THIS AVALANCHE FORECAST EXPIRED ON February 25, 2019 @ 6:50 pm
Avalanche Forecast published on February 25, 2019 @ 6:50 am
Issued by Steve Reynaud - Tahoe National Forest

MODERATE avalanche danger will exist in near and above treeline terrain due to a wind slab avalanche problem.  Human triggered wind slab avalanches remain possible.  Low avalanche danger will continue in protected below treeline terrain.  Avalanche danger is expected to dramatically increase this evening.  This forecast is good for 12 hours and will be updated by 7pm.

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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    Very Likely
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    Very Large
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SW winds along with new snow today will continue to build wind slabs and cornices on NW-N-NE-E-SE aspects in near and above treeline terrain.  Gale force SW winds have been transporting snow and scouring windward areas for over 36 hours.  Snow available for transport is becoming limited until additional new storm snow picks up this morning.  Newly forming wind slabs along with continued building of existing wind slabs and cornices are expected throughout the day.  Wind slab avalanches up to size D2 (large enough to bury or injure a backcountry user) are possible.

Avoid steep wind loaded slopes and areas below large cornices.  Blowing snow, cornice formation, and wind pillows will indicate where wind slabs may exist.  Make a travel plan with your group that avoids these specific wind loaded terrain areas.   

recent observations

*  A small natural wind slab avalanche (D1) was reported on the east bowl of Mt. Judah (Donner Summit area) in open above treeline terrain.  A small skier triggered wind slab avalanche (D1) was unintentionally triggered on the NW side of Castle Peak (Donner Summit area).  In Johnson Canyon (Donner Summit area) an intentionally triggered wind slab avalanche failed on a small test slope.

*  Strong to gale force winds reported throughout the forecast region with intense blowing snow at most locations.  Areas of firm exposed crusts are present in many wind scoured locations.

*  Snowpack tests targeting the Feb 14 rain crust at Polaris Point (Carson Pass area) showed sudden planar results on a graupel layer buried 120cm down on top of the rain crust with the Deep Tap test.

Weather and CURRENT CONDITIONS
weather summary

Big changes have occurred with the forecasted storm this week.  A major pacific storm is approaching our area today.  A winter storm warning has been issues by the NWS for 10am Monday through 4am Thursday.  Starting this afternoon/evening, snow should be pretty steady until Thursday am.  Gale force SW winds will be throughout most of the storm with gusts of 90 to 110mph on the higher ridges.  Snow totals are dramatic if the forecast verifies:  up to 3' at lake level, with 4 to 8' above 7000'.  Snow levels are forecasted to start at 4500-5500 and should rise into Tuesday.  Snow levels could top out on Wednesday at 6000-7000' before dropping again into the end of the storm.  A short break should occur on Friday before another potential storm is lined up for Saturday and Sunday.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 20 to 25 deg. F.
Max. temperature in the last 24 hours: 30 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 50 to 80 mph
Maximum wind gust in the last 24 hours: 110 mph
New snowfall in the last 24 hours: Trace to 2 inches
Total snow depth: 108 to 135 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 snow in the morning...then snow developing in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 50% increasing to 90% in the afternoon. Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 100%. Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 100%.
Temperatures: 31 to 37. deg. F. 27 to 30. deg. F. 32 to 37. deg. F.
Mid Slope Winds: Southwest 15 to 30 mph with gusts to 45 mph increasing to 30 to 50 mph with gusts up to 70 mph in the afternoon. Southwest 30 to 45 mph with gusts to 70 mph. Southwest 30 to 45 mph with gusts to 75 mph.
Expected snowfall: 70% probability of 2 to 5 inches. 30% probability of 1 to 2 inches. | SWE = up to 0.40 inch. 80% probability of 10 to 17 inches. 20% probability of 17 to 24 inches. | SWE = up to 1.20 inches. 70% probability of 8 to 14 inches. 30% probability of 14 to 18 inches. | SWE = up to 1.15 inches.
For 8000 ft. to 9000 ft.
Monday Monday Night Tuesday
Weather: Partly cloudy then becoming mostly cloudy. Chance of snow in the morning...then snow developing in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 50% increasing to 90% in the afternoon. Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 100%. Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 100%.
Temperatures: 25 to 31. deg. F. 23 to 27. deg. F. 27 to 32. deg. F.
Ridge Top Winds: Southwest 45 to 75 mph with gusts to 115 mph. Southwest 45 to 70 mph with gusts to 120 mph. Southwest 45 to 70 mph with gusts to 115 mph.
Expected snowfall: 70% probability of 3 to 5 inches. 30% probability of 1 to 3 inches. | SWE = up to 0.40 inch. 70% probability of 12 to 18 inches. 30% probability of 18 to 25 inches. | SWE = 0.75-1.25 inches. 70% probability of 11 to 18 inches. 30% probability of 18 to 25 inches. | SWE = 0.80-1.30 inches.
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