Pressure Lugano − Zürich Lugano−Zürich
+0.5hPa
Neutral
↑ Foehn possible ↓ Northerly flow Foehn possible Northerly flow Altdorf (km/h) - - - forecast
Above 4 hPa there is foehn at Visp 4 times out of 10.
Lugano−Zurich pressure, simple version Lugano−Zurich · simple
+0.5hPa
Neutral
Friday 04.09 Saturday 05.09 Sunday 06.09 +8 +4 0 -4 -8 South foehn North foehn The line leaves the dashed band = foehn possible on that side.
Pressure Domodossola − Sion Domodossola−Sion
+0.1hPa
Neutral
↑ Foehn possible ↓ Northerly flow Foehn possible Northerly flow - - - forecast
Above 4 hPa across the Simplon: foehn at Visp half the time.
Pressure Visp − Evionnaz Visp−Evionnaz
-0.5hPa
Neutral
↑ Down-valley ↓ Up-valley Down-valley Up-valley Visp (km/h) - - - forecast
Valley wind regime. Not to be read as a foehn.
700 hPa wind over the southern crest 700 hPa · ~3000 m
+1.8km/h
Neutral
↑ Southerly flow ↓ Northerly flow Southerly flow Northerly flow - - - forecast
Above +20 km/h from the south, what drives the foehn is in place.
North−south temperature at 2500 m ΔT nord−sud · 2500 m
+0.6°C
Neutral
↑ South colder ↓ South warmer South colder South warmer - - - forecast
A south colder by 4 °C or more can push foehn across the passes.
Visp no foehn 3/5
as of 21:10
Direction at Gütsch (90-240°) 149° Direction on site 253° Wind or gust 14 km/h Humidity below the limit 42.1 % Potential temperature -5 K Sion no foehn 3/5
as of 21:10
Direction at Gütsch (90-240°) 149° Direction on site 274° Wind or gust 10.4 km/h Humidity below the limit 37.5 % Potential temperature -5 K Aigle no foehn 2/5
as of 21:10
Direction at Gütsch (90-240°) 149° Direction on site 139° Wind or gust 2.9 km/h Humidity below the limit 82 % Potential temperature -13.7 K The other foehn valleys
Five criteria must hold together. Four out of five is not a foehn.
The wind in the Rhone valley Viège → Evionnaz
down-valley wind light drainage valley breeze
No established down-valley wind on the valley floor right now.
Binn and Jeizinen: why they are not in the strip
Foehn works down the valley: the chain says more than one station.
Neutral
↑ Southerly flow ↓ Northerly flow Southerly flow Northerly flow
It often picks up there without ever coming down into the Rhone valley.
Neutral
- - - Valley mixed - - - Cold air on the floor
Above 0.75 the foehn can reach the ground; below 0.38 it stays above you.
Rain in Ticino Locarno / Sion
0.0mm
Neutral
Locarno (south) Sion (north)
Rain in the south and dry here: the air comes back down dry and warm.
Foehn signature at Sion Sion
gust Temperature Humidity - - - forecast
All three must move together. One on its own is not enough.
Forecasts: Open-Meteo. On Lugano − Zürich and Visp − Evionnaz the solid part comes from MeteoSwiss measurements. On the other graphs it comes from the model: no source covers Domodossola, and a 700 hPa wind cannot be measured from the ground.