How to Read SNOTEL Data for Backcountry Trip Planning

What is SNOTEL?

SNOTEL (Snow Telemetry) is a network of automated snowpack and weather monitoring stations operated by the USDA Natural Resources Conservation Service (NRCS) across the western United States. According to the NRCS, there are currently over 850 active SNOTEL sites across 12 western states including Alaska — with 96 stations in Montana alone. These stations collect data on precipitation, snow depth, snow water equivalent, and temperature in real time, transmitting via satellite or cellular every hour.

For backcountry skiers, SNOTEL is one of the most valuable free data sources available. Understanding what each measurement means — and its limitations — can meaningfully improve your trip planning decisions.

The Key Measurements

Each SNOTEL station records several distinct variables. These are the ones that matter most for trip planning:

Snow Water Equivalent: The Most Important Number

The NRCS defines SWE as the depth of water that would result if the entire snowpack were to melt instantaneously — making it the most direct measure of how much water is stored in the mountains. It's measured by a snow pillow, a fluid-filled bladder buried at the station that registers the weight of snow above it. Unlike snow depth, which fluctuates with wind and settling, SWE gives a stable picture of actual water content.

A common density for freshly fallen snow is around 10%, meaning a SWE increase of 0.1 inch typically corresponds to about 1 inch of new snow. This also means that during large storms, tracking SWE increase is often a more accurate gauge of snowfall than the depth sensor alone — which can underreport new snow as the existing snowpack compresses under the added weight.

How Often is Data Updated?

Most SNOTEL sites in Montana transmit via GOES satellite, with data processed and available online at roughly 40 minutes past each hour. About 25% of Montana stations use cellular transmission, processed at 5 minutes past the hour. All times are reported in Pacific Standard Time year-round, so Montana stations will appear 1–2 hours behind local time depending on the season.

It's worth noting that while data is collected hourly, only the midnight readings (00:00) are thoroughly reviewed and edited by NRCS staff on business days during winter. Extra sensor readings — including wind, soil moisture, relative humidity, and solar radiation — are not currently edited or quality-controlled.

Limitations to Know

SNOTEL sites are intentionally placed in forested locations at mid-mountain elevations where environmental inputs remain relatively consistent year to year. As the NRCS notes, sites are not typically located in alpine settings because wind can transport snow significantly from day to day — resulting in a measurement of wind redistribution rather than actual snowfall. This means a station reading may not reflect conditions on exposed ridgelines or at higher elevations above treeline.

Snow depth sensors are also prone to blank or invalid readings during active snowfall or windy conditions, because the ultrasonic signal used to measure depth can be blocked or scattered before returning to the sensor. If you see a missing or erratic depth reading, fall back on SWE — it's a far more reliable measurement in those conditions.

Finally, be cautious when interpreting percent-of-normal figures late in the season. Because median SWE values are very small in early June, even a modest snowpack can read as 500–600% of normal — which looks dramatic but may represent very little actual water. Always consider the full seasonal picture alongside the current reading.