1.   As exceptionally chilly air arrives aloft at high altitudes, the atmosphere will become unstable, increasing the risk for isolated weak tornadoes or coastal waterspouts.

2.   A weak tornado touched down near Fresno, Calif., on Thursday as a severe thunderstorm rumbled across the San Joaquin Valley.

3.   Several weak tornadoes were noted in Arkansas on Thursday, although witnesses said no thunder could be heard.

4.   The National Weather Service concluded that a weak tornado was imbedded in the storm as it moved through the county.

5.   The roughness associated with tall buildings may interfere with the development of the circulation of weak tornadoes.

6.   There is some indication that the roughness associated with tall buildings or undulating terrain may interfere with the establishment of the circulation of weak tornadoes.

7.   There is some indication that the roughness associated with tall buildings interferes with the establishment of the circulation of weak tornadoes.

8.   A weak tornado may have caused damage in Nassau County that included windows blown out of a school, the National Weather Service said.

9.   One strong storm there produced a weak tornado.