Questions and Tips

Filter the resort list by state or pass, or use the Resorts menu at the top. Tap a mountain and its full forecast opens right there: the snow still to come, the main accumulation window, the uncertainty, the daily strip, hour-by-hour detail, charts, every model, the probabilities, lift wind and source links. Star a mountain to keep it under My Mountains at the top of the list.

Tap the star next to any mountain. Starred mountains show under My Mountains at the top of the resort list. Stars are saved on this device only; there's no account.

Yes. Pick Epic, Ikon or Indy in the pass menu above the resort list. The list then shows only mountains on that pass. The Resorts menu at the top still lists every mountain. Pass lineups change every season, so check the pass's own site before you buy.

Tap any mountain. Use the section links under its name to jump to Snowfall, Temperature, Wind, Precipitation, Models or Probabilities. On the home page, switch the resort list between Snow, Temperature and Wind.

Yes. Tap a model's name above the snow chart to hide or show it, or use the quick sets: Short-range (the high-resolution models that see two days out), Global (the big models that see a week out) or Blend only. Move your finger or mouse across the chart to read the snow, temperatures and wind for that hour. Your choice is remembered on this device.

Every mountain has its own page, like Killington. Copy the address from your browser and send it.

Every day we check what each model said one to three days earlier against what airport weather stations near the resorts actually measured. The results are under Forecast Accuracy. Upslope gives more weight to the models doing best in each part of the mountains. The aim is for the blend to beat any single model, but we don't score the blend itself yet, so that's a goal rather than a proven result. These scores measure rain and melted snow at valley airports, not snowfall on the summits.

As a rule of thumb, the next two days are usually close, three to five days out is a good guide to whether a storm is coming, and six to seven days out is a heads-up only.

It's each model's bias over the last 30 days: all the precipitation it forecast one day ahead, compared with what the airport stations measured. Too wet means it forecast 25% or more above what fell, A bit wet 10–25% above, About right within 10%, and A bit dry or Too dry the same on the low side. Airports sit in valleys, which usually get less than the mountains, so most models lean wet here. Use it to compare models with each other, not as proof they'll overshoot at the summits.

It's the individual-model spread: the lowest and highest total among the weather models. A narrow spread means the models agree. A wide spread means the storm track or the snow-rain line is still uncertain, so plan for the middle and watch for updates. For 7-day totals only the models that run a full week count; HRRR, NAM and HRDPS stop after about two days.

It's different from the middle 80% of ensemble runs, shown with the odds and as the blue band on the snow chart. That comes from 82 reruns of two global models and usually tells you more about the odds of a big total. When the main forecast is much snowier than most ensemble runs, we say so, because it means the higher number is shaky.

Two of the models, the American GFS and the European, are each rerun dozens of times with slightly different starting weather. Upslope counts how many of those 82 runs reach each total. If 57 of 82 runs reach 6″, that's about a 70% chance.

It compares this forecast with the one from about a day ago over the same days. “Trending up: 6″ yesterday, 9″ now” means the models have been adding snow, which often keeps happening as a storm gets closer.

The models run separately for each summit and base. Mid-mountain sits halfway up, and its temperature and snow are worked out between the two, with the rain/snow split set by the halfway temperature adjusted for humidity. It's most useful on days when it rains at the bottom and snows on top.

Upslope forecasts the summit and the base separately, and resort reports usually measure at one spot mid-mountain. Wind also moves snow around: exposed summits can measure less and sheltered glades much more. Treat our numbers as what falls, not what you'll find in every trail.

When rain or a thaw is followed by a freeze, the surface sets up hard. Upslope flags those mornings and says whether they should soften by midday.

Each mountain has a rough gust level where wind starts to matter for upper lifts, lower when the wind blows from the direction it's most exposed to. On a mountain's full forecast, the summit wind grid shows the modeled gust for every hour from 8 AM to 4 PM, the direction it comes from (NW, SW and so on), and shading for lower, elevated or high wind exposure. It's modeled weather, not lift status: actual lift operations are decided by each resort.

Before a mountain's usual opening day, Upslope shows when it typically opens alongside the snow forecast. In the last six weeks or so before that date, it also notes nights cold enough to make snow. Opening dates are typical ones, not announcements.

At least six hours in a row when mid-mountain sits at 26°F or colder once humidity is counted. That's when most snow guns work well. Dry air is why resorts can make snow when the thermometer reads above freezing. It tells you the weather allows it, not that a resort will run its guns: that depends on water, staff and plans we can't see. We only mention it in the weeks before a mountain usually opens.

About every six hours, shortly after each new round of model runs. The time of the last update is at the top of the home page.

Model forecasts from NOAA (HRRR, NAM, GFS and the National Weather Service Blend), ECMWF, Environment Canada (HRDPS and GEM) and Germany's DWD (ICON), served by Open-Meteo. Measured precipitation for the scoreboard comes from airport weather stations via the Iowa Environmental Mesonet.

Yes, and there is no account to make.