You are here
Avalanche Advisory for 2016-01-19 06:47:03
- EXPIRED ON January 20, 2016 @ 6:47 amPublished on January 19, 2016 @ 6:47 am
- Issued by Nick Meyers - Shasta-Trinity National Forest
Bottom Line
Below and near treeline, the avalanche danger is LOW, all aspects. Above treeline, the danger is MODERATE for wind and storm slabs within new accumulating snow. South/southwest winds will create new wind and storm slabs today. New snow totals could reach 4-8 inches accompanied by southwesterly winds blowing 40-50 mph and loading primarily NW-N-NE-E facing slopes, but not limited to. Slopes steeper than 35 degrees should be most suspect during the mid to late afternoon hours.
Avalanche Problem 1: Wind Slab
-
Character ?
-
Aspect/Elevation ?
-
Likelihood ?CertainVery LikelyLikelyPossible
Unlikely -
Size ?HistoricVery LargeLargeSmall
New wind slabs have begun to form early this morning, near and above treeline. Up to 8 inches of new snow is expected today and increasing winds which will cause wind slab avalanche danger to rise throughout the day. Slabs will likely be small to medium in size and depth and certainly big enough to bury a person. Winds have remained relatively calm in the past 24 hours though will pick up today and reach 40-50 mph in exposed areas, blowing out of the southwest and loading primarily, but not limited to, NW-N-NE-E facing slopes. Some SE and W slopes will likely see some cross-loading. Becoming able to identify wind drifted snow is a important skill to have for winter backcountry travel. Cornice formations, wind pillows, hollow sounding-hard snow, visible blowing snow and snow surface patterns are very good indicators of potential wind loading.
Avalanche Problem 2: Storm Slab
-
Character ?
-
Aspect/Elevation ?
-
Likelihood ?CertainVery LikelyLikelyPossible
Unlikely
-
Size ?HistoricVery LargeLargeSmall
Any soft slab issues today will likely be minimal. New storm slabs may build in protected areas below and near treeline, out of the wind zone. Mid to late afternoon will present the best time for storm slab instability. Convex rollovers are a common trigger area for a soft slab avalanches. New snow is falling on top of the widespread rain crust this morning. Some areas one may find heavier snow on top of lighter density snow. Dig a quick hand pit, or a full pit for that matter and look at the layers in the snowpack. You don't have to be a snow geek like us to be able to identify weaker snow underneath stronger snow. Hand pits can be very easily done and are helpful in determining the hardness of the layers in the snowpack, bonding of the old snow and new snow and also in identifying potential shear in weak layers/density changes within the new snow.
Avalanche Problem 3: Cornice
-
Character ?
-
Aspect/Elevation ?
-
Likelihood ?CertainVery LikelyLikelyPossible
Unlikely
-
Size ?HistoricVery LargeLargeSmall
Cornices of varying size have formed along ridge tops hanging over leeward, wind loaded aspects. Give them plenty of space and use them to help identify wind loaded areas and aspects. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise, even on flat ground above the slope. Even small cornices have enough mass to be destructive and deadly. Cornice failure can trigger wind slab or storm slab avalanches.
Forecast Discussion
The storms are stacked and a progressive weather pattern laces the globe in the northern hemisphere. Over the next several days, several short waves will eject over the forecast area. Each wave will bring a round of precipitation and wind. Snow levels will fluctuate and we will experience some warming later this week unfortunately. As we speak, rain is falling in Mt Shasta City and it's snowing in the mountains with snow levels around 5,000 feet this morning, rising to 5,500 feet. Tonight some lingering precipitation may accumulate a couple more inches of snow with snow levels near 4,500 feet. Wednesday will be partly cloudy and serve as a brief break in weather systems. South/southwest winds will peak today and tonight, 40-50+ mph above treeline. Below treeline, wind speeds will be less and likely gusty. Watch out for falling snow (tree bombs!) when the wind picks up!
THIS SEASON PRECIPITATION: Since October 1st (the wet season), we have received 16.66 inches of water, normal is 19.48 inches, putting us at 85% of normal. For the month of January and year of 2016 we've received 7.17 inches of water, normal is 4.27 inches, putting us at 167% of normal
Recent Observations
The snowpack has locked up pretty well due to warm temperatures and rain on snow recently. Both Jon and I thought that yesterday, at least at higher elevations near/above treeline, that the snow would be more powder-like. Instead, to our surprise we found a widespread and occasionally breakable rain crust. The 3cm rain crust was observed on all aspects up to 9,000 feet, though a local observed firm conditions up to 10,000 feet when he was able to sneak up into the upper ramparts of the Old SKi Bowl during a brief break in visibility. While some blown in gullies were hosting decent skiing on supportable crust with a bit of new snow on top, overall the pencil hard crust prevails and breakable at times. Weather stations continue to show settlement in the snowpack as did snow around trees (see picture).
