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Avalanche Advisory for 2016-03-16 06:56:27
- EXPIRED ON March 17, 2016 @ 6:56 amPublished on March 16, 2016 @ 6:56 am
- Issued by Nick Meyers - Shasta-Trinity National Forest
Bottom Line
MODERATE avalanche danger exists near and above treeline for remaining wind slabs on W-NW-N-NE-E aspects. LOW danger will be found below treeline on all aspects. Human trigger of lingering wind slabs may be possible on slopes 37 degrees and steeper. Loose wet snow instabilities may develop on southerly aspects during the warmest portions of the day. Continue to evaluate the snow carefully and identify features of concern. Use caution on steeper slopes.
Avalanche Problem 1: Wind Slab
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Naturally triggered wind slabs have occured over the weekend, however several days of sun and settlement in the snowpack have allowed wind slabs to gain strength. Gale force winds out of the south loaded NW-N-NE slopes and cross loaded westerly and easterly aspects. Windward slopes are scoured down to crust or hard, wind packed sastrugi features. Very little existing snow remains for new wind transport, however remaining wind slabs on steep slopes could still be reactive and human triggering remains possible. Try to identify where wind loading has taken place by looking for remaining cornices, wind pillows that are soft to hard in nature, and other wind formations such as ribs behind trees. These are all good signs that wind loading is occurred. Slopes 37 degrees and steeper near and above treeline on leeward aspects are the areas of most concern for today.
Avalanche Problem 2: Loose Wet
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Loose wet snow instabilities such as roller balls, pinwheels, and point release loose wet avalanches will be possible as temeratures increase and the sun bakes southerly facing aspects. Gradual warming, with Thursday being the warmest day of the week, could cause unconsolidated new snow to begin to produce roller balls and donut rolls. These are signs that larger loose wet point releases are possible. While much of the time these types of avalanches are not an immediate threat to life, they certainly could sweep you into undesireable terrain. Mt Shasta is also capable of producing large loose wet slides and we are getting into the time of the year when they become a real possibility. While we likely won't see anything very large this week, as we move into spring, larger loose wet slides should be on your mind during those hot Spring days!
Forecast Discussion
Nothing but blue skies shining at us for the next couple days... While Spring is in the air and caused a few flora's to start sprouting, Winter is not over yet. No need to worry now as the remainder of the work week will remain clear and calm. The lower elevations of the forecast area will see high temperatures in the mid 50's with a high of 59 degrees on Thursday, forecast for Bunny Flat area. Castle Lake could see temps in the 60's. It won't be until Saturday that we see a chance of more precipitation. Winds will be light as well in the mountains this week... enjoy your choice of recreation. There are a lot of options currently!
THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 35.35 inches of water, normal is 33.0 inches, putting us at 107% of normal. For the month of March we've received 9.83 inches of water, normal is 3.5 inches, putting us at 280% of normal, and finally... for the year of 2016 we've received 25.86 inches of water, normal is 17.79 inches, putting us at 145% of normal .
Recent Observations
Warm temperatures and sunny skies has continued to consolidate our 4 feet of fresh snow that fell over a 3 day period this past weekend. Another 2 inches of settlement was recorded in the last 24 hours, on top of the 3-5 inches yesterday, for a total of about 7 inches. Since the end of the storm on Sunday evening, we've seen 10-12 inches of settlement in some areas!
The snowpack is variable and in a transitional state and will remain so for the week likely. Mt Shasta's famous spring corn just doesn't happen overnight! The aspect and elevation you choose will be important if you hope to find good snow today! Below 6,500 feet, sourtherly facing slopes are firm, crusty and somewhat supportable. Some northerly aspects below this elevation could hold some decent powder. As one gains elevation and approaches near and above treeline areas, the snow does get better but variable will be the word of the day. Southerly aspects remain wind hammered. Strong southerly winds punished south aspects as well as cross loaded some West and East aspects. Sastrugi features and wind buffed snow is most common above treeline. Below and near treeline, many broken tree tops littering the forest floor have been observed over the forecast area. Sledders have been finding soft snow on shadier aspects above 6,500 feet, however surface conditions of the snow may be funky.
We've received a few reports of avalanche debris observed from the weekend's storm. Debris was observed on the NW side of Gray Butte and also on the E/SE side of Gray Butte. Both of those slide paths are near treeline, wind loaded and are frequent flyers in the avalanche world, so not surprising! Since the storm however, the snow stability has been very good. Again, widespread settlement and several days of sun has consolidated the snowpack well and no new avalanches/instability have been reported.
Avalanche concerns for today will be low for any potentially unstable wind slabs on leeward W-NW-N-NE-E aspects, slopes 37 degrees and steeper near and above treeline. You may find loose dry sloughing snow on steep shaded Northerly facing aspects, but they will be small and likely very inconsequential. Loose wet snow instabilities will become more of a problem on southerly aspects as the week progresses and temperatures warm up. We may or may not see loose wet style instabilities today. Continue to practice safe travel techniques and be sure to evaluate the snow and terrain before committing to a slope.
