THIS AVALANCHE FORECAST EXPIRED ON April 18, 2020 @ 6:59 am
Avalanche Forecast published on April 17, 2020 @ 6:59 am
Issued by Steve Reynaud - Tahoe National Forest

Scattered showers and thunderstorms will become possible today.  Loose wet and wet slab avalanche problems will continue for our area.  MODERATE avalanche danger will exist 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: Loose Wet
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A better refreeze of the snow surface overnight with temperatures at or below freezing at most locations above 8000'.  Partly sunny skies this morning with warming temperatures will melt the snow surface and break down existing melt freeze crusts.  Scattered showers or thunderstorms could increase this loose wet avalanche problem.  Rain could dissolve existing bonds within the upper snowpack accelerating the melt process.  Avalanche activity and size will be dependent on how much warming is received and potential rain at your specific location.   

This is a good day to get an early start with a potential shorter window for recreating in the mountains.  Thunderstorms with possible lightning could be a concern as the day progresses.  Avoid steep terrain and deep wet snow where the surface crust is no longer supportable. 

Avalanche Problem 2: Wet Slab
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Wet slab avalanches failing on the March 24 buried surface hoar layer continue to remain a concern.  The buried surface hoar layer, down 1 to 2 feet deep, has showed improved strength over the last couple days at multiple locations.  Wet slab avalanches are notoriously difficult to forecast with a high degree of uncertainty as to the likelihood of occurrence.

Timing and terrain choices can help limit exposure to these wet slab avalanches.  Avoid deep wet snow and steep terrain later in the day as the snowpack loses supportability.  

recent observations
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Observations from Mt. Houghton (Mt. Rose area) and Stevens Peak (Carson Pass area) both showed a good overnight refreeze of the snowpack.  Melt freeze crusts started to soften as early as 9am with good corn snow between 9-11am in sun exposed areas. 

Observations targeting the March 24 buried surface hoar were repeated on Mt. Judah (Donner Summit area).  Observations from April 13 showed unstable snowpack test results on the buried surface hoar layer while yesterday showed no unstable results.  An improvement in stability on this layer has been seen in multiple locations over the last couple days.

Diurnal melt freeze conditions exist on all aspects.

Weather and CURRENT CONDITIONS
weather summary

Partly sunny skies and warming temperatures this morning will quickly be replaced with increasing clouds, scattered showers, and possible thunderstorms.  Lightning will also be a concern today-mainly along the Sierra Crest.  A few inches of snowfall or a snow/graupel mix could occur above 8000', with scattered rain showers at lower elevations.  Unsettled spring weather will continue through Monday. 

 

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 28 to 32 deg. F.
Max. temperature: 45 to 54 deg. F.
Average ridgetop wind direction: E
Average ridgetop wind speed: 10 to 25 mph
Maximum ridgetop wind gust: 48 mph
New snowfall: 0 inches
Total snow depth: 53 to 77 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Friday Friday Night Saturday
Weather: Mostly cloudy. Isolated snow showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Snow levels below 7000 feet increasing to 7500 feet in the afternoon. Chance of precipitation is 50%. Mostly cloudy. Slight chance of thunderstorms in the evening. Scattered showers. Snow levels 7500 to 8000 feet. Chance of precipitation is 50%. Partly cloudy. Scattered showers. Snow levels 7000 feet increasing to 8000 feet in the afternoon. Chance of precipitation is 25%.
Temperatures: 44 to 50. deg. F. 29 to 34. deg. F. 45 to 51. deg. F.
Mid Slope Winds: Light winds. Light winds. Light winds becoming west 10 to 15 mph in the afternoon.
Expected snowfall: Little or no accumulation. | SWE = less than 0.10 inch. up to 1 inch above 7500 feet. | SWE = up to 0.15 inch. No accumulation. | SWE = trace amounts.
For 8000 ft. to 9000 ft.
Friday Friday Night Saturday
Weather: Cloudy. Isolated snow showers in the morning, then numerous showers and slight chance of thunderstorms in the afternoon. Snow levels below 7000 feet increasing to 8000 feet in the afternoon. Chance of precipitation is 60%. Mostly cloudy. Widespread showers and slight chance of thunderstorms in the evening, then isolated snow showers after midnight. Snow levels 8000 feet. Chance of precipitation is 55%. Partly cloudy. Scattered showers. Snow levels 7000 feet increasing to 8000 feet in the afternoon. Chance of precipitation is 25%.
Temperatures: 38 to 44. deg. F. 26 to 31. deg. F. 39 to 45. deg. F.
Ridge Top Winds: East 15 to 25 mph in the morning becoming light. West 10 to 15 mph. West 10 to 20 mph.
Expected snowfall: 40% probability up to 2 inches. 60% probability little or no accumulation. | SWE = less than 0.15 inch. 70% probability up to 2 inches. 30% probability of 2 to 4 inches. | SWE = up to 0.25 inch. 30% probability up to 1 inch. 70% probability no accumulation. | SWE = trace amounts.
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