* WHAT. An extended period of temperatures up to 30 degrees below normal. Very cold wind chills of 0 to 15 degrees below zero. * WHERE. Portions of north-central and western Maryland, northwest and western Virginia, and eastern West Virginia. * WHEN. From 4 AM Monday to 1 PM EST Tuesday. * IMPACTS. The dangerously cold wind chills could cause frostbite on exposed skin in as little as 30 minutes. An extended period of well below freezing temperatures could cause pipes to rupture.

* WHAT. An extended period of temperatures up to 30 degrees below normal. Very cold wind chills as low as 15 degrees below zero. * WHERE. Portions of north central and western Maryland, northwest and western Virginia, and the eastern panhandle of West Virginia. * WHEN. From 4 AM Monday to 1 PM EST Tuesday. * IMPACTS. The dangerously cold wind chills could cause frostbite on exposed skin in as little as 30 minutes. An extended period of well below freezing temperatures could cause pipes to rupture.

* WHAT. Very cold wind chills as low as 5 degrees below zero expected. * WHERE. Portions of DC, central, northeast, and northern Maryland, and central, northern, and northwest Virginia. * WHEN. From 7 PM this evening to 10 AM EST Tuesday. * IMPACTS. Frostbite and hypothermia will occur if unprotected skin is exposed to these temperatures. Wind chill values can lead to hypothermia with prolonged exposure. * ADDITIONAL DETAILS. To prevent water pipes from freezing, wrap or drain or allow them to drip slowly.

* WHAT. Very cold wind chills as low as 10 degrees below zero expected. * WHERE. Carroll and Frederick MD Counties. * WHEN. Until 1 PM EST Tuesday. * IMPACTS. The dangerously cold wind chills could cause frostbite on exposed skin in as little as 30 minutes. An extended period of well below freezing temperatures could cause pipes to rupture.

* WHAT. An extended period of temperatures up to 30 degrees below normal. Very cold wind chills as low as 15 degrees below zero. * WHERE. Portions of north central and western Maryland, northwest and western Virginia, and eastern and panhandle West Virginia. * WHEN. Until 1 PM EST Tuesday. * IMPACTS. The dangerously cold wind chills could cause frostbite on exposed skin in as little as 30 minutes. An extended period of well below freezing temperatures could cause pipes to rupture.

* WHAT. For the Small Craft Advisory, northwest winds 10 to 20 kt with gusts up to 30 kt and waves 2 to 4 ft. For the Freezing Spray Advisory, moderate accumulation of freezing spray. * WHERE. Chesapeake Bay from Pooles Island MD to Smith Point VA, Tidal Potomac from Cobb Island MD to Smith Point VA, Chester River to Queenstown MD, Eastern Bay, Choptank River to Cambridge MD and the Little Choptank River, and Tangier Sound and the inland waters surrounding Bloodsworth Island. * WHEN. For the Small Craft Advisory, until 5 AM EST Tuesday. For the Freezing Spray Advisory, until 6 PM EST this evening. * IMPACTS. Operating a vessel in freezing spray is hazardous. Freezing spray may render mechanical and electronic components inoperative. Ice accretion on decks and superstructures may result in some loss of stability. Conditions will be hazardous to small craft.

* WHAT. For the Small Craft Advisory, northwest winds 10 to 20 kt with gusts up to 25 kt. For the Freezing Spray Advisory, moderate accumulation of freezing spray. * WHERE. Chesapeake Bay from Pooles Island MD to North Beach MD, Tidal Potomac from Cobb Island MD to Smith Point VA, Chester River to Queenstown MD, and Eastern Bay. * WHEN. For the Small Craft Advisory, until 5 AM EST Tuesday. For the Freezing Spray Advisory, until 6 PM EST this evening. * IMPACTS. Operating a vessel in freezing spray is hazardous. Freezing spray may render mechanical and electronic components inoperative. Ice accretion on decks and superstructures may result in some loss of stability. Conditions will be hazardous to small craft.

* WHAT. Very cold wind chills as low as 10 degrees below zero. * WHERE. Portions of north central and western Maryland, northwest and western Virginia, and eastern West Virginia. * WHEN. Until 1 PM EST Tuesday. * IMPACTS. The cold wind chills could result in hypothermia if precautions are not taken.

* WHAT. Very cold wind chills as low as 5 degrees below zero expected. * WHERE. Portions of DC, central, northeast, and northern Maryland, and central, northern, and northwest Virginia. * WHEN. From 7 PM this evening to 10 AM EST Tuesday. * IMPACTS. The cold wind chills could result in hypothermia if precautions are not taken.

* WHAT. Very cold wind chills as low as 10 to 15 below zero expected. * WHERE. Adams, Cumberland, Dauphin, Franklin, Lancaster, Lebanon, Perry, and York Counties. * WHEN. From 7 PM this evening to noon EST Wednesday. * IMPACTS. Frostbite and hypothermia are possible if precautions are not taken.

* WHAT. For the Small Craft Advisory, northwest winds 10 to 20 kt with gusts up to 25 kt. For the Freezing Spray Advisory, moderate accumulation of freezing spray. * WHERE. Chesapeake Bay from Pooles Island MD to North Beach MD, Tidal Potomac from Cobb Island MD to Smith Point VA, Chester River to Queenstown MD, and Eastern Bay. * WHEN. For the Small Craft Advisory, until 5 AM EST Tuesday. For the Freezing Spray Advisory, until 6 PM EST this evening. * IMPACTS. Operating a vessel in freezing spray is hazardous. Freezing spray may render mechanical and electronic components inoperative. Ice accretion on decks and superstructures may result in some loss of stability. Conditions will be hazardous to small craft.

