THIS AVALANCHE FORECAST EXPIRED ON April 21, 2020 @ 6:57 am
Avalanche Forecast published on April 20, 2020 @ 6:57 am
Issued by Andy Anderson - Tahoe National Forest - Sierra Avalanche Center

Sunshine this morning and rain showers this afternoon should provide enough warming for avalanches of loose wet snow to become possible on mid to low elevation slopes again today. At upper elevations where this afternoon's precipitation falls as snow, loose wet avalanches may remain unlikely. Slabs of wet snow may also still warrant concern in some areas. The avalanche danger will rise to MODERATE at mid to low elevations and should remain LOW at upper elevations today. 

1. Low

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Above Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

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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Mostly clear skies and below-freezing temperatures should have allowed a good refreeze to occur last night. Cooler temperatures and some wind today should cause this refreeze to last longer than it has on previous days. Despite these cooling influences, the strong April sun will work to soften the snow on sun-exposed slopes this morning. By this afternoon rain showers below ~7500 ft will add to the warming and loose wet avalanches will become possible on steep slopes. Some of these could entrain enough snow to bury a person. Above ~7500 ft where precipitation is forecast to fall as snow, the refreeze may last through the day and significant loose wet avalanches may remain unlikely. 

Expect firm icy snow conditions on slopes this morning. It may take longer for the snow surface to soften today and some areas may not soften at upper elevations. In areas where rain does fall on the snow, it will quickly become wet and unsupportable.

Avalanche Problem 2: Wet Slab
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Recent warming and rain have continued to consolidate the layers in the snowpack making wet slabs less of a concern. Still, enough uncertainty surrounds wet slab avalanches that this problem deserves some consideration for now. If a wet slab avalanche does occur, it could involve enough snow to bury or injure a person.

Using timing and terrain to avoid wet snow and/or steep terrain can help avoid wet slabs.

recent observations
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Yesterday a firm refrozen surface existed in most places in the Carson Pass area and on Relay Peak in the morning. By mid-morning (9:30-10:30) this refreeze had already started to become unsupportable on sunny slopes below 8800 ft near Carson Pass and up to about 9600 ft on Relay Peak. 

Observers reported several recent loose wet avalanches large enough to bury a person in the Round Top/Summit City area. These likely occurred on Saturday. 

Weather and CURRENT CONDITIONS
weather summary

Yesterday's afternoon clouds cleared out during the night and temperatures dropped below freezing on all but a few of the remote sensors above 6000 ft. After some sunshine this morning, clouds should start to build over the area due to a weak low-pressure system moving into the region this afternoon. This system could bring some precipitation with light rain expected below about ~7500 ft and light snow above ~7500 ft. The forecast also calls for increased W winds and slightly cooler temperatures. Tomorrow should see this low-pressure moving out of the area and the start of a warming trend that should continue through most 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: 27 to 30 deg. F.
Max. temperature: 42 to 44 deg. F.
Average ridgetop wind direction: WSW
Average ridgetop wind speed: 15 to 20 mph
Maximum ridgetop wind gust: 45 mph
New snowfall: trace to 0 inches
Total snow depth: 54 to 77 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Monday Monday Night Tuesday
Weather: Mostly cloudy. Scattered showers in the afternoon. Snow levels below 7000 feet increasing to 7500 feet in the afternoon. Chance of precipitation is 25%. Mostly cloudy then becoming partly cloudy. Isolated showers in the evening. Snow levels 7500 feet. Chance of precipitation is 20%. Mostly sunny. Isolated showers in the afternoon. Snow levels 7500 feet increasing to 8500 feet in the afternoon. Chance of precipitation is 15%.
Temperatures: 43 to 49 deg. F. 26 to 31 deg. F. 50 to 56 deg. F.
Mid Slope Winds: Light winds becoming west around 15 mph with gusts to 25 mph in the afternoon. West around 15 mph with gusts to 25 mph in the evening becoming light. Light winds.
Expected snowfall: Little or no accumulation. | SWE = less than 0.10 inch. 80% probability no accumulation. 20% probability up to 1 inch. | SWE = trace amounts. No accumulation. | SWE = trace amounts.
For 8000 ft. to 9000 ft.
Monday Monday Night Tuesday
Weather: Mostly cloudy. Isolated snow showers in the afternoon. Snow levels below 7000 feet increasing to 7500 feet in the afternoon. Chance of precipitation is 30%. Mostly cloudy then becoming clear. Scattered snow showers in the evening. Snow levels 7500 feet. Chance of precipitation is 25%. Mostly sunny. Isolated showers in the afternoon. Snow levels 7500 feet increasing to 8500 feet in the afternoon. Chance of precipitation is 15%.
Temperatures: 35 to 43 deg. F. 23 to 28 deg. F. 42 to 50 deg. F.
Ridge Top Winds: Light winds becoming west around 15 mph with gusts to 25 mph in the afternoon. West around 15 mph with gusts to 30 mph in the evening becoming light. Light winds.
Expected snowfall: 60% probability of less than 1 inch. 40% probability of 1 to 2 inches. | SWE = less than 0.20 inch. 80% probability no accumulation. 20% probability up to 1 inch. | SWE = less than 0.10 inch. 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