Years with a La Niña tend lead to more frequent and unpredictable black ice in New England. It's quite clear in late fall as nights fall below freezing and days are above freezing- nobody salts the roads, so black ice forms nearly every night and melts by noon the next day instead of forming and immediately being salted during colder El Niño years due to temps falling, consistently, below 0C, day and night. Not much science here, just how it is since the black ice is only an issue due to human elements and not due to a meteorological issue.