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Forecast for the Provo Area Mountains

Mark Staples
Issued by Mark Staples for
Thursday, February 14, 2019
Today there are a bunch of avalanche problems. Slabs of new snow, wind drifted snow and possibly wet snow could fracture and produce an avalanches 1-4 feet deep. With a heavy load of snow overnight and additional wind loading, big, deep, hard slab avalanches breaking on buried weak layers are a possibility. These larger slides could be 8-10 feet deep.
For these reasons, the avalanche danger is HIGH at upper elevations where strong southerly winds are depositing snow and avalanche terrain should be avoided. All other elevations and aspects have a CONSIDERABLE danger which means you need to have careful snowpack evaluation, cautious route-finding, and conservative decision making.
If headed out today - Stay away from and don't get under slopes steeper than 30 degrees. Go to wind sheltered slopes less than 30 degrees in steepness above 8000 feet.
ROOF AVALANCHES - With such warm temperatures and rain possible, watch for avalanches sliding off roofs. Be especially watchful of kids playing near any house with a large load of snow on the roof. Roof avalanches have killed children in the past.
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Avalanche Warning
THE FOREST SERVICE UTAH AVALANCHE CENTER IN SALT LAKE CITY HAS ISSUED A BACKCOUNTRY AVALANCHE WARNING.
* TIMING...IN EFFECT THROUGH FRIDAY MORNING
* AFFECTED AREA...ALL THE MOUNTAINS OF NORTHERN UTAH, TO INCLUDE THE BEAR RIVER AND WASATCH RANGE, AND THE WESTERN UINTAS.
* AVALANCHE DANGER...STRONG WINDS ALONG WITH HEAVY DENSE SNOW ALONG WITH RAIN-ON-SNOW AT THE LOWER ELEVATIONS WILL CREATE DANGEROUS AVALANCHE CONDITIONS AND A HIGH AVALANCHE DANGER
* REASON/IMPACTS...NATURAL AND HUMAN TRIGGERED AVALANCHES WILL BE LIKELY ON MANY ASPECTS AND ELEVATIONS
Special Announcements
The accident reports for the four avalanche fatalities are all finalized with some first-hand accounts and worth reading. We all have something to learn so that we can get home safely to our loved ones.
Jan 18 Electric Lake Accident (Skyline area)
Jan 25 Laurel Peak Accident (Moab area)
Feb 7 Circleville Mtn Accident (Southwest area near Beaver, UT)
Feb 9 Chalk Creek Accident (Western Uintas)
The latest UAC Podcast was just released: The Message and the Messengers - A Conversation with Alex Hamlin. In this podcast, we sit down with Alex Hamlin. For over fifteen years, Alex Hamlin has worked at the intersection of storytelling and outdoor sport, with experience at magazines, global retail brands and creative agencies....
Weather and Snow
Since yesterday morning the Provo area mountains received 10-17 inches of very heavy snow that contains 1.5 to 1.8 inches of water (10-15% density).
Temperatures are near freezing at 7000 feet and in the upper 20s F at 8000 feet.
South and southwest winds blew strong yesterday and overnight. This morning they eased a little bit and are averaging 15-20 mph gusting to 25-40 mph at most ridgelines. At 11,000 feet, wind gusts are reaching 50-60 mph.
Today, most snowfall is tapering off but should return this evening when the rain/snow line could be as high as 8000 feet. This means that temperatures will be rising through the day and could be near 40 degrees F at 8000 feet by this afternoon. You may see some rain but not too much. Winds will continue from the south and southwest at similar speeds. Skies should stay cloudy, but the sun could poke through occasionally.
February has been a snowy month. The snowpack has a significant load on it and it's hard to appreciate. In trying to understand how much weight has been added to the snowpack, Evelyn Lees said it's like putting an elephant on top of her Subaru. That's a lot of weight. Below is a graph of the snow water equivalent recorded at Sundance. To put these numbers in perspective, the average total annual precipitation at the SLC airport is 16.5 inches.
It has also been windy with most of the strong winds coming from the south.
Recent Avalanches
Most ski areas had limited operations at upper elevations due to strong winds. There were some natural avalanches involving the new snow that were detected by UDOT overnight in Little Cottonwood Canyon and they are triggering more this morning with explosives.
UPDATE 0800: Check out this observation that we received this morning of wet snow avalanches at 7500 feet in Mill Creek Canyon (West Porter Fk). It is relevant for low elevation areas in the Provo area mountains.
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Avalanche Problem #1
New Snow
Type
Location
Likelihood
Size
Description
The new snow is dense and heavy. It should be a little upside down, but I'm not sure. Upside down means there is dense snow on top of lighter snow which happens when temperatures warm during a storm. The main issue will be soft slab avalanches breaking at density changes within the new snow. Look for cracking and collapsing as a sign of instability. Also, jump on small test slopes to assess stability in the new snow.
ALSO, watch for any RAIN today as the rain/snow line creeps up to near 8000 feet. I don't expect a soaking rain, but any amount of rain could cause wet avalanches in the new snow. If it does start raining, the new snow could produce wet loose slides, but being so dense, I'd expect shallow wet slab avalanches.
Avalanche Problem #2
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
Strong south and south west winds were ripping yesterday and into the evening. At 11,000 feet they were gusting 60-90 mph yesterday afternoon. Even lower, sheltered ridgelines had winds blowing 30 mph gusting 45 mph.
These winds have formed both soft and hard slabs of wind drifted snow at mid and upper elevations and could be several feet thick. I wouldn't mess with them because they could make big avalanches. You may find some wind drifting even at low elevations.
Photo below shows strong southerly winds two days ago looking south over Little Cottonwood Canyon.
Avalanche Problem #3
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
Basically there are two persistent weak layers we've been tracking. One is near the ground. The other was the snow surface that was buried at the start of February and now has 3-4 feet on top of it. Both of these layers have been gaining strength. HOWEVER - the biggest avalanches happen when a strong snowpack is loaded by big storms because everything has it's breaking point. Last night's snowfall wasn't the largest we've seen but it's all adding up.
There have been some large avalanches triggered by ski patrols. Some breaking at the ground.
What to do in the backcountry? This is a hard avalanche problem to assess. You can ignore it and things will probably be ok. For me, probably isn't good enough. For today and even much of this weekend, I would avoid big avalanche paths and the runout zones. Especially any that face east, north and west. These paths have been and will continue to be top loaded and cross loaded by strong southerly winds. Natural avalanches aren't likely but surprising things happen during weather like this.
General Announcements
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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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