Avalanche Advisory: Thursday - Apr 4, 2019

THIS AVALANCHE ADVISORY EXPIRED ON April 6, 2019 @ 6:39 am
Avalanche Advisory published on April 4, 2019 @ 6:39 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

This Avalanche Advisory is in effect for April 4-5

Thursday 4/4 - Heightened avalanche conditions for WET-LOOSE avalanches will exist on all ASPECTS at all elevations today. Recent new snowfall being affected by solar input and warm temps will continue to cause avalanche activity. Human triggered avalanches may be possible on specific terrain features. Evaluate snow and terrain carefully and identify features of concern.

Friday 4/5 – Fresh WIND SLAB will be the primary concern with the addition of 2” of new snow and potentially deeper accumulations for Friday. This new snow is in addition to previous accumulations Tues (6”) and Thurs (~1”). Strong SW WINDS will work to transport snow to NORTHERLY-EASTERLY aspects at upper and middle elevations. 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.

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Below Treeline
Avalanche Problem 1: Loose Wet
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Thursday 4/4- The snowpack is continuing to warm and transition to spring like conditions. Last night saw only a few hours of below freezing temperatures at 9000ft. This minimal freeze combined with solar input (even when diffused by cloud cover), and cloud cover producing potential greenhouse effects, will lead to moist and wet snow conditions on virtually all aspects. 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. Also be on the lookout for active roller balling, pinwheels, or recent avalanche activity. Although slides will generally be small in size, they could be exponentially worse in exposed areas, where a fall could be nasty, or for simply just injuring your lower leg whilst getting tangled up in a thick moving slough of snow.

Friday 4/5 –A harder freeze overnight Thursday night into Friday and cooler temperatures for the day Friday will decrease the danger of Wet-loose activity for the forecast zone. Wet-loose conditions should be of minimal concern Friday, but still pay attention at lower elevations and in topography with previously existing unconsolidated and hollow snow around boulders, rock outcrops, and trees. Conditions may still heat up in the morning hours before the brunt of the next storm moves into the area later Friday. Again, 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.

 

Avalanche Problem 2: Wind Slab
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Thursday 4/4 - Prevailing SOUTHERLY winds combined with ~6” of new snowfall from Tuesday as well as trace amounts Thursday have the potential to load NORTHERLY-EASTERLY slopes throughout the forecast zone today and tonight. Pay particular attention when traveling in terrain that is exposed from above, where avalanche danger may escalate with new snowfall and loading wind.

Friday 4/5 –New WIND SLAB on leeward NORTHERLY-EASTERLY aspects will be of most concern Friday. Increasing moderate to strong SW WINDS and additions of new snowfall over the course of Thursday and Friday could lead to wind slab development in the upper to middle elevations. 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. Evaluating specific terrain features and freshly formed new wind deposited snow will be key to travel in the mountains the next few days.

 

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4/3 – Buttermilk Area – Basin Mtn –Pt releases on North aspects

4/3 – Mammoth Area – Iron Mtn & Mammoth Crest –natural activity

4/3 – Bishop Creek Area – Bishop Bowl – snow conditions

4/3 – Bridgeport – Sweetwater Mtns – snow conditions

4/2– Mammoth Area – Sherwins – new dense snow

Weather and CURRENT CONDITIONS
weather summary

Thursday 4/4 –A weak system affects the area today with isolated snow showers slated for the afternoon and evening. A trace to 1” of new snow is possible. A sunny start to the day is likely as the system is set to sweep over the area later in the day. SW winds 15-20 mph with gust up to 30 mph above 10000ft are on tap. Temperatures will still be well above freezing at 36-46F at lower elevations while 29-35F will keep things just a bit cooler up high, but not by much.

 Friday 4/5 – Stormy conditions return to the area with stronger winds at 15-25mph with gusts of 40 in the lower elevations with slightly higher rates for the upper elevations (15-30mph & gusts to 50mph). Snow totals predictions have dramatically decreased from initial predictions with around 2” slated for our area. Will have to wait and see if more significant accumulations potentially fall on the Sierra crest starting in the afternoon. Temperatures of 32-42F below 10000ft and 23-31F in the higher mountains are slated for the area which should hold wet-loose snow conditions in check.

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. Isolated showers in the afternoon. Snow levels below 7000 feet increasing to 7500 feet in the afternoon. Chance of precipitation is 15%. Mostly cloudy. Scattered snow showers. Snow levels 7000 feet. Chance of precipitation is 30%. Partly cloudy then becoming mostly cloudy. Scattered snow showers through the day. Snow levels 7000 feet. Chance of precipitation is 65%.
Temperatures: 36 to 46. deg. F. 23 to 28. deg. F. 32 to 42. deg. F.
Mid Slope Winds: Southwest around 15 mph with gusts to 25 mph. Southwest around 15 mph with gusts to 30 mph. Southwest 15 to 25 mph with gusts to 40 mph.
Expected snowfall: 30% probability up to 1 inch. 70% probability of 0 inches. | SWE = less than 0.10 inch. in. 70% probability up to 1 inches. 30% probability of 1 to 2 inches. | SWE = less than 0.10 inch. in. 70% probability up to 2 inches. 30% probability of 2 to 4 inches. | SWE = up to 0.15 inch. in.
Over 10,000 ft.
Thursday Thursday Night Friday
Weather: Mostly cloudy. Isolated snow showers in the afternoon. Snow levels below 7000 feet increasing to 7500 feet in the afternoon. Chance of precipitation is 15%. Mostly cloudy. Scattered snow showers through the night. Snow levels 7000 feet. Chance of precipitation is 30%. Mostly cloudy. Isolated snow showers in the morning, then widespread snow showers in the afternoon. Snow levels 7000 feet. Chance of precipitation is 70%.
Temperatures: 26 to 34. deg. F. 17 to 22. deg. F. 23 to 31. deg. F.
Ridge Top Winds: Southwest 15 to 20 mph with gusts to 30 mph. Southwest 15 to 25 mph with gusts to 35 mph. Southwest 15 to 30 mph with gusts to 50 mph.
Expected snowfall: 40% probability up to 1 inch. 60% probability 0 inches. | SWE = less than 0.10 inch. in. 70% probability up to 1 inch. 30% probability of 2 to 4 inches. | SWE = less than 0.10 inch. in. 70% probability up to 2 inches. 30% probability of 2 to 4 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.

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