Mountains / Data & sources

Data, sources & the honest caveats

Live weather sources, current pass-planning information and historical-data status

Current pass decisions still need source dates. The bundled historical snow layer is legacy local context while its original source-acquisition provenance is rebuilt and verified. This page distinguishes that holding state from independently sourced pass prices and access rules.

Choose the right weather view

Use each source for the question it can answer. A forecast, a model snow signal and a resort report measure different things.

Start with the season, then narrow to your trip

Months ahead, compare the regional climate pattern and keep travel options flexible. As departure approaches, use short-range forecasts, then check operator reports, roads and cameras. Your pass dates, terrain preferences and total budget remain separate decisions.

What is the U.S. winter outlook?

NOAA Climate Prediction Center. The winter planner compares rolling three-month temperature and precipitation outlooks. NOAA categories describe the lower, middle or upper third of the historical distribution. Equal chances means no category is favored; it does not promise an average winter.

Our percentage labels show the lower edge of the published probability band. A 40%+ wetter-category label is not 40% more precipitation, a snowfall total, or the chance that it snows on your holiday. Temperature and precipitation remain separate signals. Overlapping winter windows are not independent monthly predictions.

Check the issue and use-before dates. Unavailable or expired categories are withheld. Forecast skill varies with location, season and lead time; this site has not established a resort-level accuracy score for these outlooks.

Compare U.S. winter windows →

Official NOAA maps ↗ · NOAA methods and forecast skill ↗

What is the Canadian winter outlook?

Environment and Climate Change Canada / CanSIPS. The Canadian comparison shows separate below-, near- and above-normal probabilities for seasonal temperature and precipitation, relative to 1991–2020. The imported fields use a coarse 1° grid, approximately 100 km. Nearby mountains may share the same grid point; the display lists its distance from the mountain.

These are regional signals, not mountain snowfall forecasts. Rounded probabilities can total slightly more or less than 100%. They are not directly interchangeable with NOAA’s category-band labels, so we do not rank U.S. and Canadian mountains by comparing those numbers.

Read the model month, refresh time and use-before date. Held, unavailable or expired source data is withdrawn. An open page checks Canadian source availability again on focus and periodically while active; reload to fetch a newer issue.

Compare Canadian winter windows →

Official seasonal outlooks ↗ · ECCC data documentation ↗

What is the European winter outlook?

ECCC / global CanSIPS. Separate three-month temperature and total-precipitation category probabilities are available for 50 tracked destinations in the Alps, Spain, Andorra and Scandinavia. The reference is 1991–2020. Every issue requires the complete set of 24 original probability fields, validated catalogue points and original source hashes.

A coarse 1° cell can serve several mountains. Shared probabilities do not distinguish their elevation, beginner terrain, snowfall or valley return runs. The site has not verified resort forecast skill. Read the exact window, grid distance, model month and UTC expiry; held, incomplete and expired issues remain unavailable.

The European projection shares the original global fields and issue hold with Canada, but has a separate catalogue and publication. It cannot substitute a Canadian row for a missing European forecast. Open tabs recheck availability; reload for a newer issue.

Compare European seasonal windows → · Compare European trips and whole-group quotes →

Original CanSIPS field documentation ↗ · Independent Copernicus seasonal products ↗

For an independent source check, match Copernicus’s own issue month, model system, variable and three-month calendar window. Its hindcast reference and verification definitions differ; its charts do not validate the CanSIPS values here.

What does “normal” look like locally?

NOAA NCEI 1991–2020 station normals. Reviewed monthly baselines are available for 13 destinations. Expand “What is normal?” in a mountain guide or trip comparison to see temperature and, where supplied, snowfall totals and historical frequency.

The frequency table shows average days per calendar month with snowfall of at least 1 inch (2.54 cm), at least 3 inches (7.62 cm), and daily highs at or below 32°F (0°C). The 3-inch days are included in the 1-inch days. These are separate station metrics, not powder-day odds, open-terrain estimates or snowfall predictions for your holiday.

Each reading preserves the station name, elevation, distance, contributing year count and quality flag. Metrics may use different record lengths. A normal can use fewer than 30 years or include statistically filled gaps; provisional records are labeled. Missing temperatures, snowfall and frequency fields remain unavailable. Station averages are not summit-adjusted and are not the exact regional category thresholds used by the seasonal outlook.

These baselines provide historical context, not a forecast for this winter. They remain separate from the older snowfall records and rankings still under review. The dates beside each station distinguish its temperature/snowfall-total review from its frequency review; expanding coverage does not refresh older source checks. Nearby Tahoe City supplies Northstar context. The reviewed Mammoth and Heavenly stations supply temperature context but no snowfall fields.

