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Avalanche Advisory
| Advisory: Provo Area Mountains | Issued by Drew Hardesty for Sunday - January 15, 2017 - 7:30am |
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bottom line The danger will rise to MODERATE on the steep sunlit slopes today with daytime warming. A low-probability high consequence Moderate danger exists for triggering a potentially unsurvivable 2-4' deep avalanche below 7500' in elevation. Triggering a stabilizing storm slab is unlikely but not impossible with heavy loads (cornices, sluffs, a falling skier). Use extreme caution traveling along the heavily corniced ridgelines and continue to use safe travel protocol: make a plan, one at a time in steep terrain, get out of the way at the bottom. Sluffing in the cold dry snow is increasingly possible in steep northerly terrain.
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special announcement We have a pile of events and classes coming up - check out the calendar of events here. New blog post - Shame and the Social Contract |
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current conditions Skies are clear in the mountains. Winds are being channeled from the east and northeast in Provo canyon and are gusting in the 20s at Arrowhead summit. Temps are in the teens. Surface Hoar abounds (see Wewer pic below). Clear skies, light winds, and high RH (relative humidity) yield yet again another crop of surface hoar. Recall that surface hoar is the winter-time equivalent of dew, but it has the mark of Cain, if the two are related. Fun to ski and ride through and beautiful as crystal, but dangerous and unpredictable if buried by another storm. Commonly, the fragile "feathers" decay or are destroyed by sun and wind in the pre-frontal environment, but worth mapping out along the topography prior to the next weather events. Riding conditions are 4 stars out of 5. Sunny aspects have fewer stars with a breakable melt-freeze crust this morning.
Rough storm totals (read Snow/SWE - Snow-Water-Equivalent). See above for the years SWE % of normal. Since last Saturday night ---------Since New Years----------------------Total snow depths Upper LCC: 37"/4.48"................. 72"/6.90".................... Total snow depths are 80-90" Upper BCC: 46"/4.78"............... 103"/8.46".................... Total snow depths are 80-95" PC ridgeline: 41"/4.70"............... 80"/7.4" ..................... Total snow depths are 75-85" Ogden 27"/2.5"-62"/7.95"............ 46"/3.71-83"/10.23..............Total snow depths are 80-100" Provo 35"/3.19" ....................... 67"/5.79" ................. ... Total snow depths are 80-120" |
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recent activity A cornice drop triggered a 16" deep and reported 500' wide soft slab on a steep east facing slope at 9500' in upper West Porter Fork of Mill Creek Canyon in the central Wasatch. (Photos: Sisk/Jamison). The original observer reported seeing debris cascading down toward him where the initial alarm undoubtedly transitioned to relief and then on to anger and disappointment.
Natural wet loose avalanches ran on some of the steepest southerly aspects with some debris piles large enough to bury a person. |
Avalanche Problem 1
| type | aspect/elevation | characteristics |
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LIKELIHOOD
 LIKELY
UNLIKELY
SIZE
 LARGE
SMALL
TREND
 INCREASING DANGER
SAME
DECREASING DANGER
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description
There remains some uncertainty about the snowpack structure below roughly 8000' involving a facet/crust layer from mid December. Diligent snow pit testing should provide good indication of how well this layer is healing. The Ogden area mountains had a very active avalanche cycle on this layering on Wednesday; the Provo mountains over a week ago. Collapsing and cracking are indicators of instability here. Hot Tip: Use snowpits to determine the extent of this layering or remain on lower angle slopes at these elevations. The storm and wind slab instabilities are rapidly healing but may still be triggered with heavy loads, such as cornice fall or another avalanche cascading down from above. |
Avalanche Problem 2
| type | aspect/elevation | characteristics |
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LIKELIHOOD
 LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
 INCREASING DANGER
SAME
DECREASING DANGER
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description
While we're not seeing a rapid rise in temperature on very low density snow, I do feel that the direct sun will allow the storm snow to again become damp, unstable and ripe for human triggering in the sunlit terrain and the low elevations on the north side of the compass. Rollerballs, pinwheels, and natural sluffs are key indicators for transitioning dry to wet snow. Those entering steep, confined south facing terrain in the afternoon are likely to create decent dry to wet avalanche debris piles in the runouts below. Hot Tip: Continually change terrain to seek "cooler" aspects (eg: east to south to west) that haven't seen the prolonged heating and direct sun...or avoid the steep sunlit aspects altogether. |
Avalanche Problem 3
| type | aspect/elevation | characteristics |
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LIKELIHOOD
 LIKELY
UNLIKELY
SIZE
 LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
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description
Enormous cornices litter the mid and upper elevation ridgelines and will break back well past the apex of the ridgeline. Give these monsters a very wide berth. Falling over with a breaking cornice may result in significant traumatic injury (at best) and/or provide for a sufficient trigger for an avalanche below. (Bill Hunt photo below). Hot Tip: Give these monsters a very wide berth.
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weather We'll have sunny skies, light northeasterly winds, and temps rising to the low 20s at 10,000', the mid 30s at 8000'. The weather pattern again becomes active by late Wednesday into early Thursday. The first storm looks to be splitting, but northern Utah may still benefit from the northern branch of the storm. Snow is likely for Thursday and again for the weekend...though let's let the models play out for greater confidence in the coming days. |
general announcements
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