qBands may be
as long as 500 km (300 mi) usually about 300-500 km (180-300 mi) in advance of cold fronts.
qStrong
vertical wind shear is essential to the development of these prefrontal waves as it ensures that updrafts will be positioned ahead of the downdrafts.
qThis feeds
moisture into the system which is also aided by gust front propagation ahead of the situation.
q