Avalanche Advisory: Sunday - Apr 1, 2018

 
 
 
 
 
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THIS AVALANCHE ADVISORY EXPIRED ON April 2, 2018 @ 6:56 am
Avalanche Advisory published on April 1, 2018 @ 6:56 am
Issued by Doug Lewis - Eastern Sierra Avalanche Center

Sunday (4/1) – As the snow begins to thaw during the day, the avalanche danger will quickly rise to MODERATE for all elevations, including Low elevations, where there’s snow. Loose Wet avalanches are especially possible in steep, rocky, or vegetated terrain. Above treeline, Loose Wet are expected to be a bit more isolated. Watch for extensive rollerballs and small point releases or deep wet snow at the surface.

* Slide For Life conditions potentially exists during the AM hours, especially in the Alpine. Firm spring snow conditions can make it incredibly hard to arrest a fall on steep slopes with possible high consequences. If planning on riding in steep or complex terrain the ability to arrest a fall is critical. Crampons, ice axes, and a helmet are strongly advised.

2. Moderate

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

2. Moderate

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

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Loose Wet
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    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
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    Very Large
    Large
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Another modest freeze overnight with lows struggling to fall below freezing. Forecasted high temperatures are expected to climb into the upper 50’s below 10,000’, upper 40’s in the upper elevations. This combination will allow the surface snow to warm quickly this AM and become wet and saturated, especially in steep and/or rocky terrain by mid-afternoon. Loose Wet avalanches are possible on all aspects but will become an issue more quickly on E-S-W aspects where there is rapid solar warming of the surface snow. Generally, the snow at the lower elevations thaws more quickly. Use extra caution in and around rock outcroppings, cliff bands, or sheltered areas where the snowpack may heat up more quickly and triggered releases are more likely. Signs of unstable snow: large roller balls, deep ski penetration, and small point releases. Loose Wet can trigger larger deeper releases, especially in the mid and lower elevations (~9000’ and below) where the snow has become isothermal and saturated. Time your travels to be out of steep sunny terrain before the snow becomes overly saturated from the heat of the day. Natural avalanches are unlikely (small point releases possible), triggered releases are possible, especially in sheltered or rocky terrain.

Loose Wet slides are dense / heavy and can be difficult to extract yourself if entrained and are capable of carrying a rider into hazardous terrain or lead to possible burial, though unlikely, when combined with a terrain trap.

* Slide For Life conditions potentially exist during the AM hours, especially in the Alpine. Firm spring snow conditions can make it incredibly hard to arrest a fall on steep slopes with possible high consequences. If planning on riding in steep or complex terrain the ability to arrest a fall is critical. Crampons, ice axes, and a helmet are strongly advised.

advisory discussion

Loose Wet – Low temperatures overnight struggled to fall below 32 degrees for any length of time. Todays forecast is calling for sunny skies with high temperatures climbing into the upper 40’s and 50’s below 10,000’, while above 10,000’, temps are forecasted to bump up against the upper 40’s. Light to moderate Southwesterly winds above treeline are forecasted, which will likely delay thawing somewhat in the upper elevations due to air mixing and convective cooling. From treeline (~10,500’) and below, winds will be very light, limiting convective cooling, so expect the snow to thaw more rapidly as the temperatures climb quickly due to minimal mixing. Solar aspects will warm the quickest, with northerly and shaded aspects following. Terrain can accentuate the problem, such as cirques and bowls, and rocky gullies can amplify and retain more heat than open slopes. Loose Wet avalanches often originate from cliffs or trees. The northerly and shaded slopes above ~9000’ are seeing strong warming at the surface but remain below freezing deeper in the snowpack. As a result, Loose Wet releases on northerly aspects are less likely to erode deeply into the snowpack and will generally be more limited in size. If you’re having trouble making turns because the snow is too deep or boot penetration becomes excessive, this is a strong sign that the surface snow is saturated and it’s time to move onto slopes with firmer snow, shady slopes, or lower angles.  

