ANKARA - Turkish Airlines canceled 142 flights to and from Istanbul and warned of further disruption in coming days as the city braced on Wednesday for heavy snow.Many of the canceled flights were domestic, but routes to European and Middle Eastern airports including Hamburg, Munich, Milan and Tehran were also hit."The light snow that has been forecast around Istanbul on 30 December is expected to increase in severity on 31 December," a statement on the company's website read."For this reason, some journeys from Istanbul Ataturk and Sabiha Gokcen airports are canceled and it is likely that there will be more weather-related problems on the same days."Snow warnings were also issued by the Istanbul Governor's Office, warning residents against going outside unless necessary, Hurriyet Daily News reported. Snowfall is expected to begin on Wednesday and continue until Jan. 2.More than 1,000 snow-clearing vehicles and other heavy machinery were on standby to try to keep the city's easily clogged road networks open, the Governor's office added.