The National Hurricane Center and National Weather Service have issued a Tropical Storm Watches for all counties along and east Interstate 95 Corridor. Tropical storm force winds and gusts could be anywhere from 39 to 73 mph. The highest gusts will likely occur along the Chesapeake Bay into the Delmarva Peninsula and Hampton Roads area.
Isaias has strengthened slightly as of the Sunday 5:00 p.m. advisory, with winds near 70 mph. The center is east of the Florida coast and moving slowly to the north-northwest. Due to the potential of Isaias strengthening to a Hurricane, a Hurricane Watch has been issued for the Southeastern North Carolina coast to Myrtle Beach, South Carolina.
A Flash Flood Watch has been issued for much of the region through Tuesday Evening. The Southern Blue Ridge can expect 2 to 4 inches of rain. The highest amounts will likely be across Central and Northern Virginia and the Upper Delmarva Peninsula, where 3 to 6 inches (locally higher) are possible. This will lead to areas of flash flooding and river flooding. Low lying and poor drainage are at the highest risk for flooding.
Rain will develop across the Lower Mid-Atlantic late Monday afternoon, first across Southern Virginia and the Southern Blue Ridge. Rain will slowly move northward late Monday night into early Tuesday morning across Virginia along with gusty winds along and on the east side of the center.
The heaviest rain is expected to develop late Monday night into the early hours of Monday morning. Most of the heaviest rain will fall on the north and west side of the center. Very heavy rain will continue through mid-afternoon Tuesday before pulling away from the Lower Mid-Atlantic. Some model guidance puts the center of the storm near the I-95 Corridor before moving it into the Central Chesapeake Bay and into the Delmarva Peninsula, while other models are 30 miles to the east.
Depending on the exact location of the center will greatly determine rainfall amounts. There will likely be a sharp cutoff from the heaviest rain totals to only a few inches across the Piedmont and Shenandoah Valley area. Hampton Roads and Eastern North Carolina will be on the “severe” side of the storm. Isolated tornadoes and waterspouts are possible. The strongest wind gusts will occur in bands of thunderstorms that rotate around the center.
As far as wind is considered, the strongest winds will be near and towards the right of the center. Stronger winds along the Chesapeake Bay are possible, with maximum gusts up to 70 mph possible. Most locations in the Greater Hampton Roads area will see wind gusts early Tuesday morning through early to mid-afternoon Tuesday in the range of 45 to 65 mph. Interaction with the jet streak is expected to hold the intensity of the storm higher than what would normally be expected for a post-landfall tropical system. Therefore, little weakening is expected when the center of the storm reaches the Mid-Atlantic.
Along I-95, wind gusts 35 to 45 mph will be possible. It’s important to note that if the system does not slow down and a faster forward motion occurs, winds may be a bit higher, but a shorter duration of high winds can be expected. Right now, we are anticipating a 6 to 8 hour window of the strongest winds to occur from Tuesday morning into the afternoon.
Minor to moderate tidal flooding is likely for locations along the sounds, Atlantic, and Chesapeake Bay as high as 1 to 3 feet above ground level. A slower moving system could greatly increase these levels and will need to be watched very carefully. Due to a full moon occurring on Monday, tides will already be higher than normal. Wave heights along the Chesapeake Bay will range 4 to 8 feet on Tuesday with 8 to 14 feet along the Atlantic Coast. Beach erosion is likely across many locations of the Atlantic.
Due to high winds and heavy rainfall causing saturated ground, there is a moderate to high threat for power outages across a large area, with the highest chance along the Chesapeake Bay, Delmarva Peninsula, and much of Eastern North Carolina. Sustained winds 25 to 35 mph and wind gusts 50 to 65 mph will likely cause downed tree limbs and branches and power lines.