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The Storm Prediction Center in Norman, Oklahoma issues a Severe Thunderstorm Watch for an area defined by a parallelogram usually 10,000 mi²or larger, which can cover more than one state. SEVERE THUNDERSTORMS CAN OCCUR IN OR NEAR THE WATCH AREA.
The Severe Thunderstorm Watch is usually issued before severe thunderstorms have developed, when conditions in the atmosphere favor development of organized or relatively widespread severe thunderstorms.
Sometimes, but not often, isolated severe thunderstorms can develop in an area not affected by a Severe Thunderstorm Watch or an event can begin to occur just before the Severe Thunderstorm Watch is issued. There are numerous variables that must come together to produce severe weather, some of which depend on features that can't be resolved within the surface or upper-level data networks, but as soon as organized severe weather is expected, a watch is issued.
DEFINITION OF ORGANIZED SEVERE WEATHER-Severe Thunderstorms that are either initiated or supported by weather features characterized by well-defined temperature or moisture gradients. In other words, if their is a warm or cold front at the surface, midlevels, or upper-levels, and other variables look favorable for thunderstorm development, then the movement of the front(s) could enhance severe weather over a large area.

The definition of a Severe Thunderstorm Warning

A Severe Thunderstorm Warning is issued by the National Weather Service in Wakefield, Virginia when severe weather is either occurring or will occur within a specified time (usually within 60 minutes) within one or several counties:

National Weather Service definition of a severe thunderstorm-

Hail 3/4" or larger, or basically the size of any coin or larger (a dime is 11/16" which the NWS accepts as 3/4")
Fallen tree limbs with a minimum diameter of an average adult's wrist (if your over 18 and a tree limb is the same diameter as your wrist or larger, then it's worth reporting).
Living trees uprooted or blown down ("Living trees" are important since dead, questionably rotted trees require much less wind to blow them down).
Any part of a permanant, well-built structure damaged or destroyed
Measured wind gust from a calibrated anemometer of 58 MPH (50 knots) or greater

How can severe weather occur before a warning is issued if the NWS is continuously monitoring the radar?

*IMPORTANT CONSIDERATIONS*

The WSR-88D (Doppler radar) is the BEST operational tool in the world for thunderstorm analysis.
The NWS IS continuously monitoring the radar, even when the sky is clear!
The radar offers over 100 "snapshots" or "products" (every 5 to 10 minutes depending on the type of weather occurring) showing different parts and characteristics of thunderstorms. Most of these products are composed of pixels, with minumum "size" or "resolution" of one degree in width and depth, and 1km in length. The resolution decreases with distance as the radar beam spreads out to as much as >1.5 nautical miles at 120 nautical miles from the radar. A few products can have resolutions of one degree in width and depth, and .5 nautical miles in length within 30 nautical miles of the radar.
Due to the differences in resolution of products at different distances, and the continuously changing nature of thunderstorms, complete, 100% sampling and analysis of every thunderstorm is impossible.
Severe weather such as 3/4" hail and downburst winds often BUT NOT ALWAYS occur on a scale of one square nautical mile or less, which sometimes is smaller than the radar product resolution. The organized severe weather outbreaks will ALMOST ALWAYS produce severe weather over areas larger than one square nautical mile.
Local surface temperature inversions (temperatures increasing with height from the surface to some height above the ground) can prevent damaging winds from reaching the ground.
Public reports of severe weather can be subjective at times. There is often a mix of hail sizes in a thunderstorm, much of which is irregularly-shaped, so a wide variety of perspectives from a wide variety of people will result in a wide variety of reports for the same storm. Magnitude of wind is also a very subjective element as is description of damage.

Why don't I witness damage or large hail every time my county is under a Severe Thunderstorm Warning?

It is important to remember that Severe Thunderstorm Warnings are issued for COUNTIES, meaning severe weather is expected SOMEWHERE WITHIN ONE OR SEVERAL COUNTIES.
The effects of any thunderstorm are very localized. Often, large hail or damaging winds will affect a neighboring town, or maybe just part of a town, and could just miss your location.
The continuously changing nature of thunderstorms sometimes results in a quick shift in the movement of the thunderstorms, causing a shift in the track of the severe weather, or even end the severe weather abruptly.

So what is the bottom line, when it comes to Severe Thunderstorm Watches and Severe Thunderstorm Warnings ?

!!!! IF A SEVERE THUNDERSTORM WARNING IS ISSUED FOR YOUR COUNTY, SEEK SAFE SHELTER AND TAKE NECESSARY PRECAUTIONS, BECAUSE YOU NEVER WANT TO TAKE THE CHANCE OF BEING A VICTIM OF A SEVERE THUNDERSTORM.
Listen to media, local television stations, NOAA weather radio, or go to our website to access statements, warnings and local storm reports. You will know what severe weather has occurred, where it has occurred, where it is moving and when the threat of severe weather has ended. It is always wise to stay updated on the latest information.

*The importance of reporting severe weather to local law enforcement or the National Weather Service.*

The National Weather Service needs to know what type of severe weather is occurring, so that we can correlate radar signatures to observed severe weather.

If the radar indicates strong winds just above the ground surface, we need to know if damage is occurring to trees or buildings. The damaging wind doesn't always reach the ground surface, and sometimes the radar indicates winds that are just on the borderline of possibly being damaging.
If the radar indicates hail, we need to know the size, so we can correlate the radar signature with your reported hail size. Reporting hail of any size is important since any hail falling at your location could mean larger hail is falling nearby.

