HLSLWX DCZ001-MDZ003>006-011-013-014-016>018-503>508-VAZ031-039-040-050>057-501-502-505-506-WVZ053-042045- Tropical Storm Isaias Local Statement Intermediate Advisory Number 29A National Weather Service Baltimore MD/Washington DC AL092020 840 AM EDT Tue Aug 4 2020 This product covers Eastern West Virginia, Central and Western Maryland, Northern and Northwestern Virginia, and District of Columbia **TROPICAL STORM ISAIAS QUICKLY APPROACHING SOUTHERN MARYLAND. LIFE THREATENING FLASH FLOODING...STRONG WINDS AND RISK OF TORNADOES THIS MORNING** NEW INFORMATION --------------- * CHANGES TO WATCHES AND WARNINGS: - None * CURRENT WATCHES AND WARNINGS: - A Tropical Storm Warning is in effect for Anne Arundel, Arlington/Falls Church/Alexandria, Calvert, Carroll, Central and Southeast Howard, Central and Southeast Montgomery, Charles, District of Columbia, Fairfax, King George, Northern Baltimore, Northwest Harford, Northwest Howard, Northwest Montgomery, Prince Georges, Prince William/Manassas/Manassas Park, Southeast Harford, Southern Baltimore, Spotsylvania, St. Marys, and Stafford * STORM INFORMATION: - About 80 miles south of Washington DC or about 110 miles south of Baltimore MD - 37.7N 76.8W - Storm Intensity 70 mph - Movement North-northeast or 25 degrees at 33 mph SITUATION OVERVIEW ------------------ Tropical Storm Isaias quickly approaching St. Mary`s County and will exit the Chesapeake Bay by midday. Life-threatening flash flooding of small streams and creeks is likely today as rainfall associated with Isaias continues to spread northward. Widespread rainfall totals of 3 to 6 inches are expected with locally higher amounts possible. The highest amounts are expected over the I-95 corridor through early afternoon. Tropical storm force winds are expected over southern Maryland. Tree damage and power outages are possible in this area. There is also a risk of isolated tornadoes across southern Maryland through this morning. Moderate coastal flooding is also likely along the western shores of the Chesapeake Bay and at Washington DC Southwest Waterfront today. Minor coastal flooding is likely along other tidal waters. POTENTIAL IMPACTS ----------------- * FLOODING RAIN: Potential impacts from the flooding rain are still unfolding along and east of I-95. Remain well guarded against life-threatening flood waters having extensive impacts. If realized, these impacts include: - Major rainfall flooding may prompt many evacuations and rescues. - Rivers and tributaries may rapidly overflow their banks in multiple places. Small streams, creeks, canals, arroyos, and ditches may become dangerous rivers. In mountain areas, destructive runoff may run quickly down valleys while increasing susceptibility to rockslides and mudslides. Flood control systems and barriers may become stressed. - Flood waters can enter many structures within multiple communities, some structures becoming uninhabitable or washed away. Many places where flood waters may cover escape routes. Streets and parking lots become rivers of moving water with underpasses submerged. Driving conditions become dangerous. Many road and bridge closures with some weakened or washed out. * TORNADOES: Potential impacts from tornadoes are still unfolding across southern Maryland. Remain well braced against a tornado event having possible limited impacts. If realized, these impacts include: - The occurrence of isolated tornadoes can hinder the execution of emergency plans during tropical events. - A few places may experience tornado damage, along with power and communications disruptions. - Locations could realize roofs peeled off buildings, chimneys toppled, mobile homes pushed off foundations or overturned, large tree tops and branches snapped off, shallow-rooted trees knocked over, moving vehicles blown off roads, and small boats pulled from moorings. Elsewhere across Eastern West Virginia, Central and Western Maryland, Northern and Northwestern Virginia, and District of Columbia, little to no impact is anticipated. * WIND: Potential impacts from the main wind event are now unfolding across southern Maryland. Remain well sheltered from dangerous wind having significant impacts. If realized, these impacts include: - Some damage to roofing and siding materials, along with damage to porches, awnings, carports, and sheds. A few buildings experiencing window, door, and garage door failures. Mobile homes damaged, especially if unanchored. Unsecured lightweight objects become dangerous projectiles. - Several large trees snapped or uprooted, but with greater numbers in places where trees are shallow rooted. Several fences and roadway signs blown over. - Some roads impassable from large debris, and more within urban or heavily wooded places. A few bridges, causeways, and access routes impassable. - Scattered power and communications outages, but more prevalent in areas with above ground lines. Elsewhere across Eastern West Virginia, Central and Western Maryland, Northern and Northwestern Virginia, and District of Columbia, little to no impact is anticipated. * SURGE: Potential impacts from the main surge event are now unfolding along the Tidal Potomac River and Chesapeake Bay. Remain well away from locally hazardous surge having moderate impacts. If realized, these impacts include: - Localized inundation with storm surge flooding mainly along immediate shorelines and in low-lying spots, or in areas farther inland near where higher surge waters move ashore. - Sections of near-shore roads and parking lots become overspread with surge water. Driving conditions dangerous in places where surge water covers the road. - Moderate beach erosion. Heavy surf also breaching dunes, mainly in usually vulnerable locations. Strong rip currents. - Minor to locally moderate damage to marinas, docks, boardwalks, and piers. A few small craft broken away from moorings. PRECAUTIONARY/PREPAREDNESS ACTIONS ---------------------------------- OTHER PREPAREDNESS INFORMATION: If you are prone to flooding or in an area under a storm surge watch or warning, be prepared for the possibility of a quick and dramatic rise in water levels. If a tornado warning is issued for your area, quickly move to the safest place within your shelter. Protect your head and body. * ADDITIONAL SOURCES OF INFORMATION: - For information on appropriate preparations see ready.gov - For information on creating an emergency plan see getagameplan.org - For additional disaster preparedness information see redcross.org NEXT UPDATE ----------- The next local statement will be issued by the National Weather Service in Baltimore MD/Washington DC around 1130 AM EDT, or sooner if conditions warrant. $$ $$