THIS AVALANCHE FORECAST EXPIRED ON April 8, 2020 @ 6:55 am
Avalanche Forecast published on April 7, 2020 @ 6:55 am
Issued by Brandon Schwartz - Tahoe National Forest

Don't be fooled by the danger rating. If you trigger a slab avalanche today it could be ugly and occur on a slope that already has many tracks on it. MODERATE avalanche danger exists at all elevations with persistent slab and loose wet avalanche problems.

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: Persistent Slab
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A skier triggered avalanche with persistent slab characteristics was reported yesterday on a slope with many previous tracks and it had wide propagation. Snowpit data from other areas and avalanches from Sunday are creating the picture of the possibility of continued persistent slab avalanches failing on barely faceted snow just below the crust at the old/new snow interface. So far this instability has been observed on N-NE-E aspects ranging from 6,800' to 10,100'. NW-N-NE-E aspects at all elevations are the main areas of concern. Avalanche size is expected at D2 with up to D3 possible.  Any avalanche of this type would involve all of the snow from this last storm, failing 1 to 3+ feet deep. Anticipate the possibility of additional avalanches occurring today on slopes with previous tracks and breaking wider than expected.

MODERATE danger persistent slabs are a difficult to manage low likelihood, high consequence situation if you choose to travel the slopes where they may lurk. The easy choices for managing this hazard are to simply say no thank you by choosing SE-S-SW-W aspects for avoidance or by entrenching on sub 30 degree slopes without steeper terrain above or to the side. Your compass and inclinometer are handy tools.

  Photo: Yesterday's avalanche on Relay Peak with many previous tracks and wide propagation.

Avalanche Problem 2: Loose Wet
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Warming today and periods of sunshine and solar radiation through and between the cloud cover will allow the strong April sunshine to create snow surface warming on all aspects. This surface warming and melt will allow for the possibility of loose wet avalanches today on all aspects. Avalanche size is expected at D1 to D2 depending on what the terrain is capable of producing.

Roller balls and pinwheels are indications of the presence of this avalanche problem. Consequences from even small loose wet avalanches can come from being pushed into or over rocks, trees, cliffs, and terrain traps below. Lower angle slopes can be used to avoid this avalanche problem.

 Photo: Loose wet avalanches yesterday on NE aspect of Flagpole Peak (Echo Summit area).

recent observations
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* A skier triggered avalanche with persistent slab behavior occurred yesterday afternoon on Relay Peak (Mount Rose area). This avalanche had wide propagation and there were many previous tracks on and adjacent to this slope when the avalanche was triggered. This avalanche likely failed on the underside of crust at the old/new snow interface. The avalanche occurred on an E aspect at about 10,100' in above treeline terrain.

* Snowpit data collected yesterday a short distance to the SW of Relay Pk on a NE aspect at 9,640' in near treeline terrain showed similar instability on barely faceted snow crystals on the underside of the crust at the old/new snow interface.

* Snowpit data and an intentional skier triggered avalanche reported Sunday on Tressle Peak (Donner Summit area) described a similar weak layer at 6,800' on E to NE aspect terrain.

* Loose wet avalanches occurred yesterday on Flagpole Peak (Echo Summit area) on steep open NE aspect terrain below 7,600'.

* More sun than expected yesterday will have led to the overnight formation of breakable crust in many areas on all aspects.

Weather and CURRENT CONDITIONS
weather summary

Spring weather is expected today with a changing mix of sun, clouds, and snow showers throughout the day. Changes from sunny to snowing may occur quickly. A day over day warming trend begins today and will last into the weekend. Ridgetop winds are forecast to remain light today but will increase to moderate to strong out of the NE tonight through tomorrow. Precipitation chances decrease for tomorrow and then go dry for the rest of the week.

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 19 to 27 deg. F.
Max. temperature: 22 to 37 deg. F.
Average ridgetop wind direction: Variable
Average ridgetop wind speed: 8 mph
Maximum ridgetop wind gust: 34 mph
New snowfall: 0 to 1 inches
Total snow depth: 73 to 95 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Tuesday Tuesday Night Wednesday
Weather: Mostly cloudy. Chance of snow. Snow levels below 7000 feet. Chance of precipitation is 40%. Partly cloudy. Slight chance of snow. Snow levels below 7000 feet. Chance of precipitation is 15%. Partly cloudy. Chance of snow through the day. Slight chance of rain in the afternoon. Snow levels below 7000 feet increasing to 7500 feet in the afternoon. Chance of precipitation is 20%.
Temperatures: 35 to 41. deg. F. 23 to 28. deg. F. 43 to 49. deg. F.
Mid Slope Winds: Light winds. Light winds becoming east around 15 mph after midnight. Gusts up to 30 mph. Northeast 15 to 20 mph with gusts to 35 mph.
Expected snowfall: 80% probability up to 1 inch. 20% probability of 1 to 3 inches. | SWE = less than 0.10 inch. Up to 1 inch. | SWE = less than 0.10 inch. Up to 1 inch. | SWE = less than 0.10 inch.
For 8000 ft. to 9000 ft.
Tuesday Tuesday Night Wednesday
Weather: Mostly cloudy. Chance of snow. Snow levels below 7000 feet. Chance of precipitation is 40%. Partly cloudy. Slight chance of snow. Snow levels below 7000 feet. Chance of precipitation is 15%. Partly cloudy. Chance of snow through the day. Chance of rain in the afternoon. Snow levels below 7000 feet increasing to 7500 feet in the afternoon. Chance of precipitation is 25%.
Temperatures: 29 to 35. deg. F. 21 to 26. deg. F. 37 to 43. deg. F.
Ridge Top Winds: Light winds becoming east around 15 mph in the afternoon. East 15 to 20 mph. Gusts up to 30 mph increasing to 45 mph after midnight. Northeast 15 to 25 mph with gusts to 50 mph.
Expected snowfall: 80% probability up to 1 inch. 20% probability of 1 to 3 inches. | SWE = less than 0.10 inch. Up to 1 inch. | SWE = less than 0.10 inch. 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