VIENNA (Reuters) -An avalanche in an area of Austria bordering Switzerland has killed four people and a fifth person is missing on an unusually dangerous day in the Alps after heavy snowfall followed by warmer weather, a spokesman for rescue services said on Friday. A separate avalanche earlier on Friday swept down a ski piste at the popular resort of Soelden, where five people had so far been rescued alive, said Patrick Ortler, supervisor of the emergency services control centre in the province of Tyrol where both avalanches happened. One further person caught in the deadly avalanche near the…