Wind ribs behind trees from S/SW winds, 6,600 feet near Gray Butte (MS Ski Park):
Several tree tops freshly broken due to strong southerly winds during this past weekend storms (Gray Butte):
Widespread settlement of snowpack visible around all trees:
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LOCAL AREA ROAD, NORDIC, AND SNOWMOBILE PARK STATUS:
The Sand Flat cross country ski trails are in good shape and ready for your cross country skis and snow shoes. These are backcountry routes marked with blue diamonds on trees. Trails are not groomed. Snow shoers, please blaze a parallel trail to cross country skiers staying out of the skin track. These trails can be accessed via the Everett Memorial Highway. Thank you, and enjoy!
The Mt. Shasta Nordic Center is open! These beautiful, groomed trails can be accessed via the Ski Park Highway. http://www.mtshastanordic.org
The Pilgrim Creek & Deer Mountain Snowmobile Parks are open! Trails have not been groomed in the past week and a half due to constant deep snow fall. Head to our "Education" tab on our website and find the snowmobile section for trail information, grooming status, and other sledder resources.
The Castle Lake Road is CLOSED at the gate. The culvert blew out and we do not know when it will be repaired. The Everett Memorial Highway is plowed to Bunny Flat and currently mostly snow free until about Red Fir Flat up.
The Five Red Flags of Avalanche Danger any time of year include: 1) Recent/current avalanche activity 2) Whumphing 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
Good Morning! In Mt Shasta City at 0500, we have a current temperature of 29 F, four degrees cooler than yesterday at this time. Skies are mostly clear with calm wind.
On Mt Shasta (South Side) in the last 24 hours...
Old Ski Bowl - 7,600 feet, the current temperature is 28 degrees F. Snow on the ground totals 172 inches with no new snow and 2.5 inches of settlement. Temperatures have ranged from 22 F to 35 F.
Gray Butte - 8,000 feet, the current temperature is 30 degrees F. Temperatures have ranged from 17 F to 34 F. Winds have been west/northwest in direction averaging 5-10 mph with a gust to 28, NW.
Mt Eddy Range (West side of Interstate-5)...
Castle Lake - 5,600 feet, the current temperature is 32 degrees. Temperatures have ranged from 24 F to 47 F. Snow on the ground totals 87 inches with no new snow and 2 inches of settlement.
Mt Eddy - 6,500 feet, the current temperature is 34 degrees F. Temperatures have ranged from 21 F to 35 F. Snow on the ground measures 102 inches with no new snow and 1 inch of settlement. Winds have been variable in nature with an average of 2 mph, and a maximum gust of 7 mph, ESE.
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.
| 0600 temperature: | 28 |
| Max. temperature in the last 24 hours: | 38 |
| Average wind direction during the last 24 hours: | Northwest |
| Average wind speed during the last 24 hours: | 5-10 mi/hr |
| Maximum wind gust in the last 24 hours: | 28 (Gray Butte) mi/hr |
| New snowfall in the last 24 hours: | 0 inches |
| Total snow depth: | 116.5 inches |
Two Day Mountain Weather Forecast
Produced in partnership with the Medford NWS
| For 7000 ft to 9000 ft | |||
|---|---|---|---|
|
Wednesday (4 a.m. to 10 p.m.) |
Wednesday Night (10 p.m. to 4 a.m.) |
Thursday (4 a.m. to 10 p.m.) |
|
| Weather | Sunny, with a high near 49. North northeast wind around 8 mph. | Clear, with a low around 35. East northeast wind 6 to 8 mph. | Sunny, with a high near 54. East northeast wind 7 to 9 mph. |
| Temperature (°F) | 49 | 35 | 54 |
| Wind (mi/hr) | North/Northeast 5-10 mph | East/Northeast 5-10 mph | East/Northeast 5-10 mph |
| Precipitation SWE / Snowfall (in) | / 0 | / 0 | / 0 |
| For 9000 ft to 11000 ft | |||
| Wednesday | Wednesday Night | Thursday | |
| Weather | Sunny, with a high near 26. Windy, with a west northwest wind 10 to 15 mph becoming north in the afternoon. | Clear, with a low around 26. Northeast wind 10 to 20 mph decreasing to 5 to 10 mph after midnight. | Sunny, with a high near 32. Northeast wind 5 to 10 mph becoming southeast in the afternoon. |
| Temperature (°F) | 26 | 26 | 32 |
| Wind (mi/hr) | West/Northwest 10-15 mph | Northeast 0 | Northeast becoming southeast 5-10 mph |
| Precipitation SWE / Snowfall (in) | / 0 | / 0 | / 0 |
