Lawinenlagebericht

Mt Hood

Northwest Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 3 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Morning update: Reduced danger ratings at upper and lower elevations due to delayed onset of snowfall.

Old, stubborn slabs may remain reactive on steep upper-elevation slopes. Small, fresh slabs will increase in size and distribution in the afternoon. Monitor for 6" deposits where you can trigger them on steep slopes.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    You'll primarily be dealing with old snow interfaces and stubborn slabs to start the day. Expect building hazards at all elevations as the storm ramps up and builds new slab hazards. Snow will fall to around 2000 ft.  Although ridgeline SE winds aren't impressive by Mt Hood standards, they're likely to be strong enough to transport snow onto atypical aspects. Hazard will develop first at middle and upper elevations below freshly formed cornices in start zones. By the end of the day, slabs 6" or deeper could exist on a variety of features including below ridgelines, on the down-wind side of morains, and into cross-loaded gullies. The danger will be highest at the end of the day, with heavy snowfall rates by the evening hours. Intense wind loading, shooting cracks, whumps, or fresh slab activity are all signs to dial it back. Within the cold, low-density snow, firmer over weaker snow layering could be more subtle than you expect, but still be reactive. When in doubt, seek wind-scoured slopes and sheltered terrain less than 35 degrees.

    (1/22/2024)

    Example: Wind transport will intensify as the day progresses. Look for slabs on lee slopes below fresh cornices such as those pictured.

    Photo: Joe Dellaporta

Avalanche Discussion

Wednesday will bring 3-5" of cold, low-density snow and improved riding conditions to all elevations on Mt Hood. 

Riders reported fun riding conditions in wind-sheltered terrain on the south side of Mt Hood on Tuesday. The sunshine warmed snow surfaces enough that we expect a crust on most aspects below 7000 ft. Strong WSW winds last weekend created old, large slabs that may hold some reactivity at upper elevations. On Monday, observers reported heavy drifting along ridgelines in Heather and Clark Canyons. A collapse reported Tuesday at 10,000 ft on the E side of the Hogsback confirms this lingering upper elevation concern. A small skier-triggered avalanche at 6200 ft on an E aspect on Tuesday (see photo in the gallery) suggests that there will be some wind slab hazard when you start your day on Wednesday.

The biggest question mark remains how new and recent interfaces will behave.  Surface hoar was widespread on most aspects at middle and lower elevations Tuesday morning. Sunshine generally baked it off E-S-W aspects, bit it could linger in wind-sheltered shaded terrain. If you find evidence of whumphs, collapses, or widely propagating cracks, these are red danger flags. Weak snow has been found near the 2/11 interface and above the early February crust, but the potential reactivity on these interfaces is expected to be more isolated and primarily at upper elevations at this point. These layers warrant a quick dig down to the early February Crust to look for weak snow in your local terrain before engaging with avalanche terrain.

Earlier this week, NWAC forecasters traveled on the south side near Timberline and found a widely propagating avalanche in the lower Salmon River Canyon (SE aspect, 6300 ft). This avalanche was pretty shallow (6-12 inches, but propagated surprisingly wide. The crown was partially filled in, so the avalanche may have occurred Friday. In a profile on an adjacent slope, the culprit layer was identified as buried surface hoar 4-6 inches below the snow surface. It was easy to spot with snowpack tests. The forecast team is unsure how widely distributed this weak layer is across the zone, but we suspect the most likely places you may find it will be on shaded slopes above 5000 ft moving forward. 

The lower elevation snowpack has endured a beating after last week's warm-up but should pick up some fresh snowfall. Below 5000 ft this may be enough to mask shallow obstacles, but open creeks and rough surfaces abound. 

Your avalanche, snowpack, or weather observations are extremely valuable to the forecasters at NWAC. Help create a more accurate avalanche forecast by submitting your observations here. 

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