Remote Forecasting Tools for Planning Trips in Snow
Introduction
Snow cover is a key consideration when planning a winter backpacking trip or a high-elevation hike in late spring or early summer. Correct assessments can mean the difference between a well-planned adventure and one that wastes time, money, and energy. Fortunately, several free digital resources can help you make informed decisions when planning routes involving snow travel.
Understanding the basics of mountain snowpacks and how to assess terrain remotely is crucial for extending your backpacking season. This article provides tips and tools for effective trip planning whenever snow is a factor, whether you're setting off tomorrow or in the coming months.
Topics this article will focus on include:
Snowpack fundamentals.
Digital tools and resources for trip planning at home.
Use cases for using these tools and complicating factors.
Photograph courtesy of https://www.researchgate.net/
Snowpack Fundamentals
Three distinct snow climates exist in mountainous regions:
Maritime snowpacks exist closer to oceans and experience heavier snowfall with comparatively warmer temperatures. These regions see storms that drop immense amounts of high-density snow with warm temperatures, leading to thick, consolidated snowpacks.
Continental snowpacks are found in regions further from the ocean at high elevations and tend to see less precipitation than maritime climates. Storms in these regions are cold and tend to drop snow in lower volumes at lighter densities. Due to the characteristics of these storms, the resulting snowpack in these regions commonly presents layers of snow that vary in density and quality.
Intermountain regions, in the simplest terms, present a hybrid of the other two climates.
The map to the left provides a general overview of snow climates throughout the western United States. It is important to remember that these are generalized assessments and that anomalies exist. During winters when more or less snow may fall than usual in any given area, mountains in a continental climate may present conditions found in a maritime environment and vice versa.
Snowpacks will evolve when exposed to gravity, changes in temperature, and insulation from continued snowfall. A temperature delta, referred to as a temperature gradient, exists where a snowpack consolidates and evolves toward consistent density.
Generally, when a snowpack sees an average change in temperature over at least 1 °C over a depth of 10cm, the snowpack will consolidate and round. This gradient is typical in deep snowpacks that commonly experience warm surface temperatures, conditions frequently seen in maritime regions.
If a snowpack does not achieve that temperature gradient, moisture will diffuse across different parts of the snowpack, causing specific layers to build weak, faceted snow grains. This behavior is standard where the snowpack is shallow or experiences exposure to frigid air temperatures, as is often found in continental climates during winter.
Photograph courtesy of https://www.avalanchecourse.com/
This hoar crystal clearly illustrates the transformed structure of snow grains as moisture diffuses out of the snowpack.
Snow metamorphosis is complex, but that does not mean that more knowledge is not valuable. If you want to dive deeper into the topic, the American Avalanche Institute’s Pro Level 2 PDF Workbook is a great resource for further exploration of these concepts. The critical takeaway is that different regions will present conditions that impact the quality of snow you will encounter. To illustrate this, imagine the following two scenarios:
A warm storm hits California's Mount Shasta and drops 6 inches of liquid water (snow-water equivalent, or SWE) in snow at 12% density, accumulating 50 inches of heavy snow.
A colder storm in Steamboat, Colorado, drops 1.5 inches of water as snow at 3% density, accumulating 50 inches of fluffy powder.
A colder storm in Steamboat, Colorado, drops 1.5 inches of water as snow at 3% density, accumulating 50 inches of fluffy powder.
The fallen snow in the Sierras, already quite dense, will consolidate further into one solid layer a couple of feet deep. The fluffy Colorado storm, on the other hand, will likely consolidate to less than a foot of snow. Given the shallower depth of the snow in Colorado and colder air temperatures typically seen in that region's climate, moisture will defuse out of the snowpack, forming faceted grains beneath the surface.
Scenarios like the one described above explain why certain regions, elevations, and aspects present different conditions during snow travel. On the same day in April, one hiker could traverse the entirety of the Bolam Glacier on Mount Shasta's north flank, firmly staying atop the snow, while another hiker could find themselves wading thigh-deep on a north aspect in Colorado.
The maritime quality of the snowpack on Mount Shasta on April 24, 2019, allowed us to ascend to the summit on the snow's firm, consolidated surface with the help of crampons.
Digital Tools for Assessing Snow Remotely
Two tools to assess snow conditions as you plan your trip are NOAA's NOHRSC (National Oceanic and Atmosphere Administration National Hydro Hydrologic Remote Sensing Center) and the National Water and Climate Center (NWCC).