YOUR REPORTS MAY RESULT IN WARNINGS THAT COULD SAVE SOMEONE ELSE'S LIFE OR PROPERTY.
WE ARE GREATLY LACKING IN SPOTTERS IN MANY TOWNS IN OUR COUNTY WARNING AREA, WHICH CONCERNS US.
WE NEED SPOTTERS IN EVERY TOWN AND CITY IN OUR COUNTY WARNING AREA. IF YOU HAVE FRIENDS, RELATIVES, OR ANYONE
YOU KNOW IN ANY CROSSROADS OR SMALL TOWN, PLEASE HAVE THEM CONTACT Bill Sammler AT OUR OFFICE TO BECOME A SPOTTER.

Tornado Watches and Warnings-

What is the difference between a Tornado Watch and a !TornadoWarning!?

The definition of a Tornado Watch-

Atmospheric conditions over a large area, usually the size of a large state or multiple states, support the development of tornadoes for 4 hours or longer:

The Storm Prediction Center in Norman, Oklahoma issues a Tornado Watch for an area defined by a parallelogram usually 10,000 mi²or larger, which can cover more than one state. TORNADOES CAN OCCUR IN OR NEAR THE WATCH AREA.
The Tornado Watch is usually issued before tornadoes have developed, when conditions in the atmosphere favor development of severe thunderstorms that could produce tornadoes.
Sometimes, but not often, isolated severe thunderstorms with tornadoes can develop in an area not affected by a Tornado Watch or an event can begin to occur just before the Tornado Watch is issued. There are numerous variables that must come together to produce tornadoes, some of which depend on features that can't be resolved within the surface or upper-level data networks, but as soon as tornadoes are expected, a watch is issued.
DEFINITION OF A TORNADO - Rotating column of air, with some degree of vertical orientation, that is not always visible, and causes damage to objects in contact with the Earth's surface, or shows evidence that part or all of the circulation contacted the earth's surface. For a MUCH more detailed definition, see Chuck Doswell's Definition of a Tornado. A FUNNEL CLOUD is a visible tornadic circulation that does not affect the Earth's surface.

The definition of a !TornadoWarning!-

A !TornadoWarning! is issued by the National Weather Service in Wakefield, Virginia when tornadoes are either occurring or will occur within a specified time (usually within 60 minutes) within one or several counties:

How can a tornado occur before a warning is issued if the NWS is continuously monitoring the radar?

*IMPORTANT CONSIDERATIONS*

The WSR-88D (Doppler radar) is the BEST operational tool in the world for thunderstorm analysis.
The NWS IS continuously monitoring the radar, even when the sky is clear!
The radar offers over 100 "snapshots" or "products" (every 5 to 10 minutes depending on the type of weather occurring) showing different parts and characteristics of thunderstorms. Most of these products are composed of pixels, with minumum "size" or "resolution" of one degree in width and depth, and 1km in length. The resolution decreases with distance as the radar beam spreads out to as much as >1.5 nautical miles at 120 nautical miles from the radar. A few products can have resolutions of one degree in width and depth, and .5 nautical miles in length within 30 nautical miles of the radar.
Due to the differences in resolution of products at different distances, and the continuously changing nature of thunderstorms, complete, 100% sampling and analysis of every thunderstorm is impossible.
The diameter of nearly all tornadoes are less than one mile wide, and large majority of tornadoes are one-quarter mile or less in diameter, which is much smaller than the radar product resolution. Rotation can occur in some particularly severe thunderstorms, which may indicate the possibility of a tornado, and can sometimes be too small to appear on any radar products.
Local surface temperature inversions (temperatures increasing with height from the surface to some height above the ground) can prevent the damaging tornadic winds from reaching the ground.
Public reports of tornadoes and funnel clouds can be subjective at times. The base of a thunderstorm can be very ragged, and sometimes a piece of the thunderstorm's base can be moving in such a way that someone may believe it is a funnel cloud or tornado, when in fact, it may not be. Some downburst wind damage can also sometimes be interpreted as tornadic damage.

Why don't I witness damage or a tornado every time my county is under a !TornadoWarning!?

It is important to remember that !TornadoWarnings! are issued for COUNTIES, meaning a tornado is expected SOMEWHERE WITHIN ONE OR SEVERAL COUNTIES.
The effects of any thunderstorm are very localized, and tornadoes are on a scale much smaller than a thunderstorm. Often, some effect of a thunderstorm will occur in a neighboring town, or maybe just part of a town, and could just miss your location.
The continuously changing nature of thunderstorms sometimes results in a quick shift in the movement of the thunderstorms, causing a shift in the track of the severe weather, or even end the severe weather abruptly.

So what is the bottom line, when it comes to Tornado Watches and !TornadoWarnings!?

!!! IF A !TornadoWarning! IS ISSUED FOR YOUR COUNTY, SEEK SAFE SHELTER AND TAKE NECESSARY PRECAUTIONS, BECAUSE YOU NEVER WANT TO TAKE THE CHANCE OF BEING A VICTIM OF A TORNADO.
Listen to media, local television stations, NOAA weather radio, or go to our website to access statements, warnings and local storm reports. You will know what severe weather has occurred, where it has occurred, where it is moving and when the threat of severe weather has ended. It is always wise to stay updated on the latest information.

*The importance of reporting severe weather to local law enforcement or the National Weather Service.*

The National Weather Service needs to know what type of severe weather is occurring, so that we can correlate radar signatures to observed severe weather.

