Some Mountain Information Network (MIN) reports contain acronyms to communicate snowpack test results and other information. Below is a list of the most used acronyms and their meaning. This list is meant to help you better understand these MIN reports. It is not meant as an instruction on how to interpret the results.
Snowpack tests involve digging a large square hole in the snow (aka a pit), then isolating a column of snow to test the reactivity of weak layers within it. Watch this video by forecaster Mike Conlan for instructions on a variety of snowpack tests:
Snowpack tests are indicative of a specific location only. The snowpack can vary tremendously across different elevations, aspects, and even the same slope. If you see test results in a MIN report, consider them as one piece of a much larger avalanche conditions puzzle.
We often see compression test results in MIN reports, as it is the easiest snowpack test to perform. This test is used to identify weak layers in the snowpack and assess their strength. Conducting a CT involves isolating a 30x30 cm column, placing the flat part of the shovel on top of the column, and applying a series of taps to the shovel blade with increasing strength.
There are three topics of interest: the number of taps required to cause a fracture; the character of the fracture; and the depth of the layer that fractured.
Results are ususally recorded in this style: CTM15 down 32, SP.
In this example:
- CTM15 means compression test moderate that took 15 taps to trigger a fracture
- Down 32 is the depth of the weak layer that failed
- SP indicates the fracture character.
Layer fails while isolating column
Tap column from wrist
Tap column from elbow
Tap column from shoulder
No fracture occurred
Fracture character is a description of how the weak layer responds to the load of the compression test. There are five types of fracture character broken into three major classes: sudden, resistant, or break. Sudden failures indicate a greater likelihood of slab avalanches than resistant failures and breaks. Watch this video by Dr. Bruce Jamieson, a leading avalanche researcher, to learn more about fracture character.
A thin planar fracture suddenly crosses the column in one loading step AND the block slides easily on the weak layer.
The fracture crosses the column with a single loading step and is associated with a noticeable collapse of the weak layer.
A planar result that requires more than one tap to slide, or where the block does not slide easily.
Occurs when a weak layer is squished down over a series of taps.
A non-planar, irregular fracture
We also see these extended column test (ECT) results in the MIN. The ECT assesses both initiation (how much force it takes a weak layer to fail) and propagation (how far the failure will spread across the column, and, possibly, across the slope). The ECT involves isolating a column 90cm x 30cm, placing the shovel blade on top of the column at one end, and applying the same series of taps as the compression test. Results are recorded in this style:
- ECTP15 means a fracture propagated across the entire column on the 15th tap (from the elbow).
- ECTN25 would mean a fracture occurred on the 25th tap (from the shoulder), but it did not propagate.
Fracture crosses the entire column during isolation.
Fracture crosses the entire column on the ## tap, or a fracture is observed on the ## tap and crosses the column on the next one.
Fracture observed on the ## tap but does not propagate across the column on either that tap or the next one.
No fracture observed during the test.
Snow hardness, or density, is a common measurement taken during a snow profile and indicates the relative strength of various layers throughout the snowpack. The person conducting the snow profile will first identify the separate layers, and then assess each layer’s hardness using their hand, a pencil, or a knife.
Fist in glove
Very light snow (powder)
Four fingers in glove
One finger in glove
Blunt end of a pencil
Very hard snow
Too hard to insert a knife
Total height of the snowpack
Height of storm snow (amount that's fallen in the latest storm)
Below treeline elevation
We hope this helps you understand the Mountain Information Network better. If you have any questions, please email firstname.lastname@example.org.