the MJO could affect our weather on or after the 10th of March.

---

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.

---

ESAC is operating on a limited budget and is supported by its members and the community. Please help support the Center by becoming a member today. Visit the Support area for more information.