If the radar indicates strong winds just above the ground surface, we need to know if damage is occurring to trees or buildings. The damaging wind doesn't always reach the ground surface, and sometimes the radar indicates winds that are just on the borderline of possibly being damaging.
If the radar indicates hail, we need to know the size, so we can correlate the radar signature with your reported hail size. Reporting hail of any size is important since any hail falling at your location could mean larger hail is falling nearby.
Report any rotation seen at the base of the thunderstorm, including funnel clouds, so that we can correlate rotation we see on the radar to tornadoes, or developing tornadoes. Many rotations, that we see within thunderstorms on the radar, never become tornadoes, so we need your help in reporting tornadoes and funnel clouds to us.

YOUR REPORTS MAY RESULT IN WARNINGS THAT COULD SAVE SOMEONE ELSE'S LIFE OR PROPERTY.
WE ARE GREATLY LACKING IN SPOTTERS IN MANY TOWNS IN OUR COUNTY WARNING AREA, WHICH CONCERNS US.
WE NEED SPOTTERS IN EVERY TOWN AND CITY IN OUR COUNTY WARNING AREA. IF YOU HAVE FRIENDS, RELATIVES, OR ANYONE YOU KNOW IN ANY CROSSROADS OR SMALL TOWN, PLEASE HAVE THEM CONTACT Bill Sammler AT OUR OFFICE TO BECOME A SPOTTER.

Special Marine Warnings-

The definition of a Special Marine Warning-

A Special Marine Warning is issued by the National Weather Service in Wakefield, VA when the following conditions exist in the Atlantic Waters between Fenwick Island, DE and Currituck Beach Lighthouse in Corolla, NC, and the Chesapeake Bay south of Smith Point:

It is important to remember that when a Severe Thunderstorm Watch or Tornado Watch is issued for coastal locations, the appropriate areas of the Atlantic Waters and Chesapeake Bay are also included in the watches.

Why do waterspouts and 34+ knot wind gusts sometimes occur before a Special Marine Warning is issued?

Convective wind gusts of 34 knots or greater

A large majority of Special Marine Warnings are issued before the strong winds reach the water. Often, strong or severe thunderstorms will have a history of strong or damaging winds on land, so the radar operator can anticipate the effects on the water.
Most commercial and pleasure boaters receive their marine weather forecasts and information from the U.S. Coast Guard, listening to specific radio frequencies.

After the National Weather Service issues a Special Marine Warning the U.S. Coast Guard (among others) receives the warning and retransmits it over their specific radio frequency, a process that can take up to 10 minutes. Usually thunderstorms with strong convective wind gusts move at approximately the same speed as the wind gusts themselves, which can be a considerable distance.
Consider a thunderstorm that is moving at 50 knots, it could track 9 miles in the 10 minutes it may take the U.S. Coast Guard to retransmit the warning. Most small craft and pleasure boaters stay within 10 miles of the shore.

Waterspouts

Often associated with elatively weak showers and thunderstorms, many of which have little or no lightning and thunder.
Often associated with showers and thunderstorm with very little rain and/or affect a very localized area.
NWS Doppler radar often has difficulty detecting such small, relatively weaker rotations of waterspouts (compared to land-based tornadic circulations).

Why don't I witness winds greater than or equal to 34 kt or a waterspout every time a Special Marine Warning is issued for my marine area?

Special Marine Warnings are issued for areas between specific points of the Atlantic Waters out to 20 nautical miles offshore, and the Chesapeake Bay. The severe weather may be occurring in another part of the specified area. The breakpoints are as follows:

Chesapeake Bay

Smith Point
Windmill Point
New Point Comfort
Cape Henry

Atlantic waters

Fenwick Island, DE
Chincoteague, VA
Parramore Island, VA
Cape Charles, VA
Virginia Beach, Virginia
Virginia/North Carolina border
Currituck Beach Lighthouse in Corolla, NC

The continuously changing nature of thunderstorms sometimes results in a quick shift in the movement of the thunderstorms, causing a shift in the track of the severe weather, or even end the severe weather abruptly.

So what is the bottom line when it comes to Special Marine Warnings?

!!! IF A SPECIAL MARINE WARNING IS ISSUED FOR YOUR LOCATION, SEEK SAFE HARBOR, AND PREPARE FOR STRONG WINDS, CHOPPY SEAS, AND/OR WATERSPOUTS, BECAUSE YOU NEVER WANT TO TAKE THE CHANCE OF BEING A VICTIM OF A SEVERE THUNDERSTORM OR WATERSPOUT.
Listen to media, local television stations, NOAA weather radio, or go to our website to access statements, warnings and local storm reports. You will know what severe weather has occurred, where it has occurred, where it is moving and when the threat of severe weather has ended. It is always wise to stay updated on the latest information.

*The importance of reporting severe weather to local law enforcement, The Coast Guard, or the National Weather Service.*

The National Weather Service needs to know what type of severe weather is occurring, so that we can correlate radar signatures to observed severe weather.

If the radar indicates strong winds just above the ground surface, we need to know if damagin gwinds are occurring, that could capsize boats and build waves. The damaging wind doesn't always reach the water surface, and sometimes the radar indicates winds that are just on the borderline of possibly being damaging.
Report any rotation seen at the base of the thunderstorm, including funnel clouds and waterspouts, so that we can correlate rotation we see on the radar to waterspouts, or developing waterspouts. Waterspouts are somtimes too small or weak to be detected by radar. Additionally, many rotations, that we see within thunderstorms on the radar, never become waterspouts, so we need your help in reporting waterspouts and funnel clouds to us.

