dust storm

These storms are typical in the Great Plains of the United States behind a surface cold front or dry line when the winds are strong and can blow topsoil into the air. The topsoil is most easily blown when it is loose from recent plowing and dry from a lack of rainfall. The National Weather Service (NWS) criterion for a dust storm is winds greater than or equal to 48 kilometers per hour (30 miles per hour) causing blowing dust to reduce visibility to 0.8 kilometers (0.5 miles) or less. When visibility is reduced to 400 meters (0.25 miles) or less, the NWS will issue and advisory to warn motorists that driving conditions are hazardous.