Tropical Rainstorm Debby triggering torrential downpours, Appalachian flooding
As Debby accelerates over the interior northeastern United States, torrential rain will ease drought in some areas but bring flash flooding of urbn areas and small streams as well as major river flooding.
AccuWeather Flooding Expert Alex Sosnowski details the major risk of flooding as Debby continues to barrel across the Northeastern U.S. Several parts of the region are receiving months worth of rain.
After gathering more moisture from the Atlantic earlier this week along the Carolina coast, Debby has raced across the interior northeastern United States, where it continued to unload rain heavy enough to trigger flooding in some areas and raise the possibility of a few tornadoes in others, AccuWeather meteorologists say.
Debby tracked inland over North Carolina and Virginia on Thursday before swinging across Pennsylvania on Friday morning and then upstate New York on Friday afternoon.
Debby transitioned to what AccuWeather meteorologists call a tropical rainstorm early Friday morning. This designation intends to continue to raise public awareness of ongoing impacts that may be damaging and life-threatening.
Debby's greatest ongoing threat: Flooding rain
Only Debby's increasing speed will be somewhat of a limiting factor for rainfall, which will range from 2 to perhaps 8 inches in a large part of Pennsylvania and central and eastern upstate New York, western New England and part of southern Quebec. Much of the rain, which is equivalent to the historical average of all of August in some cases, will pour down in a matter of hours.
Much of the interior Northeast will be at high risk to lives and property from Debby, largely due to the travel impacts from heavy rain and the likelihood of flash flooding and river flooding.
"In many areas of the Northeast, much of the rain will not be absorbed by the landscape very well and quickly run off into basements, catch basins, small streams and then the larger rivers," AccuWeather Senior Director of Forecast Operations Dan DePodwin said.
The town of Westfield, Pennsylvania, located in the north-central part of the state, was blasted by flash flooding on Friday. The flooding swept away numerous structures and vehicles and prompted swift water rescues.
It is possible that additional flash flooding will quickly evolve into more life-threatening situations in some communities in the interior Northeast.
Flooding in urban areas and along small streams is a certainty as the heaviest rain pushes into northern New York, northern New England, and southern Quebec into Friday night. Motorists should be prepared for flooded roads or portions of roads that may have been washed out or filled with gravel and other debris in hilly areas.
Summer-long drought conditions, for example, in parts of western Virginia and West Virginia may negate some of the rain's effects. However, even in drought locations, enough rain may fall to lead to at least some incidents of urban flooding and rapid rises on small streams.
Some areas that have been repeatedly hit by flooding this summer, such as parts of northeast New York, Vermont and New Hampshire, could be hit hard again.
Farther to the east, in the Interstate 95 corridor from Philadelphia, New York City and Boston, the main threats from Debby will be associated with flash urban flooding, storm surge flooding, strong wind gusts and even tornadoes.
Washington, D.C., was temporarily under a tornado warning as a remnant band of intense downpours and gusty thunderstorms swung through the metro area during the morning rush hour on Friday.
Strong winds, tornadoes a threat in part of interior Northeast
With Debby to track inland, winds and tropical air will kick up on the storm's eastern flank and cause trouble.
Strong south-southeast winds will expand as Debby moves northward. Gusts during and outside of thunderstorms will range from 40-60 mph from parts of the Appalachians to the Atlantic coast with an AccuWeather Local StormMax™ gust of 70 mph. The StormMax is most likely on the higher peaks in the Presidential Range in northern New England and along the New England coast.
"The combination of tropical-storm-force winds will have trees bobbing and tipping in the saturated soil, and a number may topple over that can lead to property damage and power outages," AccuWeather Meteorologist Brandon Buckingham said.
Even though Debby is likely to transition to more of a non-tropical system, it will retain enough tropical characteristics and bands of thunderstorms, especially near and east of the storm center for a time.
Because of this brief tornadoes may be spawned.
Some of the tornadoes could be wrapped in rain, making it difficult to see them approaching. Where these occur along the coast, waterspouts are also possible.
Debby to draw in cooler, less humid air in its wake
Debby will become intertwined with a non-tropical storm approaching from the Upper Midwest late this week.
The pair of systems will then speed off to the northeast into southern Canada this weekend. West to northwest breezes in the wake of the storm duo will then draw in much cooler and less humid air across the Northeast. It may take until Saturday night or Sunday for that less humid air to reach the Atlantic coast.
River flooding to continue in Debby's wake
The weather will improve from northwest to southeast across the region this weekend. However, some may be nervously watching river levels.
It often takes several days after a heavy rain event for the larger rivers to fully respond to the runoff. Because of the amount of rain that is forecast to fall from Debby and earlier downpours, some rivers in the region may experience moderate to major flooding this weekend into early next week.
Those living along or having commercial or agricultural property along flood-prone rivers without levee protection may need to take preventative action.
Want next-level safety, ad-free? Unlock advanced, hyperlocal severe weather alerts when you subscribe to Premium+ on the AccuWeather app. AccuWeather Alerts™ are prompted by our expert meteorologists who monitor and analyze dangerous weather risks 24/7 to keep you and your family safer.
Report a Typo