YOUR REPORTS MAY RESULT IN WARNINGS THAT COULD SAVE A FELLOW BOATER'S LIFE OR PROPERTY.
WE ARE GREATLY LACKING IN MARINE OBSERVATIONS IN THE CHESAPEAKE BAY AND ATLANTIC WATERS, WHICH CONCERNS US.

WE NEED MARINE OBSERVATIONS OVER OUR ENTIRE MARINE AREA. IF YOU HAVE FRIENDS, RELATIVES, OR ANYONE YOU KNOW THAT GOES BOATING ON THE CHESAPEAKE BAY OR ATLANTIC WATERS, PLEASE ENCOURAGE THEM TO REPORT WIND AND SEA CONDITIONS TO THE COAST GUARD, SPECIFICALLY REQUESTING THAT THE INFORMATION BE RELAYED TO THE NATIONAL WEATHER SERVICE.

Flash Flood Watches and Warnings-

What is the difference between a Flood Watch and a Flash Flood Watch?

The major difference between a Flood Watch and a Flash Flood Watch, is the duration of the rainfall needed to produce flooding.

A Flood Watch implies a longer period of relatively lighter rains, adding up to a large amount of rain, while a Flash Flood Watchimplies a shorter period of heavier rain. Generally, if flooding is expected within 6 hours of the onset of rain, a Flash Flood Watch is most appropriate.
If flooding is expected beyond 6 hours after the onset of rain, a Flood Watch is most appropriate. The 6 hour threshold is very subjective and varies from forecaster to forecaster. REGARDLESS OF THE TYPE OF WATCH, FLOODING CAN OCCUR AT ANY TIME, SO BE ALERT.

Another difference between Flood Watches and Flash Flood Watches is the type of flooding it implies.

Flash flooding by definition suggests rapidly rising water, such as a surge of water heading rapidly downstream in a creek or small river. It could also be rapidly rising water on roadways, which can cause motorists to become stranded in vehicles, or even worse, washed into creeks and small rivers due to rapid runoff.
Longer-term flooding implies a slower or more steady rise in the water levels of creeks, streams and larger rivers. Roads can also become flooded, but it is usually more gradual, allowing motorists to monitor conditions more closely.

What is the difference between a Flash Flood Watch and a Flash Flood Warning?

The definition of a Flash Flood Watch-

Atmospheric conditions over a large area, varying in size from multiple counties to multiple states, support the development of heavy rain and/or thunderstorms that are capable of producing flash flooding:

The National Weather Service in Sterling, Virginia and Raleigh, North Carolina issue Flash Flood Watches for an area consisting of multiple counties, which can cover more than one state. Flash flooding generally occurs within 6 hours of the beginning of the heavy rain.
The Flash Flood Watch is usually issued before heavy rain and/or thunderstorms have developed, when conditions in the atmosphere favor development of heavy rain and/or thunderstorms over an area consisting of multiple counties.
Sometimes, but not often, flash flooding can occur in an area not affected by a Flash Flood Watch or an event can begin to occur just before the Flash Flood Watch is issued. There are numerous variables that must come together to produce flash flooding, some of which depend on features that can't be resolved within the surface or upper-level data networks, but as soon as flash flooding is expected, a watch is issued.

The definition of a Flash Flood Warning-

A Flash Flood Warning is issued by the National Weather Service in Wakefield, Virginia when heavy rain has been occurring, and flash flooding is either occurring or will occur within a specified time (usually within 60 minutes), within one or several counties:

National Weather Service definition of flash flooding-

How can flash flooding occur before a warning is issued if the NWS is continuously monitoring the radar?

*IMPORTANT CONSIDERATIONS*

The WSR-88D (Doppler radar) is the BEST operational tool in the world for thunderstorm analysis.
The NWS IS continuously monitoring the radar, even when the sky is clear!
The radar offers over 100 "snapshots" or "products" (every 5 to 10 minutes depending on the type of weather occurring) showing different parts and characteristics of thunderstorms. Most of these products are composed of pixels, with minumum "size" or "resolution" of one degree in width and depth, and 1km in length. The resolution decreases with distance as the radar beam spreads out to as much as >1.5 nautical miles at 120 nautical miles from the radar. A few products can have resolutions of one degree in width and depth, and .5 nautical miles in length within 30 nautical miles of the radar.
Due to the differences in resolution of products at different distances, and the continuously changing nature of thunderstorms, complete, 100% sampling and analysis of every thunderstorm is impossible.
The radar estimates rainfall, but can only offer a rough calculation of how much rain has fallen over any given area. Even though rainfall estimation is questionable, the radar is the BEST operational tool in the world for rainfall estimation..
Public reports of life-threatening flooding can be subjective at times. Nuisance urban flooding and water across secondary roads can be described in a variety of ways.

Why don't I witness flash flooding every time my county is under a Flash Flood Warning?

It is important to remember that Flash Flood Warnings are issued for COUNTIES, meaning flash flooding is expected SOMEWHERE WITHIN ONE OR SEVERAL COUNTIES.
The effects of any thunderstorm or heavy rain band are very localized. Often, flooding thunderstorm rains will affect a neighboring town, or maybe just part of a town, and could just miss your location.
The continuously changing nature of thunderstorms sometimes results in a quick shift in the movement of the thunderstorms, causing a shift in the track of the heavy rain, or even end the heavy rain abruptly.

So what is the bottom line, when it comes to Flash Flood Watches and Flash Flood Warnings ?

