Ogden Avalanche Advisory

Forecaster: Drew Hardesty

BOTTOM LINE

Danger by aspect and elevation on slopes approaching 35° or steeper.
(click HERE for tomorrow's danger rating)


Danger Rose Tutorial

An overall MODERATE danger exists in the backcountry. With daytime heating, pockets of CONSIDERABLE will exist on all steep sun-exposed slopes. Natural and human triggered avalanches will be likely. Timing and route-finding will be critical to avoid wet avalanche activity. I still don't trust most of the steep terrain.

CURRENT CONDITIONS

Oughta be another scorcher today with temps skyrocketing into the 40s and 50s. Winds are light and variable. Overnight lows at the mid and upper elevations remained at or just above freezing. Still, clear skies and light wind should support a thin, albeit supportable, refreeze on the sunny aspects. The window for travel on these crusts will be narrower today - don't overstay your welcome as the crusts become unsupportable. Plan to be a step ahead of the thaw and play your aspects - work east, then south, then westerly facing terrain. Patches of soft settled powder can be found in the shady sheltered terrain. Sunscreen and skin wax is highly recommended.

RECENT ACTIVITY

We heard of little in the way of avalanche activity from Ogden to Provo and everywhere in between.

THREAT #1
WHERE PROBABILITY SIZE TREND
      Over the next 10 hours.

Warning! Snow geek musings below. Otherwise skip to the bottom line.

Settlement, creep, and glide. All good terms to describe the often slow deformation of the snow on the ground. New snow just on the ground is mostly air and over time that 12" settles to maybe 7". You often see settlement cones around trees and saplings particularly on a warm day after a cold storm. Put that snowpack on an incline and the entire snow pack glides downhill, though quite slowly (unless it avalanches - see Stairs Gulch, Broads Fork and Mill B South of BCC). But if you pick apart the snowpack, the upper layer(s) tend to flow - or creep - downhill faster than the mid and base layers. (Differential creep rate - you can't make this stuff up.) This is where we can have problems, particularly in a structured, layered snowpack such as the one we have now. These differential rates can exacerbate the stresses on the weak interfaces or discontinuities that have come to define our snowpack.

Add free meltwater percolating down to these interfaces? - if the vertically driven water reaches an impermeable membrane (crusts, significant density changes) and is forced to move laterally, it can easily dissolve the weak bonds at these interfaces, resulting in a slab avalanche.

Full propagation along weak interfaces still noted by Kobernik and Meisenheimer here (amazing video). Ifound full propagation as well within the mid-pack on southerly aspects. Doesn't inspire much confidence.

THREAT #2
WHERE PROBABILITY SIZE TREND
      Over the next 11 hours.

Natural and human triggered wet activity is likely today on all steep sun-exposed slopes with daytime warming. As described earlier, the window will be narrow for travel on the steep sunny aspects. Beyond that, the snow becomes weak and unsupportable and the odds of triggering a wet sluff or slab dramatically increases.

Adding a wrench into things - Corn Slabs - can be deceiving. Unusual phenomena, they act is if they're stable - you're riding on-top-of the supportable 'corn', but at a trigger point, one can collapse the crust, pulling out a hard slab, often breaking out above. Collapsing on the crust is a a hint to these rare, but significant players.

THREAT #3
WHERE PROBABILITY SIZE TREND
      Over the next 10 hours.

Cornices will also become more sensitive with the heating. Be conservative while approaching the ridgelines. Also - as a matter of objective hazard - hard wind and sun crusts in the alpine provide for slick slide-for-life surfaces. An ice axe or ski pole axe or whippet may be useful.

MOUNTAIN WEATHER

The heat wave brings temps into the 40s and 50s. Winds will be light and variable. A Pacific storm system off the BC coast will bring some cloud cover and increasing southwesterly winds later Sunday eve through the week but we shouldn't see much in the way of precip until next weekend.

GENERAL ANNOUNCEMENTS

If you trigger an avalanche in the backcountry - especially if you are adjacent to a ski area – please call the following teams to alert them to the slide and whether anyone is missing or not. Rescue teams can be exposed to significant hazard when responding to avalanches, and do not want to do so when unneeded. Thanks.

Salt Lake and Park City – Alta Central (801-742-2033)

Ogden – Snowbasin Patrol Dispatch (801-620-1017)

Provo – Sundance Patrol Dispatch (801-223-4150)

Dawn Patrol Forecast Hotline, updated by 05:30: 888-999-4019 option 8.

Twitter Updates for your mobile phone http://utahavalanchecenter.org/twitter)

Daily observations are frequently posted by 10 pm each evening.

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UDOT canyon closures UDOT at (801) 975-4838

Wasatch Powderbird Guides does daily updates about where they'll be operating on this blog http://powderbird.blogspot.com/ .

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We will update this forecast tomorrow morning. Thanks for calling.

This information does not apply to developed ski areas or highways where avalanche control is normally done.  This advisory is from the U.S.D.A. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur.

This advisory provided by the USDA Forest Service, in partnership with:

The Friends of the Utah Avalanche Center, Utah Division of State Parks and Recreation, Utah Division of Emergency Management, Salt Lake County, Salt Lake Unified Fire Authority and the friends of the La Sal Avalanche Center. See our Sponsors Page for a complete list.