Avalanche Advisory: Monday - Feb 4, 2019

THIS AVALANCHE ADVISORY EXPIRED ON February 5, 2019 @ 6:53 am
Avalanche Advisory published on February 4, 2019 @ 6:53 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

Avalanche danger continues at HIGH for today.  Over 5ft of snow has fallen at many higher elevation areas since beginning Friday night.  An additional 2-3ft is likely by tomorrow morning, accompanied by continued very strong SW winds.  Large avalanches will continue to be very likely.  Travel in or under avalanche terrain is NOT recommended.  

4. High

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Above Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

4. High

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Near Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

4. High

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Below Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
    Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Wind Slab
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As snowfall intensities increase again today accompanied by continued strong S to SW winds, large sensitive wind slabs will be widespread in all areas where terrain results in decreased wind speeds and deposition.  The leeward side of ridges, sidewalls of gullies, the edges of forests and across open slopes will be the most obvious places to find these wind slabs.  Remember winds can deposit snow at far greater rates than it can fall from the sky!  Avoid being on or under slopes steeper than 30° with denser wind deposited snow.

Avalanche Problem 2: Storm Slab
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Snowfall intensity will increase significantly today from yesterday, with up to 3” an hour possible at times.  Dangerous storm slabs in all areas protected from the wind will be likely.  Watch for shooting cracks and avoid even small steeper slopes that end in a gully or terrain trap.  Don’t let the significant loose dry surface sloughing fool you into thinking that what is slightly more dense deeper down can’t be triggered resulting in a larger and even more dangerous storm slab avalanche.  Travel on or under slopes greater than 30° is NOT recommended.  

Avalanche Problem 3: Loose Dry
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Colder temperatures will result in decreasing density of new snowfall, making significant Loose Dry avalanching certain on slopes with any kind of steepness today where unconsolidated snow exists.  The amount of snow entrained in these loose dry sloughs will be plenty to carry and bury a person on their own, regardless of their potential to step down and trigger a larger slab avalanche.

advisory discussion

The shear amount of new snow that has fallen since Friday night could result in avalanches running much further than expected.  Areas such as Mammoth Rock Bowl in the Sherwins come to mind when thinking about a large avalanche occurring near a ridge-top and running into what is usually thought of as low-angle safe terrain.  Be aware of what is above you!  

Besides avalanches, be aware of the very real dangers that exist with deep snow emersion! Tree-wells are especially concerning, but falling anywhere in unconsolidated snow today will be a great struggle to get up from without a partner nearby to help save you.  And watch out in town around buildings with heavy snow-loads hanging on roofs!

The persistent slab problem was replaced by the more immediate concern over very likely significant loose dry avalanching today.  That isn’t to say that deeper weaker layers, especially in areas with prior shallow snow-packs, are not concerning.  It is just that now with the amount of new snow that has fallen, very large avalanches are possible everywhere.

Weather and CURRENT CONDITIONS
weather summary

*Winter Storm Warning in effect until 4pm Tuesday

*Blizzard Warning in effect until 10pm Monday

Our winter storm of the season continues with another 3-4ft of snow likely at higher elevations before tapering off thru the day tomorrow.  Winds will be very strong from the south to southwest gusting up to 90mph over ridge-tops.  Temperatures will continue to drop until reaching near zero degrees Tuesday night.  Sunshine, our long lost friend, should return for a couple of days on Wednesday and Thursday before uncertain chances of more snow returns.     

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: Cloudy. Snow. Cloudy. Snow. Cloudy. Snow.
Temperatures: 22 to 30. deg. F. 8 to 13. deg. F. 14 to 20. deg. F.
Mid Slope Winds: South 20 to 35 mph with gusts to 65 mph. Southwest 15 to 30 mph with gusts to 60 mph. Southwest 15 to 20 mph. Gusts up to 50 mph decreasing to 30 mph in the afternoon.
Expected snowfall: 70% probability of 14 to 22 inches. 30% probability of 22 to 30 inches. | SWE = up to 1.15 inches. in. 70% probability of 9 to 17 inches. 30% probability of 17 to 24 inches. | SWE = 0.55-0.80 inch. in. 80% probability of 4 to 8 inches. 20% probability of 9 to 15 inches. | SWE = 0.20-0.45 inch. in.
Over 10,000 ft.
Monday Monday Night Tuesday
Weather: Cloudy. Snow. Cloudy. Snow. Cloudy. Snow.
Temperatures: 15 to 20. deg. F. 2 to 7. deg. F. 8 to 13. deg. F.
Ridge Top Winds: Southwest 40 to 60 mph with gusts to 90 mph. Southwest 35 to 55 mph with gusts to 80 mph. Southwest 30 to 45 mph with gusts to 70 mph decreasing to 20 to 30 mph with gusts to 45 mph in the afternoon.
Expected snowfall: 70% probability of 17 to 25 inches. 30% probability of 25 to 37 inches. | SWE = 0.80-1.30 inches. in. 70% probability of 11 to 19 inches. 30% probability of 20 to 29 inches. | SWE = 0.55-1.05 inches. in. 80% probability of 5 to 12 inches. 20% probability of 12 to 18 inches. | SWE = 0.35-0.50 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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