!!! - IF A FLASH FLOOD WARNING IS ISSUED FOR YOUR COUNTY, SEEK HIGH GROUND AND TAKE NECESSARY PRECAUTIONS, BECAUSE YOU NEVER WANT TO TAKE THE CHANCE OF BEING A VICTIM OF FLASH FLOODING.
Listen to media, local television stations, NOAA weather radio, or go to our website to access statements, warnings and local storm reports. You will know what heavy rain and flash flooding has occurred, where it has occurred, where it is moving and when the threat of flash flooding has ended. It is always wise to stay updated on the latest information.

*The importance of reporting flash flooding and 2.00"+ rainfall in less than 3 hours to local law enforcement or the National Weather Service.*

The National Weather Service needs to know what type of heavy rain and flash flooding is occurring, so that we can correlate radar signatures to observed heavy rain and flash flooding.

If the radar indicates a thunderstorm or heavy rain that is producing large rainfall estimates, we need to know if the radar estimates are accurate, and if flash flooding is occurring. Flash flooding doesn't always occur when very heavy rain is observed, and sometimes the radar overestimates, or underestimates rainfall.
If the radar indicates heavy rain, we need to know how much has fallen, so we can correlate radar signatures with your reported rainfall amount. Reporting flash flooding on roadways, or rising creeks and rivers is very important, it could mean that more serious flooding could be nearby, or developing.

YOUR REPORTS MAY RESULT IN WARNINGS THAT COULD SAVE SOMEONE ELSE'S LIFE OR PROPERTY.
WE ARE GREATLY LACKING IN SPOTTERS IN MANY TOWNS IN OUR COUNTY WARNING AREA, WHICH CONCERNS US.

WE NEED SPOTTERS IN EVERY TOWN AND CITY IN OUR COUNTY WARNING AREA. IF YOU HAVE FRIENDS, RELATIVES, OR ANYONE YOU KNOW IN ANY CROSSROADS OR SMALL TOWN, PLEASE HAVE THEM CONTACT Bill Sammler AT OUR OFFICE TO BECOME A SPOTTER.

Flood Watches and Warnings-

What is the difference between a Flood Watch and a Flash Flood Watch?

The major difference between a Flood Watch and a Flash Flood Watch, is the duration of the rainfall needed to produce flooding.

A Flood Watch implies a longer period of relatively lighter rains, adding up to a large amount of rain, while a Flash Flood Watch implies a shorter period of heavier rain. Generally, if flooding is expected within 6 hours of the onset of rain, a Flash Flood Watch is most appropriate.
If flooding is expected beyond 6 hours after the onset of rain, a Flood Watch is most appropriate. The 6 hour threshold is very subjective and varies from forecaster to forecaster. REGARDLESS OF THE TYPE OF WATCH, FLOODING CAN OCCUR AT ANY TIME, SO BE ALERT.

Another difference between Flood Watches and Flash Flood Watches is the type of flooding it implies.

Flash flooding by definition suggests rapidly rising water, such as a surge of water heading rapidly downstream in a creek or small river. It could also be rapidly rising water on roadways, which can cause motorists to become stranded in vehicles, or even worse, washed into creeks and small rivers due to rapid runoff.
Longer-term flooding implies a slower or more steady rise in the water levels of creeks, streams and larger rivers. Roads can also become flooded, but it is usually more gradual, allowing motorists to monitor conditions more closely.

The rivers for which NWS Wakefield, Virginia issues River Flood Warnings are as follows:

Rivanna River at Palmyra, affecting Fluvanna County
James River at Cartersville, Westham and City Locks, affecting Fluvanna, Goochland, Powhatan, Henrico and Chesterfield Counties including the City of Richmond
Appomattox River at Farmville, Matoax, Matoaca and Petersburg, affecting Prince Edward, Cumberland, Amelia, Powhatan, Chesterfield and Dinwiddie Counties including the cities of Farmville and Petersburg
Nottoway River at Rawlings, Sebrell, and Stony Creek, affecting Brunswick, Dinwiddie, Greensville, Sussex and Southampton Counties
Meherrin River at Lawrenceville and Emporia, affecting Brunswick and Greensville Counties including the city of Emporia.

What is the difference between a Flood Watchand a Flood Warning?

The definition of a Flood Watch-

Atmospheric conditions over a large area, varying in size from multiple counties to multiple states, support the development of heavy rain and/or thunderstorms that are capable of producing flooding:

The National Weather Service in Sterling, Virginia and Raleigh, North Carolina issue Flood Watches for an area consisting of multiple counties, which can cover more than one state. Flooding generally occurs 6 to 24 hours after the beginning of the heavy rain.
The Flood Watch is usually issued before heavy rain and/or thunderstorms have developed, when conditions in the atmosphere favor development of heavy rain and/or thunderstorms over an area consisting of multiple counties.
Sometimes, but not often, flooding can occur in an area not affected by a Flood Watch or an event can begin to occur just before the Flood Watch is issued. There are numerous variables that must come together to produce flooding, some of which depend on features that can't be resolved within the surface or upper-level data networks, but as soon as flooding is expected, a watch is issued.

The definition of a Flood Warning-

A Flood Warning is issued by the National Weather Service in Wakefield, Virginia when heavy rain has been occurring, and flooding is either occurring or will occur within a specified time (usually within 60 minutes), within one or several counties:

National Weather Service definition of flooding-

How can flooding occur before a warning is issued if the NWS is continuously monitoring the radar?

