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Forecast for the Salt Lake Area Mountains

Drew Hardesty
Issued by Drew Hardesty on
Sunday morning, December 18, 2022
Areas of CONSIDERABLE avalanche danger exist on all northwest through east facing aspects at ALL ELEVATIONS (even LOW ELEVATIONS) for triggering avalanches 1-4' deep and hundreds of feet wide. These avalanches may be triggered at a distance, even from below. Areas of MODERATE avalanche danger exist on all other aspects and elevations. You can also trigger new soft slab avalanches of wind blown snow in the upper elevations today.
Avoid traveling on, below, or adjacent to slopes 30 degrees or steeper on northwest through north thorough the easterly aspects. Safe and excellent riding can be found on low angle slopes with nothing steeper above you.
Low
Moderate
Considerable
High
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Special Avalanche Bulletin
DANGEROUS AND UNUSUAL AVALANCHE CONDITIONS WILL LAST THROUGH AT LEAST THIS WEEKEND. HEAVY SNOWFALL THIS PAST WEEK HAS CREATED DANGEROUS AVALANCHE CONDITIONS AT ALL ELEVATIONS. DON'T BE LURED BY THE BEAUTIFUL SUNNY SKIES AND FRESH POWDER INTO THINKING AVALANCHE CONDITIONS ARE SAFE WHEN THEY ARE NOT.
DO NOT TRAVEL ON, UNDERNEATH, OR ADJACENT TO SLOPES 30 DEGREES OR STEEPER ON SLOPES FACING NORTHWEST, NORTH, NORTHEAST, AND EAST WHERE TRIGGERING LARGE AND DANGEROUS AVALANCHES IS LIKELY. THIS INCLUDES LOW-ELEVATION FOOTHILLS WHERE AVALANCHES CAN OCCUR NOT FAR FROM PARKING AREAS AND TRAILHEADS.
Special Announcements
Park City Mountain Resort is planning on opening the Jupiter Lift area this weekend. Please avoid the Scott's and Pinecone areas for the rest of the season.
Weather and Snow
Skies are clear. Under a building inversion, mountain temperatures are in the upper teens up high, the single digits down low. Winds are westerly, blowing 15mph with gusts to 20mph. Riding conditions are nothing short of sublime although solar aspects will have a thin crust this morning before it thaws. Nit-pickers will complain of a bit of wind damage up high.
WOW, what a storm. Snow on the ground now sits at 85" in upper LCC, 60" in upper BCC, and 40-50" along the PC ridgeline.
Snowfall totals since Sunday night include:
  • Cottonwoods: 2.5' - 6' snow containing 1.5" - 2.75" SWE (snow water equivalent)
  • Park City: 1.5' - 3' snow containing 1" - 1.5" water SWE
For today, we'll have sunny skies with light westerly winds. Temperatures will warm to the low to mid-20s. For the outlook, we'll be under a zonal (westerly) then cool northwest flow with embedded disturbances through the week. We may pick up a few inches with a mid-week storm.
Get caught up in significant weather and avalanche activity over this past week by reading our Week in Review.
Recent Avalanches
Drew has published a blog "Dangerous and Unusual Avalanche Conditions" describing the avalanche activity over this past week.
THERE WERE THREE SIGNIFICANT AVALANCHE ACCIDENTS THIS WEEK with serious injuries. Two injured parties required rescues. The avalanches broke down over 2' deep into the layer of November facets. These avalanches occurred at low elevations below 8,000':
Tuesday - Pink Pine Ridge 7,800' North-facing 2-3' deep, 60' wide. FINAL REPORT. UAC staff visited the area on Wednesday, but due to avalanche danger, chose not to approach the avalanche.
Wednesday- Thomas Fork in Neffs Canyon 7,200' North-facing 2' deep 200' wide. Read the preliminary report.
Friday, December 9, an avalanche accident on Santaquin Peak in the Provo mountains that failed in the persistent weak layer of faceted snow also involved serious injuries. The avalanche was 1-2' deep and 600' wide.
(rescue from Pink Pine, pc: Wasatch Backcountry Rescue)
Skiers descending south on Lone Peak triggered some shallow soft slabs of wind drifted snow on steep rollovers at 9600' yesterday.
Avalanche control work along the southern part of the PC ridgeline triggered two sizeable hard slab avalanches failing on our PWL. They were on steep east and northeast facing slopes at 9500' and 9300', respectively and 1-4' deep. The largest was 250' wide.
On Friday, near Grandview Peak, a snowmobiler remotely triggered (triggered at a distance) a soft slab failing on our PWL (persistent weak layer) of weak faceted grains. The avalanche was on a steep northeast facing aspect at 9200' with estimated dimensions of 2' deep and 300' wide. (photo below). Mark Staples rode up to investigate and his report yesterday is HERE>
There were other avalanches this past week that occurred at low elevations below 8,000, including Lambs Canyon, Daly Canyon, and Summit Park.
Check out all the avalanches HERE and if you see an avalanche, please report it.
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Avalanche Problem #1
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
There is weak, sugary faceted snow (a persistent weak layer, or PWL) on almost all aspects and elevations throughout the Wasatch Range. This PWL has been buried by several feet of storm snow and wind-drifted snow which has created dangerous avalanche conditions, with three serious avalanche accidents this past week. WHAT IS UNUSUAL is that each of these avalanche accidents took place in the lower elevations bands below 8000’. What this means is that these avalanches can occur not far from parking lots or trailheads.This PWL is especially dangerous on aspects facing northwest through north and east where triggering avalanches is likely.
There were other avalanches this past week that occurred at low elevations below 8,000, including Lambs Canyon, Daly Canyon, and Summit Park.
Although avalanches involving this PWL are less likely on solar aspects facing west through south, there is too much uncertainty given the amount of snow we have received this past week and avalanches failing in this PWL are still possible.
HEAT MAP OF ALL (MOSTLY PWL) AVALANCHES SINCE NOV 29
TREND: Slowly decreasing in sensitivity and spatial extent. Size remains the same.
Avalanche Problem #2
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
Westerly winds overnight have had plenty of low-density snow to blow around and you are likely to find sensitive slabs of wind-drifted snow at the upper elevations. The new soft slabs will be most pronounced on north through east through south facing slopes. The avalanche in Snake Creek on Thursday likely failed due to recent wind loading and there were other reports of sensitive wind drifts from Thursday.
Any wind slab avalanche that you trigger has the potential to step down into deeper weak layers in the snowpack, creating a very large and dangerous avalanche.
Look for evidence of fresh drifts and wind slabs that look wavy, rounded, smooth, and pillowy, and avoid those slopes. Signs of sensitive wind-drifted snow include cracking and collapsing of the more dense drift over lower density snow below.
Long running dry sluffs are still possible in the cold, dry snow...and may transition to wet loose sluffs with today's direct sun and warming temperatures.
TREND: Decreasing danger
Additional Information
Mark Staples has also written a season summary HERE.
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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