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Thu, Mar 21, 2019 at 7:13 AM
Issued by: Spencer Logan

Today

 

Tomorrow

Moderate (2) Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully.   Moderate (2) Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully.
Moderate (2) Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully.   Moderate (2) Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully.
Low (1) Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.   Low (1) Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
  Danger Scale

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Summary

It is now unlikely you can trigger an avalanche, but if you do though it will be very large and unsurvivable. That's a big "but." These types of avalanches will not provide you with typical warning signs like shooting cracks or whumpfing. They will break deep in the snowpack, span many terrain features, and run to the valley floors. Avoidance is the easiest way to make sure you are not involved. The only sure way to avoid dangerous avalanches right now is to stick to lower angle slopes with no avalanche terrain above you. Consider avoiding travel through avalanche run outs or under ridgelines with large cornices.

If you decide to move into steeper terrain today, remember to consider the consequences that triggering a very large and destructive avalanche has. Not only for you, but others may be below you.  

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Avalanche Problem

 
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N
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E
W
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NE
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SW
Above Treeline
Near Treeline
Below Treeline
Certain
Very Likely
Likely
Possible
Unlikely
Historic
Very Large
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Avalanche Character Aspect/Elevation Likelihood Size

What You Need to Know About These Avalanches


Deep Persistent Slab avalanches are destructive and deadly events that can release months after the weak layer was buried. They are scarce compared to Storm or Wind Slab avalanches. Their cycles include fewer avalanches and occur over a larger region. You can triggered them from well down in the avalanche path, and after dozens of tracks have crossed the slope. Avoid the terrain identified in the forecast and give yourself a wide safety buffer to address the uncertainty.

Avalanche Problem

 
problem icon
N
S
E
W
NW
NE
SE
SW
Above Treeline
Near Treeline
Below Treeline
Certain
Very Likely
Likely
Possible
Unlikely
Historic
Very Large
Large
Small
Avalanche Character Aspect/Elevation Likelihood Size

What You Need to Know About These Avalanches


Loose Wet avalanches occur when water is running through the snowpack, and release at or below the trigger point. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.

Avalanche Problem

 
problem icon
N
S
E
W
NW
NE
SE
SW
Above Treeline
Near Treeline
Below Treeline
Certain
Very Likely
Likely
Possible
Unlikely
Historic
Very Large
Large
Small
Avalanche Character Aspect/Elevation Likelihood Size

What You Need to Know About These Avalanches


Persistent Slab avalanches can be triggered days to weeks after the last storm. They often propagate across and beyond terrain features that would otherwise confine Wind and Storm Slab avalanches. In some cases they can be triggered remotely, from low-angle terrain or adjacent slopes. Give yourself a wide safety buffer to address the uncertainty.

Weather Forecast for 11,000ft Issued Thu, Mar 21, 2019 at 1:10 PM by Spencer Logan Statewide Weather Forecast
  Thursday Night Friday Friday Night
Temperature (ºF) 20 to 25 25 to 30 15 to 20
Wind Speed (mph) 5 to 15 10 to 20 5 to 15
Wind Direction S W W
Sky Cover Mostly Cloudy Mostly Cloudy Mostly Cloudy
Snow (in) 3 to 6 2 to 5 0 to 3

Archived Forecasts

  • Select Forecast: Valid

Thu, Mar 21, 2019 at 7:52 AM
Issued by: Ben Pritchett Statewide Weather Forecast  

Deep Persistent Slab avalanches are scary. Their consequences are ultimate. They are unsurvivable. In addition, they are fickle and hard to predict. Your best bet is to avoid where they could happen, which are large avalanche paths that did not run huge in March.

The pattern is pretty clear. During our historic first two weeks of March, these huge avalanches ran from large alpine and near treeline avalanche paths, on all aspects. The snowpack structure that led to these avalanches remains in place on many slopes that did not avalanche in March. You can recognize these slopes that have not avalanched by their smooth and deep looking snow cover. When you compare the lack of avalanche evidence on these to the slopes that did slide, it's not too difficult to distinguish which is which. Grey skies and flat light today may obscure the picture, so if in doubt, assume it hasn't gone yet.

The slopes that did avalanche are easy to identify given a few key observations. They have deep debris piles near the bottom of the paths, many chock-full of broken trees. In the start zones, the crowns of snow above these old avalanches remain visible. Depending upon when the big avalanche released, you'll find none to several feet of snow deposited on the old bed surfaces. So far, we've received no reports of avalanches on the March bed surfaces. In general, there the basal weak layers in these paths are dramatically disturbed, and the fledgling slabs not very stiff. It's worth investigating the potential of a thinner Persistent Slab avalanche on one of these bed surfaces, but to the best of our knowledge there's been no slab avalanches running again on the slopes that released in early March.

The Deep Persistent Slab avalanche problem is not as prevalent on the Grand Mesa or anywhere below treeline. Although it has become unlikely for you to trigger a deep avalanche, it is not impossible in isolated terrain features. Wet loose snow sluffing is the primary concern. You can easily manage these types of problems by moving onto shady, cooler slopes as the snow begins to warm.

 


  • Wet slab avalanche debris in Yule Creek. Note the frozen waves in the snow. A D4 dry Persistent Slab avalanche ran from the other side about a week earlier and the debris piles overlap one another. (full)
  • A very large (D4) Wet Slab avalanche on the west side of Treasure Mountain. Likely ran around March 13, 2019. (full)
  • Short video of some historic avalanches that ran in March in the Yule Creek drainage.
  • A large Wet Slab avalanche on the west side of Treasure Mountain likely ran on March 13. Smaller loose wet point releases ran on March 19. (full)

See more photos & videos

Five Day Trend

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Avalanche Observations
Report Date # Elevation Aspect Type Trigger SizeR SizeD
View Wed Mar 20 - >TL NE HS N R4 D4
View Wed Mar 20 - >TL W WS N R4 D4
View Wed Mar 20 - TL W WS N R3 D2.5
View Wed Mar 20 - TL SE WS N R3 D2.5
View Wed Mar 20 - >TL NW HS N R3 D2.5
View Wed Mar 20 - >TL E HS N R2 D2
View Wed Mar 20 - >TL S WS N R2 D2

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Field Reports
Report Date Observer Snowpack Obs Avalanches Media
View Wed Mar 20 Brian Lazar No Yes (7) Yes (9)
View Wed Mar 20 Scott Messina No Yes (2) Yes (4)
View Tue Mar 19 Morgan Boyles No Yes (1) Yes (5)
View Tue Mar 19 Matt Huber No No Yes (1)
View Mon Mar 18 Josh Vogt No No Yes (8)
View Mon Mar 18 Matt Huber No Yes (1) Yes (3)

See All Field Reports

Weather Observations
Station Date Time Temperature Relative Humidity Wind Speed Wind Direction Max Gust 24 Hr Snow
Chapman Tunnel Thu Mar 21 2:00 PM 43 - - - - 1.0
Independence Pass Thu Mar 21 2:00 PM 36 - - - - 2.0
Ivanhoe Thu Mar 21 2:00 PM 38 - - - - 1.0
Sunlight Thu Mar 21 3:00 PM 34 51 3 120 - -
Schofield Pass Thu Mar 21 2:00 PM 37 - 4 258 - 1.0

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