*IMPORTANT CONSIDERATIONS*

The WSR-88D (Doppler radar) is the BEST operational tool in the world for thunderstorm analysis.
The NWS IS continuously monitoring the radar, even when the sky is clear!
The radar offers over 100 "snapshots" or "products" (every 5 to 10 minutes depending on the type of weather occurring) showing different parts and characteristics of thunderstorms. Most of these products are composed of pixels, with minumum "size" or "resolution" of one degree in width and depth, and 1km in length. The resolution decreases with distance as the radar beam spreads out to as much as >1.5 nautical miles at 120 nautical miles from the radar. A few products can have resolutions of one degree in width and depth, and .5 nautical miles in length within 30 nautical miles of the radar.
Due to the differences in resolution of products at different distances, and the continuously changing nature of thunderstorms, complete, 100% sampling and analysis of every thunderstorm is impossible.
The radar estimates rainfall, but can only offer a rough calculation of how much rain has fallen over any given area. Even though rainfall estimation is questionable, the radar is the BEST operational tool in the world for rainfall estimation..
Public reports of life-threatening flooding can be subjective at times. Nuisance urban flooding and water across secondary roads can be described in a variety of ways.

Why don't I witness flooding every time my county is under a Flood Warning?

It is important to remember that Flood Warningsare issued for COUNTIES, meaning flooding is expected SOMEWHERE WITHIN ONE OR SEVERAL COUNTIES.
If a River Flood Warning is issued, flooding is expected to be confined primarily along the rivers.
The effects of any thunderstorm or heavy rain band are very localized. Often, flooding thunderstorm rains will affect a neighboring town, or maybe just part of a town, and could just miss your location.
The continuously changing nature of thunderstorms, or areas of heavy rain, sometimes results in a quick shift in the movement of the thunderstorms, causing a shift in the track of the heavy rain, or even end the heavy rain abruptly.

So what is the bottom line, when it comes to Flood Watches and Flood Warnings ?

!!! - IF A FLOOD WARNING IS ISSUED FOR YOUR COUNTY, OR FOR A NEARBY RIVER, SEEK HIGH GROUND AND TAKE NECESSARY PRECAUTIONS, BECAUSE YOU NEVER WANT TO TAKE THE CHANCE OF BEING A VICTIM OF FLOODING.
Listen to media, local television stations, NOAA weather radio, or go to our website to access statements, warnings and local storm reports. You will know what heavy rain and flooding has occurred, where it has occurred, where it is moving and when the threat of flooding has ended. It is always wise to stay updated on the latest information.

*The importance of reporting flooding and 2.00"+ storm-total rainfall to local law enforcement or the National Weather Service.*

The National Weather Service needs to know what type of heavy rain and flooding is occurring, so that we can correlate radar signatures to observed heavy rain and flooding.

If the radar indicates a thunderstorm or heavy rain that is producing large rainfall estimates, we need to know if the radar estimates are accurate, and if flooding is occurring. Flooding doesn't always occur when very heavy rain is observed, and sometimes the radar overestimates, or underestimates rainfall.
If the radar indicates heavy rain, we need to know how much has fallen, so we can correlate radar signatures with your reported rainfall amount. Reporting flooding on roadways, or rising creeks and rivers is very important, it could mean that more serious flooding could be nearby, or developing.

YOUR REPORTS MAY RESULT IN WARNINGS THAT COULD SAVE SOMEONE ELSE'S LIFE OR PROPERTY.
WE ARE GREATLY LACKING IN SPOTTERS IN MANY TOWNS IN OUR COUNTY WARNING AREA, WHICH CONCERNS US.

Coastal Flood Watches and Warnings-

What is the difference between a Coastal Flood Watch and a Coastal Flood Warning?

The definition of a Coastal Flood Watch-

Strong onshore winds are expected to produce minor coastal flooding, and possibly moderate to severe coastal flooding, along some portion of the Atlantic or Chesapeake Bay shoreline:

The National Weather Service in Sterling, Virginia and Raleigh, North Carolina issue Coastal Food Watches for an area consisting of multiple coastal counties, which can cover more than one state. Coastal flooding generally occurs during the high tide after the Coastal Flood Watch is issued.
Sometimes, but not often, minor coastal flooding can occur in an area not affected by a Coastal Flood Watch or an event can begin to occur just before theCoastal Flood Watch is issued. There are numerous variables that must come together to produce coastal flooding, some of which depend on features that can't be resolved within the surface or upper-level data networks, but as soon as coastal flooding is expected, a watch, warning or statement is issued.

The definition of a Coastal Flood Warning-

A Coastal Flood Warning is issued by the National Weather Service in Sterling, Virginia or Raleigh, North Carolina when moderate or greater coastal flooding is either occurring or will occur during high tides, within one or several coastal counties:

An extended period of strong onshore winds can push water into the coast much like a hurricane storm surge.
Strong north winds can push Chesapeake Bay water into Hampton Roads.
Strong east or southeast winds can push Chesapeake Bay water into the mouth of the York, James, Rappahannock and Potomac Rivers, producing flooding on the Peninsula, Middle Peninsula and Northern Neck
Strong west or east winds can produce flooding along the north shore of the Albemarle Sound.

National Weather Service definition of minor, moderate and severe coastal flooding-

Minor flooding is described as tides 2 feet or less above minimum flood stage, causing nuisance flooding.
Moderate flooding is described as tides 2 to 3 feet above minimum flood stage, often producing some damage to permanent structures along the water's edge, closing some roads and producing significant beach erosion.
Major or Severe flooding is described by tides 4 feet or more above minimum flood stage causing significant damage to buildings, widespread road closures and significant erosion.

