Forecast for the Provo Area Mountains

Issued by Drew Hardesty for Thursday, February 7, 2019 - 7:20am
Areas of CONSIDERABLE danger exist on many slopes in the mid and upper elevations with a MODERATE danger down low. Some avalanches may be triggered at a distance or from below. Long running natural avalanches may be possible in the high alpine wind affected terrain. Avoid avalanche runout zones (especially on Timpanogos and Box Elder). Avoid being on or beneath the heavily corniced ridgelines.
Low
Moderate
Considerable
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Special Announcements
An AVALANCHE WARNING continues for the Western Uintas and the Manti-Skyline Plateau. If you're headed that way or know someone who is, please spread the word and have them check in with that area's forecast.
Weather and Snow
Along a cool west-northwest flow, a trace to 2" fell overnight, pushing storm totals since Saturday night to 34' of snow and 3.65" of water. Moderate to strong winds, mostly along ridgetops but occasionally getting into mid elevation terrain, have also added stress to the snowpack. These are significant loading events. West-northwest winds are generally 15mph with gusts to 25. The highest, most exposed anemometers are averaging 35-40mph with gusts near 60. Temps are in the low single digits on either side of zero.
Snow depths are 80-90". Skiing and riding conditions are out of this world. People lives are changed by conditions like these.

Overcast skies and light flurries should fade away by the afternoon toward partial clearing. Mountain temps will be in the single digits up high, the low teens at other elevations. Winds will be west-northwesterly blowing 15mph. I do have some concern that the winds will remain gusty along the highest peaks and ridgelines through early afternoon.

A weak system should produce another 2-4" Saturday/Saturday night with another storm Sunday night into early Tuesday. Perhaps another 5-10"? Another possibly going south for Valentine's Day...and perhaps another after that?...Stay tuned -
Recent Avalanches
A natural avalanche likely occurred yesterday in upper Primrose Cirque above Aspen Grove on Timpanogos. It was large and destructive and thousands of feet wide. Thanks Matt Turley for the photo below. There was also a very large natural 3-8' deep on the 4th on the southern end of Timp at 8500-9000' elevation (est).
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Avalanche Problem #1
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
Yesterday's winds found their way into the mid-elevations with observers noting shooting cracks on steep rollovers. With continued moderate west to northwest winds at the mid-elevations and strong gusts up high, wind slabs will continue to be cause for concern. They'll be more prominent on steep north to east to south facing slopes up high and crossloaded into gullies and to the lee of other terrain features. Cracking like below are signs to choose alternate terrain. Noted the scalloping and rounded nature of the wind drifts in the pic. (pc:Stefankowski)
Avalanche Problem #2
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
There are two persistent weak layers of concern.
  1. Weak surface snow and patches of surface hoar buried Saturday night. This layering has likely been the culprit in at least four avalanches in the Cottonwoods. These have been 1-3' deep on wind drifted north to northeast 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; snow pit tests should also be reliable indicators for intended terrain - look for the 'thin grey line' a couple feet down in the snowpack (pic below). Caution should be observed as these may be triggered on approach or from below.
2. Enough snow and wind have tipped the balance in some areas to produce avalanches down near the ground 3-6' deep. These will be much more prominent in terrain that has avalanched previously this winter and may require more of a significant trigger to snap the rubber band. The large slides along the Park City ridgeline on Tuesday, and the Little Water Peak slide on Monday (observation) highlight this problem. These slides were triggered from cornice falls and were on steep, wind-loaded slopes facing northeast. Tuesday's natural from South Monitor highlights how large these avalanches can be. (pc: Mark White). In contrast to the more shallowly buried weak layers, cracking and collapsing are unlikely to be present and snow tests may be highly variable. These are lower-probability high consequence.

It's a touch outdated, but looking at the Avalanche Problem Toolbox will also provide good details and travel advice on these two types of avalanches (previously Persistent Slab and Deep Slab) .
Avalanche Problem #3
New Snow
Type
Location
Likelihood
Size
Description
Lower density cold smoke will sluff with provocation and perhaps naturally on the steepest terrain of all aspects. While more predictable in nature, loose snow avalanches can pack quite the punch and entrain lots of snow in steep, sustained and enclosed terrain (couloirs and gullies). Ski cuts are effective but it's key to continue from area of safety to area of safety, moving across the slope. Snowshoers should not attempt this technique.
Additional Information
Mark Staples has a nice piece on the importance of quick snow pits in Backcountry magazine. INFO.
The Wisdom of the Crowds applies directly to you and other backcountry skiers and riders, from the novice to the expert.
General Announcements
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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