Avalanche Advisory: Thursday - Mar 26, 2020 | Eastern Sierra Avalanche Center

THIS AVALANCHE ADVISORY EXPIRED ON March 27, 2020 @ 6:28 am
Avalanche Advisory published on March 26, 2020 @ 6:28 am

Issued by Steve Mace - ESAC

Bottom Line

10” of new snow has been recorded in the Mammoth area over the last 24 hrs. this new snow was accompanied by strong winds out of the southwest. Fresh and sensitive wind slabs will be the primary concern today on northerly and easterly aspects near and above treeline. CONSIDERABLE avalanche danger exists at upper elevations, and MODERATE danger exists mid and lower elevations. The size and distribution of fresh wind slabs may increase this morning if winds remain higher than expected. Loose-dry avalanches will also be possible today in steep and sheltered terrain. Heightened avalanche conditions exist, conservative decision making, and cautious route-finding is recommended.

3. Considerable

Above Treeline

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

2. Moderate

Near Treeline

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

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

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10” of new snow was recorded in the Mammoth area over the last 24 hours bringing the storm total to 14”. This snow was accompanied by strong to very strong winds southwest winds. Wind speeds are forecasted to drop significantly today which may limit new slab development. However fresh wind slabs deposited during the storm may be large and are likely sensitive to human triggers. NW-N-E-SE aspects at mid and upper elevations will be of greatest concern. 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, large drifts, dense hollow feeling snow, and recent cornice growth can help you identify and avoid areas of recent wind deposit.

Avalanche Problem 2: Loose Dry

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Field observations indicated the new snow from yesterday’s storm to be very low density and unconsolidated. With 1-3" of snow possible today and continued cold temperatures, loose dry avalanches will be likely in steep and sheltered terrain. Be particularly cautious on slopes over 35° in areas with terrain features that may increase the consequences of an avalanche. Steep confined gullies, cliff bands, creek beds, and mid-slope benches all pose an increased hazard.

advisory discussion

Yesterday’s storm produced more new snow than expected and led to a notable rise in the avalanche hazard. This storm was concentrated in the northern part of the range, the Bishop area received significantly less snow. You can expect the avalanche hazard to be higher in the Mammoth area and areas to the north.

It is important to remember that we are still dealing with a shallow snowpack. Shallowly buried rocks and trees remain a significant hazard, particularly at lower elevations. Now is a good time to tone it down. Every care should be taken to avoid injuries and unnecessary risk at this point in time.

recent observations

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3/25- Mammoth Area- Natural wind slab activity, new snow, strong winds in the Sherwins

3/25- June Lake- Sensitive Wind slab activity

3/24- Virginia Lakes- Strong winds, reactive wind slabs

3/24- Mammoth Area- Strong winds in the Lakes Basin

Weather and CURRENT CONDITIONS

weather summary

Expect mostly cloudy skies and cold temperatures with scattered snow showers throughout the day today. 1-3” of snow is possible today and there is a slight chance of thunderstorms this afternoon. Winds are expected to drop this morning becoming light even at upper elevations.

Sunny skies and warmer temperatures are expected tomorrow before another period of unsettled weather moves through the region this weekend.

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 then becoming mostly cloudy. Scattered snow showers through the day. Slight chance of thunderstorms in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 55%.	Mostly cloudy then becoming clear. Slight chance of thunderstorms and isolated snow showers in the evening. Snow levels below 7000 feet. Chance of precipitation is 25%.	Sunny.
Temperatures:	21 to 29. deg. F.	6 to 12. deg. F.	30 to 38. deg. F.
Mid Slope Winds:	Light winds.	North around 15 mph in the evening becoming light.	Light winds.
Expected snowfall:	80% probability of 1 to 3 inches. 20% probability of 3 to 5 inches. \| SWE = up to 0.15 inch. in.	Up to 1 inch. \| SWE = less than 0.10 inch. in.	0 in.

Over 10,000 ft.

	Thursday	Thursday Night	Friday
Weather:	Partly cloudy then becoming mostly cloudy. Isolated 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 60%.	Mostly cloudy then becoming clear. Scattered snow showers and slight chance of thunderstorms in the evening. Snow levels below 7000 feet. Chance of precipitation is 30%.	Sunny.
Temperatures:	13 to 20. deg. F.	Zero to 6 above zero. deg. F.	23 to 29. deg. F.
Ridge Top Winds:	Light winds.	North around 15 mph with gusts to 25 mph.	Northwest around 15 mph with gusts to 25 mph.
Expected snowfall:	80% probability of 1 to 3 inches. 20% probability of 3 to 5 inches. \| SWE = up to 0.15 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.