Foehn chart for the Alps
The forecasted pressure gradient (unit hectopascal, hPa) between Bolzano in northern Italy and Innsbruck in Austria shows the strength of foehn winds over the Alps. If we have a positive pressure gradient, that means the surface pressure in Innsbruck is lower than in Bolzano, south foehn comes up in the austrian Alps (wind from south). The intensity of foehn winds increases with larger pressure gradients.
Empirically we need at least a pressure gradient of 4 hPa for the breakthrough of foehn winds in most alpine valleys and at least 8 hPa for the breakthrough in the adjacent lowland.
The forecast is based on model output statistics (MOS) by Meteomedia and is updated every hour.