Some small, Loose Dry snow surface instabilities have been observed in the BWRA's new snow. Warm temps today through next Tuesday may cause these surface instabilities to change from Loose Dry to Loose Wet avalanches on sunny aspects. Loose Wet sloughs have a better chance of entraining more snow and building momentum into bigger, more destructive avalanches. North aspects and cold, clear nights are still supporting the faceting process near the surface and within the snowpack - watch for persistent weaknesses in steep (37 degrees or greater), shaded terrain features.
The Bottom Line: Generally stable conditions with only minor Loose Dry sloughs observed in the BWRA. Warm temps through the weekend will increase the likelihood of Loose Wet avalanches on sunny aspects.
Discussion: Soft (F and 4F) Storm Slabs and Wind Slabs formed across the BWRA during the storm event and vary in thickness up to about 30cm deep; none have shown shooting cracks or propensity to slide on the old snow surface or on failure planes within the new snow.
The new snow load, even where wind-loaded, was not enough to trigger persistent weaknesses on north aspects or elsewhere in the BWRA. Sunny aspects still have the very strong melt/freeze crust to support the new snow, and the new snow appears to have bonded well to this crust.
The new snow appears to be bonding well to the old snow surface; failure planes have been identified within the new snow layer in small column tests (CT's) though they have not shown any propagation in larger column tests (ECT's) or when ski- and sled-testing small slopes and pockets of windslab.
One observer reported a D2 Storm Slab / Wind Slab avalanche on Sunday on a N aspect near treeline in the Mammoth area triggered by his party, no one was caught. Other observers in the Virginia Lakes area report generally stable conditions with only minor surface sloughing.
Combinations of slabs and faceted layers persist on cold, shaded aspects near and above treeline in the BWRA, though they have not been reactive in the recent storm event, or in column tests or slope tests.
Forecast: High pressure, warm temps, and light winds through Tuesday should bring another melt/freeze cycle to the mountain snowpack. A Pacific Trough low pressure system may reach the CA coast next Wednesday, bringing cooler temps and chance of precip, though snow/rain is expected to be light.
Storm Event: Snow started falling in the BWRA last Friday afternoon and ended Tuesday around 1700. The storm came in cold (27 degrees F) and remained well below freezing throughout the precipitation period. The bulk of the precip occurred Friday afternoon through Saturday morning for 10" of accumulation. Leavitt Lake picked up another 4" Saturday afternoon and overnight. Scattered snow showers continued Sunday morning through Tuesday morning, adding a few more inches in parts of the BWRA.
Light/moderate variable winds (mostly SW-W-NW-N-NE-E) throughout the precip event created soft (4F) wind slabs in leeward pockets near and above treeline in the BWRA.
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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