Avalanche Advisory published on January 28, 2020 @ 6:58 am
This advisory is valid for 24 hours
Issued by Steve Reynaud - Tahoe National ForestT_h
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How to read the advisory

Increasing winds will create wind drifted snow in near and above treeline areas today.  MODERATE avalanche danger will exist in near and above treeline areas due to wind slabs, with  LOW avalanche danger in below treeline terrain.


  • Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
  • Natural avalanches unlikely; human-triggered avalanches possible.
  • Small avalanches in specific areas; or large avalanches in isolated areas.
weather

A weak low pressure system will move past our area to the north today.  There is a slight chance of some light valley rain and mountain snow in the northern portion of the forecast area.  SW winds will increase into the strong to gale force range over the higher ridges this afternoon.  Temperatures cool for Wednesday as high pressure starts to build into the region with a NE flow.  NE winds could gust as high as 70-85mph over the upper exposed ridges on Wednesday.  A warming trend builds into the weekend with well above average temperatures into Saturday. 

recent observations

Observations from Mt. Judah (Donner Summit area) showed a mostly stable snowpack.  Light rain was falling on Donner Summit in the morning with a breakable surface crust below 7500'.  Wind slabs were non reactive on multiple test slopes below 7800'.  Blowing snow and larger new cornices were seen above 8000' along the summit ridge.  Snowpack tests targeting the Jan 4 weak layer showed this layer has gained strength and failure of this layer is unlikely moving forward. 

Similar conditions were seen at Blue Lakes (Carson Pass area).  Breakable crusts existed below 8000', with over 1' of snow in wind blown locations above 8000'.  Buried surface hoar was found beneath the newest crust.  Multiple snowpack tests and informal observations did not indicate that this layer was a concern.

Both locations reported multiple small D1 loose wet avalanches that occurred during the recent rain events. 

Avalanche Problem #1: Wind Slab

Human triggered wind slab avalanches will be possible today in near and above treeline areas.  SW winds have increased this morning and are forecasted to be in the strong to gale force range today.  Blowing snow should be limited to areas near and above 8000', above the recent rain where lighter snow that can be wind transported exists.  Wind slabs are expected to be larger along the Sierra Crest where 6 to 8'' or more of recent storm snow exists for wind transport. 

Blowing snow, built out cornices, scoured ridges, and wind pillows will all be clues to where new wind slabs exist.  Use caution around these areas and manage terrain to avoid areas of concern.   

CURRENT CONDITIONS  CURRENT CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
0600 temperature: 18 to 31 deg. F.
Max. temperature in the last 24 hours: 27 to 35 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 25 to 45 mph
Maximum wind gust in the last 24 hours: 62 mph
New snowfall in the last 24 hours: inches
Total snow depth: 46 to 56 inches
Two-Day Mountain Weather Forecast  Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
  Today Tonight Wednesday
Weather: Mostly cloudy then becoming partly cloudy. Slight chance of snow showers in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 10%. Clear. Snow levels below 7000 feet. Chance of precipitation is 0%. Sunny then becoming partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 34 to 40. deg. F. 17 to 22. deg. F. 34 to 39. deg. F.
Wind direction: Southwest 15 to 25 mph with gusts to 40 mph. West around 15 mph with gusts to 30 mph in the evening shifting to northeast up to 10 mph. East to northeast around 10 mph. Gust up to 25 mph.
Wind speed:
Expected snowfall: Little or no accumulation. | SWE = trace to none. in. No accumulation. | SWE = none. in. No accumulation. | SWE = none. in.
For 8000 ft. to 9000 ft.
  Today Tonight Wednesday
Weather: Partly cloudy. Slight chance of snow showers in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 10%. Clear. Snow levels below 7000 feet. Chance of precipitation is 0%. Sunny then becoming partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 28 to 33. deg. F. 15 to 20. deg. F. 29 to 35. deg. F.
Wind direction: Southwest 25 to 45 mph with gusts to 60 mph. Northwest to north 15 to 30 mph. Gusts up to 45 mph. Northeast 25 to 35 mph with gusts to 60 mph.
Wind speed:
Expected snowfall: Little or no accumulation. | SWE = trace to none. in. No accumulation. | SWE = none. in. No accumulation. | SWE = none. in.
Disclaimer

This avalanche forecast is provided through a partnership between the Tahoe National Forest and the Sierra Avalanche Center. This forecast covers the Central Sierra Nevada Mountains between Yuba Pass on the north and Ebbetts Pass on the south. Click here for a map of the forecast area. This forecast applies only to backcountry areas outside established ski area boundaries. This forecast describes general avalanche conditions and local variations always occur. This forecast expires 24 hours after the posted time unless otherwise noted. The information in this forecast is provided by the USDA Forest Service who is solely responsible for its content.

For a recorded version of the avalanche forecast call (530) 587-3558 x258