See Steamboat’s station baseline → · Northstar’s nearby Tahoe City baseline → · Compare destination context →

NOAA climate normals ↗ · Record-quality documentation ↗ · Threshold definitions ↗

As your ski day approaches

How much new snow is forecast in the U.S.?

National Weather Service / NDFD. The NWS desk shows published six-hour snowfall amounts near selected U.S. mountains. Complete intervals support 24- and 48-hour totals; missing intervals remain unavailable.

Save up to six mountains and compare the same forecast period. Check the source update, location and interval. These are gridded forecasts, not measured fresh snow or resort base depth.

Open the NWS snow desk →

NWS API documentation ↗

What weather should I plan for worldwide?

MET Norway Locationforecast. Global Mountain Weather and mountain guides offer up to 24 published future one-hour periods for departure and ski-day planning, alongside a separate six-hour outlook for the next three days. Select a window to inspect temperature and wind at its start, and liquid precipitation during the following one or six hours. Weather descriptions such as snow showers come from MET’s summary for that exact period. Missing hourly periods are left as gaps; six-hour amounts and symbols are never substituted. Unavailable readings stay unavailable.

Times default to the mountain’s zone; source updates remain in UTC. Source data older than 18 hours is withheld. The first displayed hourly period starts in the future; it is not a current observation. The same shared source snapshot supplies both views.

Compare up to four mountains over the same one-, two- or three-day period. Comparisons, trip-date projections and CSV downloads retain six-hour windows. Temperature and wind summaries use six-hourly samples, not daily extremes or gusts. Liquid precipitation is not snowfall depth; no snow-to-water ratio is assumed.

Open worldwide mountain weather →

MET forecast-period definitions ↗ · MET Norway documentation ↗ · CC BY 4.0

Where does the model show a broader snow signal?

ECMWF Open Data IFS. The snow map separates days 1–7 from days 8–15. Markers summarize the model’s snowfall-water-equivalent field near each mountain. They are not predicted inches of fresh snow, a resort ranking, or a guarantee of skiing conditions.

Read the model run and exact date window on the map. An unavailable or out-of-date source is withheld; a later model run may change the signal.

Open the snow signal map → · How to read it →

ECMWF Open Data ↗

Are there weather alerts for my mountain?

National Weather Service alerts. U.S. mountain guides and the NWS snow desk offer an on-demand check for active watches, warnings and advisories covering the mountain's mapped point. Read the full affected area, timing and NWS instructions; an alert can cover a much larger area than the ski resort.

Checks use a one-minute source cache. Snapshots older than five minutes are withheld, and expired alerts require a new check. No returned alerts does not confirm road, lift or terrain conditions. This feature does not send notifications.

Check Alta alerts → · NWS API documentation ↗

How much snow is measured at a station?

USDA NRCS SNOTEL. Snowbird, Brighton, Copper Mountain, Stevens Pass, Timberline, Park City and Grand Targhee guides offer seven daily station readings of snow depth and snow-water equivalent. Both are reported in inches, but water equivalent measures the water held in the pack. Neither daily pack changes nor water equivalent is a fresh-snow total. Separate trend charts use independent scales and leave gaps for missing measurements; the daily table keeps every exact reading visible.

These provisional readings describe a single station at its listed elevation. NRCS daily dates use the station’s fixed UTC−08:00 data time zone. Missing readings stay blank, and a series with no usable reading in the last 72 hours is withheld. Station data uses an hourly cache refresh and loads only on request. Timberline uses the nearby Mt Hood Test Site; station-location links show where each measurement is taken.

Snowbird observations → · Brighton → · Copper Mountain → · Stevens Pass → · Timberline area → · Park City → · Grand Targhee →

NRCS AWDB API documentation ↗

What does the mountain look like?

Official mountain cameras. Selected mountain guides link directly to operator camera pages, including snow stakes, base areas and upper-mountain views. Check the image timestamp and camera location: a base-area view can look very different from the summit.

Camera links are reviewed sources, not a confirmation that every feed is currently working. Seasonal or uncleared snow stakes may show accumulated snow rather than an overnight total. Confirm lift, terrain and road status with the operator before travelling.

Snowbird cameras → · Whistler Blackcomb cameras → · Niseko cameras →

Are the lifts, runs and roads actually open?

Resort and transport operators. Use the official conditions directory and the dated source links in trip tips for operating status, parking, road restrictions and reservations. Weather alone does not establish access.

Community stories help you find useful questions and local ideas. Their publication dates and source-review dates are separate from today’s conditions. A missing or overdue report is not an all-clear.

Find an official mountain report → · Browse sourced trip tips →

Check seasonal forecast accuracy and official verification →

When sharing a forecast, include the mountain, source, source update time, forecast interval and units. The time you opened this site is not the time the provider issued its forecast. The weather and observation tools above operate separately from the historical snow records currently under review.

