Snow & Weather, Manual & Automated Information, An Account of Snow History at Stevens Pass
How and why did Snow Science begin at Stevens?
In the spring of 1937 Bruce and Virginia Kehr, after paying their bills and profiting about twenty-five cents for the first ski season, decided they could make a go at the Stevens Pass ski area. The first season they operated one rope tow and lived in a small shack along side the Big Chief ski run.
With the increase of recreational snow users by the mid 40s the U.S. Forest Service saw the need to do something about the avalanche problem more and more people were encountering.
The Forest Service commissioned Montgomery Atwater to put together a research and development program in the U.S. for avalanche control methods. Monty Atwater was also commissioned to figure out how to mitigate the avalanche potential for the 1960 Squaw Valley Winter Olympics.
Due to the different type of snow pack conditions across the U.S. in different mountain ranges Monty realized the need for several research and development stations throughout the U.S. in these different climates.
Monty Atwater mainly worked out of the Alta, Utah research center. Monty commissioned Dick Stillman to run the Berthound Pass, Colorado center and Frank Fhoto to run the Stevens Pass, Washington research center.
Monty, Frank and Dick saw that in order to understand how and why avalanches happen and how to develop avalanche control methods they needed to document and record many different parameters dealing with snow. For instance-measuring snow fall every six hours gave them an idea about the rate at which snow settles and how that correlates to avalanche hazard.
Over the years they recorded weather data like snowfall, temperature, and wind speed and direction, and conducted many studies relating to avalanche control methods that are still used today.
Stevens Pass, ever since the opening season of 1937, has been a research center and that continues to this day. Stevens Pass has snow, weather and avalanche documentation dating back to 1937 and still conducts research projects relating to snow science and weather. Ski patrol monitors and records daily snow fall, wind speed and direction, temperature and other weather information.The avalanche forecasters use that information to plan avalanche hazard reduction. Stevens Pass is a Class A avalanche area and has over two hundred and thirty avalanche paths in the ski area boundary.
The ski area (being on the crest of the Cascade Range and affected by strong Pacific storms) has weather patterns that can change rapidly These circumstances can lead to avalanche hazard and snow conditions changing in minutes.
So you can see that it keeps the avalanche control people quite busy throughout the winter season.
Stevens Pass has a very active avalanche control program that monitors hourly weather and snow pack information and that conducts avalanche control mitigation in the ski area boundary to help minimize the avalanche potential to the skiing public.
Here is an account of the types of weather and snow pack information we record and why. Most of this information can be found at the Northwest Weather and Avalanche Center in Seattle.
Every 12 hour period we record various snow pack and weather observations to help us monitor the condition of the snow pack and to tell you what kind of snow conditions you might find when you come skiing.
Because snow and weather conditions can change by the minute it is important to monitor weather and snow pack information 24 hours a day during the ski season.
We make every effort to be as accurate as possible when we take this information and it is our job to report to you the weather and snow conditions as accurately as possible.
It is also very important to understand that being on the crest of the Cascade Range with cold air from the East side mixing with warmer air from West of the crest means that weather and snow conditions can and do change very rapidly.
We have seen the temperature rise several degrees in minutes. We have also felt the wind go from 0 to well over 50mph in less than a minute. Some times it snows at 36F degrees and some times it rains at 28F degrees with the inversions that form here. We have watched a snowfall of 30 inches and only been able record 15 inches because the snow settled so fast. We can also see inversions of 20F degrees at the base and 50F degrees on the top of the mountain.
At the Stevens Pass we have several snow study plots and weather stations that we take manual and automated recordings from.
Why do we take this information from designated sites?
Locating the right snow site that is the most representative of the area around it takes three to four years of data comparisons to find accuracy. Snow study plots need to be in a wind protected, undisturbed area.
Snow is made up of mostly air. If the area around the snow stakes is disturbed the snow will settle not allowing accurate readings for avalanche purposes and reporting to you how much new snow we have received. On the average we receive about 40’ of snowfall through out the season, that’s about four stories of snow, so where does it go? Settlement. When the temperature warms up or a snow cat drives over or skiers ski on it, it can settle the snow taking the air out, densifying the snow pack.
The depth of snow on a groomed, skier compacted run is quite different from undisturbed snow. On average we can see around ten to fifteen feet of snow in un-compacted areas and about two feet of snow in compacted areas. So in heavily skied areas the groomers do a lot of work to maintain a good snow level.
We have a study plot located at the top of Brooks at 4850’ elevation.. This study plot location is accessed by snowmobile for avalanche control purposes and is also automated showing temperature, total snow depth and water content of new snow. When we tell you what the Top Snow Total and the Top Temperature is, this is where the information comes from, the top of the Brooks chairlift. We also record wind speed and direction from this site.
