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Avalanche Advisory for 2013-03-15 06:55:32
- EXPIRED ON March 16, 2013 @ 6:55 amPublished on March 15, 2013 @ 6:55 am
- Issued by Nick Meyers - Shasta-Trinity National Forest
Bottom Line
Warm temperatures during the day and above freezing lows at night has kept the new snow we received last week very soft with the potential of wet, loose avalanche activity today. Slopes that are southerly facing and steeper than 35 degrees will be most prone to wet, loose instability during the warmest portions of the day. Temperatures today will be slightly cooler than yesterday and thus any instability will likely be limited to the Castle Lake area and elevations below 7,000 feet.
Avalanche Problem 1: Wet Slab
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Likelihood ?CertainVery LikelyLikelyPossible
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Loose-wet avalanches will be possible during the warmest portions of the day. Yesterday, temperatures peaked at 1300. Release of wet unconsolidated snow or slush is possible for lower elevation, sunny slopes that are steeper than 35 degrees. Loose-wet slides typically start at a point and entrain snow as they move downhill. They generally are slow moving, but can contain enough mass to sweep a rider of their feet. Some wet slide activity was observed at Castle Lake yesterday, but not on Mt. Shasta. Again, elevation and aspect will be the key factor with any loose-wet activity. The Castle Lake area and southerly slopes, 7,000 ft and lower will be most susceptible.
Recent Observations
Warm temperatures have created very soft snow on all aspects below 9,500 feet. Afternoon temperatures yesterday (3-14-13) peaked at 1300 with a high of 71 degrees out near Ash Creek Guard Station along Highway 89. On the mountain, temps hit 52 F in the Old Ski Bowl and 61 F at Caslte Lake with little wind. Lows last night did not reach freezing, except for Sand Flat, which barely reached 32 F at midnight. The north slope of Green Butte still held some dryer snow yesterday with upwards of 40cm of the new snow from last week. Only higher elevation (>9,000ft) northerly aspects may still have "powder like" snow on them.
Local observation submitted yesterday, 3-14-13 from Castle Lake area: "Wet slide activity on northeast aspect, potential leg breaker, not burial depth however...Very warm, wet snowpack...not corn yet..."
This observation was similar to what was seen on Mt. Shasta...that is: a very wet and warm upper snowpack...we saw very little in the way of roller balls, pinwheels, wet-loose sloughs, etc on the mountain. This would indicate that any wet-loose activity will be related to elevation and aspect. Sunny aspects below 7,000 feet will be most suspect for wet-loose activity today.
3-14-13...
Old Ski Bowl, 8,500 feet, 1500, 48 F, East facing - Consolidated, 30cm of new snow on top of old snowpack; bottom 15cm of new snow completely saturated with water and loose/slushy. ECTN-15...no propagation but collapse within saturated, wet/loose bottom 15cm of new snow from last week.
Old Ski Bowl, 9,300 feet, 1530, North Facing - Dry snow, wind slab up to 50cm deep on top of old snowpack, CTN (No fracture)
North side Mt. Shasta, 7,500 - 8,000 feet, NE aspect, very limited roller ball / pin wheel activity isolated to near rock outcrops on steeper slopes.
Weather and Current Conditions
Weather Summary
We could say that lately it has felt like Spring is springing but has not sprung yet in the forecast area! Warm temps have got most folks likely scrambling to get their bicycles and spring gear in order...however we hope that winter is not over yet!
A weak cold front moves into the area and will give us slightly cooler temps today and tomorrow with a very slight chance of precipitation. Northwest winds will gradually increase and reach their zenith on Sunday (NW 30-40mph). A weak high pressure will enter the area early next week...the nearest measureable precipitation will likely occur when a low enters the area next Tuesday / Wednesday.
WEATHER STATIONS - (last 24 hours):
In Mt. Shasta City at 0500, we have clear skies and a current temperature of 28 F.
On Mt. Shasta: In the Old Ski Bowl (7,600') on the south side of Mt. Shasta, we have a current temperature of 40 F. Snow on the ground totals 104 inches with 11 inches of settlement since last Sunday. Temperatures have ranged from 36 F to 52F. At Grey Butte (8,000') on the south side of Mt. Shasta winds averaged 12 mph from the NW with a max gust of 28 mph / NW. The current temperature is 39 F and temps have ranged 37 F to 47 F.
Castle/Mt. Eddy: Castle Lake - Castle Lake is hosting a current temp of 39 F. Temperatures have ranged from 39 F to 61 F. Snow depth measures 49" inches with 8 inches of settlement since last Sunday. On Mt Eddy, we have 61 inches of snow on the ground with 11 inches settlement since last Sunday. The current temperature reads 35 F with temps ranging from 35 F to 51 F. Winds have been averaging 2 mph from the WSW and gusting to 6 mph / WSW.
THIS SEASON: September and October were warm and dry with September recording exactly zero precipitation. November remained warmer than normal with precipitation almost double normal values, 9.16" vs. 5.08". A local weather COOP observed the 2nd wettest November on record. December started out wet and warm, but temperatures cooled and brought snow to very low elevations. Since our avalanche cycle near Christmas, we've had a few small storms that brought some amounts of snow to the area, but did not produced any notable avalanches. January was below normal for precipitation with a long period of high pressure and sun that kept skiing conditions somewhat meager. We've had a few storms in the past few weeks that have brought a pittance of wintery weather, but nothing to write home about! The area has been under siege by high pressure overall and giving us blue bird days for the most part. California and the Sierra Nevada have recorded the driest January and February on record. We currently have 6-10 feet of snow above 6,500 ft. Since September 1st, Mt Shasta sits at 72% of normal, 24.37" recorded; normal 33.47". For 2013, we sit at 20% of normal with 3.67" recorded and 17.59" normal.
| 0600 temperature: | 40 |
| Max. temperature in the last 24 hours: | 54 |
| Average wind direction during the last 24 hours: | NW |
| Average wind speed during the last 24 hours: | 12 mi/hr |
| Maximum wind gust in the last 24 hours: | 28 mi/hr |
| New snowfall in the last 24 hours: | 0 inches |
| Total snow depth: | 61-104 inches |
Two Day Mountain Weather Forecast
Produced in partnership with the Medford NWS
| For 7000 ft to 9000 ft | |||
|---|---|---|---|
|
Friday (4 a.m. to 10 p.m.) |
Friday Night (10 p.m. to 4 a.m.) |
Saturday (4 a.m. to 10 p.m.) |
|
| Weather | Mostly cloudy, becoming partly cloudy | Partly cloudy | Partly Cloudy |
| Temperature (°F) | 55 | 30 | 49 |
| Wind (mi/hr) | NW 5-10 | NW 5-10 | NW 10-15 |
| Precipitation SWE / Snowfall (in) | / 0 | / 0 | / 0 |
| For 9000 ft to 11000 ft | |||
| Friday | Friday Night | Saturday | |
| Weather | Partly cloudy | Partly cloudy | Partly cloudy |
| Temperature (°F) | 35 | 20 | 33 |
| Wind (mi/hr) | WNW 10-15 with gusts to 25 mph | WNW 0 | NW 15-20 mph with gusts higher. |
| Precipitation SWE / Snowfall (in) | / 0 | / 0 | / 0 |