* WHAT. Very cold wind chills as low as 5 below expected. * WHERE. In Maryland, Calvert, Charles, and St. Marys Counties. In Virginia, Albemarle, King George, Nelson, Orange, Spotsylvania, and Stafford Counties. * WHEN. From 10 PM Tuesday to 10 AM EST Thursday. * IMPACTS. Frostbite and hypothermia will occur if unprotected skin is exposed to these temperatures. Wind chill values can lead to hypothermia with prolonged exposure. Very cold temperatures can lead to hypothermia with prolonged exposure.

* WHAT. For the first Cold Weather Advisory, very cold wind chills as low as 5 below expected. For the second Cold Weather Advisory, very cold wind chills as low as 10 below expected. * WHERE. Portions of DC, central, northeast, and northern Maryland, and central, northern, and northwest Virginia. * WHEN. For the first Cold Weather Advisory, from 7 PM this evening to 10 AM EST Tuesday. For the second Cold Weather Advisory, from 10 PM Tuesday to 10 AM EST Thursday. * IMPACTS. The cold wind chills as low as 10 below zero could result in hypothermia if precautions are not taken. Frostbite and hypothermia will occur if unprotected skin is exposed to these temperatures. Wind chill values can lead to hypothermia with prolonged exposure. Very cold temperatures can lead to hypothermia with prolonged exposure.

* WHAT. For the first Cold Weather Advisory, very cold wind chills as low as 10 below. For the second Cold Weather Advisory, very cold wind chills as low as 10 below expected. * WHERE. Portions of north central and western Maryland, northwest and western Virginia, and eastern and panhandle West Virginia. * WHEN. For the first Cold Weather Advisory, until 1 PM EST Tuesday. For the second Cold Weather Advisory, from 10 PM Tuesday to 10 AM EST Thursday. * IMPACTS. The cold wind chills as low as 10 below zero could result in hypothermia if precautions are not taken. Frostbite and hypothermia will occur if unprotected skin is exposed to these temperatures. Wind chill values can lead to hypothermia with prolonged exposure. Very cold temperatures can lead to hypothermia with prolonged exposure.

* WHAT. Very cold wind chills as low as 13 below expected. * WHERE. Adams, Cumberland, Dauphin, Franklin, Lancaster, Lebanon, Perry, and York Counties. * WHEN. From 7 PM this evening to noon EST Wednesday. * IMPACTS. The cold wind chills as low as 15 below zero could result in hypothermia if precautions are not taken.

A few wind gusts to around 20 knots will be possible out of the northwest through 1 AM. Inexperienced mariners, especially those operating smaller vessels, should exercise extra caution if navigating the waters during this time.

* WHAT. Very cold wind chills as low as 13 below. * WHERE. Adams, Cumberland, Dauphin, Franklin, Lancaster, Lebanon, Perry, and York Counties. * WHEN. Until noon EST Wednesday. * IMPACTS. Frostbite and hypothermia are possible if precautions are not taken. * ADDITIONAL DETAILS. The lowest wind chills will be during the late night and early morning hours.

* WHAT. Very cold wind chills as low as 5 to 15 degrees below zero expected. * WHERE. Portions of north central and western Maryland, northwest and western Virginia and eastern and panhandle West Virginia. * WHEN. Until 10 AM EST Thursday. * IMPACTS. The cold wind chills as low as 10 below zero could result in hypothermia if precautions are not taken. Frostbite and hypothermia will occur if unprotected skin is exposed to these temperatures. Very cold temperatures and wind chills can lead to hypothermia with prolonged exposure. * ADDITIONAL DETAILS. The coldest conditions are expected Tuesday night, with widespread wind chills of 10 to 15 degrees below zero. Other nights, wind chills will be between 5 to 10 degrees below zero. During the daytime, wind chills are expected to only reach the upper single digits.

* WHAT. Very cold wind chills between 0 degrees to 10 degrees below zero expected. * WHERE. Portions of central, northeast and northern Maryland, The District of Columbia and central, northern and northwest Virginia. * WHEN. Until 10 AM EST Thursday. * IMPACTS. The cold wind chills as low as 10 below zero could result in hypothermia if precautions are not taken. Frostbite and hypothermia will occur if unprotected skin is exposed to these temperatures. Wind chill values can lead to hypothermia with prolonged exposure. Very cold temperatures can lead to hypothermia with prolonged exposure. * ADDITIONAL DETAILS. The coldest conditions are expected Tuesday night, with widespread wind chills of 5 to 10 degrees below zero. Other nights, wind chills will be between 0 degrees to 5 degrees below zero. During the daytime, wind chills are expected to only reach the low teens.

* WHAT. Very cold wind chills as low as 5 below expected. * WHERE. In Maryland, Calvert, Charles, and St. Marys Counties. In Virginia, Albemarle, King George, Nelson, Orange, Spotsylvania, and Stafford Counties. * WHEN. From 10 PM Tuesday to 10 AM EST Thursday. * IMPACTS. Frostbite and hypothermia will occur if unprotected skin is exposed to these temperatures. Wind chill values can lead to hypothermia with prolonged exposure. Very cold temperatures can lead to hypothermia with prolonged exposure. * ADDITIONAL DETAILS. The coldest conditions are expected Tuesday night, with widespread wind chills around 5 degrees below zero. Other nights, wind chills will be around or just below 0 degrees. During the daytime, wind chills are expected to only reach the low to middle teens.

* WHAT. Northwest winds 10 to 15 kt with gusts up to 20 kt. * WHERE. Chesapeake Bay north of North Beach MD, Tidal Potomac from Cobb Island MD to Smith Point VA, Patapsco River including Baltimore Harbor, Chester River to Queenstown MD, Eastern Bay, and Patuxent River to Broomes Island MD. * WHEN. Until 5 AM EST Tuesday. * IMPACTS. Conditions will be hazardous to small craft.