Winter Sports · General · Snow and mountain science
Why Does the Weather Change So Quickly in the Mountains?
Mountains force air to rise: rising air cools, the moisture in it condenses, and cloud and precipitation can form very quickly. Temperature drops with altitude; on average by about 6.5 °C per 1,000 metres (by the UK Met Office's rule of thumb, about 2 °C per 300 metres). Wind strengthens with altitude and speeds up over ridges; on the far side of the mountain, warm and strong winds such as the föhn can blow. Cold air pooling in the valleys overnight (an inversion) can make the summit warmer than the valley in the morning. That is why the weather in the valley does not show what is happening at the summit. In Turkey, the Turkish State Meteorological Service (MGM) publishes separate 5-day forecasts and snow depths for ski resorts.
As defined by the US National Weather Service (NWS), orographic lift is air being forced by terrain to rise and cool. If the air cools enough, the water vapour in it condenses and cloud forms; that is why high ground sees more widespread cloud and more precipitation.
This is the main reason the weather changes so quickly in the mountains: a sky that looks clear over the plain can turn into cloud and snow the moment the same air mass climbs the mountainside. We explain how snow crystals form in these clouds in our guide How does snow form?.
How much colder does it get as you go up?
Measure
Cooling
Source
Dry (unsaturated) air
9.8 °C per 1,000 m
NWS
Saturated air (inside cloud)
Slower than dry air; not constant, depends on the air's temperature and pressure
NWS
Standard atmosphere average
6.5 °C per 1,000 m
American Meteorological Society
Rule of thumb for mountaineers
About 2 °C every 300 m
Met Office
There is no single, fixed figure, but about 6.5 °C/km is a good starting point. For example, if there is a 1,000-metre difference between the base and the summit of a ski resort, the summit is on average 6–7 °C colder. Add wind and the temperature you feel drops even further; we explain this in our guide to wind chill.
The difference between dry and moist air is the key to the next section: the föhn.
Föhn: the warm wind on the far side of the mountain
As MeteoSwiss, the Swiss meteorological office, describes it, during a föhn:
On the windward slope, air rises and cloud and precipitation form; a wall of cloud called the föhn wall can be seen over the ridge.
On the leeward slope, the air warms as it is compressed on its way down, its humidity drops and the clouds break up: the weather is warm, windy and dry, with good visibility.
In these warm, dry currents descending the leeward slopes, the wind often reaches gale force.
Sometimes the leeward slope stays cloudy too; this is called a dark föhn (Dimmerföhn).
What it means for skiers: it can be snowing on one side of the mountain while the sun comes out on the other; but even on the sunny side, the wind can be very strong. The NWS also notes that this wind is known as the chinook in the United States.
Wind gets stronger with altitude
According to the UK Met Office, wind strengthens with altitude and speeds up over ridges and summits. The effect:
According to the NWS, wind in the mountains changes direction with the time of day:
Valley wind: By day, it blows up the valley along the warming slopes.
Mountain wind: At night, cooling, heavy air flows down the slopes (katabatic flow).
Inversion: cold valley, warm summit
Normally the air gets colder as you go up. But on clear, calm nights the ground cools quickly by radiation and cold air pools in the valleys; this is called a temperature inversion. According to the NWS, this kind of inversion forms at night and usually breaks up quickly after sunrise. The result: in the morning there can be fog and freezing cold in the valley while the summit is sunny and milder. MGM's forecast menu also has a separate Inversion Forecast (Enverziyon Tahmini) section.
Lenticular clouds: a visible warning of wind
As moist, stable air crosses a ridge, it forms waves on the leeward side; lens-shaped lenticular clouds form at the crests of these waves. According to the NWS, these clouds are a visible warning of mountain wave conditions, and the rotor zone beneath them is turbulent. If you see a smooth cloud sitting over the summit that seems not to move, assume there may be strong wind up high.
Afternoon storms
According to the NWS, thunderstorms in mountainous areas usually develop in the early afternoon, which is why starting early and getting down by midday is recommended. Keep this rule in mind when spring skiing.
When the cloud comes down: whiteout
According to the Met Office, visibility in cloud at ground level is usually below 50 metres; when snow and low cloud combine, a whiteout with effectively zero visibility develops. We explain what to do in that situation in our guide fog, whiteout and loss of visibility.