To be consistent, accurate and be able to observe trends these weather and snow readings need to be taken from the same location every time. While conditions will vary around the mountain, the Brooks site is a good indicator of what the average conditions will be.
Our Base information is taken from the Schmidt Haus study plot, located near Highway 2 at 3,950’This study plot has been at this location for about seventy years. This site is maintained by the Washington State DOT Avalanche Program. We have experimented with various Base study plots around the ski area, and the consistency of the Schmidt Haus location, as well as relevance to ski conditions, has proven to be the best spot. The information we take from the Base snow study plot is Total Snow Depth, 24 Hour Snow Fall, Hourly Snow Fall, Relative Humidity and Temperature. This information is gathered both manually and electronically.
Wind Direction and Speed
We have a wind direction and speed indicator at the top of the Tye Mill chairlift. This is the best location for snow transport readings because it is in a pass. Because of the pass this is where we read the highest wind speeds. When you call the snow report we can tell you if the wind is blowing lightly, moderately or hard. We cannot necessarily tell you the exact direction of the wind because of the orographic effect the ridges have on wind direction.
Studies on the effects that geographic features in the Stevens Pass area have on wind direction show that sometimes we have winds out of the East at lower elevations and winds out of the West at higher elevations.
How accurate are electronic weather and snow readings?
Electronics have come along way the past few decades, but you need to be able to read between the lines at times. Take for instance an Hourly Snow Fall electronic reader. If the difference between the sensor and the board is 48” and it is snowing hard, some times this will read 0 or 48” as it adjusts its self to the new snow reading.
AC voltage can play havoc on telemetry readings. DC voltage is more reliable and AC voltage is used to keep the system charged.
If something gets too close to a sensor, such as an animal, tree branches or high winds blowing the snow, you may see erratic or default readings at times.
Electronics are not a perfect world. Manual snow and weather measurements are the most reliable.
So what do we use the weather and snow pack information for?
Every 12-hour period we take weather and snow observations. We use this information for several reasons.
Avalanche Forecasting | Control
Daily monitoring of the layers within the snow pack is essential for monitoring the avalanche hazard.
Avalanche forecasting allows us to determine which measures we use to minimize avalanche hazard. Minimizing avalanche hazard could include the use of explosives, closing an affected area, or ski cutting to intentionally release avalanches.
The information we take from snow study and telemetry sites is:
- 12 Hour Snowfall (Overnight)
This gives us an idea of how much new snow we have received over night and how much the snow has been skied or compacted when Mill Valley closes for the day. It also gives you an idea of how much new snow there is that has not been skied.
- 24 Hour Snowfall
We use the 24-hour snowfall to keep track of storm snow totals and to subtract from the 12-hour snowfall to come up with a settlement rate in the new snow.
- Settlement Rate
We use the difference between the 12 hour and 24 hour snowfall totals to derive a settlement rate in percentages. This tells us how fast and how much the new snow settled over a given period of time.
Rapidly changing temperatures often lead to a change in avalanche hazard. We pay close attention to what the temperature was when it was snowing, what it is currently, and what it is forecasted to be during the day.
We look at how consistent the wind was, how fast the wind blew and what direction the wind came from. Especially during the time of snowfall we watch the wind for transporting snow onto a lee slope creating wind slabs. Wind slabs are one of the most common avalanche types that we see.
We look at snowfall intensity per-hour. Too rapid snowfall can cause avalanches. That’s why we try and keep as much area open as possible when it is snowing hard to allow as much skier compaction as possible. This helps to reduce the potential for avalanches.
We look at and measure the density of snow layers to see what the snow slab structure is.
- Layering Structure
We dig lots of test pits to investigate the structure of the snowpack and identify weak layers. We use this information to forecast what effect the next storm will have on our existing snowpack
- Natural Activity
This parameter is the most obvious sign as to how unstable the snow pack may be. When it is snowing, raining or a rapid change in weather occurs that is the time to look for natural avalanche activity.
Maintaining the Database
Weather and snow pack observations are also critical for maintaining our database. It helps us for planning of future development and for continued research and development projects for avalanche control and understanding snow science.
Reporting Conditions to Guests
In taking weather and snow pack observations we are able to report to you current conditions. Remember that because of where we are located in the Cascades the snow and weather conditions can change by the minute and many times snow and weather conditions change at daybreak. We update the Conditions page on the website several times daily, and strive to provide accurate information.
We make every effort to report the most accurate weather and condition information possible. It is also important to note that everyone interprets conditions differently. Depending on ability and skill level, what are good or great conditions to one person may be poor conditions to another. Giving you, our guest, the most accurate information we can insures that you will be able to make informed decisions about whether to ski or board with us. Knowing what to expect will help you have the best possible experience at Stevens Pass.