THIS AVALANCHE FORECAST EXPIRED ON February 9, 2019 @ 6:56 am
Avalanche Forecast published on February 8, 2019 @ 6:56 am
Issued by Brandon Schwartz - Tahoe National Forest

MODERATE avalanche danger exists today as drifting snow forms new wind slabs near treeline and above treeline. Below treeline, LOW avalanche danger continues. Expect increasing avalanche danger at all elevations over the weekend.

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.

1. Low

?

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

Ridgetop winds increased last night out of the SSW and are strong enough to move snow. With plenty of unconsolidated snow on the surface near ridgetops, areas of drifting snow are expected to form new wind slabs today even before snowfall begins. The vast majority of wind slabs will form near treeline and above treeline on NW-N-NE-E-SE aspects. Isolated wind slabs could form in other locations as well. Avalanche size up to D2 (large enough to bury or injure a person) is possible by early this afternoon in the most heavily wind loaded areas. Wind slabs will become increasingly widespread overnight as new snowfall combines with wind.

Use blowing snow to identify areas of concern. Ridgetop areas where drifting snow is depositing, especially below cornice features and wind pillows will become increasingly suspect as the day progresses. Move cautiously around any areas where new wind slabs are forming, especially if snow surface cracking is present.

recent observations

* Observations made yesterday in Davis Creek (Mount Rose area) showed increasing stability of old wind slabs formed during that last storm cycle. Minor amounts of skier triggered roller balls were noted from warming on E-SE aspects below about 7,500'. A thin sun crust may have have formed on the snow surface last night in lower elevation sun exposed areas.

* Some loose dry instability (surface sluffing) was reported yesterday in Shirley Canyon (near Squaw Valley) and to an isolated extent in the upper elevation portion of Davis Creek (Mount Rose area).

* The most recent reports of slab avalanche activity are wind slab avalanches from Feb 5 occurring on NE-E aspect terrain in Davis Creek (Mount Rose area) and near The Nipple in the Blue Lakes region of Carson Pass.

* Surface hoar up to 10 mm in size was reported yesterday from Mt. Judah (Donner Summit area) and from Shirley Canyon (near Squaw Valley).

Weather and CURRENT CONDITIONS
weather summary

Cloud cover and ridgetop winds are increasing this morning ahead of a series of approaching storm systems. Snowfall is expected to begin late afternoon or early evening and continue through this weekend. Ridgetop wind speeds are forecast to increase further on Saturday ahead of a second and stronger storm event for Saturday night and Sunday. Additional storm systems are expected next week. For the latest info on this series of storms, check with NWS Reno.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 10 to 16 deg. F.
Max. temperature in the last 24 hours: 24 to 34 deg. F.
Average wind direction during the last 24 hours: SSW
Average wind speed during the last 24 hours: 22 mph
Maximum wind gust in the last 24 hours: 52 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 94 to 111 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Friday Friday Night Saturday
Weather: Partly cloudy then becoming mostly cloudy. Chance of snow through the day. Snow levels below 7000 feet. Chance of precipitation is 30%. Cloudy. Snow likely in the evening, then snow after midnight. Snow levels below 7000 feet. Chance of precipitation is 100%. Cloudy. Snow likely in the morning, then snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 100%.
Temperatures: 25 to 30 deg. F. 18 to 24 deg. F. 23 to 28 deg. F.
Mid Slope Winds: Southwest around 15 mph. Gusts up to 25 mph increasing to 35 mph in the afternoon. South around 15 mph in the evening becoming light. Gusts up to 25 mph. Southwest around 15 mph with gusts to 30 mph increasing to 20 to 30 mph with gusts to 60 mph in the afternoon.
Expected snowfall: 30% probability up to 1 inch. 70% probability up to 0 inches. | SWE = trace amounts. 90% probability of 3 to 7 inches. 10% probability of 1 to 3 inches. | SWE = up to 0.30 inch. 90% probability of 3 to 7 inches. 10% probability of 1 to 3 inches. | SWE = up to 0.30 inch.
For 8000 ft. to 9000 ft.
Friday Friday Night Saturday
Weather: Partly cloudy then becoming mostly cloudy. Chance of snow through the day. Snow levels below 7000 feet. Chance of precipitation is 25%. Cloudy. Snow likely in the evening, then snow after midnight. Snow levels below 7000 feet. Chance of precipitation is 100%. Cloudy. Snow likely. Snow levels below 7000 feet. Chance of precipitation is 100%.
Temperatures: 20 to 25 deg. F. 14 to 22 deg. F. 19 to 24 deg. F.
Ridge Top Winds: South 15 to 30 mph with gusts to 55 mph. South 15 to 25 mph with gusts to 50 mph. Southwest 15 to 30 mph increasing to 30 to 40 mph in the afternoon. Gusts up to 70 mph.
Expected snowfall: 30% probability up to 1 inch. 70% probability up to 0 inches. | SWE = trace amounts. 90% probability of 4 to 8 inches. 10% probability of 2 to 4 inches. | SWE = 0.20-0.40 inch. 80% probability of 5 to 10 inches. 20% probability of 2 to 5 inches. | SWE = 0.20-0.45 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