Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Your greatest risk of triggering a small wet loose avalanche is on previously wind-sheltered, shaded slopes. If you sink past your boot tops in wet snow, you could trigger a wet avalanche on steep terrain. These avalanches can gain momentum as they descend, so limit your exposure to cornices and travelers above you.

Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    With crusts near or at the snow surface up to 6500 ft, plenty of wind-battered snow in exposed terrain, and a few days of snowpack settlement, we don't expect the the incoming warm temperatures and light amounts of rainfall to "shock" the snowpack. You can trigger generally small wet avalanches within 4-6" of dry snow atop the 3/14 crust in wind-sheltered terrain on shaded slopes, most notably at middle elevations. These areas will destabilize most rapidly when they first receive rain on snow, likely Sunday evening. Upper elevations have been hardened against the elements by intense winds. Sun-affected aspects and lower elevations will have a new melt-freeze crust. If this crust does break down, you can trigger wet loose avalanches.  You'd be wise to choose a test slope where you can safely push a chunk of snow and determine whether and how deeply it entrains wet snow. If it entrains more than 6", it is possible that avalanches could be larger than we expect.

    Despite the mild temperatures in the forecast, we're expecting moderate to strong ridgeline winds through Monday. You're likely to find firm snow or crusts that don't soften during the day, limiting wet loose potential, but increasing the slide for life potential, in these areas. You could easily weave between firm, icy surfaces and soft, mushy snow over short distances. Make sure you have sharps and know how to use them to arrest a fall before crossing an icy slope.

    Example: Snow sliding easily atop a crust during a period of warming.

    Photo: Joe Dellaporta

Avalanche Discussion

A mix of rain and snow started falling late Sunday afternoon at the Mt Hood Meadows base area with precipitation continuing through the evening hours, and potentially drizzle lasting longer. Snow levels area expected to climb up to near the top of NWAC forecast elevations overnight, but it's unclear how high snow levels will have risen by the time the precipitation tapers off.  Any fresh slabs forming above 6000 ft are likely to be very shallow and mostly inconsequential. Old large-very large wind slabs were unreactive to artillery by Sunday morning. Incoming warmth and potential rainfall will further accelerate any residual healing.

As we move forward into a warmer regime, periodically getting the southern fringes of an atmospheric river directed at SW British Columbia, it's worth looking back at an impressive week of winter weather on Mt Hood!

A massive storm cycle ended with a flourish in the early morning hours on Saturday. A USGS seismologist recorded a 10-minute duration natural wind slab avalanche that ran from 9,000-10,000 ft down to and along the Heather/Clark canyon flats for half a mile. The debris deposited above another D4 avalanche recorded in the early morning hours on Thursday. Mt Hood Meadows Pro Patrol and observers documented the multiple crowns on the Wyeast Face and a smaller crown on the upper Newton-Clark Glacier. Mt Hood Meadows Patrol also noted a very large avalanche originating from Superbowl that was likely explosive triggered, but was not picked up by seismic recordings.

Mt Hood Meadows has received 11" of water equivalent since 3/8, likely corresponding to more than 10 ft of snow at the highest NWAC forecast elevations and above. Precipitation tapered off in the early moring hours of 3/14, but extreme WSW winds ramped up right as the precitation eased, likely resulting in a very intense loading event for these upper elevation start zones in the early morning hours.  The final 24 hours of the storm was mostly warm up to 6500 ft, but ended with 1-4" of snow at lower and middle elevations. Over the course of the weekend, the 3/14 interface turned into a thick crust at middle elevations, but still has up to 8" of moist snow under the crust. At lower elevations, the saturated snow surface refroze Saturday night then thawed during the day Sunday, resulting in decent riding conditions. Below the surface crust, you are likely to find 2 ft of saturated snow above the next crust. Fortunately we are not expecting the kind of rainfall that would renew the potential for wet slabs.

 

 

 

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