SMWLWX The National Weather Service in Sterling Virginia has issued a * Special Marine Warning for. Tidal Potomac from Indian Head to Cobb Island MD. Tidal Potomac from Key Bridge to Indian Head MD. * Until 715 PM EDT. * At 538 PM EDT, a strong thunderstorm was located over Woodrow Wilson Bridge, moving east at 10 knots. HAZARD. Wind gusts 34 knots or greater and small hail. SOURCE. Radar indicated. IMPACT. Boaters in small craft could be thrown overboard by suddenly higher winds and waves capsizing their vessel. * Locations impacted include. Fort Washington, Gunston Hall, Woodrow Wilson Bridge, Fort Hunt, National Harbor, Mason Neck State Park, and Alexandria.

The Maryland Department of the Environment has issued a Code ORANGE Air Quality Alert Thursday for the Maryland suburban DC region. A Code Orange Air Quality Alert means that air pollution concentrations within the region may become unhealthy for sensitive groups. Sensitive groups include children, people suffering from asthma, heart disease or other lung diseases and the elderly. The effects of air pollution can be minimized by avoiding strenuous activity or exercise outdoors. For more information on ground-level ozone and fine particles visit the web site mde.maryland.gov/programs/air/AirQualityMonitoring/Pages/index.aspx.

The Maryland Department of the Environment has issued a Code ORANGE Air Quality Alert Thursday for the Baltimore City Metro and Annapolis region. A Code Orange Air Quality Alert means that air pollution concentrations within the region may become unhealthy for sensitive groups. Sensitive groups include children, people suffering from asthma, heart disease or other lung diseases and the elderly. The effects of air pollution can be minimized by avoiding strenuous activity or exercise outdoors. For more information on ground-level ozone and fine particles visit the web site mde.maryland.gov/programs/air/AirQualityMonitoring/Pages/index.aspx.

* WHAT. Heat index values up to 107 expected. * WHERE. Portions of central, northeast, northern and southern Maryland, The District of Columbia and central and northern Virginia. * WHEN. From noon to 8 PM EDT Thursday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses to occur.

SVRLWX The National Weather Service in Sterling Virginia has issued a * Severe Thunderstorm Warning for. Southwestern Prince Georges County in central Maryland. Northwestern Charles County in southern Maryland. Southeastern Fairfax County in northern Virginia. The City of Alexandria in northern Virginia. * Until 700 PM EDT. * At 623 PM EDT, a severe thunderstorm was located over Groveton, moving southeast at 15 mph. HAZARD. 60 mph wind gusts and quarter size hail. SOURCE. Radar indicated. IMPACT. Damaging winds will cause some trees and large branches to fall. This could injure those outdoors, as well as damage homes and vehicles. Roadways may become blocked by downed trees. Localized power outages are possible. Unsecured light objects may become projectiles. * Locations impacted include. Alexandria, Annandale, Springfield, Fort Washington, Fort Hunt, Groveton, Huntington, Fort Belvoir, National Harbor, Lincolnia, Lorton, Franconia, Hybla Valley, Newington, Lake Barcroft, I395 and I495 Interchange, West Springfield, Mount Vernon, North Springfield, and Hayfield.

At 639 PM EDT, a severe thunderstorm was located over Fort Hunt, moving southeast at 15 mph. HAZARD. 60 mph wind gusts and quarter size hail. SOURCE. Radar indicated. IMPACT. Damaging winds will cause some trees and large branches to fall. This could injure those outdoors, as well as damage homes and vehicles. Roadways may become blocked by downed trees. Localized power outages are possible. Unsecured light objects may become projectiles. Locations impacted include. Alexandria, Springfield, Fort Washington, Fort Hunt, Groveton, Huntington, Fort Belvoir, National Harbor, Lorton, Franconia, Hybla Valley, Newington, Mount Vernon, Hayfield, and Jefferson Manor.

SVRLWX The National Weather Service in Sterling Virginia has issued a * Severe Thunderstorm Warning for. West central Calvert County in southern Maryland. Southeastern Prince Georges County in central Maryland. Northeastern Charles County in southern Maryland. * Until 715 PM EDT. * At 633 PM EDT, a severe thunderstorm was located near Waldorf, moving southeast at 15 mph. HAZARD. 60 mph wind gusts and quarter size hail. SOURCE. Radar indicated. IMPACT. Damaging winds will cause some trees and large branches to fall. This could injure those outdoors, as well as damage homes and vehicles. Roadways may become blocked by downed trees. Localized power outages are possible. Unsecured light objects may become projectiles. * Locations impacted include. Waldorf, Prince Frederick, Saint Charles, Brandywine, Huntingtown, Hughesville, Baden, Aquasco, Bryantown, Eagle Harbor, and Northwood.

SVRLWX The National Weather Service in Sterling Virginia has issued a * Severe Thunderstorm Warning for. South central Anne Arundel County in central Maryland. Northwestern Calvert County in southern Maryland. Southeastern Prince Georges County in central Maryland. * Until 715 PM EDT. * At 628 PM EDT, a severe thunderstorm was located over Dunkirk, or near Chesapeake Beach, moving south at 10 mph. HAZARD. 60 mph wind gusts and quarter size hail. SOURCE. Radar indicated. IMPACT. Damaging winds will cause some trees and large branches to fall. This could injure those outdoors, as well as damage homes and vehicles. Roadways may become blocked by downed trees. Localized power outages are possible. Unsecured light objects may become projectiles. * Locations impacted include. Chesapeake Beach, Breezy Point, Dunkirk, Huntingtown, Owings, Baden, Aquasco, Friendship, Lower Marlboro, Mount Harmony, and Sunderland.