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Forecast for the Provo Area Mountains

Evelyn Lees
Issued by Evelyn Lees for
Saturday, February 9, 2019
Dangerous avalanche conditions. The avalanche danger is CONSIDERABLE on and below the steep, wind drifted slopes at mid and upper elevations. Human triggered avalanches are likely and natural avalanches possible. Some avalanches may be triggered at a distance or from below. Be aware of what is above you, and avoid travel in avalanche runout zones such as the bottom of gullies and couloirs and travel below slopes being loaded by the wind. The growing cornices are unstable, and will break back further than expected.
Seek out terrain without wind-drifts or wind slabs. Wind sheltered, low and mid elevation terrain with nothing steep above has a much lower avalanche danger (and much better turning conditions!).
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Special Announcements
The body of snowmobiler Bradley Stapley was recovered from an avalanche near Circleville Mountain in the Tushar mountains yesterday. Our deepest condolences to his family and friends. A preliminary accident report is HERE. This is the third avalanche fatality in Utah this winter.
Weather and Snow
The southerly winds cranked up yesterday - averaging 35 to 40 mph, and gusting into the 50s and 60s along the high ridge lines. The winds were getting well down into the mid elevations.
Today, increasing clouds and continued moderate to strong, southwesterly winds, peaking midday. A small storm that will give the mountains 2 to 5” of snow starting late this afternoon through about midnight. Temperatures will warm into the mid teens at the upper elevations to mid 20s at the mid elevations. A stronger storm will bring more snow Sunday night into Monday.
Bruce Tremper photo - winds in upper White Pine
Greg's Week in Review just published HERE.
Recent Avalanches
Non-stop avalanche activity yesterday, with the focus on wind drifted slopes facing north through easterly. A remotely triggered slide, near Primrose Cirque. Natural avalanches up to 2 feet deep and large enough to bury a person were reported in Mineral, upper Little Cottonwood, and Mill B. Explosives in the resorts and American Fork backcountry were able to pull out wind slabs and deep, wide avalanches, some breaking to the ground on facets - some were repeaters, others not. Human triggered slides included another on Pioneer (10,400’, North facing, 2” deep by 100’ wide), a slide remotely triggered off Preston Peak into Snake Creek, on a south easterly facing slope, about 3’ x 100’. Backcountry explosive testing by Powderbirds in American Fork released 3 large slides, including one sympathetically releasing 300’ away.
Video of Slide off Bob's Knob ridge line, Jake Rogers. Probably remotely triggered by skiers from the ridge line.
Photo 2 and 3 - American Fork, explosive triggered.
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Avalanche Problem #1
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
The widespread, new wind drifts are the number one avalanche concern today. Moderate to strong southwesterly winds have drifted the snow at both mid and upper elevations into soft to hard drifts. The cracky drifts will be easily triggering on steep slopes, and it will be possible to trigger these new drifts from a distance or from below. Drifts will be most widespread on north through easterly facing slopes. However, the winds can deposit snow around terrain features on almost any aspect, called cross loading. Human triggered avalanches are likely today on wind drifted slopes and natural releases possible as today’s wind continues to drift the snow.
Cornices are growing and very sensitive, and will break back much further than expected. Give them a wide berth - travel well back from the edges of ridge lines and avoid travel beneath them.
Avalanche Problem #2
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
There are two persistent weak layers of concern.
Weak surface snow and patches of surface hoar were buried Saturday night. Avalanches triggered on these layers have been 1-3' deep on wind drifted north to easterly facing slopes with elevations from 8800' to 10,200'. Some of these have run naturally, some of been triggered at a distance. Cracking/collapsing are key indicators here; in snowpits, look for the 'thin grey line' a couple feet down in the snowpack. Slides failing on faceted weak layers can be triggered from a distance, including from below.
  • Enough snow and wind have tipped the balance in some areas to produce avalanches down near the ground 3-6' deep. While more likely to occur on slopes that have avalanched previously, two of yesterday’s explosive triggered slides in Mineral Fork were on slopes that had not slid this winter. These deep slides may require more of a significant trigger, perhaps a triggered wind slab stepping down or cornice fall.
General Announcements
CLICK HERE FOR MORE GENERAL INFO AND FAQ
This information does not apply to developed ski areas or highways where avalanche control is normally done. This forecast is from the U.S.D.A. Forest Service, which is solely responsible for its content. This forecast describes general avalanche conditions and local variations always occur.
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