Avalanche Forecast
Dec 19th, 2018–Dec 21st, 2018
Alpine
Below Threshold
The avalanche danger rating in the alpine will be below threshold
Treeline
Below Threshold
The avalanche danger rating at treeline will be below threshold
Below Treeline
Below Threshold
The avalanche danger rating below treeline will be below threshold
Alpine
Below Threshold
The avalanche danger rating in the alpine will be below threshold
Treeline
Below Threshold
The avalanche danger rating at treeline will be below threshold
Below Treeline
Below Threshold
The avalanche danger rating below treeline will be below threshold
Regions: Olympics.
The Bottom Line: Heavy new snowfall and periods of strong winds have created dangerous avalanche conditions at higher elevations. At lower elevation, even small avalanches could cause injury due to exposed rocks and vegetation.
Discussion
Hurricane ridge received 2.5" water equivalent of snow from Sunday through Tuesday at temperatures just below freezing. This snow was blown by strong winds on Tuesday night. Wind and storm slabs may exist in the terrain. You are most likely encounter avalanche problems above 4500' elevation where recent snow has fallen and enough coverage exists to submerge vegetation and rocks.
Prior to Sunday, much of the southerly terrain was void of snow cover. On shaded and wind loaded north through east aspects, snow depths averaged about 4 feet as of Sunday afternoon.
Prior to Sunday, much of the southerly terrain was void of snow cover. On shaded and wind loaded north through east aspects, snow depths averaged about 4 feet as of Sunday afternoon.
Forecast Schedule
For the 2018-19 winter season, avalanche hazard ratings will be issued for the Olympics Friday through Sunday and during holidays.
On days that the Hurricane Ridge road is closed, No Rating will be applied. We will continue to provide general snowpack and weather summaries for the Hurricane Ridge area even when No Rating is issued.
On days that the Hurricane Ridge road is closed, No Rating will be applied. We will continue to provide general snowpack and weather summaries for the Hurricane Ridge area even when No Rating is issued.
Regional Synopsis
Why has the avalanche danger been so high for so long? Two reasons: A very active and wet weather pattern and widespread persistent weak layer.
For perspective, the approximate snow totals from 12/9-12/19 are:
- Mt Baker: 102â€
- Washington Pass: 55â€
- Stevens Pass: 76†mid-mountain
- Snoqualmie Pass: 68†mid-mountain
- Crystal Mountain 70†Green Valley
- Paradise: 78â€
- Mt Hood Meadows: 44†mid-mountain
- Olympics: 48â€
In many areas, a layer of buried surface hoar and/or weak sugary facets was buried on December 9th. This layer has been the cause in numerous natural, explosive, and skier triggered avalanches. As this layer gets deeper it gets harder to assess … in short, the scenario is tricky and getting more dangerous by the day.
Higher snow totals along the Hwy 542 corridor /Mt Baker area have driven several avalanche cycles during this period. Loading from recent storms has been more incremental to the east and south and we have not yet experienced a widespread cycle …
When will we reach the breaking point? It’s hard to say. What we do know is we have a deep weak layer, reports of very large explosives triggered slides at Mission Ridge and Crystal Mountain, and more storms on the way.
Be patient and continue to stick to lower angle slopes with nothing above you. This is a good time to avoid areas where avalanches can start, run, and stop.
We’d like to thank all of you who have sent NWAC your observations. If you are out in the mountains, let us know what you see.
Weather Forecast
A strong warm front lifting over the area this morning is directing heavier precipitation into the Olympics and north Cascades. Precipitation will fill in for areas further south later this morning and the trailing cold front should swing through the Washington Cascades around 1 PM. This storm system will bring heavier precipitation amounts to the volcanoes and Crystal Mt, and less precipitation for the Cascade Passes. Easterly flow will suppress snow levels in the Passes early this morning, but warmer air should push snow levels above Pass level for Snoqualmie and White Passes by late morning.
With the frontal passage strong winds aloft may mix down, creating very windy conditions in the afternoon. Snow level will lower rapidly late afternoon and overnight as colder air is advected into the region. Light to moderate snow should accumulate along the west slopes of the Cascades and Mt. Hood overnight. Westerly post-frontal winds should be blusterly overnight and ease off during the day on Friday.
Shortwave ridging will build over the area on Friday representing a relative break in the action, but there will still be a chance of showers for the mountains with lingering instability and weak onshore flow.