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Avalanche Advisory for 2018-01-09 07:00:27
- EXPIRED ON January 10, 2018 @ 7:00 amPublished on January 9, 2018 @ 7:00 am
- Issued by Andrew Kiefer - Mt Shasta Avalanche Center
Bottom Line
MODERATE avalanche danger exists above treeline, while the avalanche danger is LOW near and below treeline. New snow accompanied by continued southerly winds have recently formed wind slabs above 8,000ft on N-NE-E-SE aspects. In these specific areas, wind slabs will be sensitive to human triggering.
Avalanche Problem 1: Wind Slab
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Character ?
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Aspect/Elevation ?
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Likelihood ?CertainVery LikelyLikelyPossible
Unlikely -
Size ?HistoricVery LargeLargeSmall
Wind slabs could be up to 1ft thick, and could be triggered by the weight of a skier or rider today. Watch for obvious signs of wind loading above treeline on Mount Shasta on N-NE-E-SE aspects: blowing snow, cornices, snowdrifts, uneven snow surfaces, and hollow sounding snow. Monitor changes in the height of new snow throughout the terrain, and check to see how the new snow has bonded to the old snow surface. Avoid convex slopes 35 degrees and steeper with evidence of a wind slab problem.
Forecast Discussion
We hit the low end of the forecasted snow totals yesterday and overnight. Five inches of new snow paired with steady southerly winds are enough to raise concern for a wind slab problem though. Wind slabs may have formed overnight, and could continue to form throughout the day today. With MODERATE avalanche danger above treeline, natural avalanches are unlikely, while human triggered avalanches are possible in specific wind loaded areas. Remember that shallow snowpack hazards are still a concern, and the recent snow has just barley covered our rocky, firm, and thin snowpack.
Recent Observations
The Old Ski Bowl weather station (7,600ft) picked up 5 inches of snow and 1 inch of SWE over the past 24 hours. Southerly winds have averaged 5-10 mph with gusts to 20 mph at the Grey Butte weather station (8,000ft). Snowfall began yesterday at 7am. By noon, Bunny Flat (6,900ft) was above the freezing level, and wet snow was beginning to accumulate. A significant change to drier snow occurred at 8,000ft in the Old Ski Bowl where 2 inches of new snow had accumulated by the early afternoon. Winds yesterday were surprisingly calm, even up to 9,500ft. Visibility above treeline was poor. No signs of unstable snow or wind slab formation were observed by 1pm yesterday.
Weather and Current Conditions
Weather Summary
Light precipitation and above normal snow levels will continue through Thursday night. Highs today will be in the mid 30’s to low 40’s. Strong winds will blow out of the southwest and shift northwest by this afternoon. Below treeline areas should see a mix of light rain and snow, while 1-2 inches of snow may accumulate above treeline. Snow levels will start near 7,000ft today and drop to 5,000ft by tomorrow. We received the bulk of precipitation for the week over the past 24 hours. Mostly cloudy skies and little snow accumulation are expected while the unstable weather continues. High pressure will return on Friday.
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THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 7.65 inches of water, normal is 17.10 inches, putting us at 45% of normal. For the month of January and 2018, we have received 1.82 inches of water, normal is 1.89 inches, which is 96% of normal. Mount Shasta finished off 2017 with 44.82 inches of water; normal observed value is 43.21, which is 103% of normal.
Always check the weather before you attempt to climb Mount 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) | 43 | 40 | 44 | 42 | 1 | N | ||||||
| Sand Flat (6750 ft) | 34 | 32 | 36 | 33 | 10 | 1 | .5 | 1 | ||||
| Ski Bowl (7600 ft) | 32 | 27 | 33 | 31 | 24 | 5 | 1 | 0 | ||||
| Gray Butte (8000 ft) | 32 | 25 | 32 | 30 | 9 | 28 | S | |||||
| Castle Lake (5870 ft) | 38 | 31 | 38 | 34 | 0 | 0 | 0 | |||||
| Mount Eddy (6509 ft) | 35 | 30 | 35 | 33 | 1 | 8 | S | 8 | 1 | 1 | ||
| 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 | |||
|---|---|---|---|
|
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 | Rain and snow before 10am. Then rain showers between 10am-4pm. Chance of precipitation 100%. | Snow likely. Chance of precipitation 60%. | Snow likely mainly before 10am. Mostly cloudy. Chance of precipitation 30%. |
| Temperature (°F) | 39 | 28 | 35 |
| Wind (mi/hr) | South/Southeast 10-15 mph, gusting 20 mph | North/Northwest 5-10 mph, gusting 15 mph | South/Southeast 10-15 mph, gusting 25 mph |
| Precipitation SWE / Snowfall (in) | / .5 | / .5 | / <.5 |
| For 9000 ft to 11000 ft | |||
| Tuesday | Tuesday Night | Wednesday | |
| Weather | Snow and windy. Chance of precipitation 100%. | Snow likely and windy. Wind chill values near -4 degrees F. Chance of precipitation 60%. | Windy then snow possible.. Chance of precipitation 30%. |
| Temperature (°F) | 25 | 21 | 27 |
| Wind (mi/hr) | West/Southwest 15-25 mph, gusting 40 mph | West/Northwest 1-3 | West/Northwest 35-45 mph, gusting 60 mph |
| Precipitation SWE / Snowfall (in) | / 1-3 | / <1 | / .5 |
