By Kristina Pydynowski, AccuWeather senior meteorologist
June 18,2017, 3:55:47PM,EDT
Steamy air surging into the northeastern United States will cause the risk for flooding downpours and severe thunderstorms to ramp up Sunday night into Monday.
With humid air pouring northward, showers and thunderstorms will dot parts of the mid-Atlantic and New England this Father's Day.
There may be a few instances of flash flooding and damaging winds, though the risk for severe weather will be greatest from the eastern Great Lakes to the Tennessee Valley on Sunday afternoon and evening.
Sunday night into Monday, the danger to lives and property will increase elsewhere in the Northeast.
“A concerning weather pattern is developing across the Northeast,” AccuWeather Senior Meteorologist Dave Samuhel said.
“Abundant moisture is already flowing northward out of the Gulf of Mexico and Caribbean and will be reinforced by a flow straight from the deep tropics,” he said. “Meanwhile, a strengthening cold front will very slowly cross the Northeast Sunday night through Monday night.”
These ingredients will combine to create widespread heavy downpours across most of the Northeast, according to Samuhel.
The severe weather later on Sunday will transition to a band of slow-moving heavy rain and embedded thunderstorms overnight. This line will crawl to and across the central and southern Appalachians into Monday.
Despite a dry start to the month, downpours returned this week and have left the ground in many areas overly saturated. Johnstown, Pennsylvania, was inundated with more than 4 inches of rain Thursday into Friday.
An additional 1-2 inches of rain Sunday night into Monday with locally higher amounts may quickly cause low-lying and poor drainage areas to flood and bring smaller streams out of their banks.
Flood-related watches, warnings
Northeastern US interactive radar
Storms in eastern half of US may foul Father's Day outings while heat builds in Southwest
Anyone extending their weekend camping trip by a day will want to prepare to move to higher ground.
“There is a severe weather threat as well in the Northeast,” Samuhel said. “Due to strengthening winds aloft, damaging winds cannot be ruled out.”
The severe weather danger will be greatest east of the Appalachians on Monday afternoon and evening.
The threat zone will stretch from Roanoke, Virginia, to Washington, D.C.; Philadelphia and Harrisburg, Pennsylvania; New York City and Albany, New York; Hartford, Connecticut; Springfield, Massachusetts; and Brattleboro, Vermont.
In addition to damaging winds, there can be an isolated tornado and a few hail reports.
“But flooding will be the main overall threat,” Samuhel said.
While the initial line of thunderstorms can produce damaging winds, additional downpours may follow and repeat over the same areas into Monday night.
Remember to never walk or drive across a flooded road. A mere 12 inches of rushing water can carry away a small car. Only 6 inches is needed to knock over an adult.
Even where flooding does not ensue throughout the Northeast, slow travel may result on the roads and in the air. Downpours will create hazards for motorists by reducing visibility and heightening the risk of vehicles hydroplaning when traveling at highway speeds.
Those with outdoor plans will face possible postponements. The stormy weather threatens to interfere with the Major League Baseball game in Baltimore on Monday evening between the Orioles and Cleveland Indians.
Setting the stage for the severe thunderstorms will be the warm and steamy air surging across the Eastern Seaboard. With the thunderstorms not expected until the evening hours, vacationers will be flocking to the mid-Atlantic beaches to beat the warmth. However, swimmers will face the continued danger of rip currents.
The passage of the cold front will allow less humid air to usher into the Northeast on Tuesday. However, spottier showers and thunderstorms may still create headaches for those with outdoor plans into at least midweek.