Every state and territory is forecast to be affected by a northwest cloudband that will stretch nearly 4000km across the country this week. Northwest cloudbands form when warm, moist tropical air originating over the Indian Ocean moves poleward and is forced to rise over colder air in the mid-latitudes, before connecting with a cold front that drags the system eastwards. Southern Australia relies on northwest cloud bands to replenish soil moisture during winter crops. They generally occur betwee