Avalanche Advisory: Thursday - Apr 11, 2019

THIS AVALANCHE ADVISORY EXPIRED ON April 13, 2019 @ 6:38 am
Avalanche Advisory published on April 11, 2019 @ 6:38 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

This Avalanche Advisory is in effect for April 11-12

Danger ratings will no longer be formally issued as they can change over multiple day periods

Thursday 4/11 – Fresh WIND SLAB will be the primary concern on ALL ASPECTS at High elevations. Recent additions of light snowfall Tuesday and Thursday afternoon combined with recent strong NORTHERLY winds will likely produce sensitive areas of loaded snow. Wind direction is also slated to switch to a more WESTERLY pattern today, moving fresh snow dynamically. Human triggered avalanches may be possible in leeward deposition zones such as couloirs and alpine cirques. Evaluate snow and terrain carefully and be on the lookout for red flags such as recent avalanche activity, shooting cracks, and pillows, or fat looking snow surfaces. Also maintain awareness for wet-loose avalanches on S-W aspects if solar aspects start to heat up.

Friday 4/12 – Heightened avalanche conditions for WET-LOOSE avalanches will exist primarily on E-S-W ASPECTS at all elevations. Recent new snowfall getting cooked by solar input and warming temps will likely cause avalanche activity. Human triggered avalanches, as well as natural avalanches, may be possible on specific terrain features such as tight and confined couloirs, heated rock bands, cliffs, and cornice lines. Evaluate snow and terrain carefully and identify features of concern.

 

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Avalanche Problem 1: Wind Slab
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Thursday 4/11 - New WIND SLAB on leeward SOUTHERLY-EASTERLY aspects will be of most concern Thursday, but ALL ASPECTS could be suspect with changing winds to the west today. There is still cold soft snow residing in much of the high sheltered northerly terrain that has been actively stripped by the recent Northerly winds. This old transportable snow is in addition to the recent light snowfall of Tuesday and new snow predicted for today. Plenty of snow was visibly being transported up high on Wednesday from the Northerly winds. Be vigilant for potential fresh wind slab on ALL ASPECTS up high today. Evaluating specific terrain features and looking for freshly formed wind deposited snow will be key to travel in the mountains the next few days.

Friday 4/12 - Prevailing NORTHERLY-WESTERLY winds combined with new snowfall from Tuesday and Thursday will load primarily E-S-W slopes throughout the forecast zone, but ALL ASPECTS should be given consideration in relation to fresh wind slab formation. Terrain conducive to wind loading such as leeward cirques, gullies, cornice lines and catchment areas will be most sensitive to both human and natural triggers. Pay particular attention when travelling in terrain that is exposed from above, where avalanche danger may escalate with new snowfall and loading wind.

 

Avalanche Problem 2: Loose Wet
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Thursday 4/11 – The snowpack is continuing to transition to spring like conditions, but it is taking a while with the unsettled weather and ongoing light accumulations of new snow.  Last night saw a good hard freeze with temperatures lowering to the 20’s at 9000ft which will help lock up the snowpack. This freeze combined with cooler and stormy weather Thursday will help minimize the wet-loose avalanche problem, but you should still perform your own local assessment as the forecast area is large, and lengthy north to south… weather forecasts are tricky for our remote area. Check the snow for supportability by checking for boot penetration, and be on the lookout for active snow shedding such as roller balls and loose snow avalanches.

Friday 4/12 –A forecasted hard freeze Thursday night will help keep things locked up Friday, but the main issue will be the warming and loosening of the newly fallen snow. Wet-loose avalanche problems will rise to the forefront of concerns Friday as there will be increased solar input, warmer temperatures and fresh deposited snow residing on sunny aspects. This will be a perfect scenario for wet-loose avalanche conditions. Pay attention at all elevations and particularly to topography where rock features are getting heated up above skiing terrain (E-S-W). Be on the lookout for active roller balling, pinwheels, or recent avalanche activity. Also, check the snow for supportability by taking off your ski or snowboard and seeing what your boot penetration is, if you’re going beyond boot top, it may be time turn around. Although slides will generally be small in size, they could be exponentially worse in exposed areas, where a fall could be nasty.

 

advisory discussion

As the second ski season is in full swing, the ESAC forecasters would again like to THANK all the folks out there that continue to post observations to the website.  This is invaluable information for everybody to see and hear about. Good turns will be had for some time to come, so please let us know what your finding out there.  THANKS SO MUCH & Happy Trails!!!

recent observations
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4/10 – Crowley Area - McGee Mountain – new snow, minor wind slab

4/10 – Convict Area – Old Man’s Bowl – snow conditions

4/10 – Bishop Creek – Table Mtn –recent wet loose avalanches

4/9 – Mammoth Area – Sherwins – snow conditions

4/9– Mt Tinemaha – multiple wet loose avalanches this week

Weather and CURRENT CONDITIONS
weather summary

Thursday 4/11 –A weak system affects the area today with snow showers on tap for the afternoon and evening.  2” of new snow may be possible.  Partly sunny start to the day with increasing clouds is likely as the system is set to move over the area later in the day.  NW to W winds 15-20 mph with gusts up to 40 mph above 10,000ft are predicted. Temperatures will be cooler with 25-35F at lower elevations while 21-29F will keep things chilly up high.

 Friday 4/12 –Partly cloudy, then sunny conditions return Friday with continued northerly winds, but at slightly lower velocities. All elevations above 8000’ could see 15-25mph North winds with gusts to 35mph. Temperatures of 33-44F below 10,000ft and 27-33F in the higher mountains are slated for the area which will start to loosen the snowpack up, especially new snow deposits from previous days. A Sunny weekend is forecast for the area before chance of snow and inclement weather returns Sunday night and Monday.

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: Mostly cloudy. Slight chance of snow showers in the morning, then snow showers likely in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 70%. Mostly cloudy. Chance of snow showers through the night. Snow levels below 7000 feet. Chance of precipitation is 50%. Partly cloudy then becoming sunny. Snow levels below 7000 feet. Chance of precipitation is 10%.
Temperatures: 30 to 40. deg. F. 17 to 23. deg. F. 33 to 41. deg. F.
Mid Slope Winds: West 15 to 20 mph with gusts to 30 mph. North around 15 mph with gusts to 35 mph. North around 15 mph with gusts to 30 mph.
Expected snowfall: 60% probability up to 2 inches. 40% probability of 1 to 3 inches. | SWE = less than 0.10 inch. in. 60% probability up to 1 inch. 40% probability of 2 to 4 inches. | SWE = less than 0.10 inch. in. No accumulation. | SWE = none. in.
Over 10,000 ft.
Thursday Thursday Night Friday
Weather: Mostly cloudy. Slight chance of snow showers in the morning, then snow showers likely in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 75%. Mostly cloudy. Chance of snow showers in the evening. Snow levels below 7000 feet. Chance of precipitation is 55%. Partly cloudy then becoming sunny. Snow levels below 7000 feet. Chance of precipitation is 5%.
Temperatures: 23 to 31. deg. F. 12 to 17. deg. F. 27 to 33. deg. F.
Ridge Top Winds: West 15 to 25 mph with gusts to 35 mph. North 15 to 25 mph with gusts to 35 mph. North 15 to 25 mph with gusts to 35 mph.
Expected snowfall: 70% probability up to 2 inches. 30% probability of 3 to 4 inches. | SWE = up to 0.15 inch. in. 60% probability up to 1 inch. 40% probability of 3 to 4 inches. | 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.

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