Concerns for any existing weak layers are minimal. Snow stability seemed very good from observations yesterday and any avalanche danger will lie within the new snow we are receiving currently. Near and above treeline travel should still call for standard caution when wind loaded features, large snow pillows, leeward ridgelines and hollow sounding slabs are encountered. As for any storm slabs, only the new snow on top of the 3cm rain crust should be a concern for the storm slab avalanche problem. Cornices still remain and some are probably getting pretty big!
Settlement in snowpack visible around tree trunks. About 4-8 inches of settlement has occurred in the past several days.
Remember, your skin track up the hill is just as important as your ski line down. Choose safe up tracks... don't just follow the skin track that is set if you're not comfortable with the route. Breaking trail is a lot easier than getting caught in an avalanche. Also, tracks on a slope does NOT mean the slope is safe.
Only one at a time on a given slope. Use safe zones and make sure they are safe! Use good communication between group members. Avoid large groups. Talk about your route plan for the day and be ready to adjust your plan as you notice unstable snow such as shooting cracks, whoomfing, recent avalanches, and/or rapid accumulation of snow.
_______________________________________________________________________________________________________________________________________________
LOCAL AREA ROAD, NORDIC and SNOWMOBILE PARK STATUS:
The Sand Flat cross country ski trails are in great shape and ready for your cross country skis or snow shoes. These are backcountry trails 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 are being groomed currently. 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 plowed to the Vista Point. The Everett Memorial Highway is plowed to Bunny Flat.
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 42 F, six degrees warmer than yesterday at this time, with rain falling at this time.
On Mt Shasta (South Side) in the last 24 hours...
Old Ski Bowl - 7,600 feet, the current temperature is 27 degrees F. Snow on the ground totals 102 inches with 4 inches new snow and 1 inch settlement. Temperatures have ranged from 20 F to 28 F.
Grey Butte - 8,000 feet, the current temperature is 26 degrees F. Temperatures have ranged from 20 F to 29 F. Winds have been averaging 10 mph, southwest in nature with a max gust to 28 mph, southwest also.
Mt Eddy Range (West side of Interstate-5)...
Castle Lake - 5,600 feet, the current temperature is 32 degrees F. Temperatures have ranged from 27 F to 37 F. Snow on the ground measures 65 inches with a 1-3 inches of new snow and 1-2 inches settlement.
Mt Eddy - 6,500 feet, the current temperature is 30 degrees F. Temperatures have ranged from 20 F to 33 F. Snow on the ground measures 73 inches with a trace of new snow and 4 inches of settlement. Winds have averaged 2 mph, southwest in direction with a max gust of 11 mph, south/southwest.
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: | 31 |
| Max. temperature in the last 24 hours: | 32 |
| Average wind direction during the last 24 hours: | West/Southwest |
| Average wind speed during the last 24 hours: | 5-10 mi/hr |
| Maximum wind gust in the last 24 hours: | 28 mi/hr |
| New snowfall in the last 24 hours: | 2-4 inches |
| Total snow depth: | 84 inches |
Two Day Mountain Weather Forecast
Produced in partnership with the Medford NWS
| For 7000 ft to 9000 ft | |||
|---|---|---|---|
|
Tuesday (4 a.m. to 10 p.m.) |
Tuesday Night (10 p.m. to 4 a.m.) |
Wednesday (4 a.m. to 10 p.m.) |
|
| Weather | Snow, windy | Snow showers, breezy | Partly sunny |
| Temperature (°F) | 33 | 25 | 35 |
| Wind (mi/hr) | South 20-30 mph | West/Southwest 15-20 mph | West/Southwest 5-10 mph |
| Precipitation SWE / Snowfall (in) | / 4-8 | / 1-2 | / 0 |
| For 9000 ft to 11000 ft | |||
| Tuesday | Tuesday Night | Wednesday | |
| Weather | Snow, windy | Snow showers, windy | Mostly cloudy, breezy |
| Temperature (°F) | 24 | 18 | 26 |
| Wind (mi/hr) | West/Southwest 40-50 mph | West 7-10 | West 20-30 mph |
| Precipitation SWE / Snowfall (in) | / 7-10 | / 1-3 | / 0 |
