Subject	thunderstorm
Predicate	be produced at
Object	cold fronts
Modality	Modality Occurrences often 2
Polarity	POSITIVE
Plausibility	0.1849
Neighborhood Sigma	0.1849
Local Sigma	1.0000
Example Sentences	Sentence Occurrences Source thunderstorms are often produced at cold fronts 2 Answers.com Questions