 

 

 

 

recent observations

Mammoth Rock Bowl, Sherwin Trees: Warming (3/31)

Old Man's Bowl: Tracking Warming (3/31)

Lower Esha (3/29)

Red Cone: Thaw (3/29)

Little Slide Canyon: Snowpit and Obs (3/28)

Lundy Canyon: Stability and Warming (3/28)

Solitude Canyon: Warming (3/28)

Temperatures @ 0400

Loc                                          Highs/Lows

Virginia Ridge, 9409’:             52/33 deg F, no freeze
Tioga Pass, 9972’:                 48/26 deg F. 8hrs freezing
Agnew Pass, 9355’:               55/28 deg F, 5hrs freezing
June Mt., 9148’:                    53/35 deg F, no freeze
Mammoth Pass, 9500’:           58/29 deg F, 5hr freezing
Sesame Plot, 9014’:               52/34 deg F, no freeze
Ch. 22-MMSA, 10,067’:          47/36 deg F, no freeze
Summit-MMSA, 11,053’:         39/30 deg F, 3hrs freezing
Rock Creek, 9600’:                 50/26 deg F, 6hrs freezing
South Lake, 9580’:                 59/27 deg F, 7hrs freezing
Sawmill, 10,200’:                    51/23 deg F, 8hrs freezing 

 

 

 

Weather and CURRENT CONDITIONS
weather summary

Sun thru Thursday - A fast moving system moving through Oregon today will create breezy conditions this afternoon with gusts around 25-30 mph. Winds will stay breezy overnight along the ridgetops, shifting to the north and weakening some on Monday. Today (Sunday), temperatures will be well above average (10-15 F), moderating somewhat to 5 degrees above average on Monday as cooler air moves through northern Nevada. Tuesday calm winds with temperatures rising back to well above seasonal. A nearly zonal flow will prevail Wednesday-Thursday with extensive high clouds and temperatures remaining mild and typical afternoon breezes.

Friday-Saturday - Abundant moisture will push into the west coast Friday followed by a strong trough Friday night and Saturday. Dynamics at first are not that impressive with precipitation partly due to warm advection Friday. QPF was kept on the light side with this initial push of moisture with best chances for rain Friday along the Sierra. Snow levels rise behind this first wave possibly reaching as high as 10000 feet Friday afternoon. A brief letup in the precipitation will occur early Friday night as the main atmospheric river approaches northern CA ahead of main trough. Snow levels will remain high (probably above 8000-9000 feet) at least until the upper trough gets close enough to the west coast for temperatures aloft to finally begin cooling with the most notable cooling occurring toward the end of the main precipitation event. The warm nature of this moisture push promises mostly rain before 18Z Saturday with precipitation intensifying as it works south down the Sierra Saturday. As the trough and front work southeast through the area Saturday afternoon, the moisture tap will get cut off from north to south with a brief period of heavy snow for the highest elevations as snow levels drop. Current QPF projections are for 2-2.5" along the crest. Strong west winds will develop midday Saturday as the cold front works across the area. The trough quickly exits Saturday night with a ridge developing Sunday for mild and drier conditions along with lighter winds.

 

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Sunday Sunday Night Monday
Weather: Sunny Clear Partly Cloudy
Temperatures: 49 to 59 deg. F. 30 to 35 deg. F. 45 to 53 deg. F.
Wind Direction: Light winds becoming southwest Southwest West
Wind Speed: 10 to 15 mph in the afternoon. Gusts up to 35 mph. 10 to 20 mph. Gusts up to 40 mph decreasing to 30 mph after midnight. 10 to 20 mph with gusts to 35 mph.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Sunday Sunday Night Monday
Weather: Sunny Clear Partly cloudy
Temperatures: 38 to 48 deg. F. 25 to 30 deg. F. 33 to 42 deg. F.
Wind Direction: Southwest Southwest West
Wind Speed: 15 to 25 mph with gusts to 35 mph. 20 to 30 mph with gusts to 45 mph. 20 to 30 mph with gusts to 45 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 Snowpack Summary is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.

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