# What is a SNOW forecast and how it works

The ski season has begun. In this article we will discuss how to check snow forecasts and which one to believe.

### What is a weather forecast in general?

The forecast we’re used to is a result of the complex work of lots of formulas and algorithms.

The point is the place the forecast is calculated for. Let’s take a point on the map, for instance, an alpine skiing spot. We can calculate certain parameters for it – humidity, precipitation, cloudiness etc. These are the initial conditions for a complex equation system.

It’s just a fragment of equations solved by supercomputers. They are solved for several points at once regularly.

Let’s imagine a bath of cold water. There’s a speck of dust in one corner and a glass of boiling water in another. How will it influence the particle’s movement? It’s as hard to make a weather forecast as to predict that.

### Grid

A point is the spot for which we calculate the forecast introducing the available parameters.

It’s too costly to calculate forecasts for every square meter. That’s why intervals are used, for instance, a forecast for every point with a 1km interval.

Those points make up a grid.

Solving complex equations for many locations constitutes a forecast model.

According to the model, the forecast doesn’t change between the points. That’s why a smaller resolution model (1mm) will be more accurate than a 10 or 20km one.

To know the weather at a certain point the global picture is necessary first – that’s what global models do.

Regional models work on a certain territory. For example, the WRF8 covers only Europe, the global GFS27 – the whole world.

Global models - GFS, ECMWF, ICON Global.

Local models - AROME, OpenWRF, WRF, NEM.

### What is the source of the data?

Models need to be “fed” constantly. The main data sources are weather stations, satellites, radars.

The Earth’s atmosphere is a very complex system, that’s why an absolutely accurate forecast is impossible. The forecast is 90% accurate for today and tomorrow, 75% - in a 7-day period, and much less – in a month. It’s better not to trust a more than 14-day forecast.

### Forecast in the mountains

There are lots of factors in the mountains impeding accurate forecasts – they can be trusted for a 7-day period at the most. We’ll explain why.

Short days and different slope exposure

Due to a complex terrain there are much fewer daylight hours here than at lowlands. Because of this air at valleys cools quickly and doesn’t get warm enough during the short day.

Exposure is the cardinal direction of the slope or the direction in relation to sunlight. It’s warmer on the slope facing the sun most of the day. The model has to take all those factors into account, that’s why a specific model would be necessary for each mountain.

Precipitation

There’s a large amount of precipitation in the mountains as humid air starts rising and cooling after bumping against mountain ranges and the moisture condenses.

Local winds

Wind movement in the mountains is very hard to predict. There are small “local” models calculating forecasts for a certain valley. The wind often blows along the valley – the air “flowing” down and

“leaking” away from the valley.

Temperature changes

Temperature changes occur due to the height of the mountains. For instance, it’s always colder at the top.

Each region has its own peculiarities, that’s why we recommend writing to Windy.app chats. There are lots of locals there who’ll give you hints on the slope’s characteristics.

FYI

• 15cm of snow in 24h is considered as an intense snowfall. Fresh snow can make fractures and cliffs unnoticeable.

• An intense snowfall means poor visibility potentially leading to injuries because of stones among other things.

• Storm wind from 30 m/s is strong – better not to go riding.

• Wind cooling – below zero temperatures and a strong wind. Frostbites are possible.

Where can I check the forecast?

There’s SNOW profile in Windy.app for all winter resorts.

Open any winter resort and choose SNOW profile under the forecast.

Send us your ideas and requests! Don’t forget to share your impressions in chats.

Have a good season!