A series of storm systems moved quickly across the lower 48 States until reaching the East Coast as a strong ridge of high pressure over the western Atlantic Ocean blocked their eastward progression. Due in part to this slowdown, severe weather and heavy rainfall occurred in portions of the southern Great Plains, lower Mississippi Valley, Southeast, and mid-Atlantic during April 17-19. Moderate to heavy precipitation (1.5-4 inches) also occurred over the western Great Lakes region, Tennessee and central Ohio Valleys, parts of New England, and northwestern Washington. Light to moderate precipitation (0.5-2 inches) was widespread in the Northwest, eastern Great Basin, northern and southern thirds of the Rockies, northern Plains, and the eastern third of the Nation. Only portions of the Southwest, central Rockies and Plains, and western Corn Belt saw little or no precipitation. Weekly temperatures averaged above-normal for much of the contiguous U.S., except for subnormal readings across the Southeast and western and southern Alaska. Light to moderate precipitation along the southern and southeastern Alaskan Coast and light showers on the windward side of the Hawaiian Islands maintained conditions in both states. Changes were made in Puerto Rico as spotty heavy showers provided some relief to short-term D0 and D1 areas, but where the rains missed, some deterioration occurred.
With near- to record wetness in many parts of the country this winter and in 2018, the April 16 USDM had the lowest percent of area in drought (D1-D4) for