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Avalanche Advisory for 2017-12-29 06:00:25
- EXPIRED ON December 30, 2017 @ 6:00 amPublished on December 29, 2017 @ 6:00 am
- Issued by Nick Meyers - Shasta-Trinity National Forest
Bottom Line
LOW avalanche danger and normal caution continue. Generally safe avalanche conditions exist. Sparse coverage and firm and icy slopes present significant travel hazards on Mt Shasta.
Avalanche Problem 1: Normal Caution
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Character ?
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Aspect/Elevation ?
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Likelihood ?CertainVery LikelyLikelyPossible
Unlikely -
Size ?HistoricVery LargeLargeSmall
Normal caution is advised. The firm, icy, and thin snowpack continues to create backcountry travel hazards. Moving through steep terrain above treeline is challenging and dangerous. Arresting a fall in these conditions would be difficult. Watch out for rocks. Low angle slopes with smooth ground cover offer the best skiing and riding conditions.
- Ski and ride one at a time in avalanche terrain.
- Don’t regroup in run-out zones.
- Avalanche rescue skills are always essential when you travel in avalanche terrain.
Forecast Discussion
October and November storms laid a shallow snowpack at high elevations on Mount Shasta. During Thanksgiving week, it rained up to 10,000ft. This rain event was followed by cold and clear weather which capped the snow surface at 7,000ft and above with a crust, while below, it eliminated any existing snow on the ground. We have had two small storm events this December totaling 10 inches of snow and less than 1 inch of water. Otherwise, high pressure has dominated our weather pattern. Precipitation is well below average, and a large portion of our advisory area is free of snow. Mt Shasta and Ash Creek Butte are the only areas with a (barely) usable snowpack. Modest precipitation is not expected until the first week of January. This weekend will be mostly sunny and windy.
Recent Observations
The snowline slowly creeps upward. Very little coverage exists below 6,500ft. The height of snow ranges from 30-100cm between 6,500-9,500ft. The rain crust that formed on Thanksgiving continues to lock up the lower snowpack. This slick, icy layer is the primary snow surface near and above treeline. North and east aspects below treeline, 20-25cm of recycled powder (the December 3rd and December 20th storms) exists at the snow surface. South and some west aspects, near and above treeline, patches of corn snow can be found. Snowpack stability is very good throughout the advisory area. Rocks, down trees, small tree tops and bushes are widespread.
Weather and Current Conditions
Weather Summary
A brief storm system will move inland today and impact regions well to the north of the Mt Shasta area. Increasing clouds and windy conditions is all that we will get out of this one. A slight chance of light showers exists, but forecasts are not showing any accumulation of snow and/or precipitation. The front will pass and upper level ridging builds again, bringing more low clouds and fog. For the long-term, models are conflicting and show a low predictability. Overall, it doesn't look like any atmospheric rivers will impact our region for the New Year. We hope that our weather sources are wrong.
For in depth reading on this seasons ridiculously resilient high pressure, check out this link: AER's Arctic Oscillation Blog: the author indicates the prolonged high pressure ridging is very likely related to far below normal sea ice in the Bering Sea between Alaska and Russia.
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THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 5.83 inches of water, normal is 14.45 inches, putting us at 40% of normal. For the month of December, we have received .29 inches of water, normal is 7.09 inches, which is 4% of normal. And finally for the year of 2017, we received 44.82 inches of water, normal is 42.45 inches, putting us at 105% of normal.
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.
24 Hour Weather Station Data @ 4:00 AM
| Weather Station | Temp (°F) | Wind (mi/hr) | Snow (in) | Comments | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cur | Min | Max | Avg | Avg | Max Gust | Dir | Depth | New | Water Equivalent | Settlement | ||
| Mt. Shasta City (3540 ft) | 26 | 26 | 56 | 35 | 1 | N | ||||||
| Sand Flat (6750 ft) | 32 | 32 | 50 | 37 | 15 | 0 | 0 | 0 | ||||
| Ski Bowl (7600 ft) | 41 | 37 | 48 | 42 | 19 | 0 | 0 | 0 | ||||
| Gray Butte (8000 ft) | 40 | 37 | 45 | 41 | 18 | 37 | WNW | |||||
| Castle Lake (5870 ft) | 43 | 41 | 50 | 45 | 9 | 0 | 0 | |||||
| Mount Eddy (6509 ft) | 39 | 37 | 53 | 44 | 2 | 7 | WSW | 11 | 0 | 0 | ||
| Ash Creek Bowl (7250 ft) | station down | |||||||||||
| Ash Creek Ridge (7895 ft) | station down |
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 sunny and breezy | Partly to mostly cloudy | Mostly cloudy, slight chance of showers in AM, becoming partly sunny. |
| Temperature (°F) | 48 | 36 | 43 |
| Wind (mi/hr) | South 10-15 mph | South 10-15 mph | Southwest 5-10 mph |
| Precipitation SWE / Snowfall (in) | / 0 | / 0 | / 0 |
| For 9000 ft to 11000 ft | |||
| Friday | Friday Night | Saturday | |
| Weather | Mostly sunny, windy | Partly to mostly cloudy, windy | Mostly cloudy, slight chance of showers in AM, becoming partly sunny, windy |
| Temperature (°F) | 43 | 45 | 25 |
| Wind (mi/hr) | West 30-40 mph, gusts higher | West 0 | West 20-30 mph, gusts higher |
| Precipitation SWE / Snowfall (in) | / 0 | / 0 | / 0 |
