The warm temps last night, and increasing clouds and warm temps this afternoon may result in a window of opportunity for Loose Wet avalanches on steep terrain, especially in areas protected from wind (winds are expected to increase through today, which may cool the snow surface - particularly at higher elevations). Cooler temps, higher winds, and cloud cover through early next week should mitigate much of these wet snow instabilities.
The Bottom Line: The snowpack is generally stable on all aspects and elevations. Shallow wet snow instabilities develop with the daily warming of surface snow. It is still possible to trigger small Loose Wet avalanches in steep terrain, especially where the wet surface snow overlies hard, smooth crusts below.
Discussion: The BWRA experienced a wet avalanche cycle last Sat, Sun, and Mon - small natural- and human-triggered Loose Wet and Wet Slabs - as cloudy skies, warm days, and overnight warm temps prevailed. Clear skies and cooler overnight temps on Tues, Wed, and Thurs returned the snowpack to a melt/freeze cycle and less avalanche activity. Last night, temps remained well above freezing with a low of 38degF, though clear skies probably allowed a thin crust to develop.
The snowpack has been through long-term melt/freeze cycles, and as a result, free water drainage is well established and temp profiles are relatively flat (nearing isothermal in many places). Almost all layers below 9800' are showing a trend toward rounding. Pockets of cold, dry, weak snow persist near and above 10,000' on shaded aspects and shaded snow cover. Column tests have revealed mostly difficult or no failures on small columns, and no failures in standard extended column tests.
The snow surface on E-S-W aspects has been in a melt/freeze cycle for the last four days, yielding decent skiing from mid-morning to early afternoon; North aspects and shaded snow cover remain cold or frozen much of the day with clear skies.
A snowpit yesterday on a SE aspect at 9800' revealed the easiest failure in a small column test that I've seen in a while: CTM (11) RP. The failure occurred in a layer of weak, clustered rounded grains sandwiched between two layers of water ice about 30cm down from the surface.
A non-standard extended column test (total length of column=120cm) targeting that same layer did not fail until I forced my shovel blade behind the column, which caused a Sudden Planar failure, and the whole column popped off its base and onto the floor of the snowpit. A very significant warming event - such as prolonged heavy rain - could activate this layer; I suspect the current and expected diurnal melt/freeze regime will not activate this layer.
Snowpits on N and E aspects in the 9500' elevation band revealed predominantly rounded or frozen layers and difficult or no results from column tests.
Overnight in the BWRA, temps remained well above freezing (low of 38degF), though clear skies probably allowed snow surface cooling. Today will be warm and sunny with increasing clouds and winds this afternoon and cooler temps tonight and tomorrow.
High pressure today shifts to the East to be replaced by a weak system approaching from the Pacific Northwest coast. The weak system and cold front will bring an increase in winds and clouds this afternoon and overnight, though no precip is expected as far south as the BWRA.
A colder, stronger system moves through the area Sunday night and Monday, bringing higher winds, cloud cover, cooler temps, and precip north of Highway 50. Another high-pressure ridge sets up over CA/NV by mid-next week.
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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