Spring & Summer Severe/Hazardous Weather Terms

WATCHES

Excessive Heat Watch - An excessive heat watch is issued when excessive heat is possible. Heat indexes are forecast at 105 degrees or higher for a period of two hours or more.

Fire Weather Watch - A fire weather watch is issued when there is the possible development of conditions favorable for forest, grass or brush fires and the conditions support extreme fire danger and/or fire behavior.

Flood Watch - A flood watch is issued for the potential of rapid flooding. This can be caused from torrential downpours, dam breaks, or the breakup of ice jams. A flood watch may also be issued when the onset of flooding is much slower, usually greater than six hours. The body of the watch describes the cause of the potential flooding and some possible results if flooding were to materialize. The watches are usually issued up to 12 hours prior to the possible flood event.

High Wind Watch - This product is issued when there is the potential of high wind speeds developing that may pose a hazard or is life threatening. The criteria for this watch is the potential for sustained non-convective (not related to thunderstorms) winds greater than or equal to 40 mph and/or gusts greater than or equal to 58 mph.

Severe Thunderstorm Watch - A severe thunderstorm watch outlines an area where hail up to 1 inch in diameter or larger, and/or damaging thunderstorm winds are expected to occur. Tornadoes may be possible.

Tornado Watch - A tornado watch outlines an area where conditions are favorable for the development of tornados in and close to the watch area. During the watch, people should review tornado safety rules and be prepared to move a place of safety if threatening weather approaches.

Particularly Dangerous Situation (PDS) Watch - "Particularly Dangerous Situation" is used in rare situations when long-lived, strong and violent tornadoes are possible. This enhanced wording may also accompany severe thunderstorm watches for exceptionally intense and well organized convection wind storms. PDS watches are issued when the likelihood of significant events is boosted by very volatile atmospheric conditions.


WARNINGS

Excessive Heat Warning - An excessive heat warning is issued when heat indexes will generally reach 105 degrees or higher for a period of two hours or more.

Flash Flood Warning - A flash flood warning signifies a short duration of intense or rapid flooding of counties, communities, streams, or urban areas. Flash floods may result from torrential downpours, dam breaks, or the breakup of ice jams.
Action: Take action immediately - move to higher ground, do not drive through flooded roadways.

Flash Flood Emergency - In exceedingly rare situations, when a severe threat to human life and catastrophic damage from a flash flood is imminent or ongoing, the phrase flash flood emergency may be included in a flash flood warning or statement.
Action: Take action immediately - move to higher ground, do not drive through flooded roadways.

Flash Flood Statement - A flash flood statement provides supplemental information on active flash flood warning, such as updated observations and impact information. It will provide the latest information on the flash flooding situation.

Areal Flood Warning An areal flood warning may be issued for any high flow, overflow, or inundation in a geographical area which threatens life and property and isnt appropriately covered by a flash flood warning or flood warning for forecast points.

Flood Statement - A flood statement is issued after a Flood Warning. It will provide the latest information on the flooding situation.

High Wind Warning - A high wind warning is issued when sustained winds (not of thunderstorm origin) are predicted to reach 40 mph or greater for at least one hour, or any gust of wind is expected to be 58 mph or greater.

Severe Thunderstorm Warning - A severe thunderstorm warning is issued when large hail or damaging wind is occurring or imminent. Severe thunderstorms can also produce tornadoes with little or no advance warning. Severe thunderstorms will also produce frequent and dangerous lightning and occasionally torrential rainfall.
Action: Seek safe shelter immediately. Criteria: Hail - 1" or larger; Wind - 58 mph or greater.

Severe Weather Statement - A severe weather statement provides follow-up information on severe weather conditions (severe thunderstorm or tornadoes) which have occurred or are currently occurring.

Special Marine Warning - A product issued for potentially hazardous weather conditions usually of short duration (up to 2 hours) producing sustained marine thunderstorm winds or associated gusts of 34 knots or greater; and/or hail 3/4 inch or more in diameter; and/or waterspouts. It is also used for short duration non-thunderstorm events such as a strong cold front, gravity wave, squall line, etc., lasting less than 2 hours and producing winds or gusts of 34 knots or greater.
Action: Boaters should move to safe harbor.

Red Flag Warning - A red flag warning is issued when favorable conditions exist for forest, grass or brush fires to exhibit extreme fire danger and/or fire behavior. It is a combination of factors consisting of dry fuels, low humidity, and increased winds. .

River Flood Warning - A river flood warning is issued for specific communities or points along a river where flooding is imminent or occurring. River flood warnings will provide crest forecasts.
Action: move to higher ground; do not drive through flooded roadways

Tornado Warning - A tornado warning is issued when a tornado is imminent or occurring. The warning may be issued when a tornado is either indicated by Doppler radar or sighted by trained spotters.
Action: Seek shelter immediately, preferably below ground in a substantial building.

Tornado Emergency- An exceedingly rare tornado warning or statement issued when there is a severe threat to human life and catastrophic damage from an imminent or ongoing tornado. This tornado warning is reserved for situations when a reliable source confirms a tornado, or there is clear radar evidence of the existence of a strong, damaging tornado, such as the observation of debris.
Action: Seek shelter immediately, preferably below ground in a substantial building.


ADVISORIES

Dense Fog Advisory - A dense fog advisory is issued when widespread fog will reduce visibility to one-fourth mile or less.

Heat Advisory - A heat advisory is issued when heat index is expected to reach at least 100F but less than 105F

Urban & Small Stream Flood Advisory - Alerts the public to flooding which is generally only an inconvenience (not life-threatening) to those living in the affected area. It is issued when heavy rain will cause flooding of streets and low-lying places in urban areas. Also used if small rural or urban streams are expected to reach or exceed bank-full. Some damage to homes or roads could occur.