On https://nwcc-apps.sc.egov.usda.gov/imap/ you will find a map displaying remote weather stations throughout the American West. Clicking on any of the icons will present a popup with more information about the station and several reports demonstrating the data it collects.
To observe some of the utility of this application:
Click on a weather station
Select Data Reports
Click "30-Day Daily Table"
From here, you can review a 30-day history of date collected at the weather station including temperature, wind, and precipitation.
We'll keep things simple in this article, but it is important to note that you can click on "Create/Modify Report" at the top of your chart to observe data recorded in years past. This feature greatly expands the potential to observe trends and predict what conditions you may expect during any given week.
https://www.nohrsc.noaa.gov/interactive/html/map.html is a tool that uses these remote weather stations and data collected via aircraft and satellites to represent snow data on a map visually. The interface includes many options for tweaking your map, but only a few are needed to inform your trip planning.
In addition to using the search bar, you can click and drag on the map to focus on a region. By default, your drop-down for Select Physical Element will show SWE, but you can also change this to Snow Depth (among many other options). In the Select Date field, you can specify when in recorded history you would like to make your observation. You can then click “Redraw Map” to refresh the page with your new visualization.
Spending a few minutes exploring this tool will quickly reveal its value. It provides a comprehensive view of current snow conditions across North America and allows you to access observations from any point in recorded history. These references enable you to compare current conditions with past years and create an informed forecast of what to expect in the coming months.
The NOHRSC provides the option to export snow overlays and weather stations as KMZ files using the links on this page: https://www.nohrsc.noaa.gov/earth/.
Clicking "Latest Snow Reports and Stations / Analyses Overlays," or one of the dates will download the file. In Google Earth, click "File" and "Import KML / KMZ file" to display the overlay on your map. Observing the location of a weather station in a 3D model of the terrain can be especially useful for concluding what to expect in certain terrain features.
Freshly fallen snow and the density of old snow can portray misleading data. When checking snow depth, it is also valuable to examine the total SWE, as it offers additional insight into the properties of the snowpack and how it may evolve. This is also an excellent reason to explore the data reports provided by remote weather stations, which comprehensively examine the snowfall, wind, and temperatures the snowpack experienced over time. Once you understand a snowpack's metamorphic processes, you can make informed predictions about how the snow has transformed, given your observations.
Another complicating factor is that the colored overlays showing snow depths are broad. While they reflect a general overview of snow depth that you may encounter, the actual depth, or existence of snow, can change depending on the terrain. Furthermore, digital modeling of snow cover does not address whether or not road access is available. In cases where it is necessary to gather such information, I resort to contacting gear shops, forest service, and public works offices in nearby towns.
In some cases, searching social media and YouTube can be another reliable way to assess conditions from afar. I have found these platforms to be especially effective when evaluating popular and commonly documented locations. For example, on the day this article was published, a YouTube search for "Gannett Peak 2024" sorted by the most recently uploaded listed three videos posted within the last month. An Instagram search for #gannettpeak or check-ins at the location returns many recent images, some with descriptions detailing conditions on the route.
Dream Lake in Rocky Mountain National Park on May 19, 2024. Notice how the snow is isolated to specific terrain features despite the NOHRSC overlay depicting a "blanket" of coverage for that date.
Example Use Cases
Say it's March 20, and you aim to section-hike the CDT from Colorado's Wolf Creek to Slumgullion Pass during the coming summer. Checking data over the past decade for June 20 reveals that, generally, the terrain you plan to cross is clear of snow. However, observing SWE data on June 20, 2019, shows significantly more snow across the route that year. Further examination reveals that 2019 experienced a similar SWE on March 20 as your current year. While weather leading to June could create more favorable conditions, given what you've seen during a similar snow season in 2019, it is probably best to plan your trip a few weeks later.
This tool has also been invaluable in planning ski trips. Over the years, I have learned that committing a trip plan to specific location risks ending up in poor ski conditions. Ever since a costly trip to Alaska in 2018 that resulted in poor skiing (but still a good bit of fun), I keep my options open and my eyes on the NOHRSC to ensure I end up skiing where snow is abundant and best in quality. High amounts of SWE and overnight freezes observed at weather stations in any given range are usually positive indicators of good ski conditions.
Whether you plan to ski, hike, backpack, or predict what watersheds may offer extended white-water seasons, these tools can be valuable whenever you suspect snow may influence your trip. As with all tools, these become more useful as you practice using them and learn more about how the data they collect impacts terrain. Spend time exploring their interfaces and what they can provide to head into trips more informed and, with any luck, more enjoyable outcomes.