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A small craft advisory is a type of wind warning issued by the National Weather Service in the United States. In Canada a similar warning is issued by Environment Canada. It is issued when winds have reached, or are expected to reach within 12 hours, a speed marginally less than gale force. A Small Craft Advisory may also be issued when sea or lake ice exists that could be hazardous to small boats.
A winter storm warning is a hazardous weather statement issued by Weather Forecast Offices (WFO) of the National Weather Service (NWS) in the United States to alert the public that a winter storm is occurring or is about to occur in the area, usually within 36 hours of the storm's onset.
A winter weather advisory is a hazardous weather statement issued by Weather Forecast Offices (WFO) of the National Weather Service in the United States when one or more types of winter precipitation—snow, rain and snow mixed, freezing rain or sleet—presenting a hazard, but not expected to produce accumulations meeting warning criteria, are forecast within 36 hours of the expected onset of precipitation or are occurring in the advisory's coverage area.
A blowing snow advisory was issued by the National Weather Service of the United States when wind driven snow reduces surface visibility and possibly hampers traveling. Blowing snow may be falling snow, or snow that has already accumulated but is picked up and blown by strong winds. This advisory was discontinued beginning with the 2008–09 winter storm season, replaced by the winter weather advisory for snow and blowing snow. However, if the storm is judged to be dangerous by local forecasters, a winter storm warning for heavy snow and blowing snow may be issued.
An ice storm warning is an hazardous weather statement issued by the Weather Forecast Offices of the National Weather Service in the United States which indicates freezing rain produces a significant and possibly damaging accumulation of ice. The criteria for this warning vary from state to state, but typically an ice storm warning will be issued any time more than 1⁄4 inch (6.4 mm) of ice is expected to accumulate in an area; in some areas, the criterion is 1⁄2 inch (13 mm).
At sea, a storm warning is a warning issued by the National Weather Service of the United States when winds between 48 knots and 63 knots are occurring or predicted to occur soon. The winds must not be associated with a tropical cyclone. If the winds are associated with a tropical cyclone, a tropical storm warning will be substituted for the storm warning and less severe gale warning.
A red flag warning is a forecast warning issued by the National Weather Service in the United States to inform the public, firefighters, and land management agencies that conditions are ideal for wildland fire combustion, and rapid spread. After drought conditions, when humidity is very low, and especially when there are high or erratic winds which may include lightning as a factor, the Red Flag Warning becomes a critical statement for firefighting agencies. These agencies often alter their staffing and equipment resources dramatically to accommodate the forecast risk. To the public, a Red Flag Warning means high fire danger with increased probability of a quickly spreading vegetation fire in the area within 24 hours.
A flash flood warning is an hazardous weather statement issued by national weather forecasting agencies throught the world to alert the public that a flash flood is imminent or occurring in the warned area. A flash flood is a sudden, violent flood after a heavy rain, or occasionally after a dam break. Rainfall intensity and duration, topography, soil conditions, and ground cover contribute to flash flooding.
A particularly dangerous situation (PDS) tag is enhanced wording first used by the Storm Prediction Center (SPC), a national guidance center of the United States National Weather Service, for tornado watches and eventually expanded to use for other severe weather watches and warnings by local NWS forecast offices. It is issued at the discretion of the forecaster composing the watch or warning and implies that there is an enhanced risk of very severe and life-threatening weather, usually a major tornado outbreak or a long-lived, extreme derecho event, but possibly another weather hazard such as an exceptional flash flood or fire.
A flash flood watch is issued by the National Weather Service when conditions are favorable for flash flooding in flood-prone areas, usually when grounds are already saturated from recent rains, or when upcoming rains will have the potential to cause a flash flood. These watches are also occasionally issued when a dam may break in the near future.
A flood warning is closely linked to the task of flood forecasting. The distinction between the two is that the outcome of flood forecasting is a set of forecast time-profiles of channel flows or river levels at various locations, while "flood warning" is the task of making use of these forecasts to make decisions about whether warnings of floods should be issued to the general public or whether previous warnings should be rescinded or retracted.
An urban and small stream flood advisory is issued when ponding of water of streets, low-lying areas, highways, underpasses, urban storm drains, and elevation of creek and small stream levels is occurring or imminent. Urban and small stream flood advisories are issued for flooding that occurs within three hours after the excessive rainfall. These advisories are issued on a county by county basis by the local Weather Forecast Office and are generally in effect for 3 to 4 hours.
A lake wind advisory is issued by the United States National Weather Service local forecast offices when windy conditions on area lakes are expected to be hazardous for boaters and other recreational events on or around lakes.
A river flood warning is issued by the National Weather Service of the United States when forecast points with formal river gaging sites and established flood stages along rivers, where flooding has already been forecast, is imminent or occurring. The National Weather Service defines river flooding as "the inundation of normally dry areas as a result of increased water levels in an established water course."
A river flood watch is issued by the National Weather Service of the United States when flooding at formal forecast points with river gaging sites and established flood stages is possible. Flooding may be caused by various reasons, such as heavy rain in the vicinity of the river, melting snow, and/or ice jams.
A wind chill watch is issued by the National Weather Service of the United States when the wind chill could reach dangerous levels within the next 12 to 48 hours. The exact definition required to issue a watch varies from state to state or from National Weather Service county warning areas to another, but if forecasters believe conditions are favorable for life-threatening wind chills meeting local criteria, a watch will be issued. People going outside should plan to protect themselves against hypothermia and frostbite.
A wind chill warning is a hazardous weather statement issued by local forecast offices of the National Weather Service (NWS) in the United States and previously by the Meteorological Service of Environment and Climate Change Canada (ECCC) when wind chills are forecast to reach values low enough for residents and travelers to be succeptible to life-threatening medical conditions or death associated with accelerated body heat loss.
A Hazardous Seas Warning is issued by the National Weather Service of the United States when wave heights and/or wave steepness values reach certain criteria. These criteria are defined by the local forecast office. Such tall waves can pose a serious threat to vessels that do not seek shelter.
A Hazardous Seas Watch is issued by the National Weather Service of the United States when there is an increased threat of high wave heights and/or wave steepness values reach a certain criteria, but the occurrence, timing, and/or location are still uncertain. The criteria are set by the local forecast offices. Such tall waves can pose a serious threat to vessels that do not seek shelter.
A Freezing Spray Advisory is issued by the National Weather Service of the United States to warn vessels that accumulation of freezing water droplets due to a combination of cold water, wind, cold air, and vessel movement is possible, however, accumulations are not expected to reach rates of 2 cm per hour.
References
- ↑ The Weather Channel. "Local Severe Weather Alerts Help". Archived from the original on 12 July 2011. Retrieved 17 May 2011.
- ↑ Seattle National Weather Service Forecast Office. "River Flood Advisory (FLS)" (PDF). Appendix H – Products Examples – Watches, Warnings, Advisories, and Statements. Retrieved 17 May 2011.