Avalanche Forecast Olympics

Date Issued: Valid Until:

Dennis D'Amico,

Avalanche Forecast

Wed Jan. 30th · 6:00PM

Alpine

Danger Ratings Below Threshold

Treeline

Danger Ratings Below Threshold

Below Treeline

Danger Ratings Below Threshold

Alpine

Danger Ratings Below Threshold

Treeline

Danger Ratings Below Threshold

Below Treeline

Danger Ratings Below Threshold
The Bottom Line: We are in for another day of fair weather and mild temperatures. The ongoing melt-freeze cycle will continue to keep the snowpack strong and avalanches unlikely. The biggest hazard will be related to difficult travel conditions caused by very firm, icy slopes, or breakable crusts. The next avalanche forecast with a hazard rating for the Olympics will be issued Thursday evening, valid for Friday.

Avalanche and Snowpack Discussion

A few reports from the Olympics trickled in last weekend and told a story of natural loose wet avalanches releasing on sunny slopes near and above treeline along with generally limited snow cover below 4000’. Multiple crusts are easily identifiable in the snowpack, pointing back to the numerous rain events that have occurred this season. We expect generally safe avalanche conditions to continue in the Hurricane Ridge area on Thursday. Difficult travel conditions will likely pose the biggest hazard Thursday. 

The road to Hurricane Ridge is scheduled to open this week and our professional observer team is working to gather more specific snowpack and avalanche observations from the Hurricane Ridge area.

Forecast schedule

For the 2018-19 winter season, avalanche hazard ratings will be issued for the Olympics Friday through Sunday and during holidays. We will resume issuing ratings when access is once again available following the recent government shutdown.

General snowpack and weather summaries will be available on days that the Hurricane Ridge road is closed.

Weather Forecast

Thu 31st Jan 14:26 - Dennis D'Amico

Weather Synopsis for Thursday night through Saturday

An approaching frontal system has blanketed the north and central Cascades in a high overcast this afternoon. Areas further south will begin to fill in tonight as the system approaches the coast.

Precipitation should begin for the Olympics and Mt. Baker area later this evening, but precipitation won't make much progress inland as the front becomes more north-south oriented and slows. Locally moderate to even heavy precipitation is expected in the Mt. Baker area on Friday, with a secondary bullseye for the Paradise/Crystal area. 

Snow levels will lower late tonight but won't cool further until the front slowly kicks east of the Cascades Friday night. Snow levels look rather unimpressive (mild) with this system. Easterly flow may initially drag down snow levels to 4000-4500 feet for Stevens and Snoqualmie early Friday morning, but snow levels are expected to quickly settle above all the major Pass levels on Friday. 

The frontal boundary will split and shear as it passes inland Friday evening with showers quickly diminishing toward Saturday morning. The Pacific Northwest will be in the weather equivalent of no man's land on Saturday with westerly (zonal) flow over the area and storm systems located to our north and south. Snow/freezing levels for the Cascades will stay constant on Saturday in the 4000-5000 ft range.

Regional Synopsis

Tue 29th Jan 09:00

January, 29, 2019

Well, here we are towards the end of January and deep into a week-long high pressure ridge. The snowpack survived extremely warm temperatures and sunny skies over the weekend with minimal new wet avalanche activity reported. This break in the weather allowed for avalanche danger to steadily decline in all regions. At this moment, avalanche hazard is limited in all zones.

We’ve been hearing a variety of tales from backcountry travelers over the past week. We’ve heard reports of extremely firm slopes creating slide-for-life conditions. Others reported perfect spring like snow. Some encountered difficult breakable crust. And, for a lucky few, softer, drier, mid-winter snow has been found.

So, what do we make of all this? Well, we can use a few ideas to sum up the current state of the snowpack. I’d like to call it: North, South, East, West.

North-South:

While a high elevation rain event, towards the end of the last storm, formed surface crust in many regions, it’s the constant melt-freeze cycles from the past week, that caused a divergence in the Northerly and Southerly snowpacks.

South: On sunny aspects, the sun drove warming and melting of surface snow. Most days, the snow surface softened on steep, southerly slopes receiving direct sunshine. Long, cool, winter nights allowed for the surface to freeze again. This repeating melt-freeze pattern created a thicker, firmer, and more supportable surface. Any weak surface snow, such as near surface facets or surface hoar, melted during the day limiting its development. For the fortunate, well timed travelers, this cycle resulted in some great spring like snow conditions. For those unfortunate enough to be traveling too early in the day, or on days where clouds and cooler temperatures delayed the snow surface thawing, very firm travel conditions were encountered.

North: On shady slopes, things haven’t exactly been soft. The crust formed at the end of the last storm extends to high elevations (Mt. Hood 7000+ft, South Cascades 6500 ft, Passes and Central Cascades 6000 ft. and West-North 5500 ft.). Only areas in the East Cascades seemed to escape the wrath of this breakable crust. Without the help of the sun, shady slopes haven’t been softening even during this period of warm weather. Instead, the surface crust underwent some weakening. Observations found faceting on top of and below this crust. In some locations, this caused the crust to begin to degrade, becoming less supportive. NSFs Jan 28 2019.jpg tell, but this is a good time to get out and see where those potential weak layers exist.

Near surface facets developed on shaded snow surfaces in many areas. These facets are from near Mt Baker. Photo: Lee Lazzara


East-West:
It’s not uncommon for our east-side forecast zones to experience lingering persistent weak layers (PWL’s). This season, we’ve also seen several different PWL’s in our western zones. By in large, this break in the weather gave the snowpack time to gain strength in all zones.

West: While you may find some weak snow in the upper few inches of the snowpack, the mid and lower snowpack has been found to be quite strong. Firm rounded grains, stout  crust, and strong frozen melt-forms make up the majority of the snowpack at this time.

East: The east-side snowpack continues to be highly variable. You may find deep strong snowpacks closer to the crest or you could encounter shallow weak snowpacks areas further east. While there are number of potentially weak interfaces, there are two more common layers we’ve got our eyes on.

  1. January 22nd surface hoar and small facets. You can find these just under the recent storm snow, about a foot down. .

  2. December 26th surface hoar. This layer can be found from 16” to 40” down and is still producing clean, planar shears with tests.


You are most likely to find these layers to be preserved on wind sheltered, shady, and open slopes above 5,500ft. These layers are likely to be more reactive further east, where the snowpack is less than 4 feet deep and variable especially east of highway 97. What’s the future of these buried PWL’s? How long will they hang around? Often, persistent weak layers go “dormant” during periods of high pressure such as this. They may or may not become reactive with the next storm. It’s tough to say at this point. We’ll have to keep tracking them and gaining information to round out our understanding of these layers.

The lower eastern slopes and the Columbia River. Snow exists at low elevations, but snowpack depths are shallow. Photo: Matt Primomo


Weather forecasts suggest that this high pressure ridge is coming to an end later this week. As the weather changes, expect avalanche conditions to change too. Make sure to check the forecast if you are planning on getting out this weekend.