Avalanche Advisory: Saturday - Feb 2, 2019

THIS AVALANCHE ADVISORY EXPIRED ON February 3, 2019 @ 7:00 am
Avalanche Advisory published on February 2, 2019 @ 7:00 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

Avalanche danger is HIGH today.  Up to a foot+ of dense snow fell overnight and 2-3ft+ more is expected before nightfall, all accompanied by ideal moderate wind loading speeds from the south.  Deadly avalanches are 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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Intense snowfall throughout today accompanied by ideal moderate south winds will continuously build large dangerous wind slabs anywhere that terrain results in decreased wind speeds and deposition.  This will most obviously be on the leeward side of ridges, the sidewalls of gullies, and across exposed slopes.  Concern will be greatest on E-N-W facing terrain.  Avoid being on or under areas of denser wind deposited snow.  Deadly natural avalanches will become increasingly likely, and human triggered avalanches very likely. 

Avalanche Problem 2: Storm Slab
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Intense rates of dense snowfall today will result in sensitive storm slabs in all areas protected from the wind.  As snow accumulates throughout today, large natural storm slab avalanches will become increasingly possible, and human triggered storm slab avalanches will be likely.  Be particularly weary of subtle convexities where a storm slab avalanche is most likely to be triggered.  Fragile surface hoar was found in various areas over the last two days, which could lead to even more sensitive triggering and avalanches propagating farther across a slope than expected.  Travel on or under slopes in the mid-30° range and steeper is not recommended.  

Avalanche Problem 3: Persistent Slab
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Various layers of buried weaker snow have been found throughout the forecast area. Although these have been gaining strength and have not been concerning over the past week, the intense new snow load will likely reawaken some of these layers, particularly where shallower snow packs exist.  The force of a smaller wind slab or storm slab avalanche, or simply the heavy new load of snow alone, could result in larger avalanches than expected failing on these deeper weak layers of snow.  Give suspect slopes a wide berth.   

advisory discussion

The intense snowfall and the moderate winds should be convincing enough to avoid traveling on or under avalanche terrain through at least early next week.  If you need to slide on steeper slopes this is a great time to make use of the controlled slopes of Mammoth or June Mountains. But even there with continual snow loading remember to ski or ride with a partner, and wearing a beacon on days like these is always a good idea.   

 

recent observations
Submit Snowpack Observations
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-2/1 - Pine Creek - Elderberry Canyon: Firm crusts and underlying weak sugary snow.

-2/1 - Mammoth - Sherwins: Melt-freeze crusts, areas of new surface hoar.

-2/1 - Mammoth - Sherwins: isolated areas of new small surface hoar, underlying weak layers.

-2/1 - June - Behind June: Firm surfaces, some surface facets.

-1/31 - Bishop Creek: Areas of surface hoar.

Weather and CURRENT CONDITIONS
weather summary

*WINTER STORM WARNING IN EFFECT FROM NOW THRU 4PM TUESDAY 

A series of strong pacific storms will bring heavy snow and strong gusty winds thru Tuesday, with the heaviest snowfall expected to occur throughout today.  A foot of dense snow has already fallen overnight on Mammoth Mtn, with another 2-3feet+ expected at higher elevations before nightfall.  Winds will be moderate from the south with some strong ridgetop gusts up to 75mph.  

1-2ft of additional snow looks likely for each 12 hour period after today thru Tuesday, except for Sunday during the day where less than a foot is expected.  Overall snow-line will be dropping throughout this period with snow becoming less dense, but there will be periods of fluctuation resulting in periods of heavier snow over lighter snow.    

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Saturday Saturday Night Sunday
Weather: Heavy snow. Cloudy. Snow. Cloudy. Snow.
Temperatures: 29 to 34. deg. F. 19 to 24. deg. F. 25 to 32. deg. F.
Mid Slope Winds: South 15 to 25 mph with gusts to 45 mph. South 15 to 30 mph. Gusts up to 45 mph increasing to 55 mph after midnight. Southwest 20 to 35 mph with gusts to 65 mph.
Expected snowfall: 80% probability of 16 to 24 inches. 20% probability of 12 to 16 inches. Liquid Amount...1.00-1.50 inches. in. 80% probability of 8 to 14 inches. 20% probability of 5 to 8 inches. Liquid Amount...Up to 0.70 inch. in. 70% probability of 3 to 9 inches. 30% probability of 8 to 12 inches. Liquid Amount...0.25-0.50 inch. in.
Over 10,000 ft.
Saturday Saturday Night Sunday
Weather: Heavy snow. Cloudy. Snow. Cloudy. Snow.
Temperatures: 23 to 28. deg. F. 14 to 19. deg. F. 17 to 24. deg. F.
Ridge Top Winds: South 30 to 50 mph with gusts to 75 mph. South 30 to 45 mph with gusts to 75 mph. Southwest 40 to 60 mph with gusts to 90 mph.
Expected snowfall: 80% probability of 22 to 30 inches. 20% probability of 16 to 22 inches. Liquid Amount...1.10-2.10 inches. in. 80% probability of 9 to 17 inches. 20% probability of 6 to 9 inches. Liquid Amount...0.50-1.00 inch. in. 70% probability of 6 to 12 inches. 30% probability of 12 to 16 inches. Liquid Amount...0.40-0.65 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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