What are some of the estimated minimum flood levels along the Maryland, Virginia and North Carolina Shores?

Tide levels are measured feet above Mean Lower Low Water (MLLW), which is the average of all of the lowest tides each day (there are usually 2 low tides each day, one of which is lower than the other). Mean Sea Level (MSL) is the average of all high and low tides.

Virginia - Atlantic Coast

Chincoteague - 3.0 feet MLLW
Watchapreague - 7.5 feet MLLW
Cape Charles - 3.0 feet MLLW

Virginia - Eastern Chesapeake Bay

Tangier Island - 2.0 feet MLLW
Muddy Creek - 2.0 feet MLLW

Virginia - Western and Southern Chesapeake Bay

Urbanna - 3.0 feet MLLW
Gwynn Island - 5.5 feet MLLW
Gloucester Point - 5.0 feet MLLW
Yorktown - 4.0 feet MLLW
Norfolk - 5.0 feet MLLW

Maryland

Ocean City - 5 to 6 feet MLLW

North Carolina - Atlantic Coast of Currituck County

Corolla - 4.0 to 5.0 feet MLLW

North Carolina - Albemarle and Currituck Sounds (no tidal effects on the sounds)

Edenton - 4.0 feet
Harvey Point - 4.0 feet
Hertford - 4.7 feet
Winfall - 2.8 feet
Elizabeth City - 3.5 feet
Wade Point 2.7 feet
Tip of Camden County - 3.4 feet
Knotts Island area - 3.0 feet

If you would like historical tide data for the Hampton Roads area from past significant storms, click here .

Why don't I witness flooding every time my county is under a Coastal Flood Warning?

It is important to remember that Coastal Flood Warnings are issued for COUNTIES, meaning flooding is expected SOMEWHERE WITHIN ONE OR SEVERAL COUNTIES.
If a Coastal Flood Warning is issued, flooding is expected to be confined primarily along the immediate coast in unprotected areas. Some areas of the Virginia Eastern Shore are protected by smaller bays and islands. All counties along the coast of Virginia, Maryland and North Carolina have their areas that are, to some degree, protected, and some areas more prone to coastal flooding.

So what is the bottom line, when it comes to Coastal Flood Watches and Coastal Flood Warnings ?

!!! - IF A COASTAL FLOOD WARNING IS ISSUED FOR YOUR COUNTY, SEEK HIGH GROUND AND TAKE NECESSARY PRECAUTIONS, BECAUSE YOU NEVER WANT TO TAKE THE CHANCE OF BEING A VICTIM OF COASTAL FLOODING.
Listen to media, local television stations, NOAA weather radio, or go to our website to access statements, warnings and local storm reports. You will know what coastal flooding has occurred, where it has occurred, and when the threat of coastal flooding has ended. It is always wise to stay updated on the latest information.

*The importance of reporting coastal flooding to local law enforcement or the National Weather Service.*

The National Weather Service needs to know what type of coastal flooding is occurring, so that we can correlate winds and tide levels to actual flooding.

Once we can correlate flooding in certain areas with tide levels and winds, we can taylor coastal flood threat information to more specific locations in future storms.
Reporting flooding on roadways, or damage to homes and businesses is very important. It could mean that more serious flooding could be nearby, or developing.

YOUR REPORTS MAY RESULT IN WARNINGS THAT COULD SAVE SOMEONE ELSE'S LIFE OR PROPERTY.
WE ARE GREATLY LACKING IN SPOTTERS IN MANY TOWNS IN OUR COUNTY WARNING AREA, WHICH CONCERNS US.

Federal Meteorological Handbook No. 11 - Doppler Radar Meteorological Observations, Parts A-D. U.S Department of Commerce, National Oceanic and Atmospheric Administration, Office of the Federal Coordinator for Meteorological Services and Supporting Branch, Washington, DC.

Advanced Spotter's Training Guide, NOAA PA 92055 (Available from local NWS Offices)

Thunderstorms and Lightning, the Underrated Killers, NOAA PA 92053, January 1994 (Available from local NWS Offices)

Tornadoes, Nature's Most Violent Storms, NOAA PA 92052, September 1992 (Available from local NWS Offices)

Marine Information and Services Provided by the National Weather Service in Wakefield, Virginia (Available from the NWS in Wakefield, Virginia)

Flash Floods and Floods, the Awesome Power, NOAA PA 92050, July 1992 (Available from local NWS Offices)

Welcome to the NWS Wakefield, VA

Severe Weather Information Page

Severe Thunderstorm Watches and Warnings-

What is the difference between a Severe Thunderstorm Watch and a Severe Thunderstorm Warning?

The definition of a Severe Thunderstorm Watch

Atmospheric conditions over a large area, usually the size of a large state or multiple states, support the development of severe thunderstorms for 4 hours or longer:

The definition of a Severe Thunderstorm Warning

A Severe Thunderstorm Warning is issued by the National Weather Service in Wakefield, Virginia when severe weather is either occurring or will occur within a specified time (usually within 60 minutes) within one or several counties:

National Weather Service definition of a severe thunderstorm-

How can severe weather occur before a warning is issued if the NWS is continuously monitoring the radar?

*IMPORTANT CONSIDERATIONS*

Why don't I witness damage or large hail every time my county is under a Severe Thunderstorm Warning?

So what is the bottom line, when it comes to Severe Thunderstorm Watches and Severe Thunderstorm Warnings ?

*The importance of reporting severe weather to local law enforcement or the National Weather Service.*

Tornado Watches and Warnings-

What is the difference between a Tornado Watch and a !TornadoWarning!?

