|Avalanche Advisory published on February 28, 2015:||Issued by Nick Meyers at 7:01am|
Above treeline, there is MODERATE danger for triggering shallow wind slab avalanches, small to medium in size, on upper elevation slopes in steep, wind exposed terrain that is NE-E-SE-S-SW facing.
The avalanche danger is LOW for below treeline areas and all aspects.
Near treeline, the danger is LOW with pockets of MODERATE.
|danger scale:||1. Low||2. Moderate||3. Considerable||4. High||5. Extreme|
A couple inches of new snow combined with steady northwest wind has formed isolated wind slabs primarily above tree line and in wind exposed slopes. Spatial variability is going to be the main concept today. While some areas are going to be scoured down to the old, firm snowpack, steeper slopes and isolated pockets in extreme terrain could host small to medium size wind slabs.
Slopes steeper than 35 degrees and NE-E-SE-S-SW facing and near ridge crests and the lee side of terrain features should be the most suspect. Danger will exist for newly deposited wind slabs sliding on the old snow surface.
Be on the lookout for instability such as cracking in the snow surface and also smooth, rounded deposits of wind drifted snow.
Snow did fall on Mount Shasta yesterday from passing showers with periods of sun poking through. Not a lot of snow was squeezed from yesterday's storm, which is typical for cold systems that come from the north, it was enough to act like a zamboni and smoothed out the snow surface. Moderate northwest winds steadily blew through most of the day transporting snow by scouring wind exposed terrain, and depositing it in any dimple, gully bottom, low point etc. For the most part, ski conditions yesterday from just above tree line (8,500 feet) to Bunny Flat was "dust on crust" with the occasional soft turn in patches that had collected up to 4-5 inches of wind deposited snow. It made for an enjoyable ski descent, however, it also presents our avalanche problem for the day which we'll get to in a minute.
For the past couple of weeks, we have experienced day after day of sunshine and mostly mild temperatures working their melt/freeze magic. This has made for a bomber snow pack in terms of stability. That means it's very strong, isothermal, equitemperature, with no persistent weak layers of any concern. This has also resulted in an overall smooth and firm snow surface that the new snow from yesterday is resting on. The moderate north-northwest winds have deposited the new snow into shallow pockets on SW-S-SE-E-NE aspects . The cooler temperatures during this storm made for lighter density snow, however, occasional sun breaks in between snow showers warmed up the new snow enough to create a change in density (ie. settlement) within wind deposited patches on leeward slopes.
Concern for today and the remainder of the weekend will lie within the wind slab avalanche problem. The Old Ski Bowl weather station recorded close to another 2 inches of new snow in the last 24 hours. Grey Butte station has shown northwest winds blowing steadily during the storm, 20-30 mph with gusts to 64 mph, then dropping to 5-10 mph and variable in direction. These northwest winds have transported the new snow onto leeward aspects and formed small to medium slabs of varying thickness, 1-6 inches deep. This spatial variability of scoured snow and wind slab patches will shape one's snow concerns for today. Smooth, round slabs have formed on top of the old snow surface and could be triggered by a skier or rider. That said, numerous hand shear tests and ski cuts within shallow wind slabs resulted in good bonding between new and old snow layers. Weak layers were above the old snow at density changes within the new snow. Leeward areas above tree line, near ridgelines and extreme terrain will be the best areas to find this avalanche problem (think S-SE aspects of Casaval Ridge above tree line and other similar slopes). - Jon Dove
Left: 4-5" thick wind slab on SE aspect of Casaval Ridge, 8,400 feet (J Dove)
Right: A ski traverse across SE aspect of Casaval, occasional, very small slabs 1-3 inches deep were triggered on lower angle slopes (J Dove)
Castle Lake and Mt Eddy zones are still hosting shallow snowpacks. All areas below about 6,000 feet in the forecast area are hosting patchy snow with dirt showing around trees and in sunny spots.
Report your observations to the MSAC! A photo, a few words... send them in! (email@example.com or 530-926-9614)
Castle Lake area has a shallow snowpack. Skiing is out of the question at this point due to lack of snow.
