THIS AVALANCHE FORECAST EXPIRED ON January 11, 2020 @ 6:48 am
Avalanche Forecast published on January 10, 2020 @ 6:48 am
Issued by Brandon Schwartz - Tahoe National Forest

Strong winds from both the SW and NE have drifted snow and deposited it as small unstable wind slabs on a variety of slopes above treeline and near treeline. Warming conditions today may allow for some minor wet snow instability on slopes in direct sun. MODERATE avalanche danger exists in wind exposed areas above treeline and near treeline with LOW avalanche danger below treeline.

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.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    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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Small unstable wind slabs have been present the past two days near treeline and above treeline from new snow and SW winds. A strong NE wind event occurred last night with plenty of snow available for drifting. Winds are back to SW today and increasing in speed so expect more drifting. At this point, slabs of wind drifted snow could be encountered on any aspect in near treeline to above treeline terrain. Expect a mix of scoured slopes and drift deposited wind slabs in adjacent areas. Avalanche size D1 is expected with size D2 possible in the most heavily wind drifted areas.

Today will be all about identifying where wind slabs are present and moving cautiously around them. Identify wind slabs by looking for blowing and drifting snow, recent cornice and wind pillow formations, and areas of smooth looking slope. Snow surface cracking today is a sign of an unstable wind slab.

    Photos: D1 wind slabs from the past two days above treeline and near treeline.

Avalanche Problem 2: Loose Wet
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Warming conditions today may allow for some minor loose wet snow instability in sun exposed areas, mainly on SE-S-SW aspects. Conditions along the northern portion of the Sierra Crest are most conducive to this instability today where a couple of inches or more of recent new snow exists.

Exercise caution on or below steep slopes where roller balls and/or more than a couple of inches of wet surface snow are present. Expect increased snow surface warming near exposed rocks and in wind protected areas.

recent observations
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* Light snowfall events since Tuesday night have favored the Sierra Crest and deposited 5 to 6 inches over the northern portion of the forecast area and around an inch over the southern portion of the forecast area.

* Small reactive size D1 wind slab avalanches have been intentionally triggered over the past two days in the northern portion of the forecast area along the Sierra Crest in near treeline to above treeline terrain on N-NE-E aspects. Snowpack failure has been occurring on top of the Jan 4 rain crust.

* Weak snow in the upper snowpack (facets and low density DFs) around the Dec 12 and Jan 4 rain crusts are in a monitoring state for potential problems under anticipated storm conditions next week.

Weather and CURRENT CONDITIONS
weather summary

A break in the weather will occur today with sunny skies. Ridgetop winds shifted to the NE yesterday and were strong overnight. Winds are shifting back to the SW this morning. Wind speeds will increase through the day today, becoming gale force tonight. Another round of light snowfall is forecast for tonight into tomorrow. Air temperature inversion conditions are in place this morning with single digits to teens on the mountain valley floors and mid 20s across the upper elevations. Two significant storms are on the horizon for next 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: 25 to 26 deg. F.
Max. temperature: 25 to 29 deg. F.
Average ridgetop wind direction: SW shifting to NE
Average ridgetop wind speed: SW 20 mph | NE 34 mph
Maximum ridgetop wind gust: SW 28 mph | NE 56 mph
New snowfall: Trace to 3 inches
Total snow depth: 43 to 46 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Friday Friday Night Saturday
Weather: Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%. Clear then becoming partly cloudy. Chance of snow after midnight. Snow levels below 7000 feet. Chance of precipitation is 30%. Mostly cloudy. Chance of snow. Snow levels below 7000 feet. Chance of precipitation is 55%.
Temperatures: 37 to 43. deg. F. 22 to 27. deg. F. 28 to 33. deg. F.
Mid Slope Winds: Light winds becoming southwest around 15 mph in the afternoon. Gusts up to 30 mph. Southwest 15 to 20 mph with gusts to 55 mph increasing to 25 to 35 mph with gusts to 75 mph after midnight. Southwest 25 to 35 mph with gusts to 70 mph decreasing to 15 to 25 mph with gusts to 50 mph in the afternoon.
Expected snowfall: No accumulation. | SWE = none. 30% probability up to 1 inch. 70% probability no accumulation. | SWE = less than 0.10 inch. 60% probability up to 2 inches. 40% probability no accumulation. | SWE = up to 0.15 inch.
For 8000 ft. to 9000 ft.
Friday Friday Night Saturday
Weather: Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%. Clear then becoming partly cloudy. Chance of snow after midnight. Snow levels below 7000 feet. Chance of precipitation is 30%. Mostly cloudy. Chance of snow. Snow levels below 7000 feet. Chance of precipitation is 55%.
Temperatures: 33 to 39. deg. F. 18 to 23. deg. F. 24 to 29. deg. F.
Ridge Top Winds: West 15 to 25 mph with gusts to 55 mph. Southwest 25 to 35 mph increasing to 35 to 55 mph after midnight. Gusts up to 120 mph. Southwest 35 to 50 mph with gusts to 90 mph decreasing to 25 to 35 mph with gusts to 65 mph in the afternoon.
Expected snowfall: No accumulation. | SWE = none. 30% probability up to 1 inch. 70% probability no accumulation. | SWE = less than 0.10 inch. 60% probability of 1 to 3 inches. 40% probability no accumulation. | SWE = up to 0.15 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