Eastern Sierra - Sun May 2 2010
Eastern Sierra avalanche advisory |
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The avalanche danger rating is estimated to be LOW this morning and might increase to MODERATE by miday, depending on elevation, aspect and the wind. |
It was a cool and windy spring day yesterday. The sun came out and temperatures shot up to the mid 40’s above 9500 ft. The temperature at the Sesame Street study plot on Mammoth Mountain warmed up to 52 degrees while higher elevations at Ellery Lake and Tioga Pass reached 50F. The north winds kept elevations above 11,000 feet in the upper 30’s. Reports from the Tioga Pass area came from people finding hard and fast conditions in the sheltered chutes off the Dana Plateau and wet snow below about 9,000 to 9,500 ft depending on the aspect.
Even with the cold north winds blowing today, the sun did its work on all aspects in the Rock Creek and upper Hilton Creek area. Observations revealed numerous small point release sluffs and rollerballs coming from rock outcrops or the sides of gullies. Based on my observations during this alternating cold to warm weather of the last few weeks, I expect more wet snow activity today with the peak of the wet snow cycle occurring on Monday.
Temperatures will be a few degrees warmer today and Monday will also be warm before a cool down by Wednesday. Be aware of how soft and moist the snow is and don’t start kicking steps up a steep sun exposed gully at noon. Look for signs of instabilities such as roller balls originating near rock outcrops.
Stay well back from the edge of ridges until you are certain about any cornices. Avoid overhead exposure from steep rocky slopes and cornices, especially after prolonged sun-exposure.
My observer extraordinaire and colleague Josh has left for his real world job. Because there is now almost no data arriving from the field, this forecast is based primarily on my observations yesterday, weather observations from remote stations, forecast weather, and personal experience. Expect significant variability in conditions in each canyon and from one day to the next. You may find additional snowpack and avalanche information on Splitboard.com, Telemarktips.com forums.
It's easy to tell what's happening out there, but due to variability, lack of observations and the speed with which things can change, it's difficult to issue realistic danger ratings. The Low/Moderate ratings reflect average conditions, and may not indicate what's actually happening at any given time or place. Beware of rapid loss of strength in the snow, especially on south slopes if the sun comes out.
Cool gusty north winds could not keep temperatures from warming to the 50’s today at the 8,000 to 9,000 ft elevations. High pressure ridging over the eastern Pacific is giving us north winds that will continue for most of the day.
Mid elevations will reach the low to mid 50’s today with nights getting down to the upper 20’s. Higher elevations will reach the mid 40’s and elevations above 11,000 ft will be in the high 30’s with lows in the teens. Gusty north winds continue today with gusts to 55 mph at mid elevations and 65 mph over the ridge tops.
By Tuesday next week, cold temperatures and windy weather returns, though no precipitation is expected.
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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