Avalanche Advisory: Wednesday - Mar 20, 2019

THIS AVALANCHE ADVISORY EXPIRED ON March 21, 2019 @ 6:35 am
Avalanche Advisory published on March 20, 2019 @ 6:35 am
Issued by Steve Mace - ESAC

The avalanche danger will rise to CONSIDERABLE today at mid and upper elevations and MODERATE at lower elevations.  Upwards of 6" of new snow fell last night in the Mammoth area. Couple this with increased southerly winds today and we can expect fresh sensitive wind slab development on northerly aspects at mid and upper elevations.  

3. Considerable

?

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

3. Considerable

?

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

2. Moderate

?

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
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Snowfall totals from last night will vary throughout the range but there is ample new snow available for transport. While continued snowfall will be minimal today moderate winds are expected to persist. Expect fresh sensitive wind slab development to on northerly aspects at mid and upper elevations. 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.   Surface clues such as blowing snow, recent cornice growth and uneven snow surfaces can help identify and avoid areas of recent wind deposit. 

advisory discussion

Our recent stint of spring-like conditions has been a welcome change to the heavy snowfall of February. However as winter returns this week it will be important to keep in mind that the mixture of warm sunny days and cold clear nights have left us with variable surface conditions. Southerly aspects received intense solar warming this past week, leading to a consolidating and in some places diminishing snowpack.  Shaded northerly terrain saw pretty extensive near surface faceting with recent observations noting loose sugary snow on the surface or buried underneath shallow melt-freeze crusts.  While this kept ski conditions enjoyable it may lead to poor bonding between the new snow and the old, adding to the sensitivity of fresh wind slabs.  

Make no mistake the danger trend is increasing, in addition to the wind slab concern if snowfall totals are more than expected we may start to see some signs of storm slab development even at lower elevations. Today is a good day to be aware of the conditions in your local areas and to keep track of how changing weather conditions are affecting the stability.  An important factor to consider as more active weather returns to the range is the variability of our forecast area.  While Mammoth received 6” last night snow totals may be less in the southern reaches of the zone.  This elevates the importance of localized assessment. We encourage you to continue to submit your observations as these help us provide more accurate information in turn.  Thank you for your continued support.

Weather and CURRENT CONDITIONS
weather summary

Winter returns to the area today.  Expect mostly cloudy skies today with intermittent snow showers throughout the day. Snowfall is expected to increase this afternoon with a slight chance of thunderstorms this evening.  

Temperatures today will be in the mid to upper 20’s at upper elevations, dropping into the teens overnight. Moderate south winds are expected today with gusts of 60 mph on ridge tops.  Tonight we can expect increasing snow showers as the winds decrease and shift to the west.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Wednesday Wednesday Night Thursday
Weather: Mostly cloudy. A chance of snow showers in the morning, then widespread snow showers and slight chance of thunderstorms in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 70%. Mostly cloudy. Widespread snow showers and slight chance of thunderstorms in the evening, then snow showers likely after midnight. Snow levels below 7000 feet. Chance of precipitation is 70%. Mostly cloudy. Snow showers likely. Snow levels below 7000 feet. Chance of precipitation is 55%.
Temperatures: 31 to 39. deg. F. 18 to 24. deg. F. 30 to 38. deg. F.
Mid Slope Winds: South to southwest 10 to 20 mph with gusts to 40 mph. Northwest to north 10 to 20 mph. North to northwest 10 to 20 mph.
Expected snowfall: 70% probability up to 1 inch. 30% probability 1 to 2 inches. | SWE = less than 0.10 inch. in. 60% probability of 1 to 3 inches. 40% probability of 2 to 4 inches. | SWE = up to 0.20 inch. in. up to 2 inches. | SWE = less than 0.15 inch. in.
Over 10,000 ft.
Wednesday Wednesday Night Thursday
Weather: Mostly cloudy. A chance of snow showers in the morning, then widespread snow showers and slight chance of thunderstorms in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 70%. Mostly cloudy. Widespread snow showers and slight chance of thunderstorms in the evening, then snow showers likely after midnight. Snow levels below 7000 feet. Chance of precipitation is 70%. Mostly cloudy. Snow showers likely. Snow levels below 7000 feet. Chance of precipitation is 60%.
Temperatures: 22 to 28. deg. F. 12 to 17. deg. F. 22 to 28. deg. F.
Ridge Top Winds: Southwest 20 to 35 mph with gusts up to 60 mph decreasing to 15 to 25 mph in the afternoon. West winds 10 to 20 mph becoming north 15 to 25 mph after midnight. West to northwest 15 to 25 mph.
Expected snowfall: 70% probability up to 1 inch. 30% probability 1 to 3 inches. | SWE = less than 0.10 inch. in. 60% probability of 1 to 3 inches. 40% probability of 2 to 4 inches. | SWE = up to 0.25 inch. in. up to 2 inches. | SWE = up to 0.15 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.

ESAC receives support from ...