Avalanche Advisory: Saturday - Dec 28, 2019

THIS AVALANCHE ADVISORY EXPIRED ON December 29, 2019 @ 6:13 am
Avalanche Advisory published on December 28, 2019 @ 6:13 am
Issued by Steve Mace - ESAC

Fresh, sensitive wind slabs on easterly, southerly, and westerly aspects will keep the avalanche danger at CONSIDERABLE today at upper elevations, and MODERATE at mid-elevations.  LOW danger exists in sheltered areas and at lower elevations. 

Use cautious route-finding and conservative decision making as you travel 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.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
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  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Moderate to strong northerly winds will continue to impact the area today leading to continued slab development on more solar aspects. Over the last few days, the winds have been predominantly out of the North Northeast, and significant flagging has been observed on ridge tops throughout the forecast area. We may see a slight shift in the wind direction to the Northwest today, elevating concern on more easterly aspects as well. You can expect the size, sensitivity, and distribution of dangerous wind slab to increase as you travel up in elevation today. Use surface clues such as blowing snow, recent cornice growth, and uneven snow surfaces to help you identify and avoid areas of recent wind deposit. Do your own localized assessments and be suspect of terrain features that encourage drifting such as the leeward sides of ridgelines, gully features, and cross-loaded depressions.   

advisory discussion

A brief winter storm on Christmas night brought a substantial load of new low-density snow to areas north of June lake, while the more southern reaches of the forecast area saw very little. This has led to a significant discrepancy in corresponding avalanche danger and problem distribution. While storm instabilities, particularly loose dry avalanche potential has been a real concern in areas north of Mammoth, these concerns have been much less in areas that received less snow.  Wind slabs will be the exception to this trend. While there is certainly more snow available for transport in the northern reaches of the forecast area, the risk of sensitive wind slabs will be present throughout the range. Be on the lookout for fresh wind loading regardless of where you decide to make your weekend plans.

If you do decide to venture into areas north of June Lake, expect the potential size of wind slabs to increase substantially. It’s also worth extra caution in steep confined terrain that is more sheltered from the wind where there is still a chance of loose dry activity. Even a small loose slough could entrain enough snow to carry a skier through unpleasant terrain.  

The 2019/20 season has been exceptional thus far here on the east side with several significant storms and unseasonable cold temperatures.  While the ski quality has been very good, it is essential to remember that preseason conditions still exist throughout the forecast area. Recent snow has hidden many obstacles, but rocks, fallen trees, open creeks, and other hazards are still lurking just below the surface. Pick your travel routes carefully, slow it down, and lets all hope for another long winter season. 

Weather and CURRENT CONDITIONS
weather summary

You can expect another pleasant day today with clear skies and chilly temperatures. Northerly winds will continue to impact the area today with sustained mid-slope speeds expected in the 15-25 mph range and ridgetop gusts reaching as high as 50 mph.

A weak low-pressure system is expected to impact the area tomorrow evening and into Monday, bringing light snow showers and slightly warmer temperatures.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Saturday Saturday Night Sunday
Weather: Sunny. Partly cloudy. Mostly cloudy. Slight chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 20%.
Temperatures: 29 to 35. deg. F. 15 to 20. deg. F. 30 to 38. deg. F.
Mid Slope Winds: Northwest 15 to 20 mph with gusts to 40 mph. Northwest around 15 mph with gusts to 35 mph. Southwest 15 to 20 mph. Gusts up to 30 mph increasing to 40 mph in the afternoon.
Expected snowfall: 0 in. 0 in. No accumulation. | SWE = trace amounts. in.
Over 10,000 ft.
Saturday Saturday Night Sunday
Weather: Sunny. Partly cloudy. Mostly cloudy. Slight chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 25%.
Temperatures: 23 to 29. deg. F. 11 to 16. deg. F. 22 to 30. deg. F.
Ridge Top Winds: North 20 to 30 mph with gusts to 50 mph. Northwest 15 to 30 mph with gusts to 45 mph. Southwest 15 to 30 mph with gusts to 40 mph.
Expected snowfall: 0 in. 0 in. No accumulation. | SWE = trace amounts. 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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