Winter Storm Warning in Effect: Heavy snow possible throughout Mercer County. Total snow accumulations of 4 to 8 inches. Snow is expected to start 10 p.m. Tuesday to 4 a.m.Thursday. A Winter Storm Warning for snow means severe winter weather conditions will make travel hazardous. The State of New Jersey declared a State of Emergency beginning at 8 p.m. Tuesday. This page will be updated as information develops.