Avalanche Advisory: Saturday - Apr 20, 2019

THIS AVALANCHE ADVISORY EXPIRED ON April 21, 2019 @ 5:39 am
Avalanche Advisory published on April 20, 2019 @ 5:39 am
Issued by Steve Mace - ESAC

*Advisories will continue to be issued 4 days a week through April 21st. After the 21st, we will be issuing weekly snowpack summaries on Thursdays until May 9th. Danger ratings will no longer be formally issued as conditions can change over multiple day periods. *

* This Avalanche Advisory is in effect for Saturday, April 20th*

Transitional springtime conditions exist throughout the forecast area with heightened avalanche hazard in specific areas. Expect daytime warming to increase the risk of Loose Wet avalanches at all elevations.  You can also expect fresh sensitive wind slabs to develop on specific terrain features at mid and upper elevations as a small spring storm makes it way through the area bringing up to 2” of new snow at upper elevations. Evaluate snow conditions and terrain carefully and avoid features of concern.

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Avalanche Problem 1: Loose Wet
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Mostly cloudy skies will limit the solar gain today, and moderate winds may help to keep things cool. However, relatively warm overnight temperatures coupled with some green housing effects may lead to enough surface warming to make loose wet avalanches more concerning today. Be on the look out for wet, sticky snow surface, rollerballs and increasing boot penetration as these are all signs of surface warming and may foreshadow larger point release avalanches.  Several days of warm spring weather has helped transition and settle much of the snowpack, particularly on solar aspects.  Problem areas today are going to be in places where the snow is more transitional such as upper elevations or more shaded aspects.  Be on the look out for areas with warm loose surface snow and be cautious at lower elevations where today’s showers may come as rain.

Avalanche Problem 2: Wind Slab
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An oncoming storm should begin to impact the region today.  Precipitation totals will likely be small, but they are sure to be higher at upper elevations.  Couple this with moderate to strong SW winds and you can expect to find fresh, sensitive wind slabs developing on Northerly and Easterly terrain at mid and upper elevations. While resulting avalanches are likely to be small and aren’t expected to pose a significant hazard to backcountry travelers, there may be enough snow to take you off your feet or carry you though unpleasant terrain.  Problem areas will be specific to terrain features that encourage drifting. The leeward sides of ridgelines, gully features, and cross-loaded depressions are all suspect.  Be particularly cautious in extreme terrain or on steep, unsupported slopes where the consequences of an avalanche are heightened, and be ready for increasing wind slab concern should this storm come in stronger than predicted.  Inversely, if no snow materializes with the storm today the risk of wind slabs developing will be very low. Surface clues such as blowing snow, recent cornice growth and uneven snow surfaces can help to identify and avoid areas of recent wind deposit. 

advisory discussion

As our unsettled spring continues remember to keep an eye on changing conditions.  Timing is everything in the mountains as it is in life. It’s a good idea to start early and try and be off suspect slopes before they warm up and become sloppy and sticky.  It’s also worth remembering that as the snow line creeps up route finding is becoming more challenging.  In addition, the last few days of warm weather without a hard overnight freeze has left the snow at lower elevations very loose unsupportable making for difficult travel conditions. In addition to elevated avalanche concern, this type of snow can put your knees at risk.  Take it slow; the spring season is still young.

Weather and CURRENT CONDITIONS
weather summary

Expect mostly cloudy skies today with scattered showers, strong southwest winds, and warm temperatures. Daytime highs are expected to reach into the low 40’s at upper elevations and 50’s at lower elevations. A small spring storm will impact the area today with up to 2” of snow expected in the upper elevations.  With freezing levels around 9000’, expect lower elevation precipitation to come in the form of rain.  Strong southwest winds will impact the area today with gusts expected to reach 60 mph on ridge tops.

Scattered showers will continue into the evening hours but only trace amounts of precipitation are likely. Expect things to calm down after midnight as the temps drop into the teens and winds drop slightly and shift to the west.  Tomorrow promises to be more pleasant with sunny skies in the morning becoming partly cloudy in the afternoon, moderate north winds and isolated afternoon showers.

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: Mostly cloudy. Scattered showers. Snow levels 9000 feet. Chance of precipitation is 25%. Partly cloudy then becoming clear. Isolated snow showers in the evening. Snow levels 8500 feet decreasing to 7000 feet after midnight. Chance of precipitation is 10%. Partly cloudy. Slight chance of snow showers in the afternoon. Snow levels below 7000 feet increasing to 7500 feet in the afternoon. Chance of precipitation is 15%.
Temperatures: 41 to 51. deg. F. 24 to 30. deg. F. 38 to 48. deg. F.
Mid Slope Winds: Southwest 15 to 20 mph increasing to 15 to 30 mph in the afternoon. Gusts up to 60 mph. West 15 to 30 mph. Gusts up to 55 mph decreasing to 35 mph after midnight. North 15 to 20 mph with gusts to 40 mph.
Expected snowfall: 80% probability up to 1 inch. 20% probability of 1 to 2 inches. | SWE = less than 0.10 inch. in. Up to 1 inch. | SWE = none. in. Less than 1 inch. | SWE = less than 0.10 inch. in.
Over 10,000 ft.
Saturday Saturday Night Sunday
Weather: Mostly cloudy. Scattered snow showers. Snow levels 9500 feet. Chance of precipitation is 45%. Mostly cloudy then becoming clear. Isolated snow showers in the evening. Snow levels 8500 feet decreasing to 7000 feet after midnight. Chance of precipitation is 15%. Sunny then becoming partly cloudy. Slight chance of snow showers in the afternoon. Snow levels below 7000 feet increasing to 7500 feet in the afternoon. Chance of precipitation is 20%.
Temperatures: 30 to 40. deg. F. 19 to 24. deg. F. 29 to 37. deg. F.
Ridge Top Winds: Southwest 20 to 30 mph with gusts to 45 mph increasing to 25 to 40 mph with gusts to 60 mph in the afternoon. Southwest 25 to 40 mph with gusts to 60 mph becoming west 15 to 20 mph with gusts to 35 mph after midnight. North 15 to 25 mph. Gusts up to 40 mph.
Expected snowfall: Up to 2 inches. | SWE = less than 0.10 inch. in. Less than 1 inch. | SWE = trace amounts. in. Up to 1 inch. | SWE = less than 0.10 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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