It will need to be pretty horrendous before they would consider closing the pistes. The winds would need to be A LOT more severe that 15 - 17km/h I can assure you. Even "usual" blizzards wouldn't close the pistes as this happens fairly often during periods of heavy snow. You wouldn't however, want to go off-piste without checking with the local guides office because lots of fresh snow also means avalanche risk! But because the pistes get groomed every day there is little or no risk of ...
It will need to be pretty horrendous before they would consider closing the pistes. The winds would need to be A LOT more severe that 15 - 17km/h I can assure you. Even "usual" blizzards wouldn't close the pistes as this happens fairly often during periods of heavy snow. You wouldn't however, want to go off-piste without checking with the local guides office because lots of fresh snow also means avalanche risk! But because the pistes get groomed every day there is little or no risk of avalanches on the "tourist" slopes.
You may have a particularly cold and blowy days skiing if the weather is bad, but i doubt that they would close the pistes and shut down the ski lifts etc.
They may temporarily shut down the gondolas but you will still be able to use the t-bar, button and some of the ski lifts (not gondolas) which will allow you to carry on skiing.