Avalanche Advisory: Thursday - Mar 28, 2019

THIS AVALANCHE ADVISORY EXPIRED ON March 29, 2019 @ 6:40 am
Avalanche Advisory published on March 28, 2019 @ 6:40 am
Issued by Steve Mace - ESAC

CONSIDERABLE avalanche danger exists at mid and upper elevations while MODERATE hazard resides at lower elevations.  Fresh, sensitive wind slabs and storm instabilities remain the primary concern today. Avalanche hazard will be heightened in areas that received higher snowfall totals like the Mammoth zone and areas further to the north.   Dangerous avalanche conditions exist; careful localized assessment and conservative terrain selection will be essential today.

3. Considerable

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

3. Considerable

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

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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Just under 10” of new snow has been recorded at the base of Mammoth Mountain in the last 24hr.   It’s very likely that more snow fell at higher elevations. This snowfall was accompanied by strong SW winds. While snow showers are expected to diminish, moderate winds will persist throughout the day. It’s important to remember that moderate wind speeds are the most effective at moving snow and creating wind slabs. Expect fresh sensitive wind slabs to vary in size and distribution.  Problem areas will be primarily on northerly and easterly 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 you identify and avoid areas of recent wind deposit. 

Avalanche Problem 2: Storm Slab
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As the current storm exits the region the sensitivity of storm slab avalanches will decrease. However, it will not be impossible to find residual storm instabilities today, particularly in areas that received higher amounts of precipitation.  Wumphing, shooting cracks and recent avalanches are all signs of nearby hazard. Heightened caution is advised on slopes over 35°, 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 around 10” of new snow and it’s likely that totals were higher further to the north, the southern reaches of the forecast area remained relatively dry.  Localized assessment will be crucial, and the potential for storm instabilities will greatly decrease in areas that received less snowfall.

advisory discussion

Precipitation totals from our most recent storm will vary greatly across the forecast region affecting the size and distribution of potential avalanches accordingly.  Pay close attention to new snow totals in your area and be aware of how the wind is affecting the landscape. We have seen more human-triggered avalanches in the last week then throughout the majority of the season. Most of these incidents involved wind slab avalanches and many were very close calls.  With a new load of fresh snow and continued loading winds things have only gotten more sensitive.  Careful route selection and conservative decision-making will be crucial today don’t let the fresh snow lure you into making poor decisions.

recent observations
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3/27- Mammoth Area, Snow conditions in the Sherwins

3/26- Rock Creek, Large Skier triggered Avalanche

3/26- Mammoth Area, Strong winds in the Sherwins

3/26-Mammoth Area, Snow conditions in Red Cone

3/25- Lundy Canyon, Snow conditions

3/24- Birch Creek, Skier triggered avalanche on the Thumb

3/24- Bridgeport area, Skier triggered avalanche on Kettle peak

3/23- Lee Vining, Skier triggered avalanche, Ripper chute

 

Weather and CURRENT CONDITIONS
weather summary

Expect partly cloudy skies today with a chance of snow showers and isolated thunderstorms throughout the day.  Temperatures will be in the mid to high 20’s at upper elevations. Moderate to strong SW winds will continue today with ridge top gusts expected around 50 mph.  About 1” of snow is expected today 

Snow showers will diminish and wind speeds will continue to drop tonight as this recent storm leaves the region. Tomorrow looks like it will be pleasant partly cloudy skies, no expected precipitation, and light to moderate winds west winds.

High pressure will persist through the weekend bringing warm dry weather. Mild spring storms may return next week though at this point precipitation estimates are low.

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: Partly cloudy. Chance of snow showers through the day. An isolated thunderstorm possible in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 30%. Partly cloudy then becoming clear. Chance of snow showers. Snow levels below 7000 feet. Chance of precipitation is 15%. Partly cloudy.
Temperatures: 29 to 39. deg. F. 14 to 20. deg. F. 32 to 42. deg. F.
Mid Slope Winds: Southwest 15 to 25 mph with gusts to 35 mph. Southwest 15 to 20 mph. Gusts up to 30 mph. West around 10 mph.
Expected snowfall: 60% probability up to 1 inch. 40% probability no accumulation. | SWE = less than 0.10 inch. in. 80% probability no accumulation. 20% probability 1-2 inches | SWE = trace amounts. in. 0 in.
Over 10,000 ft.
Thursday Thursday Night Friday
Weather: Partly cloudy. Chance of snow showers through the day. An isolated thunderstorm possible. Snow levels below 7000 feet. Chance of precipitation is 35%. Partly cloudy. Slight chance of snow showers. Snow levels below 7000 feet. Chance of precipitation is 20%. Partly cloudy.
Temperatures: 21 to 29. deg. F. 8 to 13. deg. F. 25 to 31. deg. F.
Ridge Top Winds: Southwest 20 to 35 mph with gusts to 50 mph. Southwest 15 to 30 mph with gusts to 50 mph. West 10 to 15 mph.
Expected snowfall: 60% probability up to 1 inch. 40% probability no accumulation. | SWE = less than 0.10 inch. in. 80% probability no accumulation. 20% probability 1-2 inches. | SWE = trace amounts. 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.

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