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Avalanche Advisory for 2015-03-23 03:41:29

  • EXPIRED ON March 24, 2015 @ 3:41 pm
    Published on March 23, 2015 @ 3:41 pm
  • Issued by Jon Dove - Shasta-Trinity National Forest

The avalanche danger is currently LOW for most elevations and aspects... however pockets of MODERATE avalanche danger will exist at near and above treeline due to wind loaded S-SE-E-NE-N aspects 35 degrees and steeper.  The potential exists for small human triggered wind slabs on these aspects.

Carry a beacon shovel and probe. Wear a helmet. Know how to use your ice axe and crampons.

 

 

 

 

 

 

 

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Avalanche Problem 1: Wind Slab

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Moderate to strong SW-W-NW winds have accompanied the 6-9 inches (15-23 cm) of new snow received in the last 24 hours.  Wind slabs of up to 2 feet (60 cm) thick have developed on leeward slopes (SE-E-NE-N) resting on a smooth and firm old snow surface.  Another 0.24 inches of water is forecast for Monday night and Tuesday morning with more moderate to strong winds at mid and upper elevations (9,500-13,000+ feet).  This could translate into 3-5 inches (7-12cm) of new snow.  Use caution by avoiding travel on SE-E-NE-N aspects.  

Don't let your guard down as winter weather has returned!

Recent Observations

-SPECIAL UPDATE DUE TO NEW SNOW FROM RECENT STORM ACTIVITY-

Updated at 3:00 pm on Monday, March 23rd (daily weather stats will not be updated, but weather synopsis will be accurate)

Today was a great day for powder lovers!  The recent snow that has fallen came "right side up" (meaning the storm came in warm and cooled as it passed) and was fun to ski.  A ski descent from Helen Lake at 10,450 feet following the moraines down along Avalanche Gulch proper proved to be a wise choice.  It offered less wind affected snow and lower angle slopes.  Mt. Shasta was blessed with anywhere from 6-9 inches (15-23cm) of new snow in the last 24 hours with the majority of that precipitation falling late yesterday and last night.  Moderate to high SW-W-NW winds transported snow and buffed the tops of convexities (moraines) creating winds slabs of up to 60 cm on SE-E-NE-N aspects.  

A snow pit was dug on a SE aspect at 10,500 feet, where the moraine at Helen Lake meets the base of Casaval Ridge.  Observed was 12.5 inches (31 cm) of new, wind affected snow on top of firm, old snow.  An extended column test was performed resulting in a score of ECTN 20.  At that score a fracture occurred at a change in density of the new snow at 7.5 inches deep (19 cm).  It was a crack, not a sudden drop, with no propagation.  Further taps had no results, and when the column was pulled on with a shovel it sheared with poor quality at the density change at 19cm. 

A fast moving short wave system will brush across our area late tonight into Tuesday morning bringing what models show as 0.24 inches of water.  This could translate into a few more inches of snow.  Breezy WSW winds of up to 35-40 mph with higher gusts at the mid and upper elevations (9,500-13,000+ feet) will continue to transport snow.  This will deepen existing wind slabs on SE-E-NE-N aspects.  Current avalanche danger of most slopes and aspects is LOW with pockets of MODERATE at near and above tree line on SE-E-NE-N aspects on slopes of 35 degrees and steeper.  Be cautious with route decision making, avoiding leeward aspects, known avalanche paths, and run out zones.

Temperatures are forecast to spike on Wednesday increasing the chance for loose, wet snow instabilities later in the week on S-SE-E facing aspects, especially in the afternoon hours.  

Photos:
Left-Shay Stem ski touring up Climber's Gully, Avalanche Gulch 3/23/2015 - Photo: Jon Dove

Right-Group break on ski descent along edge of Avalanche Gulch proper  3/23/2015 - Photo: Jon Dove

Continue to always use safe travel methods: carry situational awareness on your skin up the mountain, choose safe routes and watch for what others are doing, ski one at a time, stop in safe zones!