Wind Advisory - A wind advisory is issued when sustained winds are expected to be between 31 and 39 mph for an hour or more, or any instantaneous wind gust between 46 mph and 57 mph is expected.


WEATHER TERMS

Cold Air Funnels
A funnel cloud or (rarely) a small, relatively weak tornado that can develop from a small shower or thunderstorm when the air aloft is unusually cold (hence the name). They are much less violent than other types of tornados.

Derecho
A widespread, fast-moving windstorm associated with convection. Derechos are typically produced by a thunderstorm complex, where the thunderstorms become organized on a scale larger than the individual storms and form a convective system. Derechos can produce damaging straight-line winds over areas hundreds of miles long and more than 100 miles across.

Downburst
A strong downdraft current of air from a thunderstorm, often associated with intense thunderstorms. Downbursts may produce damaging winds at the surface.

Flash Flood
A rapid and extreme flow of high water into a normally dry area, or a rapid rise in a stream or creek above a predetermined flood level, beginning in a short period of time from the causative event. Flash floods typically occur as the result of very heavy rainfall in a short period of time over a relatively small area. It may also be caused by a dam break..

Flood
A condition that occurs when water overflows the natural or artificial confines of a stream or body of water, or accumulates by drainage over low lying areas. This flood is any high flow of water, overflow, or inundation by water which causes or threatens damage.

Funnel Cloud
A condensation funnel extending from the base of a towering cumulus cloud associated with a rotating column of air that is not in contact with the ground and hence, different from a tornado. A condensation funnel is a tornado, not a funnel cloud if
a.) it is in contact with the ground;
b.) a debris cloud or dust whirl is visible beneath it.

Gust Front
The leading edge of gusty surface winds caused by thunderstorms. Sometimes these winds occur with a roll cloud or shelf cloud and can be quite distant from the originating thunderstorm.

Lightning
A visible electrical discharge produced by a thunderstorm. The discharge may occur within or between clouds, between the cloud and air, or between a cloud and the ground.

Severe Thunderstorm
A thunderstorm producing a tornado and/or, damaging winds of 58 mph or higher, and/or hail 1 inch in diameter or larger. Structural wind damage may imply the occurrence of a severe thunderstorm.

Squall Line
A line of active thunderstorms, either continuous or with breaks, including contiguous precipitation areas resulting from the existence of thunderstorms.

Straight-Line Winds
Generally, any wind that is not associated with rotation, used mainly to differentiate them from tornadic winds. See downburst.

Thunderstorm
A local storm produced by a cumulonimbus cloud, and accompanied by thunder and lightning, strong wind gusts, heavy rain and sometimes hail. A cumulonimbus cloud is a cauliflower-shaped cloud that usually has a height taller than or equal to its width.

Tornado
A violently rotating column of air that comes in contact with the ground, usually, descending from the base of a thunderstorm. In Ohio, many tornadoes are obscured by hills, trees or heavy rain.

Winter Weather Terms

Winter Storm Warning: Issued when hazardous winter weather in the form of heavy snow, heavy freezing rain, or heavy sleet is imminent or occurring. Winter Storm Warnings are usually issued 12 to 24 hours before the event is expected to begin.

Winter Storm Watch: Alerts the public to the possibility of a blizzard, heavy snow, heavy freezing rain, or heavy sleet. Winter Storm Watches are usually issued 12 to 48 hours before the beginning of a Winter Storm.

Winter Storm Outlook: Issued prior to a Winter Storm Watch. The Outlook is given when forecasters believe winter storm conditions are possible and are usually issued 3 to 5 days in advance of a winter storm.

Blizzard Warning: Issued for sustained or gusty winds of 35 mph or more, and falling or blowing snow creating visibilities at or below ¼ mile; these conditions should persist for at least three hours.

Lake Effect Snow Warning: Issued when heavy lake effect snow is imminent or occurring.

Lake Effect Snow Advisory: Issued when accumulation of lake effect snow will cause significant inconvenience.

Wind Chill Warning: Issued when wind chill temperatures are expected to be hazardous to life within several minutes of exposure.

Wind Chill Advisory: Issued when wind chill temperatures are expected to be a significant inconvenience to life with prolonged exposure, and, if caution is not exercised, could lead to hazardous exposure.

Winter Weather Advisories: Issued for accumulations of snow, freezing rain, freezing drizzle, and sleet which will cause significant inconveniences and, if caution is not exercised, could lead to life-threatening situations.

Dense Fog Advisory: Issued when fog will reduce visibility to ¼ mile or less over a widespread area.

Snow Flurries: Light snow falling for short durations. No accumulation or light dusting is all that is expected.

Snow Showers: Snow falling at varying intensities for brief periods of time. Some accumulation is possible.

Snow Squalls: Brief, intense snow showers accompanied by strong, gusty winds. Accumulation may be significant. Snow squalls are best known in the Great Lakes region.

Blowing Snow: Wind-driven snow that reduces visibility and causes significant drifting. Blowing snow may be snow that is falling and/or loose snow on the ground picked up by the wind.

Sleet: Rain drops that freeze into ice pellets before reaching the ground. Sleet usually bounces when hitting a surface and does not stick to objects. However, it can accumulate like snow and cause a hazard to motorists.

Freezing Rain: Rain that falls onto a surface with a temperature below freezing. This causes it to freeze to surfaces, such as trees, cars, and roads, forming a coating or glaze of ice. Even small accumulations of ice can cause a significant hazard.


For a more detailed glossary of weather terms, consult the National Weather Service Glossary, with information on more than 2000 terms, phrases, and abbreviations used by the NWS. http://w1.weather.gov/glossary/