Eastern Sierra - Sun Apr 4 2010
Eastern Sierra avalanche advisory |
The avalanche danger is LOW this morning. As new snow accumulates this afternoon and evening, there will be an increasing chance of triggering wind slabs on slopes steeper than 35 degrees and the avalanche danger will increase to MODERATE and possibly CONSIDERABLE by Monday morning. This storm has the possibility of producing locally heavy snowfall. |
The calendar reads April, but the conditions are more like January. It’s cold and windy, and most importantly, we are about to get a winter type storm complete with a foot or more of cold dry powder and strong gusty winds. New snow is going to fall on settled powder in the trees and firm slabby snow in exposed areas. While high snow ratios are expected, even dry light snow can be compacted by the wind. If the storm sweeps through tonight as forecast, those old surfaces will be loaded rapidly and the avalanche danger will rise.
My primary concern for tomorrow afternoon and Monday is wind slabs. Winds picked up last night and I expect strong southwesterly winds to drift old snow and storm snow rapidly near ridgelines and across exposed slopes at lower elevations. Crusts on sun-exposed slopes will limit the amount of snow available for transport. By Monday morning I expect you’ll find drifts near ridgelines, as well as some cross-loaded gullies and other features further downslope. Winds are expected to remain from the southwest and west direction and this means that windslabs will exist on mostly northerly aspects. On slopes steeper than about 35 degrees, these fresh wind slabs may be sensitive to the weight of a person
A winter storm will affect our area by this afternoon with increasing winds and snow showers. The upper elevations are looking at 1 – 2 feet of new snow falling overnight and into Monday morning.The National Weather Service has a Winter Storm Warning posted for our area from 5 PM this afternoon through 9AM Monday.
The jet stream will steer an unusually cold Gulf of Alaska low into the Sierra today. The core of the jet will drop south into southern Nevada and the entire Sierra is favored for snowfall. Snow begins this afternoon and continues into Monday morning. Heavy snowfall rates of over 2 inches per hour are expected tonight. Expect blizzard conditions over Conway and Deadman Pass this evening.
Easter Sunday will be cold cloudy and windy. Mid elevations will see temperatures in the upper 20’s and southwest winds gusting to 50 mph by afternoon. Elevations above 10,000 ft will see highs from 15-25 with west and southwest winds gusting to 60 mph by the afternoon.
After Monday, high pressure will build in, bringing warming conditions- until the weekend when another cold storm is due.
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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