Mt Hood

The bottom line: You might find new wind slabs on lee slopes Wednesday where strong east winds have transported available surface snow, mainly above treeline. Following several days of very warm weather, surface crusts of varying strengths are making for difficult travel conditions. Smooth hard crusts may create a hazard for falls and uncontrolled slides. Continue to choose terrain carefully and carry the basic avalanche safety equipment, a transceiver, shovel, and a probe.

January 15, 2019

We’re about a month into our avalanche season and well into the heart of winter. In the past month, the snowpack has grown from near non-existent to over a 100 inches deep at Mt Baker. Remote weather stations show most snow depths across the region are at 62-77% of normal with Mt Baker and Crystal Mountain at 93% and 90% respectively. Check out the latest climatological snow depths for more details.

Much of the last month has been filled with elevated avalanche danger, numerous avalanche warnings, and several widespread large natural avalanche cycles. While the active weather patterns and growing snowpack have been a welcomed sight, it’s been hard to catch our breath. Quieter weather in the middle of January has offered a break in the non-stop storms and allowed avalanche danger to drop in all zones. Looking forward to more unsettled weather, there are a few things on our mind here at the avalanche center.

Calm weather in mid-January

A period of calm weather heading into the middle of the month shaped a variety of snow surfaces. As of January 15th, you could find a range of wind transported snow, crusts (both thin/breakable and thick/supportive), rime, surface hoar, and weak, dry snow on the snow surface. This will determine our next interface to track,  as storm snow accumulates. The big take-away is that you should track surface conditions from the 16/17th and how that interface changes based on aspect and elevation.

There were a few interesting weather factors during the mid-January calm weather that contributed to surface variations. While clear skies and warm temperatures were the norm in many locations (especially west of the Cascade Crest), temperature inversions and cold east flow cooled valleys and passes. The sun is still low in the sky and hasn't been strong enough to drive significant melting of snow surfaces. Hence, many slopes developed only thin crusts. Additionally, fog limited both the effects of the sun and surface hoar growth at lower elevations and in valleys.

Old Persistent Weak Layers

A high elevation rain event on January 3rd did us a favor in many locations. Besides heavily stressing old weak layers, the rain created a very strong melt-freeze crust, making it extremely difficult to trigger deep avalanches.

There are a few exceptions, and they can be found mainly in the eastern forecast zones. The East-North zone around the Methow Valley and WA Pass did not experience significant rain above 5500 ft, potentially leaving some older weak layers intact. Areas further east including, but not limited to, Icicle Creek and the Wenatchee Mountains did not receive enough rain to form a strong thick crust. In all of these areas, older persistent weak layers are still suspect.

Higher Elevations and Remote Trailheads
Stormy weather over the last month has been keeping most of us closer to common trailheads and recreating at near and below treeline. With nice weather on tap, some of you may be thinking about heading into higher elevation terrain and exploring around more remote trailheads. If you are heading out, take time to consider a few key pieces of information.

We’d like to thank our NWAC Community for all the wonderful public observation this year. If you are heading out into the mountains, we appreciate you taking the time to let us know what you saw. This is a great way to contribute to the creation of your avalanche forecast. You can submit observations here.

Enjoy the sunshine!

Weather Synopsis for Tuesday night through Thursday

Tuesday has quickly transitioned from blue bird high pressure to a mostly cloudy afternoon as high pressure departs to the east and the region begins seeing the effects of the west coast trough. Moisture has spread northward through the day from a trough that extends to southern California. Most of the energy associated with the trough has been spent in California and the PNW will only see occasional light showers in bands rotating northward through Wednesday afternoon.

Freezing levels have lowered substantially by Tuesday with many NWAC sites 10-20 degrees cooler than yesterday at the same time!

Strong easterly winds persist across the Cascades and through the passes keeping sub-freezing air in the lower elevations.

Some light precipitation will spread northward Wednesday but amounts will be very light as the main energy moves inland well south of the area.

A stronger low-pressure system will approach the offshore waters late Wednesday and move NE offshore Thursday. More significant precipitation should rotate across the area Wednesday night with wi little break between bands during the day Thursday.