A few small Wet Loose avalanches have been observed in the BWRA, though they have remained shallow and have quickly lost momentum as soon as the slope angle decreases. Wet Slab avalanches are possible on steep terrain (37 degrees or greater) if we get enough warming and water percolation in the snowpack to lubricate the surface of the prominent melt/freeze crust, and/or free water reaches persistent weak layers on predominantly Northerly aspects.
The Bottom Line: The snowpack is generally stable with minor surface wet snow instabilities. Significant warming and water percolation could lead to failure at the interface between surface snow and the hard melt/freeze crust below, and at persistent weak layers (PWL's) deeper in the snowpack.
Discussion: Surface and near-surface snow conditions remain fairly consistent as the very supportive melt/freeze crust underlying the surface snow remains widespread, and we have re-entered a melt/freeze cycle on all but due North aspects. The BWRA saw little precipitation (up to 4" at the Levitt Lake Snotel site) with Wednesday's brief storm event - old sowmobile and ski tracks were partly filled in. The snow surface is soft in many places (10-30cm deep) from soft Wind Slabs, well-preserved storm snow from 2 weeks ago, Wednesday's small contribution, and mid-day warm melt/freeze snow.
North aspects remain cold and dry at high elevations harboring PWL's though these layers have shown little propensity for failure or propagation in column and slope tests. Some north aspects have shown sastrugi development, possibly from the moderate to high winds Tuesday night and Wednesday.
The best chance for snow surface warming will probably be TODAY below 10,000' with sunny skies, warm temps, and light winds, and TOMORROW with cloudy skies (to retain heat), and warm winds...watch for isolated pockets of wet instabilities - some slopes (shaded aspects) and terrain features (steep, rocky features with thin snow cover) still harbor PWL's that could fail with significant warming and water percolation through the snowpack. A disturbance Sunday and a trough next week will bring cooler temps and cloud cover to the Eastern Sierra, reducing the likelihood of wet avalanches.
Yesterday, most snow surfaces below 10,000' were moist a few centimeters down - not enough to cause significant instability. One new small Wet Loose avalanche was observed below the Five Fingers chutes above Leavitt Lake. Sastrugi had formed on a NNE aspect above 10,000' in the drainage west of Ski Lake, and similarly reported on North aspects by an observer in the Virginia Lakes basin.
A snowpit on a NNE aspect revealed cold, dry snow and persistent weak layers at the bottom of the snowpack; these layers showed little propensity for failure or propagation.
Digging for beacon practice on many flat areas and almost any aspect other than due North, has been very difficult due to the widespread melt/freeze crust that is up to 60cm thick and interlocked with water ice forms.
An upper level ridge keeps the BWRA in a warming and drying trend through Saturday. A disturbance moves north of the BWRA on Sunday, bringing cooler temps and stronger winds, but not expected to bring precip this far south. Next week's trough may bring light precip in the form of showers and possible thunderstorms.
This snowpack summary applies only to backcountry areas in the Bridgeport Winter Recreation Area. Click here for a map of the area. This snowpack summary describes general avalanche conditions and local variations always occur. This snowpack summary expires in 48 hours unless otherwise noted. The information in this snowpack summary is provided by the USDA Forest Service who is solely responsible for its content.
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