For folks that plan on climbing Mt. Shasta:  Route conditions on Casaval Ridge, Sargents Ridge, and Avalanche Gulch are currently good.  That being said, the snow will be variable in depth with the new snow received and the accompanying winds.  There is a little bit more snow and high winds in the immediate forecast for tonight as well.   Ice fall from rime ice that has built up on the Red Banks and other rock outcroppings will start to occur when the weather pattern clears and warms up by Wednesday.  A helmet, crampons, and a mountain axe are necessary equipment and should be used. 

Castle Lake and Mt Eddy zones are still hosting a shallow snowpack. All areas below about 6,000 feet in the forecast area are hosting patchy snow with dirt showing around trees and in sunny spots.  For Castle Lake, skiing is out of the question at this point due to lack of snow.

Report your observations to the MSAC! A photo, a few words... send them in! (nimeyers@fs.fed.us or 530-926-9614)

Sand Flat Winter Trails: OPEN, however snow depths are meager and the Lower Sand Flat road is exposed dirt. We recommend heading up to Bunny Flat and touring up the road or anywhere higher in elevation!

Pilgrim Creek Snowmobile Park: CLOSED due to lack of snow

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Terrain:  Remember most of the terrain that we like to play on is greater than 30 degrees.  Avalanches are possible on anything steeper than 30 degrees.  Avoid cornices, rock bands, terrain traps and runout zones of avalanche paths.

Weather:  Most of our areas avalanche danger will occur 24-48 hours after a storm. We still can see persistent weak layers from time to time and we always will be sure to let you know about that!  Heed the basic signs: Wind (significant snow transport and depositions), Temperature (rain/snow/rain/snow, which in turn weakens the snowpack), and Precipitation (Snow or rain add weight and stress to the current snowpack).

SnowpackIf snow accumulates, give the snowpack a chance to adjust to the new snow load before you play on or near steep slopes (greater than 30 degrees).  Most direct action avalanches occur within 24-48 hours of recent snowfall.  Watch for obvious signs of snowpack instability such as recent natural avalanche activity, collapsing of the snowpack (often associated with a “whumphing” sound), and shooting cracks. If you see these signs of instability, limit your recreation to lower angle slopes.

Human Factor: Don’t forget to carry and know how to use avalanche rescue gear. You should NOT be skiing or climbing potential avalanche slopes without having beacons, shovels, and probes.  Only one person in a group should be exposed to potential avalanche danger at a time.  Remember, climbing, skiing, and riding down the edge of slopes is safer than being in the center.  Just because another person is on a slope doesn't’t mean that it is safe.  Be an individual!  Make your own decisions.  Heed the signs of instability: rapid warming, “whumphing” noises, shooting cracks, snowing an inch an hour or more, rain, roller balls, wind loading, recent avalanche activity.

The Five Red Flags of Avalanche Danger any time of year include:  1) Recent/current avalanche activity  2) Whumpfing sounds or shooting cracks  3) Recent/current heavy snowfall  4) Strong winds transporting snow  5) Rapid warming or rain on snow.

 


 

    Weather and Current Conditions

    Weather Summary

    In Mt Shasta City this morning at 0500, we have cloudy skies with light rain, and a current temperature of 47 F degrees. 

    WEATHER STATION INFORMATION (0500hrs):

    On Mt Shasta (South Side) in the last 24 hours...

    Old Ski Bowl - 7,600 feet, the current temperature is 31 F. Snow on the ground totals 80 inches, with a trace of new snow and no settlement.  Temperatures have ranged from 29 F to 44 F.

    Gray Butte - 8,000 feet, the current temperature is 30 F. Temps have ranged from 28 F to 39 F. Winds have been primarily southwest averaging 12 mph with max gusts to 28 mph, SW.

    Castle Lake and Mt Eddy (West side of Interstate-5)... 

