 Rainbands in advance of warm occluded fronts and warm fronts are associated with weak upward motion , and tend to be wide and stratiform in nature . In an atmosphere with rich low level moisture and vertical wind shear , narrow , convective rainbands known as squall lines generally in the cyclone 's warm sector , ahead of strong cold fronts associated with extratropical cyclones . Wider rain bands can occur behind cold fronts , which tend to have more stratiform , and less convective , precipitation . Within the cold sector north to northwest of a cyclone center , in colder cyclones , small scale , or mesoscale , bands of heavy snow can occur within a cyclone 's comma head precipitation pattern with a width of 32 kilometres ( 20 mi ) to 80 kilometres ( 50 mi ) . These bands in the comma head are associated with areas of frontogensis , or zones of strengthening temperature contrast . Southwest of extratropical cyclones , curved flow bringing cold air across the relatively warm Great Lakes can lead to narrow lake effect snow bands which bring significant localized snowfall . 
