THIS AVALANCHE FORECAST EXPIRED ON April 6, 2020 @ 6:59 am
Avalanche Forecast published on April 5, 2020 @ 6:59 am
Issued by Andy Anderson - Tahoe National Forest - Sierra Avalanche Center

As the storm intensifies, heavy snow and gale-force winds will create very dangerous avalanche conditions in the backcountry today. Large unstable slabs of wind drifted snow and softer slabs of storm snow will exist on steep slopes in both exposed and sheltered terrain. During the day, the avalanche danger will increase to HIGH near and above treeline and CONSIDERABLE below treeline.

Travel in or below avalanche terrain is not recommended today.

4. High

?

Above Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

4. High

?

Near Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

3. Considerable

?

Below Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
    Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Wind Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Gale force SW winds and new snow during the night have already formed fresh slabs of wind drifted snow on wind-loaded and cross-loaded NW-N-NE-E-SE aspects. Additional wind and more intense snowfall today will cause these already fragile wind slabs to grow in size and extent. As the day progresses, expect natural wind slab avalanches to occur. If people venture onto steep wind-loaded slopes, human-triggered wind slab avalanches are very likely. By this afternoon wind slabs could grow to several feet deep. Wind slab avalanches would easily entrain enough snow to bury a person or maybe a car. In some isolated areas, it is not impossible for wind slab avalanches to break below the old snow surface on older weak snow. 

Avalanche Problem 2: Storm Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Snowfall rates of 2-3 in/hr and other changes during the storm will create fragile slabs of storm snow in more sheltered terrain. The soft slabs of storm snow will grow larger and more widespread as more snow accumulates today. Human-triggered storm slab avalanches will become likely on steep slopes and some natural avalanches may also occur. These storm slabs could break on weaknesses within the storm snow or may fail on the old snow surfaces. In some isolated areas, they may overload weak layers below the old snow surface like the old surface hoar layer. Storm slab avalanches could entrain enough snow to bury a person.

Forecast discussion

Today's intense storm will cause conditions to grow increasingly worse. The snowpack will become increasingly unstable. On top of this, the storm makes terrain evaluation, over the snow travel, and group communication difficult due to high winds, blowing snow, and low visibility. If someone gets hurt, rescue would be delayed or impossible due to dangerous conditions. Today would be a good day to catch up on your favorite book or show. 

recent observations
Submit Observations

Observations yesterday on Tamarack Peak revealed mostly firm or breakable crusts on the snow surface. In some areas the morning sun softened the surface snow and some less consolidated snow existed in a few isolated spots. Observations this week have shown these mostly firm surface conditions across the entire forecast area. 

The buried surface hoar layer still exists in some places but snowpit tests and data from this week indicated that it has gained strength.

Weather and CURRENT CONDITIONS
weather summary

The storm began yesterday afternoon and gained strength overnight. The SW winds along the ridgetops have increased to gale force. So far 7 to 10 inches of new snow has accumulated along the Sierra Crest N of Emerald Bay with 4 to 6 inches S of Emerald Bay. The forecast calls for snowfall to intensify today with snowfall rates of 2-3 inches per hour at times through this evening and continued strong SW winds. The heavy snowfall should start first in the northern end of the forecast area and extend south as the day progresses. More snow and wind will continue tonight. By tomorrow morning snow totals could reach 1 to 3 feet along the Sierra Crest. The storm should start to decrease in intensity during the day tomorrow but snow showers could linger across the area through Tuesday.  For more details check in with the Reno NWS.

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 21 to 29 deg. F.
Max. temperature: 28 to 35 deg. F.
Average ridgetop wind direction: SW
Average ridgetop wind speed: 35 to 50 mph
Maximum ridgetop wind gust: 102 mph
New snowfall: 4 to 10 inches
Total snow depth: 57 to 83 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Sunday Sunday Night Monday
Weather: Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 95%. Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 95%. Mostly cloudy. Snow likely in the morning, then snow and slight chance of thunderstorms in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 80%.
Temperatures: 32 to 38 deg. F. 21 to 26 deg. F. 30 to 35 deg. F.
Mid Slope Winds: South 15 to 30 mph with gusts to 50 mph. Southwest 15 to 20 mph. Gusts up to 40 mph decreasing to 25 mph after midnight. Light winds. Gusts up to 25 mph in the morning.
Expected snowfall: 80% probability of 7 to 10 inches. 20% probability of 10 to 14 inches. | SWE = 0.70-1.15 inches. 70% probability of 5 to 10 inches. 30% probability of 10 to 15 inches. | SWE = 0.55-0.80 inch. 80% probability of 1 to 4 inches. 20% probability of 4 to 6 inches. | SWE = up to 0.20 inch.
For 8000 ft. to 9000 ft.
Sunday Sunday Night Monday
Weather: Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 95%. Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 95%. Mostly cloudy. Snow likely in the morning, then snow and slight chance of thunderstorms in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 85%.
Temperatures: 27 to 33 deg. F. 17 to 22 deg. F. 25 to 31 deg. F.
Ridge Top Winds: South 30 to 45 mph with gusts to 90 mph. Southwest 15 to 30 mph with gusts to 50 mph decreasing to 15 to 20 mph with gusts to 35 mph after midnight. Southwest around 15 mph. Gusts up to 35 mph decreasing to 25 mph in the afternoon.
Expected snowfall: 80% probability of 9 to 14 inches. 20% probability of 14 to 20 inches. | SWE = 0.80-1.30 inches. 70% probability of 6 to 12 inches. 30% probability of 12 to 18 inches. | SWE = 0.50-1.00 inch. 80% probability of 2 to 4 inches. 20% probability of 4 to 6 inches. | SWE = up to 0.30 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