If you are headed to Truckee or Tahoe or Reno this weekend, you should carry chains. Caltrans is alerting motorists traveling over the Donner or Echo Summits tonight and tomorrow to be prepared for travel delays. The first of a series of winter storms, including high winds, is predicted to arrive this evening and continue through tomorrow, resulting in winter driving conditions. A second, less intense storm is predicted to arrive Sunday evening and last into Monday morning. The National Weather Service has issued a Winter Storm Warning for the Sierra and eastern Sacramento Valley. Snow accumulations of one to two feet are predicted for summit passes. High winds may create white-out, low visibility conditions over the summits. Heavy rains in valley and foothill areas will result in wet, slippery surfaces and potential roadway flooding.