Avalanche Advisory: Monday - Mar 2, 2020

THIS AVALANCHE ADVISORY EXPIRED ON March 3, 2020 @ 6:44 am
Avalanche Advisory published on March 2, 2020 @ 6:44 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

CONSIDERABLE avalanche danger exists above and near Treeline today. Moderate avalanche danger resides below Treeline. 8-16” of new snow combined with dynamic wind directions (W-SW-N-NE-E) & extreme velocities will have produced WIND SLAB on ALL ASPECTS. Heaviest accumulations were centered on the Mammoth area with reactive wind slab reported yesterday. Pay close attention to complex terrain such as couloirs, rockbands and convex terrain which could be cross-loaded and have erratic loading patterns from the multiple wind directions. Careful route-finding and conservative decision making are 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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New snow yesterday was very light and low density, and with very cold overnight temperatures in the single digits combined with extreme NE winds, this new snow was stripped, removed, and transported widely last night. With all the varying wind direction (W-SW-N-NE-E) over the course of the past 48 hours, expect fresh WIND SLAB on ALL ASPECTS Monday. Sensitive Wind slabs near and adjacent to ridgeline were reactive to skier and explosive trigger yesterday with some slides running healthy distances (500ft). The prevailing NE winds last night will have stripped a lot of starting zones and terrain, but also cross loaded other northerly terrain with features conducive to capturing transported snow. Much of this new snow has been deposited on very firm and slick surfaces where bonding between the new and old snow may be problematic. Identify fat looking pillows of snow and be particularly wary of new cornice development, areas adjacent to ridgeline, gullies, and terrain adjacent to rock bands and collection zones. Take time to communicate with your partners, develop a good plan, and be ready to adjust and change your route.

Avalanche Problem 2: Loose Dry
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Although most terrain likely got stripped by the extreme overnight NE winds, cold overnight temperatures and low density light snow could produce conditions where LOOSE DRY sloughing may present hazard in extreme and confined terrain. This scenario may be found in more sheltered and wind protected zones and where snow settled after being suspended by turbulent overnight winds. Take note if venturing into tight and confined areas or unsupported slopes above cliffs where even a small slough may drag you across surfaces full of rocks and other obstacles.

advisory discussion

Winds, warm temperatures and melt-off all have contributed to producing old snow surfaces that will make it less advantageous for new snow to bond to. There is also the simple fact that much of the snowpack is very thin and hazardous in relation to existing obstacles and challenging skiing surfaces. This first significant snowfall in over 6 weeks will just be hiding a lot of nasty stuff below. Take note; this has not been the season to ski with abandon in the backcountry.

Snow Totals for the past 48hrs as of 630am Monday March 02. (These are sheltered weather plots, locally higher amounts are certain)

Virginia Lakes 9409ft = 2-3”

Agnew Pass near Tuolumne Meadows 9355ft= 12”

June Mountain weather plot 9148ft=5”

Mammoth Pass near Mammoth Lks  9500ft=16”

Rock Creek 9600ft=4”

Sawmill near Big Pine/Bishop area 11919ft=5-6”

recent observations
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3/1- Mammoth Area – Sherwins –Reactive Wind Slab

3/1 – VA Lakes –Snow conditions near Black Mountain

2/28 – VA Lakes –snow conditions

2/27 – Mammoth Lakes Basin –George Lk Ridge snow profile

Weather and CURRENT CONDITIONS
weather summary

After a wintry day in the mountains Sunday we’ll return to sunny conditions, above freezing temperatures and northerly winds Monday. Partly cloudy conditions will give way to sunny skies as N-NE winds of 35-55mph will subside to lower velocities in the afternoon, with gusts still potentially hitting 75mph during the morning. 22-30F above 10000ft witha high of 37F in the lower mountains. Clear, sunny and warmer conditions set in again for the middle of the week.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Monday Monday Night Tuesday
Weather: Partly cloudy then becoming sunny. Snow levels below 7000 feet. Chance of precipitation is 0%. Clear. Snow levels below 7000 feet. Chance of precipitation is 0%. Sunny. Snow levels below 7000 feet increasing to 7500 feet in the afternoon. Chance of precipitation is 0%.
Temperatures: 29 to 37. deg. F. 19 to 25. deg. F. 39 to 47. deg. F.
Mid Slope Winds: North around 15 mph with gusts to 50 mph. Northeast around 15 mph in the evening becoming light. Gusts up to 30 mph. Light winds.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Monday Monday Night Tuesday
Weather: Partly cloudy then becoming sunny. Snow levels below 7000 feet. Chance of precipitation is 0%. Clear. Snow levels below 7000 feet. Chance of precipitation is 0%. Sunny. Snow levels below 7000 feet increasing to 7500 feet in the afternoon. Chance of precipitation is 0%.
Temperatures: 22 to 30. deg. F. 17 to 22. deg. F. 31 to 39. deg. F.
Ridge Top Winds: Northeast 35 to 55 mph decreasing to 25 to 35 mph in the afternoon. Gusts up to 75 mph. Northeast 15 to 25 mph with gusts to 35 mph. North around 15 mph.
Expected snowfall: 0 in. 0 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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