THIS AVALANCHE FORECAST EXPIRED ON March 24, 2020 @ 6:59 am
Avalanche Forecast published on March 23, 2020 @ 6:59 am
Issued by Andy Anderson - Tahoe National Forest - Sierra Avalanche Center

Fresh slabs of wind drifted snow and fragile cornices should start to form in near and above treeline terrain today due to strong winds transporting old snow and new snow accumulation. In addition to these new wind slabs, an unlikely but not impossible deep slab problem still may exist on some isolated near and below treeline slopes. MODERATE avalanche danger exists 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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Increasingly strong winds from the SW should be able to move any remaining soft snow near ridgelines from the windward aspects to the leeward aspects. New snow today will provide additional material for these wind slabs. Expect to find fresh slabs of wind drifted snow on wind-loaded and cross-loaded NW-N-NE-E-SE aspects in near and above treeline terrain today. These new wind slabs should start out small and grow in size and distribution as more snow and wind impact the region. Wind transport will also build fragile cornices along ridgelines.

Identify where wind slabs exist using clues like blowing snow, cornices above a slope, scoured ridges, and wind drifted snow. Slopes in more sheltered areas should hold more consistent snow conditions. 

Avalanche Problem 2: Deep Slab
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No reports of new deep slab avalanches came in yesterday. Observations targeting the weak layer buried below the recent storm snow continue to indicate that triggering deep slab avalanches has become unlikely on a regional scale. Still, human-triggered deep slab avalanches have occurred this week and some uncertainty exists surrounding this problem. Unlikely does not mean impossible and this problem still warrants consideration.

In the unlikely event that one of these does occur it would be on an isolated terrain feature on a NW-N-NE aspect in near or below treeline terrain where the weak layer exists. Pay particular attention to areas of steep and complex terrain or steep unsupported slopes. Larger triggers like cornice failures or multiple people on a slope or smaller triggers that hit the right trigger point would be more apt to release an otherwise unlikely deep slab. If you have any doubts about the potential for a deep slab, go ahead choose a different aspect or more conservative terrain.

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Observers reported widespread surface hoar on Ebbetts Pass, Talking Mountain, Mount Tallac, and Tamarack Peak yesterday. As light snow started to fall on Talking Mountain, in the afternoon the surface hoar was still intact. 

Yesterday, snowpit tests near a deep slab avalanche that occurred on 3/21 on Powderhouse Peak as well as snowpit tests from Ebbetts Pass, Talking Mountain, Janine's Peak all found the buried crust/facet combo at the base of the recent snow. These tests also indicated that breaking this layer continues to become more difficult. No other signs of instability concerning the deep slab problem or new deep slab avalanches were reported yesterday.

Observers did see signs of warming snow including small roller balls and some small loose wet point releases on sunny slopes on Tallac, around Ebbetts Pass, and on steep sunny S and SE facing road cuts in the Mount Rose area. Wet heavy snow was also reported on southerly aspects of Talking Mountain and Powderhouse Peak yesterday afternoon. 

Weather and CURRENT CONDITIONS
weather summary

Light snow showers should begin across the region today starting in the southern part of the forecast area as a small low-pressure system moves through southern CA. A second system should follow quickly pushing into the area later today/tonight. This system should bring more snow, wind, and cooler temperatures to the forecast area through Thursday. Expect increased SW winds, cooling temperatures, and few inches of new snow today, tonight, and tomorrow. Due to the convective nature of this storm some potential for thunder and lightning also exists.  

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 23 to 30 deg. F.
Max. temperature: 37 to 41 deg. F.
Average ridgetop wind direction: Shifting between E and SW
Average ridgetop wind speed: 10 mph
Maximum ridgetop wind gust: 33 mph
New snowfall: up to 1 inches
Total snow depth: 61 to 82 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 then becoming mostly cloudy. Chance of thunderstorms and snow showers through the day. Snow levels below 7000 feet. Chance of precipitation is 50%. Mostly cloudy then becoming partly cloudy. Chance of thunderstorms and snow showers through the night. Snow levels below 7000 feet. Chance of precipitation is 45%. Mostly cloudy. Thunderstorms and snow showers likely. Snow levels below 7000 feet. Chance of precipitation is 60%.
Temperatures: 34 to 40 deg. F. 23 to 28 deg. F. 30 to 36 deg. F.
Mid Slope Winds: Light winds becoming southwest 15 to 25 mph with gusts to 45 mph in the afternoon. Southwest 15 to 25 mph with gusts to 50 mph. Southwest 15 to 25 mph with gusts to 45 mph.
Expected snowfall: 80% probability of 1 to 3 inches. 20% probability of 2 to 4 inches. | SWE = up to 0.15 inch. 90% probability of 1 to 4 inches. 10% probability of 1 to 2 inches. | SWE = up to 0.20 inch. 90% probability of 1 to 4 inches. 10% probability of 1 to 2 inches. | SWE = up to 0.20 inch.
For 8000 ft. to 9000 ft.
Monday Monday Night Tuesday
Weather: Partly cloudy then becoming mostly cloudy. Chance of thunderstorms and snow showers through the day. Snow levels below 7000 feet. Chance of precipitation is 50%. Mostly cloudy then becoming partly cloudy. Chance of thunderstorms and snow showers through the night. Snow levels below 7000 feet. Chance of precipitation is 45%. Mostly cloudy. Thunderstorms and snow showers likely. Snow levels below 7000 feet. Chance of precipitation is 60%.
Temperatures: 29 to 35 deg. F. 20 to 25 deg. F. 25 to 31 deg. F.
Ridge Top Winds: West around 15 mph increasing to southwest 25 to 35 mph in the afternoon. Gusts up to 60 mph. Southwest 25 to 35 mph with gusts to 65 mph increasing to 30 to 50 mph with gusts to 95 mph after midnight. Southwest 25 to 35 mph with gusts to 70 mph.
Expected snowfall: 80% probability of 1 to 4 inches. 20% probability of 2 to 4 inches. | SWE = up to 0.15 inch. 80% probability of 1 to 5 inches. 20% probability of 2 to 4 inches. | SWE = up to 0.30 inch. 80% probability up to 4 inches. 20% probability of 2 to 4 inches. | SWE = up to 0.25 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