Avalanche Forecast
Regions: Cascades - East.
The avalanche danger will remain low with cool overnight temperatures, light precipitation, and partial cloud cover. If you find localized areas of over 6 inches of accumulation in the Wenatchee Mtns, use caution on slopes steeper than 35 degrees. Keep typical spring considerations in mind, like wet snow avalanches, cornices, and timing your travel to be off slopes before warming makes them wet and weak.
Discussion
Snow and Avalanche Discussion:
While there are no official avalanche problems in the forecast there are a few potential hazards to keep in mind. Snowfall Wednesday night into Thursday will generally be light, but could result in localized areas of more than 6 inches of accumulation near Blewett Pass and Mission Ridge. If you find over 6 inches of fresh snow on the ground, use caution on slopes steeper than 35 degrees and watch for possible loose snow avalanches. Overall, snow accumulations will be minimal in the majority of the zone.
Variable surface conditions could pose a challenge for some travelers. You may find a range of conditions from soft, new snow, firm frozen surfaces, and punchy, unsupportive wet snow. You may find small isolated drifts near the highest ridges from recent east wind. Creeks are beginning to open up. Rain may keep the low elevation slopes moist. While temperatures have cooled, we’re not completely out of the woods for wet avalanches. Wet slab, loose wet, glide avalanches, and cornice falls all have been a concern in the past week. Continue to monitor the upper snowpack and asses the strength of any wet or frozen layers. Watch for small loose wet avalanches in areas where new snow gets warmed by the sun.
On shaded aspects, the snowpack only started producing wet avalanches with rain and the warm temperatures in the past week. Here, the snowpack still has very weak facets underneath a crust from early February. Recent large wet slabs on facets near the ground (3/24, Wedge Mtn and 3/23, Squilchuck State Park) are concerning, as they tell us water made its way down to these weak layers. Cooling temperatures have helped diminish concern for wet slab avalanches but you may still find areas of weak unsupportive snow at low elevations.
Large, dirty, wet slab (D3) debris on Wedge Mountain near Leavenworth. A number of logs were taken with the churning debris flow. Northeast at 3,900ft. 3/25 Photo: Matt Primomo
Snowpack Discussion
March 27th, 2019
Enter Spring
If you’ve been in the snow recently, the wintery conditions of early March may seem worlds away. You may be in for a surprise if it’s been a while since you were in the mountains. The weather has taken a turn towards spring in the last couple weeks and the Cascade snowpack the has undergone major changes. Unseasonably warm temperatures and strong sun followed a month-and-a-half of cold, winter storms. Mid-elevation weather stations stayed above freezing from March 15th-22nd with high temperatures reaching the upper 50’s to low 60’s. For an in-depth survey of the regional snowpack, we’ll divide the terrain up by aspect and elevation.
A graph showing temperatures between 4,000-5,000ft around the Cascades from the 16th-21st.
Aspects
Northerlies
Along with the warm temperatures, the spring sun has played a major role in warming snow surfaces. The result is a snowpack that varies by aspect. In most regions, shaded and northerly slopes remain relatively unchanged. Aside from some settlement and firmer or moist surfaces, the snow on north aspects is almost entirely dry. Even some low elevation north slopes are still holding snow.
Sunny slopes
The snowpack on east through south through west aspects is a different story. The strong March sun melted snow surfaces and drove melt-water into the snowpack. This is most dramatic on steep (over 35 degrees) southeast through southwest slopes below 5,000ft.  In some areas, you can find meltwater up to 3 feet below the snow surface with drainage channels well established. Between this warm period and rain events in the first half of the winter, the entire snowpack has transformed to melt forms. Of note is that as of the 27th, these solar aspects have only undergone partial freezes with lower layers remaining unfrozen. Cooler weather may continue to strengthen these slopes.
A glide avalanche (D2) released from a rock slab late on the 20th. Lichtenberg Mtn, 5,100ft, SE aspect. Other glide avalanches occurred on the 20th at Snoqualmie Pass and in Tumwater Canyon. Photo: Josh Hirshberg
Elevation
Low elevations
As you travel from low valleys to higher peaks, you’ll notice a major difference in the snowpack based on elevation. With all the low-elevation snow this winter, there are still some cold, shaded slopes holding pockets of snow down to 1,000ft, especially east of the Cascade Crest. However, most slopes below 3,000ft have lost much of their snow cover. Many low elevation, sun-exposed slopes are bare, especially in areas that previously held less than 3 feet of snow. The low elevation snowpack is no longer substantial enough to allow for easy travel over snow or widespread avalanches.
Loose wet avalanches on the south side of Table Mtn, near Mt Baker. 3/17. Photo: Pete Durr
Mid-elevations
At mid-elevations, around 3,000-5,000ft, the snowpack is still deep and layered. Many slopes at this elevation band near and west of the Cascade Crest are holding 6-10 feet of snow. This is also where you’ll find the most dramatic variation in the snowpack based on aspect.
High-elevations
Above 5,000ft you’ll encounter a snowpack similar to what you may have found around the 1st of March. Upper elevations have stayed mostly dry. The most sun-exposed slopes have surface crusts but have not seen much water or change to melt forms below the surface.