* WHAT. Heat index values up to 104 expected. * WHERE. In Maryland, Washington County. In Virginia, Shenandoah, Frederick VA, Page, Warren and Clarke Counties. In West Virginia, Morgan, Berkeley and Jefferson Counties. * WHEN. From noon today to 8 PM EDT this evening. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses to occur.

* WHAT. Heat index values up to 108 expected. * WHERE. In Maryland, Central and Southeast Montgomery and Central and Southeast Howard Counties. In Virginia, Fairfax, Stafford, Spotsylvania, Southern Fauquier and Central and Southeast Prince William/Manassas/Manassas Park Counties. * WHEN. From noon today to 8 PM EDT this evening. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses to occur.

* WHAT. Dangerously hot conditions with heat index values up to 110 expected. * WHERE. The District of Columbia, Anne Arundel, Calvert, Cecil, Charles, Prince Georges, Southeast Harford, Southern Baltimore, and St. Mary's Counties in Maryland, and Arlington/Falls Church/Alexandria and King George Counties in Virginia. * WHEN. From noon today to 8 PM EDT this evening. * IMPACTS. Extreme heat and humidity will significantly increase the potential for heat-related illnesses, particularly for those working or participating in outdoor activities.

* WHAT. Heat index values up to 106 expected. * WHERE. Portions of central and northern Maryland, and central and northern Virginia. * WHEN. From noon today to 8 PM EDT this evening. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses to occur.

* WHAT. Heat index values up to 103. * WHERE. Portions of central, north central and northern Maryland and central, northern and northwest Virginia. * WHEN. Until 8 PM EDT this evening. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses to occur.

* WHAT. Heat index values up to 105. * WHERE. In Maryland, Central and Southeast Montgomery and Central and Southeast Howard Counties. In Virginia, Fairfax, Stafford, Spotsylvania, Southern Fauquier and Central and Southeast Prince William/Manassas/Manassas Park Counties. * WHEN. Until 8 PM EDT this evening. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses to occur.

* WHAT. Dangerously hot conditions with heat index values up to 106. * WHERE. Portions of central, northeast, northern and southern Maryland, The District of Columbia and central and northern Virginia. * WHEN. Until 8 PM EDT this evening. * IMPACTS. Extreme heat and humidity will significantly increase the potential for heat related illnesses, particularly for those working or participating in outdoor activities.

SMWLWX The National Weather Service in Sterling Virginia has issued a * Special Marine Warning for. Chesapeake Bay from Pooles Island to Sandy Point MD. Chesapeake Bay north of Pooles Island MD. Chester River to Queenstown MD. Patapsco River including Baltimore Harbor. * Until 545 PM EDT. * At 448 PM EDT, strong thunderstorms were located along a line extending from near Aberdeen Proving Ground to near Middle River to near Fort Smallwood Park, moving east at 30 knots. HAZARD. Wind gusts 34 knots or greater. SOURCE. Radar indicated. IMPACT. Boaters in small craft could be thrown overboard by suddenly higher winds and waves capsizing their vessel. * Locations impacted include. North Point State Park, Fort Smallwood Park, Hart Miller Island, Gunpowder River, Bodkin Point, Tolchester Beach, Worton Point, Pooles Island, and Sevenfoot Knoll.

THE NATIONAL WEATHER SERVICE HAS EXTENDED SEVERE THUNDERSTORM WATCH 590 TO INCLUDE THE FOLLOWING AREAS UNTIL 9 PM EDT THIS EVENING THIS WATCH INCLUDES THE FOLLOWING ADJACENT COASTAL WATERS CHESAPEAKE BAY FROM POOLES ISLAND TO SANDY POINT MD CHESAPEAKE BAY FROM SANDY POINT TO NORTH BEACH MD PATAPSCO RIVER INCLUDING BALTIMORE HARBOR

* WHAT. South winds around 10 kt with gusts up to 20 kt. * WHERE. Tidal Potomac River from Key Bridge to Cobb Island MD, Chesapeake Bay north of Sandy Point MD, Patapsco River including Baltimore Harbor, Chester River to Queenstown MD, and Patuxent River to Broomes Island MD. * WHEN. From noon today to 8 PM EDT this evening. * IMPACTS. Conditions will be hazardous to small craft.

The Maryland Department of the Environment has issued a Code ORANGE Air Quality Alert Friday 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 Friday for Northern Baltimore. 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 Friday 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 100 to 104. * WHERE. Adams, Cumberland, Dauphin, Franklin, Lancaster, Lebanon, Perry, and York Counties. * WHEN. Until 8 PM EDT this evening. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses.

THE NATIONAL WEATHER SERVICE HAS ISSUED SEVERE THUNDERSTORM WATCH 590 IN EFFECT UNTIL 9 PM EDT THIS EVENING FOR THE FOLLOWING AREAS IN DELAWARE THIS WATCH INCLUDES 3 COUNTIES IN CENTRAL DELAWARE KENT IN NORTHERN DELAWARE NEW CASTLE IN SOUTHERN DELAWARE SUSSEX IN MARYLAND THIS WATCH INCLUDES 4 COUNTIES IN NORTHEAST MARYLAND CAROLINE KENT QUEEN ANNE'S TALBOT IN NEW JERSEY THIS WATCH INCLUDES 13 COUNTIES IN CENTRAL NEW JERSEY MERCER MONMOUTH IN NORTHERN NEW JERSEY HUNTERDON MIDDLESEX SOMERSET IN SOUTHERN NEW JERSEY ATLANTIC BURLINGTON CAMDEN CAPE MAY CUMBERLAND GLOUCESTER OCEAN SALEM IN PENNSYLVANIA THIS WATCH INCLUDES 5 COUNTIES IN SOUTHEAST PENNSYLVANIA BUCKS CHESTER DELAWARE MONTGOMERY PHILADELPHIA THIS INCLUDES THE CITIES OF ATLANTIC CITY, CAMDEN, CENTREVILLE, CHERRY HILL, CHESTERTOWN, DENTON, DEPTFORD, DOVER, DOYLESTOWN, EAST BRUNSWICK, EASTON, EDISON, FLEMINGTON, FREEHOLD, GEORGETOWN, GLASSBORO, HAMMONTON, MEDIA, MILLVILLE, MOORESTOWN, MOUNT HOLLY, NEW BRUNSWICK, NORRISTOWN, NORTH BRUNSWICK TOWNSHIP, OCEAN CITY, PENNSVILLE, PERTH AMBOY, PHILADELPHIA, SAYREVILLE, SOMERSET, TOMS RIVER, TRENTON, WEST CHESTER, AND WILMINGTON.