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Hazardous Weather Outlooks, Watches, Warnings and Advisories

Important Note: The criteria listed below apply to the service area of the National Weather Service (NWS) Forecast Office in Upton, NY.

Click to see NWS Eastern Region Winter Warning and Advisory Criteria

General Definitions

Outlook
Indicates the potential for significant weather events up to 7 days in advance with a forecaster confidence around 30%.

Watch
Indicates that conditions are favorable for the particular weather event in and near the Watch area, and which may pose a risk to life and property. Watches are issued up to 48 hours in advance with forecaster confidence around 50%.

Warning/Advisory
Indicates that a particular weather event is imminent or occurring. Advisories are issued if the weather event will lead to nuisance conditions, while Warnings are issued for significant weather events which will pose a risk to life and property. Warnings and Advisories are issued up to 48 hours in advance with forecaster confidence of at least 80%.

 Note: Watches and Warnings issued for Severe Thunderstorms, Tornadoes, and Flash Flooding have much shorter lead times, on the order of hours for Watches or even minutes for Warnings.

Fire Weather Watches and Warnings

Red Flag Warning
Issued to indicate that the combination of dry fuels and weather conditions will support extreme fire danger and/or fire behavior, including the potential for widespread new ignitions or control problems with existing fires.  Warning criteria typical for the spring and fall are winds sustained or frequently gusting above 25 mph, relative humidity less than 30%, and widespread rainfall less than 1/4 inch during the previous three or more days. In the summer, the rainfall criteria is extended to five or more days, as well as a Keetch-Byram Drought Index above 300 which indicates at least the top three inches of the ground are sufficiently dry. A Red Flag Warning may or may not be preceded by a Fire Weather Watch.

Flood Watches, Warnings, and Advisories

Flash Flood Warning
Issued when flash flooding is imminent, generally within the next 6 hours. This is usually issued based on observed heavy rainfall (measured or radar estimated) for dangerous small stream or urban flooding, but may also be issued for significant dam or levee failures that have occurred or are imminent.

Flood Warning for River Forecast Point
Issued when a river gauge is forecast to exceed a predetermined flood stage.

Areal Flood Warning
Issued when widespread general flooding is forecast to occur throughout an identifiable geographic area.

Flood Advisory
Issued when flooding is forecast to occur, generally within the next 6 hours, but is not expected to substantially threaten life and property.

Coastal Flood Warning
Issued when at least moderate tidal flooding is forecast to occur along coastal areas.

Coastal Flood Advisory
Issued when minor tidal flooding is forecast to occur along coastal areas.

Marine Weather Watches, Warnings, and Advisories

Hurricane Force Wind Warning
Issued when a non-tropical system is forecast to produce sustained winds or frequent gusts of 64 knots or greater.

Storm Warning
Issued for sustained winds or frequent gusts of 48 to 63 knots, not associated with a tropical system.

Gale Warning
Issued for sustained winds or frequent gusts of 34 to 47 knots, not associated with a tropical system.

Small Craft Advisory
Issued for sustained winds or frequent gusts of 25 to 33 knots and/or hazardous seas with waves of 5 feet or higher.

Special Marine Warning
Issued to convey information regarding hazardous convective activity or other short-term weather events occurring over the water or which may impact those on the water that are not covered by the current forecast.

Dense Fog Advisory
Issued when widespread fog is expected to reduce visibilitiy to 1 nautical mile or less.

Freezing Spray Advisory
Issued when freezing spray is expected to pose a significant hazard to marine vessels.

High Surf Advisory
Issued when expected high/rough surf poses a threat to life and/or property.

Low Water Advisory
Issued when tidal levels are expected to be low enough to cause problems for shipping and other marine interests.

Non-Precipitation Watches, Warnings, and Advisories

High Wind Warning
Issued when sustained winds of 40 mph or greater are forecast for 1 hour or longer, or wind gusts of 58 mph or greater for any duration.

Wind Advisory
Issued when sustained winds of 30 to 39 mph are forecast for 1 hour or longer, or wind gusts of 46-57 mph for any duration.

Excessive Heat Warning
Issued when heat index values are forecast to reach or exceed 105°F for at least 2 consecutive hours.

