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Avalanche Forecast for 2019-01-09 06:00
- EXPIRED ON January 10, 2019 @ 6:00 amPublished on January 9, 2019 @ 6:00 am
- Issued by Ryan Sorenson - Mount Shasta Avalanche Center
Bottom Line
Avalanche danger will remain elevated today. Above treeline danger is HIGH. Wind slabs and storm slabs are likely and will continue to grow in size as more than 4 inches of available water from this storm continue to fall with light to moderate south wind. Near treeline is CONSIDERABLE. Natural and human triggered storm slab avalanches are likely on steep wind protected slopes. Lingering and new wind slabs are likely on north and west aspects. Below treeline is MODERATE.
Avalanche Problem 1: Wind Slab
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Likelihood ?CertainVery LikelyLikelyPossible
Unlikely -
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Low visibility limited observations for the upper mountain yesterday. However, moderate south and east wind averaging 13 mi/hr was recorded on Gray Butte over the last 24 hours. Snow and wind will continue to build wind slabs on north and west facing aspects. These slabs may sit atop icy surfaces and crusts and could be reactive. This added weight will likely cause large natural avalanches above treeline.
Wind hasn't been as high as predicted but it is expected to pick up as the day continues. There is plenty of new storm snow available for transport as 15 inches of new snow fell in the last 24 hours. Light to moderate southerly wind capable of transporting new snow is expected to continue today.
Expect wind slabs near and above treeline on west, east, and north facing aspects, but look for them everywhere. Visual clues that indicate winds slabs are nearby are fresh cornices, blowing snow, snow drifts, and uneven snow surfaces. Avoid wind loaded slopes over 35 degrees.
Avalanche Problem 2: Storm Slab
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Character ?
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Likelihood ?CertainVery LikelyLikelyPossible
Unlikely
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Over an inch and a half of water is expected to hit today. This will equate to 8-14 inches of new snow above 5,000 feet. Storm slab avalanches are likely on steep wind protected slopes.
This storm came in warm and wet below and near treeline. This is all siting on a low density snow pack from the storm this weekend.
Storm Slabs form when new snow consolidates over a weaker layer or interface. They tend to have a short life span. They are easiest to trigger during periods of heavy snow and typically stabilize within a day or two after the storm cycle has ended.
Stay away from convex rollovers, unsupported slopes, and slopes over 40 degrees. This problem will be confined to protected areas below and near treeline.
Natural avalanches are likely and human triggered avalanches are very likely.
Avalanche Problem 3: Loose Wet
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Unlikely
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However unlikely, loose wet avalanches could pose a risk below treeline today. Even with snow levels dropping to 5,000 feet today, over 4 inches of storm water over the last 48 hours has caused saturation of snow below the snow line. Flooding and natural loose wet avalanches could happen today.
A loose-wet avalanche is a release of wet unconsolidated snow or slush. These avalanches typically occur withing layers of wet snow near the surface of the snow pack, but they may quickly gouge into lower snow pack layers.
Loose-wet avalanches generally move slowly, but can contain enough mass to cause significant damage to cars or buildings. Loose- wet avalanches can trigger slab avalanches that break into deeper snow layers.
Avoid travel on saturated wet snow at lower elevations today.
Forecast Discussion
Avalanche danger remains elevated at all elevations, so if you venture out, keep in mind the 5 red flags indicating avalanche danger:
- Recent avalanche activity *
- Cracking, blocking, or whoomphing
- Significant snowfall in 24 hours **
- Strong winds *
- Rapid warming*
* - this has happened
** - this has happened and will happen today.
Solid trip planning, group management and safe travel decisions are imperative today. Keep away from runout zones and all avalanche terrain.
Recent Observations
A substantial amount of precipitation has hit over the last 48 hours. Total storm precipitation amount is 4.26 inches. Over 15 inches of new snow has been recorded at the Old Ski Bowl (7,600 feet).
This new snow sits on top of low density snow from this weekend. The upside down layer cake is in full effect as new layers continue to add weight today.
South and east wind at Gray Butte, 8,000 feet, has remained light to moderate throughout the storm. Average wind speed is 13 mi/hr over the last 24 hours. Gusts have maxed out at 31 mi/hr at 11 p.m. last night. Temperatures have remained in the mid to upper 20s averaging 28 degrees Fahrenheit.
Low visibility limited observations yesterday. A trip up near the Old Ski Bowl saw less than an inch of new snow over a ice rain crust atop soft snow at 7,600 feet before the storm yesterday morning. This is likely buried with wet heavy new snow from last night.
Weather and Current Conditions
Weather Summary
The warm front has moved into the area bringing copious amounts of water, moderate wind, and new snow. Expect snow to continue to impact the forecast area today as another 1.5 inches of water, equating to 8-14 inches of snow, is predicted to fall in the next 12 hours. Snow levels have dropped to 5,000 feet today. Rain will continue to fall on the snow at lower elevations. A flood watch is currently in effect. South wind is expected to max out at upwards of 30 mi/hr with temperatures in the low to mid 20s today.
24 Hour Weather Station Data @ 3:00 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) | 38 | 29 | 38 | 34.5 | 1 | N | ||||||
| Sand Flat (6750 ft) | 31 | 31 | 33 | 33 | 66 | 11 | 2 | 0 | ||||
| Ski Bowl (7600 ft) | 27 | 27 | 31.5 | 29 | 79.2 | 15.1 | 3.81 | 0 | ||||
| Gray Butte (8000 ft) | 26.5 | 26.5 | 30 | 28 | 13 | 31 | SSE | |||||
| Castle Lake (5870 ft) | station down | |||||||||||
| Mount Eddy (6509 ft) | 30 | 30 | 32.5 | 31.5 | 2 | 18 | ||||||
| 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 | |||
|---|---|---|---|
|
Wednesday (4 a.m. to 10 p.m.) |
Wednesday Night (10 p.m. to 4 a.m.) |
Thursday (4 a.m. to 10 p.m.) |
|
| Weather | Rain and snow with strong south wind. Chance of precipitation is 100%. | Breezy and cloudy with snow. Chance of precipitation is 90%. | Mostly cloudy with snow showers likely. Chance of precipitation is 60%. |
| Temperature (°F) | 34 | 27 | 34 |
| Wind (mi/hr) | South 20-30 | South 10-15 | Southeast 10-15 |
| Precipitation SWE / Snowfall (in) | / 8-14 | / 3-5 | / 1-2 |
| For 9000 ft to 11000 ft | |||
| Wednesday | Wednesday Night | Thursday | |
| Weather | Blowing snow with strong south wind. Chance of precipitation is 100%. | Breezy and cloudy with snow likely. Chance of precipitation is 90%. | Cloudy with snow showers likely. Chance of precipitation is 60%. |
| Temperature (°F) | 20 | 13 | 20 |
| Wind (mi/hr) | South 20-30 | Southwest 8-14 | Southeast 20-25 |
| Precipitation SWE / Snowfall (in) | / 8-14 | / 3-5 | / 1 |
Season Precipitation for Mount Shasta City
| Period | Measured (in) | Normal (in) | Percent of Normal (%) |
|---|---|---|---|
| From Oct 1, 2024 (the wet season) | 11.82 | 17.10 | 69 |
| Month to Date (since Dec 1, 2024) | 3.41 | 1.89 | 180 |
| Year to Date (since Jan 1, 2024) | 3.41 | 1.89 | 180 |
