Here are some weather hazards to consider when skiing, with a brief explanation of each:

• Unstable snowpack and avalanches. This is the major hazard. I've linked to many of the learning goal pages, which are useful in describing some of the things to beware of:
  • Upside down snow, or higher density snow on top of lower density snow. Two key principles about snow density to keep in mind: (1) the higher the temperature, the higher the density of new snow, and (2) the faster the wind speed, the higher the density of new snow. 
  • Surface hoar, i.e. frost. This forms when there are clear skies (usually at night) and calm winds.
  • Crust layers, which may lead to failure. There is rain crust (rain-on-snow event followed by below-freezing temperatures) and melt/freeze crust (snow surface melts due to above-freezing temperatures then refreezes). Melt/freeze crust is something to think about particularly on south-facing slopes which receive more incoming solar radiation (then known as sun crust).
• Hazardous temperatures and winds, including unseasonably hot or cold conditions and wind exposure. Wind speeds are higher on ridges and mountain tops, and wind chill is important to keep in mind. 

The sources I've listed on the "Useful Links" page (live weather and snow conditions, forecasts) can all help me avoid these hazardous conditions.