In this survey, we recognize synoptic patterns which lead to comprehensive and heavy rainfall from March 16th-31st, 2019 in Iran. Therefore, data of earth and the upper atmosphere have been used. The earth data include precipitation amount of stations in the flood zones of Iran. The upper atmosphere data consist of patterns in ECMWF. Three heavy rainfall systems heavy rains in Iran, have been examined. Results shows that the establishment of Cut-off Low plays an important role in heavy rains. In the first system which is stimultaneous with the flash flood of Golestan, a transferring of dynamic low-pressure of system and its cyclonic circulation make rainfall start. The speed of circulation system was reducing, when it established over Caspian Sea and under the influence of pressure Gradiant, humid currents in the low-level of atmosphere have been moved to south and east side of the coast. In this area, heavy rains generally take place in a clod front which transports a large amount of humidity from the sea to Golestan with increasing perssur Gradient between Siberian high and Cut-off Low pressure under the influence of convection currents. A merger between low-pressur of Sudanese and Mediterranean is the main factor for the second and third systems. Heavy rains in the west side of Iran happen, because of an establishing of blocking system in the middle-level and making Cut-off Low which lasts for a few days, with transportation of humidity from various sources.