THIS AVALANCHE FORECAST EXPIRED ON January 22, 2019 @ 6:55 am
Avalanche Forecast published on January 21, 2019 @ 6:55 am
Issued by Steve Reynaud - Tahoe National Forest

CONSIDERABLE avalanche danger will exist today due to wind slab, storm slab, and deep slab avalanche problems at all elevations.  Human triggered avalanches will remain likely today.  Dangerous avalanche conditions will exist with large and destructive avalanches possible.

 

3. Considerable

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Above Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

3. Considerable

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Near Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

3. Considerable

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Below Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
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Gale force SW winds yesterday and overnight during the storm have created sensitive wind slabs on NW-N-NE-E-SE aspects in near and above treeline terrain.  These wind slabs will remain sensitive today to triggering and will be capable of being large enough to bury a backcountry user (size D2).  Winds will shift to the NW today and then to the NE this evening and be in the moderate to strong range.  With snow available for transport, expect wind slabs to form on SE-S-SW-W-NW aspects in near and above treeline terrain today and tonight.

Look for blowing snow, cornice formation, wind pillows, and previous signs of snow transport.  Avoid steep wind loaded terrain and areas with large cornices overhead. 

Avalanche Problem 2: Storm Slab
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Storm slab avalanches will be possible on all aspects in near and below treeline terrain.  These storm slabs could fail on weaknesses that formed during the storm or at the old snow/new snow interface.  Many locations above 7000' received well over a foot of new snow overnight with some areas receiving closer to 2'.

Look for cracking or collapsing within the recent storm snow.  Hand pits are an effective and manageable tool to look for storm snow weaknesses.  Avoid areas that show signs of instabilities.

Avalanche Problem 3: Deep Slab
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Deep slab avalanches will remain possible today on NW-N-NE-E aspects in above and below treeline terrain.  The buried surface hoar layer and facet/crust layer are now buried 4-7'+ deep in the snowpack with some shallow snowpack areas having the weak layers being 2-3' deep.  Uncertainty continues about these layers and their reactivity.  Human triggering this deep of a weak layer remains difficult, but the consequences of an avalanche remain very high.

Managing terrain and limiting exposure continue to be the best practices for backcountry travel with a deep slab avalanche problem.  Avoid complex terrain with multiple run out zones, areas with many trigger points like cliffs/rocks, and terrain with large overhead hazards.

recent observations

*  Rain on snow along with wet heavy snow was reported from areas below 7500' throughout yesterday morning.  Snow levels did drop to 7000' and below by mid day at most location throughout the forecast area.

*  At Carson Pass, refrozen rain crust existed at 8000' in the late morning hours with 1-2'' of new storm snow on top. 

Weather and CURRENT CONDITIONS
weather summary

The recent winter storm is winding up and exiting our area this morning.  8 to 19'' of total storm snow has fallen along the Sierra Crest above 7500' with around 1' of new snow in the Mt. Rose area.  The gale force SW winds have decreased in speed and will shift to the NW today and then to the NE later this evening.  Wind speeds should remain in the moderate to strong range into Tuesday morning.  Lingering snow showers could bring another 1 to 2'' of snow to the area through today.  The weather should clear up by Tuesday with a gradual warming trend through the week.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 15 to 19 deg. F.
Max. temperature in the last 24 hours: 34 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 40 to 80 mph
Maximum wind gust in the last 24 hours: 126 mph
New snowfall in the last 24 hours: 8 to 15 inches
Total snow depth: 72 to 100 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 then becoming partly cloudy. Snow showers likely. Snow levels below 7000 feet. Chance of precipitation is 55%. Partly cloudy then becoming clear. Snow levels below 7000 feet. Chance of precipitation is 10%. Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 25 to 30. deg. F. 10 to 16. deg. F. 32 to 37. deg. F.
Mid Slope Winds: West 10 to 15 mph. Gusts up to 45 mph decreasing to 35 mph in the afternoon. Northeast 10 to 15 mph with gusts to 35 mph. Light winds. Gusts up to 35 mph decreasing to 25 mph in the afternoon.
Expected snowfall: 60% probability 0 to 1 inch. 40% probability 1 to 2 inches. | SWE = less than 0.10 inch. No accumulation. | SWE = none. No accumulation. | SWE = none.
For 8000 ft. to 9000 ft.
Monday Monday Night Tuesday
Weather: Mostly cloudy. Snow showers likely. Snow levels below 7000 feet. Chance of precipitation is 55%. Partly cloudy then becoming clear. Slight chance of snow showers in the evening. Snow levels below 7000 feet. Chance of precipitation is 10%. Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 20 to 26. deg. F. 8 to 13. deg. F. 31 to 36. deg. F.
Ridge Top Winds: Northwest 15 to 30 mph. Gusts up to 60 mph decreasing to 40 mph in the afternoon. Northeast 15 to 30 mph. Gusts up to 55 mph increasing to 75 mph after midnight. Northeast 15 to 30 mph. Gusts up to 75 mph decreasing to 50 mph in the afternoon.
Expected snowfall: 60% probability 0 to 1 inch. 40% probability 1 to 2 inches. | SWE = less than 0.10 inch. No accumulation. | SWE = none. No accumulation. | SWE = none.
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