Avalanche Advisory: Thursday - Feb 28, 2019

THIS AVALANCHE ADVISORY EXPIRED ON March 1, 2019 @ 6:47 am
Avalanche Advisory published on February 28, 2019 @ 6:47 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

The avalanche danger is CONSIDERABLE at Upper elevations today. MODERATE avalanche danger exists at Middle and Lower elevations. SW winds with new snow accumulations (1-5") will make for increasing danger throughout the day. WIND SLAB is of most concern today.

3. Considerable

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

2. Moderate

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

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
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SW WINDS will continue to rake the forecast area at high elevations with gusts to 75mph and averaging 30-50mph. Mid/Low elevations will be affected by optimal wind speeds (15-30mph) contributing to loading on leeward NORTHERLY-EASTERLY slopes. Significant wind loading and NATURAL AVALANCHES were observed yesterday on N&E aspects and expect to find more of the same today. There was also a SKIER TRIGGERED AVALANCHE on 2/26 on a ESE aspect that was likely an old wind slab. Fresh snowfall and continued erosion of old snow surfaces from violent winds are contributing to wind slab development primarily in the upper elevations, but sensitive areas of snow were also found at and below tree line yesterday. Old snow surfaces, including smooth wind board and the 2/14 rain crust below 10000ft, will provide slick sliding surfaces for new snow and skiers alike. Look for recent avalanche activity, shooting cracks and active snow transport/wind loading while travelling today. Conservative decision making and common sense terrain choices are important in the mountains right now.

Avalanche Problem 2: Storm Slab
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Storm slab is a possibility at mid to lower elevations today. 6-10” of new snow was found around the Mammoth area yesterday, and with additional accumulations last night (2") and today (1-5") there could be areas of instability. Fairly warm temperatures at the mid-lower elevations will promote better bonding for new snow, but also could make for tensioned storm slab that could be triggered by a skier. Consideration should be given to all the shiny smooth rain crust surfaces out there residing below 10000ft that could promote an optimal surface for new snow to slide on.

advisory discussion

WIND--The main component of Avalanche Formation and very present right now in our forecast area. Although the prevailing direction is from the SW, pay attention to how the alpine environment can have dramatic effects on wind patterns and loading conditions. There is plenty of light new snow and old snow available for transport to produce dangerous avalanche conditions. Even a shallow thin wind slab can do much harm if triggered in exposed and committing terrain. Be safe and have fun out there!

recent observations
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2/27 – McGee Area - McGee Mtn – Natural wind slab & Rapid wind loading

2/27 – Mammoth Area – Red Cone – Sensitive wind slab

2/27 – Mammoth Area – Earthquake Dome – snow conditions/wind slab

2/27 – Mammoth Area – Punta Bardini – Sensitive wind slab

2/26 – Rock Creek Area – Red Mountain – Skier triggered Avalanche

Weather and CURRENT CONDITIONS
weather summary

Mostly cloudy to partly cloudy skies will be over the forecast area today with light snow accumulations of 1-5”. SW winds will continue in the 15-30mph range for the mid elevations and 30-50mph up high. Although the wind is supposed to be decreasing, velocities will still be extreme at ridge tops gusting up to 75mph. Temperatures will be above freezing (31-39F) in the lower elevations while high elevations will stay within 22-28F today. Minimal amounts of snow ~1” are on tap for tonight with a brief lull of further accumulations Friday before the next wave of precipitation hits the area Saturday.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Thursday Thursday Night Friday
Weather: Mostly cloudy then becoming partly cloudy. Chance of snow. Snow levels below 7000 feet. Chance of precipitation is 55%. Mostly cloudy then becoming partly cloudy. Chance of snow. Snow levels below 7000 feet. Chance of precipitation is 20%. Partly cloudy. Slight chance of snow in the morning. Snow levels below 7000 feet. Chance of precipitation is 10%.
Temperatures: 31 to 39. deg. F. 19 to 25. deg. F. 31 to 41. deg. F.
Mid Slope Winds: Southwest 15 to 30 mph with gusts to 60 mph. Southwest 15 to 30 mph with gusts to 60 mph. Southwest 15 to 25 mph with gusts to 50 mph.
Expected snowfall: 70% probability of 1 to 3 inches. 30% probability of 3 to 5 inches. | SWE = up to 0.20 inch. in. up to 1 inch. | SWE = less than 0.10 inch. in. No accumulation. | SWE = none. in.
Over 10,000 ft.
Thursday Thursday Night Friday
Weather: Mostly cloudy. Snow. Snow levels 7000 feet. Chance of precipitation is 75%. Mostly cloudy then becoming partly cloudy. Chance of snow through the night. Snow levels below 7000 feet. Chance of precipitation is 30%. Mostly cloudy then becoming partly cloudy. Slight chance of snow. Snow levels below 7000 feet. Chance of precipitation is 10%.
Temperatures: 22 to 28. deg. F. 13 to 18. deg. F. 24 to 30. deg. F.
Ridge Top Winds: Southwest 30 to 50 mph with gusts to 75 mph. Southwest 30 to 50 mph with gusts to 70 mph. Southwest 30 to 45 mph with gusts to 65 mph.
Expected snowfall: 70% probability of 1 to 3 inches. 30% probability of 3 to 5 inches. | SWE = 0.15-0.25 inch. in. up to 1 inch. | SWE = less than 0.10 inch. in. No accumulation. | SWE = none. in.
Disclaimer
This Avalanche Advisory is designed to generally describe avalanche conditions where local variations always occur. This product only applies to backcountry areas located outside established ski area boundaries. The information in this Avalanche Advisory is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.

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