Avalanche Forecast

Issued: Apr 3rd, 2019 11:13AM

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

Northwest Avalanche Center NWAC, Northwest Avalanche Center

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A pause between spring storms will allow for sunny skies in the afternoon. While the avalanche danger is Low, you may find areas of unsupportive wet snow where the snowpack is shallow. You may also encounter shallow, isolated drifts near ridges above 6,000ft.

Summary

Discussion

Snow and Avalanche Discussion:

A weak spring storm on Wednesday did little to change the avalanches conditions. There may have been enough new snow and wind for some small isolated drifts near ridges and on leeward sides of terrain features above 6,000ft. Sun on Thursday afternoon, could drive some small loose wet avalanches in these areas of new snow. Watch for isolated wet avalanches and areas of unsupportive wet snow at low and mid elevations, especially in areas like the Wenatchee Mountains where the snowpack is shallow and weak. On Wednesday, an observer on Blewett Pass reported areas of unsupportive wet snow below 5,000ft. Warm spring weather has taken a toll on the snowpack over the past couple weeks. The snowpack is shrinking, low elevations slopes are bare, and spring considerations are on our mind. 

Be sure to consider all the mountain hazards. The snow cover is melting away from rocks and trees, and you may easily punch through into some of these holes in the snowpack. Creeks and lake inlets/ outlets are beginning to open up. "Slide for life" hazards may exist on steep slopes. Be mindful of the potential to slide down or off consequential slopes when snow surfaces are still frozen. 

Snowpack Discussion

April 3rd, 2019

Spring snowmelt

The snowpack in much of the Cascades has changed dramatically in the past two weeks. The weather has shifted solidly to spring-like patterns. The spring warm-up started in mid-March with a prolonged period of relatively clear skies and warm temperatures. Moving into April, we’re seeing periods of unsettled spring weather bringing rain to many low and mid-elevation slopes and snow to upper elevations.

Very bare southeast aspects of Rock Mtn/Nason Ridge. April 2nd. Photo: Josh Hirshberg

Since the peak height of snow in mid to late February, mountain weather stations in the 4,000-5,000ft range show an average of 27% decrease in height of snow. Looking at weather stations in nearly every zone, the percentage decrease ranged from 22-29%. This year's spring snowmelt is much earlier than normal. Traveling in the mountains the loss of snow coverage is most noticeable on southerly, sun-exposed slopes and below 4,000ft. On northerly aspects and slopes above 5,500ft, the snowpack has seen less dramatic changes and has even maintained some dry layers.

NWAC climatological snow depth data from April 1st. You can view it on our website here.

Spring avalanche considerations

As you head into the mountains there are a few questions to ask yourself common to spring avalanche conditions:

  1. Is there any recent snow accumulation that could cause avalanches? If so, what kind of avalanches could you trigger? And where?

  2. What are the high and low temperatures of the past 24 hours as well as the forecasted temperatures during the time you’ll be in the mountains? Could these create weak, wet snow surfaces?

  3. How is the cloud cover contributing to the melting or freezing of surface snow? Did clear skies allow for a sufficient overnight freeze? Will the sun be strong enough to weaken surface layers?

Glide avalanches and holes opening up in rocky terrain near Mount Herman. Photo: Andrew Kiefer

Other considerations

In addition to daily avalanche hazard, the early snowmelt is creating some other travel considerations. Some roads and lower elevation slopes may not have enough continuous snow coverage for travel on snow machines. Holes melted around rocks, trees, and creeks could create a fall hazard. When nighttime temperatures and cloud cover allow for surface freezes, bring appropriate equipment to mitigate slip and fall hazard on steep slopes.

We are approaching the end of our daily avalanche forecasting season. The mountain weather forecast will continue into the spring, and the weather station data is available year round. Keep checking the forecast for conditions updates on the end of season information.

Valid until: Apr 4th, 2019 11:13AM