    Castle Lake - 5,600 feet, the current temperature is 37 F. Temps have ranged from 34 F to 54 F. The Castle Lake area has very little snow left on the ground.

    Mt Eddy - 6,500 feet, the current temperature is 35 F. Temps have ranged from 31 F to 44 F in the last 24 hours. Current snow depth is 20 inches with no settlement.  Winds have been variable, 1-3 mph, with gusts to 11 mph, SSW.

    WEATHER SYNOPSIS: (SPECIAL UPDATE DUE TO RECENT STORM ACTIVITY 3/23/2015 @ 3:00 pm) We will be at the southern edge of a surface low pressure that will move onshore later today (Monday) bringing a chance for more precipitation and moderate to strong winds.  Precipitation amounts of 0.24 inches of water are expected later tonight (Monday night) into Tuesday morning.  This could translate into 3-5 inches of snow above 5000 feet.  Winds will be out of the southwest to west with speeds of 35-40 mph with higher gusts on the mid to upper elevations of the mountain (9,500-13,000+ feet).  High pressure returns on Wednesday bringing back warm temperatures and mostly clear skies.  Temperatures are forecast to spike upwards of close to 10 degrees.  Clear skies and warm temperatures should be expected for the end of the week. 

    THIS SEASON PRECIPITATION: Since October 1st (the wet season) , we have received 30.84 inches of water, normal is 34.04 inches, putting us at 90% of normal. For the month of March, we sit at 0.68 inches of water, normal is 4.54, putting us at 15% of normal. For the year of 2015, we've received 11.32 inches water, normal is 18.83, equalling 60% of normal. 

     
    Snow Survey Results for March 2015 for the Sacramento, Shasta and Trinity Watersheds: 49% of normal with at average depth of 37 inches. Historic average for snow is 76.8 inches. Last year at this time we were 36% of normal. Similar years to this year are 1936, 1977, 1988, 1994.

    Always check the weather before you attempt to climb Mt Shasta. Further, monitor the weather as you climb. Becoming caught on the mountain in any type of weather can compromise life and limb. Be prepared.

    CURRENT CONDITIONS at Bunny Flat (6950 ft)
    0600 temperature: 31
    Max. temperature in the last 24 hours: 44
    Average wind direction during the last 24 hours: Southwest
    Average wind speed during the last 24 hours: 10-20 mph mi/hr
    Maximum wind gust in the last 24 hours: 28 mi/hr
    New snowfall in the last 24 hours: .05 inches
    Total snow depth: 80 inches

    Two Day Mountain Weather Forecast

    Produced in partnership with the Medford NWS

    For 7000 ft to 9000 ft
      Monday
    (4 a.m. to 10 p.m.)
    Monday Night
    (10 p.m. to 4 a.m.)
    Tuesday
    (4 a.m. to 10 p.m.)
    Weather Cloudy, rain and snow Cloudy, rain and snow becoming all snow after 11pm snow showers likely
    Temperature (°F) 36 30 31
    Wind (mi/hr) South 10-20 mph Southwest 10-15 mph Southwest 10-15 mph
    Precipitation SWE / Snowfall (in) / 2-3 inches / 3-5 inches / 1-2 inches
    For 9000 ft to 11000 ft
      Monday Monday Night Tuesday
    Weather Cloudy, snow Snow Snow showers
    Temperature (°F) 22 16 with wind chill values as low as -5 20
    Wind (mi/hr) Southwest 35-40 mph with higher gusts Southwest 2-4 inches West 30-35 mph
    Precipitation SWE / Snowfall (in) / 2-4 inches / 5-9 inches / 2-4 inches

    Disclaimer

    This advisory does not apply to Ski Areas or Highways and is for the Mt. Shasta, Castle Lake and Mt. Eddy back country. Use this information for guidance only. You may find different conditions in the back country and should travel accordingly. This advisory expires on midnight of the date it was posted unless otherwise noted.