From Weather Underground

Deep tropical moisture will continue to surge north into the eastern U.S. ahead of an area of low pressure in the Gulf of Mexico, bringing days of rainfall and the threat of flash flooding.

This tropical moisture plume is being tapped from the western Caribbean Sea by southerly winds around the western periphery of the Bermuda high and a broad area of low pressure in the Gulf of Mexico.

Add in a stalling frontal system draped over the mid-Atlantic states the tropical moisture plume will intersect and you have a formula for rounds of showers and thunderstorms in much of the East over the next several days.

Scattered showers and thunderstorms with locally heavy downpours currently stretch from Florida into the South and northward into the mid-Atlantic states.

Widespread rainfall totals of 1 to 3 inches are anticipated throughout the Southeast, with locally higher amounts in heavier thunderstorms, into this weekend.

This tropical moisture pipeline will fuel downpours that result in rainfall totals of 3 to 5 from parts of North Carolina into New Jersey.

Rainfall Forecast
Although this rain is beneficial for much of the Southeast, there could be pockets of localized flash flooding, especially in portions of the mid-Atlantic where moderate to heavy rainfall has already been observed over the past few days.

In the Washington, D.C. and Baltimore area 2 to 3 inches of rainfall has already fallen since Saturday and additional rounds of heavy rainfall will increase the threat of flash flooding.

This wet pattern will last until at least early next week, especially across the Southeast. The mid-Atlantic and Northeast will likely experience drier conditions by next Tuesday.

Needed-Rainfall in the Southeast

This rainfall is much-needed in central and southern Florida, as well as parts of Georgia and South Carolina, where drought conditions have recently developed.

As of May 8, more than 26 percent of the Sunshine State was in moderate drought, with a portion of South Florida in severe drought, according to the U.S. Drought Monitor.

Thirty percent of Georgia and roughly one-quarter of South Carolina, mainly in the southern parts of each state, were in drought.

Drought conditions as of May 8, 2018.
(U.S. Drought Monitor)
Miami only measured 0.37 inches of rainfall in February, 1.88 inches below average for the month. This dry trend was exacerbated in March, when Miami only picked up 0.19 inches, compared to the average rainfall for March – 3 inches.

This dry pattern began to shift in late April in parts of Florida, but locations such as Fort Lauderdale and Naples remained more than 6 inches below average year-to-date as of last Friday. But there appears to be hope for a wetter pattern as the wet season commences.

For more on this story go to: https://www.wunderground.com/news/2018-05-16-heavy-rain-east-tropical-moisture-mid-may