THIS AVALANCHE FORECAST EXPIRED ON February 12, 2019 @ 6:52 am
Avalanche Forecast published on February 11, 2019 @ 6:52 am
Issued by Steve Reynaud - Tahoe National Forest

MODERATE avalanche danger will exist today throughout the forecast region.  Human triggered wind slab and storm slab avalanches will be possible at all elevations. 

2. Moderate

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Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
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Large wind slabs and cornices that formed during the recent storm cycle may still be reactive today in near and above treeline terrain on NW-N-NE-E-SE aspects.  In addition, moderate to strong SW/W winds today and tonight will continue to build fresh new wind slabs.  Substantial amounts of storm snow is available for transport and these new wind slabs will continue to build in size today.

Look for blowing snow, cornice formation, wind pillows, and snow surface clues as to where wind loading is occurring.  Give yourself a wide safety margin around wind loaded terrain and large cornices.

Avalanche Problem 2: Storm Slab
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Storm totals range from 2 to 3' + of new snow over a 36 hour period.  Continued cold temperatures will slow down the settlement process of this new storm snow.  While most data suggest the recent storm snow is gaining strength, 1 report from yesterday showed propagation results from ECT's at the old snow/new snow interface along with a whumpf in the area.  Uncertainty exists about this weak layer and how widespread it could be.  Storm slabs will continue to be possible on all aspects in non-wind loaded terrain near and below treeline.

Look for cracking around skis or any signs of cohesion in the recent storm snow.  Whumpfing sounds would indicate that a weak layer is buried, reactive, and has the potential for remote triggering.  Loose dry sluffing will be possible in steep terrain where no storm slab exists and could pose travel concerns.

recent observations

*  On Andesite Peak (Donner Summit area), several natural wind slab avalanches were observed that occurred during the storm and were partially covered up by additional snow.  Signs of additional wind slab instabilities were limited.  Active wind transport was occurring and building fresh new wind slabs during the day.

*  A whumpf was reported on a SE aspect near Poulsens Peak (Squaw Valley area) with ECTP results at the old snow/new snow interface.  2 to 2.5' deep, the potential weak layer could be buried surface hoar and/or near crust facets.

*  2 to 3' of recent storm snow was reported from yesterday from multiple locations.  

Weather and CURRENT CONDITIONS
weather summary

Cold temperatures will continue with partly cloudy skies today and no snowfall expected.  SW/W winds will be in the moderate to strong range with gusts up to 60-70mph.  Winds will continue into Tuesday and increase into the afternoon as another storm begins to approach our area.  Wednesday and into Thursday, a warmer and wetter storm system impacts our region.  Lots of uncertainties exist as to snow levels and precipitation totals at this point.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: -2 to 9 deg. F.
Max. temperature in the last 24 hours: 18 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 20 to 40 mph
Maximum wind gust in the last 24 hours: 63 mph
New snowfall in the last 24 hours: Trace to 2 inches
Total snow depth: 101 to 130 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Monday Monday Night Tuesday
Weather: Partly cloudy. Slight chance of snow showers in the morning. Snow levels below 7000 feet. Chance of precipitation is 10%. Partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 5%. Partly cloudy then becoming mostly cloudy. Slight chance of snow showers in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 20%.
Temperatures: 22 to 27. deg. F. 10 to 16. deg. F. 28 to 33. deg. F.
Mid Slope Winds: Southwest around 15 mph with gusts to 35 mph. Southwest 15 to 20 mph. Gusts up to 30 mph increasing to 45 mph after midnight. Southwest 15 to 30 mph. Gusts up to 45 mph increasing to 55 mph in the afternoon.
Expected snowfall: No accumulation. | SWE = none. No accumulation. | SWE = none. 80% probability of no accumulation. 20% probability up to 1 inch. | SWE = less than 0.10 inch.
For 8000 ft. to 9000 ft.
Monday Monday Night Tuesday
Weather: Partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 10%. Partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 5%. Partly cloudy then becoming mostly cloudy. Slight chance of snow showers in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 20%.
Temperatures: 18 to 23. deg. F. 8 to 14. deg. F. 24 to 30. deg. F.
Ridge Top Winds: West 20 to 35 mph. Gusts up to 70 mph decreasing to 50 mph in the afternoon. Southwest 20 to 30 mph with gusts to 60 mph increasing to 25 to 40 mph with gusts to 75 mph after midnight. Southwest 30 to 40 mph increasing to 30 to 50 mph in the afternoon. Gusts up to 80 mph.
Expected snowfall: No accumulation. | SWE = none. No accumulation. | SWE = none. 80% probability of no accumulation. 20% probability up to 1 inch. | SWE = less than 0.10 inch.
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