Avalanche Advisory: Sunday - Mar 29, 2020

THIS AVALANCHE ADVISORY EXPIRED ON March 30, 2020 @ 6:52 am
Avalanche Advisory published on March 29, 2020 @ 6:52 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

MODERATE avalanche danger exists above treeline Sunday for WIND SLAB on Northerly-Easterly slopes. LOW danger exists near and below treeline. New snow from last night (1-2”) and predicted accumulations (2”) today will be moved to the leeward aspects from light to moderate W-SW winds. Be on the lookout for fresh shallow Wind Slab in relation to new snowfall and remain vigilant for isolated, stubborn old windslab formed during last week's storms. Cornices, unsupported slopes, areas adjacent to ridgeline, and steep convexities optimal for capturing snow are key features to identify and avoid.

* Given the current situation, an injury at this time requiring medical attention could result in serious consequences for yourself and others. Limit your risks!  

*To comply with the Inyo County Sheriff’s office request, ESAC’s forecasts and field work is now limited to Mono County.

2. Moderate

?

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

1. Low

?

Near Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

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

Northern parts of the forecast zone recorded 1-2” last night and another 2” of snow is slated to fall throughout the day today. Look for fresh shallow windslab deposits on NW-N-NE-E-SE aspects particularly in the upper elevations where W-SW winds will be stronger. The Mammoth area is still of most concern in relation to older stubborn windslab on northerly-easterly aspects formed during last week’s significant snowfall. Features of concern that should be identified and considered during travels today include fresh cornices, cross loaded drifts, pillowed snow adjacent to ridgelines, and cliffbands and rock outcroppings. Shooting cracks, audible whoompfing or visible blowing snow on peaks will be good indicators that wind slab may be forming or is present. Be heads up for any potential warming or greenhouse effects destabilizing new snow deposits especially in relation to overhead hazards such as fresh cornices. Maintain good travel protocols, such as traveling slopes one at a time (both up and down), anchoring up in safe spots, and maintaining good communication and consistent group plans and routes.

advisory discussion

Forecaster observations from the June Lake and Virginia Lakes area yesterday found good settlement and overall bonding of last week’s storm snow, but in stability tests, propagating results were still found in Extended Column Tests near the new snow/old snow interface. Periods of solar input and relatively light winds the past few days have also contributed to changing most aspects affected by sun to variable surface conditions including injury-inducing breakable crust.

If you’re not up to date, it’s worth mentioning several skier triggered slides that occurred last Thursday and Friday. Upon forecaster investigation the skier triggered slide on the Red cone approach Thursday had slid on an East aspect where the new 40cm of snow had slid on an old melt/freeze crust over a steep rolling convex granite slab in a sheltered zone that sees a lot of sun and warming effects. Friday's  triggered wind slab was on a heavily loaded north aspect on a steep fetch zone optimal for capturing mid-slope wind transported snow. Both these slides remind us to always adhere to fundamental travel protocols, constantly re-evaluate current conditions and maintain good communication with your group.

This has not been the winter, nor the time right now with all we are dealing with, to risk serious injury by skiing carelessly with our overall thin and obstacle ridden conditions.

It is also important to practice social distancing at all times, from travelling in separate cars going to the trailhead, and keeping at least 6 feet between individuals while skinning and re-grouping. We all need to do our part in preventing the spread of this Corona Virus!  

Weather and CURRENT CONDITIONS
weather summary

Temperatures Sunday should stay below freezing remaing in the 20sF for the higher elevations while 30-38F is in store below 10000ft. Mostly cloudy conditions will prevail with snow showers throughout the day with upwards of 2” of accumulation. Snow is likely this morning with light amounts and is slated to continue through the day today. Light to Moderate W-SW winds will blow at ridgetops increasing a bit tonight into tomorrow. Much warmer temperatures and sunny conditions are on tap for Monday.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Sunday Sunday Night Monday
Weather: Mostly cloudy. Scattered snow showers in the morning, then snow showers likely in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 55%. Mostly cloudy then becoming clear. Isolated snow showers in the evening. Snow levels below 7000 feet. Chance of precipitation is 20%. Partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 5%.
Temperatures: 30 to 38. deg. F. 16 to 22. deg. F. 40 to 48. deg. F.
Mid Slope Winds: Light winds. West around 15 mph. Southwest around 15 mph with gusts to 35 mph.
Expected snowfall: 80% probability up to 2 inches. 20% probability of 2 to 3 inches. | SWE = less than 0.10 inch. in. Up to 1 inch. | SWE = trace amounts. in. No accumulation. | SWE = none. in.
Over 10,000 ft.
Sunday Sunday Night Monday
Weather: Mostly cloudy. Scattered snow showers in the morning, then snow showers likely in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 60%. Mostly cloudy then becoming clear. Isolated snow showers in the evening. Snow levels below 7000 feet. Chance of precipitation is 20%. Sunny. Snow levels below 7000 feet. Chance of precipitation is 5%.
Temperatures: 22 to 29. deg. F. 11 to 16. deg. F. 34 to 40. deg. F.
Ridge Top Winds: West around 15 mph. West around 15 mph with gusts to 30 mph. Southwest 15 to 30 mph with gusts to 50 mph.
Expected snowfall: 80% probability up to 2 inches. 20% probability of 2 to 3 inches. | SWE = less than 0.10 inch. in. Up to 1 inch. | SWE = less than 0.10 inch. in. 0 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.

ESAC receives significant financial support from ...