Where to follow mountain weather in Turkey
On the Turkish State Meteorological Service's website, the Forecasts (Tahminler) menu has a Ski Resort Forecasts (Kayak Merkezi Tahminleri) section. For each ski resort, this section publishes a 5-day forecast of weather events and minimum and maximum temperatures, as well as snow depths. When reading these forecasts:
If you do not know which altitude of the resort the given temperature refers to, assume the summit will be colder.
Check wind and visibility on the resort's live information board and lift status as well.
If you are thinking of going off-piste, a weather forecast is not enough; find out about avalanche conditions too. We explain in our guide How to Read an Avalanche Bulletin that Turkey does not publish a daily avalanche bulletin with 1–5 danger levels as in Europe.
The skier who reads the weather
Someone who knows how mountain weather changes does not give up on the day just because of fog in the valley in the morning; they know the summit may be in sunshine. On an activity holiday, this knowledge makes every hour on the slopes more worthwhile. Doğadayız winter packages include accommodation, ski pass and equipment. Looking at the next day's forecast together in the evening and planning which slopes to meet on is also part of a social adventure holiday. For the programmes, see the winter activity holidays page.
Doğadayız Packages
Doğadayız packages for your level
Winter activity holidays with accommodation, ski pass and equipment included, shared with a group.
The easiest way to learn to ski: a winter activity holiday
An activity holiday puts a sport at the heart of your trip: transport, accommodation and meals are planned, so you can focus on learning on the slopes. On Doğadayız winter activity holidays, accommodation, ski pass and ski or snowboard equipment are included in every package; course packages include basic lessons with instructors affiliated with the Turkish Ski Federation, while experience packages let you practise on the slopes at your own level.
What makes the programme different is the group: sharing the slopes with people at a similar level, dinners and nights out together, and a group leader by your side at all times. Solo travellers become part of this social adventure holiday from day one. That is why we describe our programmes as a social adventure holiday.
Why does the weather change so quickly in the mountains?
Mountains force air to rise; rising air cools and the moisture in it condenses to form cloud and precipitation. On top of that, wind strengthens with altitude and speeds up over ridges, and local winds such as the föhn and inversions forming overnight can change temperature and visibility within a few hours.
How much does the temperature drop as you go up?
On average about 6.5 °C per 1,000 metres. In dry air the rate rises to 9.8 °C; in saturated air inside cloud it is lower and varies with temperature. The Met Office's rule of thumb is about 2 °C per 300 metres.
Where can I find weather forecasts for ski resorts in Turkey?
On the Turkish State Meteorological Service's website, the Ski Resort Forecasts section in the Forecasts menu publishes a 5-day forecast of weather events and minimum and maximum temperatures for each resort, along with snow depths.
Wind chill is when the temperature you feel is lower than the actual air temperature because the wind quickly carries heat away from exposed skin. According to an information card from Turkey's Ministry of Labour and Social Security, at −5 °C a 30 km/h wind feels like −13 °C. According to Environment and Climate Change Canada, when the wind chill is between −28 °C and −39 °C, exposed skin can freeze in 10–30 minutes; at lower values this drops to a few minutes. When skiing, you create part of the wind yourself: skin cools very quickly when you are coming down fast and especially when you are sitting facing into the wind on a chairlift.
A whiteout, as defined by the American Meteorological Society, is an optical phenomenon in which the observer appears to be engulfed in a uniformly white glow: over unbroken snow cover under a uniformly overcast sky, shadows, the horizon and clouds disappear, and the sense of depth and direction is lost. According to the UK Met Office, the risk increases when fog or mist combines with widespread snow cover. When skiing, this means not being able to see the gradient, the bumps or the edge of the slope. When visibility worsens, slow down, stay on the marked slope near the markers along its edge, and switch to a slope one level easier; if visibility is very poor, ski down to the nearest lift station and call it a day.
Snow is made of ice crystals that grow as water vapour turns directly into ice in clouds. Cloud droplets do not freeze straight away at 0 °C; they stay liquid in a supercooled state. According to Caltech physicist Kenneth Libbrecht, most droplets freeze at around −10 °C thanks to an ice nucleus such as a speck of dust in the air; below −40 °C no droplet can stay liquid. The frozen crystal grows by drawing the surrounding vapour onto itself. Temperature determines the crystal's shape, and humidity determines how complex it becomes: thin plates form between about 0 and −4 °C, columns and needles between −4 and −10 °C, and plates again between −10 and −22 °C; the classic six-armed star (dendrite) grows at around −15 °C in humid air. Once on the ground, snow keeps changing with temperature and wind; the snow you feel on the slope is the result of this transformation.