Historical-data holding status: the bundled 36-season climatology remains locally available as legacy context, but its original source-acquisition provenance has no reproducible receipt. We are not presenting its month tables, seasonal derivatives, or CSVs as newly verified or independently reproducible research while a clean ERA5 rebuild and hash-bound provenance sidecar are completed. This does not change dated pass-price and access snapshots; exact-date Powder Odds remains paused until its separate licensed daily archive is also configured.

Seasonal API not publishedSeasonal fields inherit the historical holding state

GET https://skipassplanner.com/api/passcast/{slug} emits a machine-readable 503 holding notice only; it does not publish seasonal API data. Do not cite or republish cached seasonal values as a newly verified public data product.

Dated pass-price and access sources remain separately usable for trip math. Use the Official Conditions Desk for direct operator pages about current operations, and official seller pages for checkout details.

Exact-date powder recordTemporarily paused pending licensed archive access

The public JSON endpoint and iframe embed are intentionally unavailable while PassCast enables its licensed, provenance-verified historical archive. This prevents a dynamic record from being served without a verified receipt; the seasonal CSVs are also in holding while the bundled historical baseline is rebuilt.

Seasonal CSV statusLegacy derivative in holding

The existing El Niño CSV depends on the same legacy historical baseline. It remains a local artifact, not a currently promoted research download, until its source provenance is rebuilt and verified.

Snow-by-month data not publishedLegacy local record remains off the public site

No public month tables or CSV are available in the holding state. The legacy local record stays off the public site until the clean rebuild is complete and reproducibly verified.

Do not treat the legacy figures as a newly verified research source, storm forecast, or operating-date promise. Use a resort's own page for current conditions and official sources for pass decisions.

Current source surfaces

Independently usable source trails during the historical-data holding state.

Dated pass prices and accessSource snapshots, not checkout guarantees

The Ski Pass Cost Calculator retains documented price snapshots, day caps, shared pools, and ticket benchmarks without relying on the paused snow model. Reported price dates are a separate calendar return loop. Recheck the operator before buying because availability, access, and checkout prices can change.

U.S. NWS snow outlookOn-demand gridpoint forecast, not a resort report

The U.S. NWS Snow Outlook loads selected National Weather Service / NDFD representative-point grids, with a saved-mountain comparison. It shows only published six-hour new-snow windows with the source link, NWS update time, HTTP Last-Modified time, and point coordinates. It is not observed snow, base depth, terrain, lifts, roads, or operating status.

“Read current forecaster notes” requests the latest Area Forecast Discussion for the office behind that grid. Named public-weather sections retain the agency’s wording and any earlier section issue times. Regional context is separate from the mountain’s numerical forecast. Products older than 12 hours, mismatched offices or unusable latest products are withheld; the direct official discussion link remains available. A retrieval does not change the source issue time.

15-day map-reading guidePermanent workflow, not a current map

The 15-Day Ski Snow Forecast Map Guide explains how to keep the 7-day and 8-day ECMWF source windows separate, what flakes and major markers mean, and why a U.S. NWS gridpoint and the operator come next. It contains no current map, marker, total, availability, conditions, or seasonal claim.

Historical material in holdingNot a newly verified research source

Do not cite the legacy seasonal fields, back-test, month-derived values, or seasonal index as a current verified data product. A clean rebuild must supply a complete source-acquisition receipt that matches the published artifact first.

Editorial boundaryUse primary operators for live details

Current operations, terrain, roads, reservations, and same-day snow conditions belong to the relevant operator. See press & editorial sources for the citation boundary.

How to cite Ski Pass Planner by PassCast during holding: cite the specific date-stamped pass-price or access source and link the relevant calculator or price-date page. For a U.S. NWS Snow Outlook value, cite its displayed National Weather Service / NDFD source link, source time, and representative point, and call it a gridded new-snow forecast—not a resort report or observed snow amount. Do not describe legacy snow, seasonal, or accuracy fields as newly verified PassCast research until the provenance rebuild is complete.

Publisher-ready source credit

Make the source trail easy to follow.

Use this for a general Ski Pass Planner by PassCast reference. During the historical-data holding state, cite the specific dated pass-price or access source behind a current planning statement. For a U.S. NWS Snow Outlook result, retain its displayed NWS source link, source time, and representative point, and describe it as a gridded new-snow forecast rather than a resort report.

Ski Pass Planner by PassCast. Data & Sources status. https://skipassplanner.com/data-and-sources. The bundled 36-season historical material is legacy context whose original acquisition provenance is not yet reproducibly verified; do not cite it as a newly verified or independently reproducible dataset.