Sand Flat Winter Trails: OPEN, trail conditions are firm and getting thin with some tree debris on snow surface.
Pilgrim Creek Snowmobile Park: OPEN, however due to lack of low elevation snow, one must drive up the road several miles before enough snow is encountered. One CANNOT DRIVE over Military Pass. Snowmobiling is not recommended due to low snow depths.
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.
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.
|CURRENT CONDITIONS AT BUNNY FLAT|
|0600 temperature:||18 deg. F.|
|Max. temperature in the last 24 hours:||31 deg. F.|
|Average wind direction during the last 24 hours:||Northwest|
|Average wind speed during the last 24 hours:||20-30 mph|
|Maximum wind gust in the last 24 hours:||64 mph|
|New snowfall in the last 24 hours:||1-2.5 inches|
|Total snow depth:||91 inches|
In Mt Shasta City this morning at 0500, we have obscured, cloudy skies and a current temperature of 36 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 18 F. We have received .20 inches of water in the last 24 hours and 2.5 inches of new snow at the Old Ski Bowl station. Snow on the ground totals 91 inches with 1-2 inches settlement. Temperatures in the last 24 hours have ranged from 18 F to 31 F.
Gray Butte - 8,000 feet, The current temperature is 18 F and temps have ranged from 18 F to 30 F in the last 24 hours. Winds have averaged 20-30 mph with gusts to 64 mph all out of the northwest up until 2100. Winds dropped off considerably and have since been 0-5 mph and variable. This drop in wind marks the end of a two day northwest wind event that began Thursday afternoon.
Castle Lake and Mt Eddy (West side of Interstate-5)...
Castle Lake - 5,600 feet, the current temperature is 27 F. Temps have ranged from 27 F to 43 F in the last 24 hours. New snow in the last 24 hours totals .5 inches with 1 inch settlement. The Castle Lake area has overall a patchy 9-10 inches of snow on the ground.
Mt Eddy - 6,500 feet, the current temperature is 23 F. Temps have ranged from 23 F to 37 F in the last 24 hours. Current snow depth is 29 inches with 1 inch settlement and .5 inches new snow in the last 24 hours.. Winds have averaged 2 mph, with gusts to 12 mph, southeast.
WEATHER SYNOPSIS: The recent, small storm received some hype over the past work week on various media outlets, however it didn't amount to much. We love the wishful thinking, however we only received a couple inches of new snow on the mountain, almost all above 7,000 feet. We saw just a skiff a snow down to as low as 6,500 feet and 1-5 inches of snow above the Bunny Flat trailhead (6,950 feet). Wind was a big theme with this storm and so many areas are scoured to the old snow with adjacent slopes covered. Temperatures have cooled several degrees today. While the forecast is calling for some lingering showers this morning down to 4,000 feet, we think it's not to likely for our area and we should see a pretty nice day on hand after 10am. Winds have died considerably and have become light and variable this morning... we should see them begin to pick up later today out of the northeast above treeline, gusty - 15-25 mph. Tomorrow should be even better, a few degrees warmer perhaps, still cool though and sunny. Another shortwave system for Sunday evening and Monday will slip by. We could see a few snow showers similar to this lastest storm... just enough to wet the whistle and mountain bike trails, but not enough in our opinion to get the powder goggles out.Sunny and warm skies will ensure for next week and our next best chance at winter will not occur until the end of next week.
THIS SEASON: Since October 1st (the wet season) , we have received 30.16 inches of water, normal is 29.23 inches, putting us at 103% of normal. For the month of February, we sit at 10.16 inches of water, normal is 6.69, putting us at 151% of normal. For the year of 2015, we've received 10.64 inches water, normal is 14.02, equalling 75% of normal.
Looking back into 2014, Mt Shasta finished off with 34.36 inches of water with normal being 43.21 inches, leaving us at 79% of normal for the year. For the month of December, Mt Shasta finished at 163% of normal, receiving 12.83 inches of water, normal is 7.85 inches.
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.
|Two-Day Mountain Weather Forecast Published On February 28, 2015|
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 at Midnight February 28, 2015.