Avalanche Advisory: Thursday - Mar 21, 2019

THIS AVALANCHE ADVISORY EXPIRED ON March 22, 2019 @ 6:33 am
Avalanche Advisory published on March 21, 2019 @ 6:33 am
Issued by Steve Mace - ESAC

Avalanche danger will remain CONSIDERABLE at upper elevations today while dropping to MODERATE at mid and lower elevations.  Wind slab avalanches remain the main concern on northerly aspects at upper and mid elevations however, there is also a possibility of seeing storm slab avalanches today in areas that received larger amounts of snow. Heightened caution is recommended if you are traveling into the backcountry 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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6-12” of new snow fell in the early morning hours yesterday in many areas throughout the range.  This snowfall was accompanied by strong SW winds. Wind speeds have dropped significantly since the storm began to clear and are predicted to stay light today even at upper elevations.  While the likelihood of continued slab development has diminished, wind slabs deposited during the storm will still be sensitive to human trigger.  Problem areas will be primarily on northerly aspects at mid and upper elevations where terrain features encourage drifting. The leeward sides of ridgelines, gully features and cross-loaded depressions are all suspect.   Surface clues such as blowing snow, recent cornice growth and uneven snow surfaces can help identify and avoid areas of recent wind deposit. 

 

Avalanche Problem 2: Storm Slab
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Storm totals yesterday exceeded our expectations and widespread sensitive storm slab activity was reported in the Mammoth area.  While the sensitivity of Storm slab avalanches has likely decreased today it will not be impossible to find residual storm instabilities.  Wumphing, shooting cracks and recent avalanches are all signs of nearby hazard.  Heightened caution is advised in steep terrain particularly in areas where terrain features increase the consequence of an avalanche. It is also important to note that this recent storm did not perform uniformly around the forecast area. While the Mammoth area received nearly a foot of new snow at upper elevations observations reported only a couple inches in the Lee Vining area.  Localized assessment will be crucial, and the potential for storm instabilities will greatly decrease in areas that received less snowfall.

Avalanche Problem 3: Loose Wet
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With relatively warm temperatures, light winds, and periods of intense sun today it may be possible to see some loose wet activity on solar aspects at lower elevations.  Be particularly aware of warming as the afternoon approaches.  Cloud cover may lead to some greenhouse effects, raising the temperature and increasing the likelihood of loose wet activity. A wet, sticky snow surface and rollerballs are both signs of surface warming and may foreshadow larger point release avalanches.

advisory discussion

Yesterday's storm took many by surprise.  Widespread avalanching was reported in areas that received enough new snow.  While these reported avalanches were small for the most part, some were large enough to bury a person and most were reported as sensitive, running fairly long distances. While things settle down it’s a good time to take stock and remind our selves that even relatively small spring storms can bring a variety of avalanche concerns. Use localized assessments and keep an eye on the weather. Conditions can change rapidly, particularly this time of year. 

Weather and CURRENT CONDITIONS
weather summary

Expect mostly cloudy skies today with scattered snow showers throughout the day.  Up to 1” of new snow is expected.  Temperatures will be in the mid to upper 20’s today at upper elevations and light winds are expected out of the west with gusts up to 25MPH on ridge tops. Expect clearing skies and temperatures in the mid teens tonight. 

 

Unseated weather will continue to impact the area through much of next week. Models are somewhat mixed but we can expect to see more precipitation in the near future.

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. Scattered snow showers in the morning, then chance of snow showers in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 55%. Mostly cloudy then becoming clear. Slight chance of snow showers in the evening. Snow levels below 7000 feet. Chance of precipitation is 20%. Sunny then becoming partly cloudy. Slight chance of snow showers in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 15%.
Temperatures: 30 to 38. deg. F. 16 to 22. deg. F. 33 to 43. deg. F.
Mid Slope Winds: Light winds becoming northwest around 15 mph with gusts to 25 mph in the afternoon. West around 15 mph in the evening becoming light. Gusts up to 25 mph. Light winds becoming southwest around 15 mph in the afternoon. Gusts up to 25 mph.
Expected snowfall: 70% probability up to 1 inches. 30% probability of 1 to 3 inches. | SWE = less than 0.10 inch. in. No accumulation. | SWE = trace amounts. in. 10% probability up to 1 inch. 90% probability up to 0 inches. | SWE = trace amounts. in.
Over 10,000 ft.
Thursday Thursday Night Friday
Weather: Mostly cloudy. Widespread 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 partly cloudy. Slight chance of snow showers in the evening. Snow levels below 7000 feet. Chance of precipitation is 20%. Sunny then becoming mostly cloudy. Slight chance of snow showers in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 15%.
Temperatures: 22 to 28. deg. F. 11 to 16. deg. F. 26 to 32. deg. F.
Ridge Top Winds: West around 15 mph with gusts to 25 mph. West around 15 mph with gusts to 30 mph. West 15 to 20 mph with gusts to 30 mph.
Expected snowfall: 70% probability up to 1 inches. 30% probability of 1 to 3 inches. | SWE = less than 0.10 inch. in. 30% probability up to 1 inch. 70% probability up to 0 inches. | SWE = trace amounts. in. 20% probability up to 1 inch. 80% probability up to 0 inches. | SWE = less than 0.10 inch. 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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