Avalanche Forecast

Issued: Jan 4th, 2020 10:00AM

The alpine rating is below threshold, the treeline rating is below threshold, and the below treeline rating is below threshold.

Northwest Avalanche Center NWAC, Northwest Avalanche Center

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Expect recently form wind slabs to still be reactive on Sunday with additional wind loading on the same slopes. Wind slabs may have formed further downslope than usual due to ongoing strong winds. Avoid steep wind loaded slopes over 35 degrees by sticking to lower angled or wind-scoured terrain. Watch for low snow hazards at lower elevations. 

Summary

Discussion

Forecast Discussion

A rapid cool down Friday night followed by strong to extreme westerly winds at ridgetop level likely formed wind slabs near and above treeline on lee aspects through the day Saturday. Winds should continue to transport snow onto similar aspects Sunday. Due to the strength of the winds, wind slabs may have formed further downslope than typical. Within the zone, deeper slabs are likely closer to the Cascade crest where more snow recently accumulated. Below this new snow and at lower elevations, the most recent rain crust can be found, likely with varying levels of thickness depending on elevation and aspect. 

At higher elevations, avoid steep wind-loaded terrain where you are likely to trigger an avalanche. Watch for cracking in the snow as a clear sign of instability and avoid open slopes steeper than 35 degrees that have firmer wind drifted snow.

Low snow depths continue to limit the avalanche danger at lower elevations. Exposed or lightly buried stumps, creeks, or rocks can amplify the consequences of a small avalanche in low snow depth areas.

Help your local forecast by submitting an observation this weekend! 

Forecast Schedule and No Rating definition

We do not have enough specific snowpack information to issue an avalanche hazard rating for the East South zone. However, even when No Rating is applied, applicable avalanche conditions and backcountry travel advice will be provided throughout the season - this forecast is updated every day, all winter long!  When weather systems produce very dangerous avalanche conditions in adjacent zones, NWAC will issue an avalanche warning for this zone as well.

Snowpack Discussion

January 02, 2020 (The regional synopsis is updated every Thursday @ 6 pm)

Happy New Year! 

The pacific northwest rung in the new year with a winter storm cycle that brought changing conditions to our region. This storm exhibited three characteristics: warm, wet, and windy. Let’s take a look at the end of 2019, the beginning of 2020, and where we can go from here. 

Wrapping up 2019

The last few days of December were generally quiet and cold. The snowpack seemed to enjoy this break in the weather. Lingering unstable snow from the pre-Christmas storms gained strength, persistent weak layers appeared to stabilize, and avalanche hazard decreased in all forecast zones. All in all 2019 ended quiet and uneventful… until the New Year’s Eve weather party showed up …  

Quiet weather led to lower avalanche danger during the last week of 2019. Hogsback, White Pass, WA. Photo: Andy Harrington

Blowing into 2020

A warm, wet, and windy weather system blew into the northwest for New Year’s Eve and New Year’s Day. This brought rapidly changing conditions and increasing avalanche hazard to all areas. 

  • Warm: Unfortunately this system brought with it warm air. Freezing levels measured near the coast reached 9000’ on the afternoon of the 31st. Many weather stations recorded above freezing temperatures during the onset of precipitation. 

  • Wet: While this system wasn’t as wet as the atmospheric river prior to Christmas, it still produced impressive water numbers in many areas. The bulk of the precipitation seemed to be focused on the Passes and Volcanoes, and water spilled over the crest to places like Washington Pass and Leavenworth. Sadly, when combined with the warm temperatures, this translated to rain well into the near treeline band (or higher) for most areas. The main exception appeared to be in the northeastern cascades, where locations like Washington Pass remained all snow. 

 

HurRidge

MtBaker

WaPass

Stevens

Leavenworth

SnoqPass

MtRainier

MtHood

Precipitation (in)

1.84

3.39

1.42

4.56

1.06

6.19

5.39

5.41

Snow (in)

-

15

-

12

0

3

10

8

Table 1: Precipitation and storm totals from selected weather stations during the New Year’s Eve Storm. “-” 24hr storm snow not measured. 

  • Windy: While the warm and wet were impressive, it’s the winds that may set this storm apart. Most weather stations recorded very strong and extreme winds during the storm. Alpental exceeded 100mph just after midnight to ring in the new year. Any dry snow at high elevations was redistributed by the wind and snow surfaces were transformed. 

Table 2: Wind speeds from New Year’s Eve from selected wind sites. Note the sustained period of winds between 40-60mph.

Eventually, temperatures cooled, the rain turned back to snow, and winds calmed. Many locations picked up additional snow as the storm wound down, but 2020 was already off and rolling with its first major storm.

New Year’s Resolutions

The active weather pattern that started the new year appears to continue. The snowpack and avalanche conditions will continue to change. So, what can your New Year Avalanche Resolutions be? 

  1. Read the forecast. This is a great way to monitor conditions even if you aren’t heading into the mountains. 

  2. Get out in the snow! Enjoy the wonderful mountains in your backyard. 

  3. Submit an observation. Tell the avalanche center what you saw while out in the snow by submitting an observation and sending in a photo. 

Thanks for all of your support in 2019 and here’s to 2020!

-Dallas

 

Valid until: Jan 5th, 2020 10:00AM