THIS AVALANCHE FORECAST EXPIRED ON December 23, 2020 @ 6:53 am
Avalanche Forecast published on December 22, 2020 @ 6:53 am
Issued by Steve Reynaud - Tahoe National Forest

MODERATE avalanche danger continues for our area.  A persistent slab avalanche problem remains a concern in below and near treeline areas.  Increased winds overnight will make unstable wind slabs in near and above treeline terrain.  Human triggered avalanches remain possible today.  

2. Moderate

?

Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

?

Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

?

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: Persistent Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

The Dec. 11 persistent weak layer is buried under about 1 foot of snow and has been a concern for over a week.  Just as it took time for this layer to facet and weaken, it has taken time for the weak layer to adjust to the current snow load and gain some strength.  Yesterday marks the first day without reports of active whumpfing on this layer from the forecast region.  Unfortunately, reports of unstable snowpack test results did come in and large variability continues from one area to the next.  This weak layer exists on W-NW-N-NE-E aspects in below and near treeline areas.

Whumpfing sounds, cracking, and/or unstable snowpack test results could indicate that this weak layer is still active in your specific area.  Limiting exposure to avalanche terrain by using only sub 30 degree angle slopes without steeper connected slopes above or to the side is the easy way to manage this avalanche problem.  

Avalanche Problem 2: Wind Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

SW winds increased overnight into the strong to gale force range at higher elevation.  Snow transport is expected with small unstable wind slabs forming last night on NW-N-NE-E-SE aspects in near and above treeline areas.  Winds will shift towards the NW today and then to the E tonight remaining gusty in near and above treeline areas and possibly transporting snow to other aspects.  Avoid areas below new cornice formation and newly formed wind pillows and drifts.   

recent observations
Submit Observations

* Unstable snowpack test results were reported from the Castle Peak area yesterday on the Dec 11 persistent weak layer.  Other reported snowpack tests from Incline Lake Peak (Mt. Rose area) and Shirley Canyon (Squaw Valley area), did not show unstable results.  No whumpfing, cracking, or other signs of instabilities were reported yesterday.

* Increasing SW winds were observed yesterday with light snow transport reported starting in the early afternoon.

* Surface hoar was reported from lower elevation areas not influenced by the recent temperature inversions.

Weather and CURRENT CONDITIONS
weather summary

A cold front moved through our area overnight bringing colder temperatures and strong to gale force SW winds.  The winds will shift towards the NW throughout the day as the cold front exits, eventually shifting E tonight, and will remain gusty at the higher elevations.  Cold overnight temperatures, lighter winds, and sunny days are expected over the next few days.  2 storms are forecasted later this week, with one on Christmas Day night (Friday night into Saturday) and one following on Sunday night.  

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 24 to 26 deg. F.
Max. temperature: 42 to 44 deg. F.
Average ridgetop wind direction: SW
Average ridgetop wind speed: 40 to 60 mph
Maximum ridgetop wind gust: 103 mph
New snowfall: 0 to trace inches
Total snow depth: 22 to 29 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Tuesday Tuesday Night Wednesday
Weather: Partly cloudy then becoming sunny. Slight chance of snow in the morning. Snow levels below 7000 feet. Chance of precipitation is 20%. Clear. Snow levels below 7000 feet. Chance of precipitation is 0%. Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 36 to 41. deg. F. 14 to 20. deg. F. 34 to 39. deg. F.
Mid Slope Winds: West around 15 mph with gusts to 35 mph in the morning becoming light. Light winds. Gusts up to 30 mph after midnight. East around 15 mph with gusts to 30 mph.
Expected snowfall: No accumulation. | SWE = trace amounts. No accumulation. | SWE = none. No accumulation. | SWE = none.
For 8000 ft. to 9000 ft.
Tuesday Tuesday Night Wednesday
Weather: Partly cloudy then becoming sunny. Slight chance of snow in the morning. Snow levels below 7000 feet. Chance of precipitation is 20%. Clear. Snow levels below 7000 feet. Chance of precipitation is 0%. Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 33 to 38. deg. F. 13 to 19. deg. F. 34 to 39. deg. F.
Ridge Top Winds: West 25 to 35 mph with gusts to 80 mph becoming northwest 15 to 25 mph with gusts to 50 mph in the afternoon. East 15 to 25 mph. Gusts up to 50 mph decreasing to 40 mph after midnight. East 15 to 25 mph with gusts to 45 mph.
Expected snowfall: No accumulation. | SWE = trace amounts. 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