The definition of a Tornado Watch-

Atmospheric conditions over a large area, usually the size of a large state or multiple states, support the development of tornadoes for 4 hours or longer:

The definition of a !TornadoWarning!-

A !TornadoWarning! is issued by the National Weather Service in Wakefield, Virginia when tornadoes are either occurring or will occur within a specified time (usually within 60 minutes) within one or several counties:

How can a tornado occur before a warning is issued if the NWS is continuously monitoring the radar?

*IMPORTANT CONSIDERATIONS*

Why don't I witness damage or a tornado every time my county is under a !TornadoWarning!?

So what is the bottom line, when it comes to Tornado Watches and !TornadoWarnings!?

*The importance of reporting severe weather to local law enforcement or the National Weather Service.*

Special Marine Warnings-

The definition of a Special Marine Warning-

A Special Marine Warning is issued by the National Weather Service in Wakefield, VA when the following conditions exist in the Atlantic Waters between Fenwick Island, DE and Currituck Beach Lighthouse in Corolla, NC, and the Chesapeake Bay south of Smith Point:

It is important to remember that when a Severe Thunderstorm Watch or Tornado Watch is issued for coastal locations, the appropriate areas of the Atlantic Waters and Chesapeake Bay are also included in the watches.

Why do waterspouts and 34+ knot wind gusts sometimes occur before a Special Marine Warning is issued?

Why don't I witness winds greater than or equal to 34 kt or a waterspout every time a Special Marine Warning is issued for my marine area?

So what is the bottom line when it comes to Special Marine Warnings?

*The importance of reporting severe weather to local law enforcement, The Coast Guard, or the National Weather Service.*

Flash Flood Watches and Warnings-

What is the difference between a Flood Watch and a Flash Flood Watch?

What is the difference between a Flash Flood Watch and a Flash Flood Warning?

The definition of a Flash Flood Watch-

Atmospheric conditions over a large area, varying in size from multiple counties to multiple states, support the development of heavy rain and/or thunderstorms that are capable of producing flash flooding:

The definition of a Flash Flood Warning-

A Flash Flood Warning is issued by the National Weather Service in Wakefield, Virginia when heavy rain has been occurring, and flash flooding is either occurring or will occur within a specified time (usually within 60 minutes), within one or several counties:

National Weather Service definition of flash flooding-

How can flash flooding occur before a warning is issued if the NWS is continuously monitoring the radar?

*IMPORTANT CONSIDERATIONS*

Why don't I witness flash flooding every time my county is under a Flash Flood Warning?

So what is the bottom line, when it comes to Flash Flood Watches and Flash Flood Warnings ?

*The importance of reporting flash flooding and 2.00"+ rainfall in less than 3 hours to local law enforcement or the National Weather Service.*

Flood Watches and Warnings-

What is the difference between a Flood Watch and a Flash Flood Watch?

What is the difference between a Flood Watchand a Flood Warning?

The definition of a Flood Watch-

Atmospheric conditions over a large area, varying in size from multiple counties to multiple states, support the development of heavy rain and/or thunderstorms that are capable of producing flooding:

The definition of a Flood Warning-

A Flood Warning is issued by the National Weather Service in Wakefield, Virginia when heavy rain has been occurring, and flooding is either occurring or will occur within a specified time (usually within 60 minutes), within one or several counties:

National Weather Service definition of flooding-

How can flooding occur before a warning is issued if the NWS is continuously monitoring the radar?

*IMPORTANT CONSIDERATIONS*

Why don't I witness flooding every time my county is under a Flood Warning?

So what is the bottom line, when it comes to Flood Watches and Flood Warnings ?

*The importance of reporting flooding and 2.00"+ storm-total rainfall to local law enforcement or the National Weather Service.*

Coastal Flood Watches and Warnings-

What is the difference between a Coastal Flood Watch and a Coastal Flood Warning?

The definition of a Coastal Flood Watch-

Strong onshore winds are expected to produce minor coastal flooding, and possibly moderate to severe coastal flooding, along some portion of the Atlantic or Chesapeake Bay shoreline:

The definition of a Coastal Flood Warning-

A Coastal Flood Warning is issued by the National Weather Service in Sterling, Virginia or Raleigh, North Carolina when moderate or greater coastal flooding is either occurring or will occur during high tides, within one or several coastal counties:

National Weather Service definition of minor, moderate and severe coastal flooding-

What are some of the estimated minimum flood levels along the Maryland, Virginia and North Carolina Shores?

Why don't I witness flooding every time my county is under a Coastal Flood Warning?

So what is the bottom line, when it comes to Coastal Flood Watches and Coastal Flood Warnings ?

*The importance of reporting coastal flooding to local law enforcement or the National Weather Service.*

IMPORTANT CONSIDERATIONS

The importance of reporting severe weather to local law enforcement or the National Weather Service.

IMPORTANT CONSIDERATIONS

The importance of reporting severe weather to local law enforcement or the National Weather Service.

The importance of reporting severe weather to local law enforcement, The Coast Guard, or the National Weather Service.

IMPORTANT CONSIDERATIONS

The importance of reporting flash flooding and 2.00"+ rainfall in less than 3 hours to local law enforcement or the National Weather Service.

IMPORTANT CONSIDERATIONS

The importance of reporting flooding and 2.00"+ storm-total rainfall to local law enforcement or the National Weather Service.

The importance of reporting coastal flooding to local law enforcement or the National Weather Service.