DANBURY — The National Weather Service confirmed that weather conditions on Thursday amounted to a blizzard in Danbury and two other southwestern Connecticut cities. In Danbury, conditions were measured at the Danbury Municipal Airport and were reported to reach blizzard criteria from 10:53 a.m. to 3:53 a.m. The NWS said the weather sensor at the airport failed, but snow was verified by radar. The official definition of a blizzard includes sustained winds 35 miles per hour or faster, considerable falling or blowing snow and visibility reduced to less than a quarter of a mile.