* WHAT. Southwest winds 10 to 15 kt with gusts up to 20 kt. * WHERE. Tidal Potomac River from Key Bridge to Cobb Island MD. * WHEN. Until midnight EDT tonight. * IMPACTS. Conditions will be hazardous to small craft.

* WHAT. Southwest winds 10 to 20 kt with gusts up to 25 kt. * WHERE. Chesapeake Bay and adjoining estuaries north of Smith Point VA, and Tidal Potomac from Cobb Island MD to Smith Point VA. * WHEN. Until 6 AM EDT Monday. * IMPACTS. Conditions will be hazardous to small craft.

* WHAT. Southwest winds 10 to 20 kt with gusts up to 25 kt. * WHERE. Chesapeake Bay and adjoining estuaries north of Smith Point VA, and Tidal Potomac from Cobb Island MD to Smith Point VA. * WHEN. Until 6 AM EDT Monday. * IMPACTS. Conditions will be hazardous to small craft.

* WHAT. Southwest winds 10 to 15 kt with gusts up to 20 kt. * WHERE. Tidal Potomac River from Key Bridge to Cobb Island MD. * WHEN. Until midnight EDT tonight. * IMPACTS. Conditions will be hazardous to small craft.

* WHAT. Heat index values up to 107 expected. * WHERE. Portions of central, north central, northeast, northern and southern Maryland, The District of Columbia and central, northern and northwest Virginia. * WHEN. Until 7 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. * WHERE. Portions of northern Delaware, central, northern, northwest, and southern New Jersey, and southeast Pennsylvania. * WHEN. Until 8 PM EDT this evening. * IMPACTS. Heat related illnesses increase significantly during extreme heat and high humidity events.

* WHAT. Heat index values up to 100. * WHERE. Portions of central and southern Delaware, northeast Maryland, and southern New Jersey. * WHEN. Until 8 PM EDT this evening. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. For the first Small Craft Advisory, southwest winds 10 to 15 kt with gusts up to 20 kt. For the second Small Craft Advisory, northwest winds 10 to 15 kt with gusts up to 20 kt expected. * WHERE. Tidal Potomac River from Key Bridge to Cobb Island MD. * WHEN. For the first Small Craft Advisory, until midnight EDT tonight. For the second Small Craft Advisory, from 6 AM to 6 PM EDT Monday. * IMPACTS. Conditions will be hazardous to small craft.

* WHAT. West winds 10 to 20 kt with gusts up to 25 kt. * WHERE. Chesapeake Bay and adjoining estuaries north of Smith Point VA, and Tidal Potomac from Cobb Island MD to Smith Point VA. * WHEN. Until 6 PM EDT Monday. * IMPACTS. Conditions will be hazardous to small craft.

* WHAT. Heat index values between 95 and 100. * WHERE. A portion of central Pennsylvania. * WHEN. This afternoon. * IMPACTS. High heat and humidity may cause heat illnesses.

THE NATIONAL WEATHER SERVICE HAS ISSUED SEVERE THUNDERSTORM WATCH 449 IN EFFECT UNTIL 10 PM EDT THIS EVENING FOR THE FOLLOWING AREAS IN PENNSYLVANIA THIS WATCH INCLUDES 33 COUNTIES IN CENTRAL PENNSYLVANIA ADAMS BEDFORD BLAIR CAMBRIA CAMERON CENTRE CLEARFIELD CLINTON COLUMBIA CUMBERLAND DAUPHIN ELK FRANKLIN FULTON HUNTINGDON JUNIATA LANCASTER LEBANON LYCOMING MCKEAN MIFFLIN MONTOUR NORTHUMBERLAND PERRY POTTER SCHUYLKILL SNYDER SOMERSET SULLIVAN TIOGA UNION WARREN YORK THIS INCLUDES THE CITIES OF ALTOONA, BEDFORD, BERWICK, BLOOMSBURG, BRADFORD, CARLISLE, CHAMBERSBURG, CLEARFIELD, COUDERSPORT, DANVILLE, DUBOIS, EMPORIUM, GETTYSBURG, HARRISBURG, HERSHEY, HUNTINGDON, JOHNSTOWN, LANCASTER, LAPORTE, LEBANON, LEWISBURG, LEWISTOWN, LOCK HAVEN, MANSFIELD, MCCONNELLSBURG, MIFFLINTOWN, MOUNT UNION, NEWPORT, POTTSVILLE, RENOVO, RIDGWAY, SELINSGROVE, SHAMOKIN, SOMERSET, ST. MARYS, STATE COLLEGE, SUNBURY, WARREN, WAYNESBORO, WELLSBORO, WILLIAMSPORT, AND YORK.