Heat Advisory
Issued when maximum daytime heat index values are forecast to reach 100 to 104°F for at least 2 consecutive hours.
NOTE: For New York City, a Heat Advisory is issued when the heat index is forecast to reach 95 to 99�F for at least 2 consecutive days or 100 to 104�F for any length of time.

Freeze Warning
Issued when overnight minimum temperatures are forecast to reach 32�F or lower during the growing season. They are usually issued to highlight the first few freezes of the fall, or unusually late freezes in the spring.

Frost Advisory
Issued when conditions are favorable for frost development during the growing season due to overnight minimum temperatures falling between 33°F to 36°F.

Air Quality Alert
Issued by the NYSDEC(Department of Environmental Conservation), NJDEP(Department of Environmental Protection), and/or CTDEP when ground ozone concentrations and/or particulate matter are forecast to become unhealthy for sensitve groups of people(Air Quality Index greater than or equal to 100).

Dense Fog Advisory
Issued when widespread fog is expected to reduce visibilitiy to 1/4 mile or less.

Severe Weather Watches, Warnings, and Statements

Severe Thunderstorm Warning
Issued when there is evidence based on radar or a reliable spotter report that a thunderstorm is producing, or forecast to produce, wind gusts of 58 mph or greater, structural wind damage, and/or hail 1 inch in diameter or greater.

Severe Thunderstorm Watch
Issued by the Storm Prediction Center when conditions are favorable for the development of severe thunderstorms over a larger-scale region for a duration of at least 3 hours. Tornadoes are not expected in such situations, but isolated tornado development can also occur.

Tornado Warning
Issued when there is evidence based on radar or a reliable spotter report that a tornado is imminent or occurring.

Tornado Watch
Issued by the Storm Prediction Center when conditions are favorable for the development of severe thunderstorms and multiple tornadoes over a larger-scale region for a duration of at least 3 hours.

Special Weather Statement for Near Severe Thunderstorms
Issued for strong thunderstorms that are below severe levels, but still may have some adverse impacts. Usually issued for the threat of wind gusts of 40-58 mph or small hail less than 1 inch in diameter.

Tropical Weather Watches and Warnings

Hurricane Warning
Issued by the National Hurricane Center when sustained winds of 74 mph or higher are forecast within the specified coastal area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane warning is issued 36 hours in advance of the anticipated onset of tropical-storm-force winds.

Hurricane Watch
Issued by the National Hurricane Center when sustained winds of 74 mph or higher are possible within the specified coastal area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane watch is issued 48 hours in advance of the anticipated onset of tropical-storm-force winds.

Tropical Storm Warning
Issued by the National Hurricane Center when sustained winds between 39 and 73 mph are forecast within the specified coastal area within 36 hours.

Tropical Storm Watch
Issued by the National Hurricane Center when sustained winds between 39 and 73 mph are possible within the specified coastal area within 48 hours.

Hurricane Wind Warning
Issued when a tropical cyclone is forecast to spread sustained winds of 74 mph or greater to inland areas.

Tropical Storm Wind Warning
Issued when a tropical cyclone is forecast to spread sustained winds between 39 and 73 mph to inland areas.

Winter Season Watches, Warnings, and Advisories

Winter Storm Warning
Issued for a winter weather event in which there is more than one of the following: snow, sleet, and ice (freezing rain), and one of the warning criteria is met. The warning criteria for snow is 6 inches expected in a 12 hour period, or 8 inches expected in a 24 hour period. The warning criteria for ice is accumulations meeting or exceeding 1/2 inch.  A winter storm warning may also be issued for heavy snow combined with strong winds of 25-34 mph that will cause blowing and drifting of the snow. A warning may still be warranted if the event is expected to exceed advisory criteria, but fall just short of warning criteria and will significantly impact mass transit and/or utilities.

Blizzard Warning
Issued for sustained winds or frequent gusts greater than or equal to 35 mph accompanied by falling and/or blowing snow, frequently reducing visibility to less than 1/4 mile for three hours or more.

Ice Storm Warning
Issued when freezing rain is expected to produce ice accumulations of 1/2 inch or greater, or cause significant disruptions to travel or utilities.

Wind Chill Warning
Issued when wind chill values will reach -25°F or colder.



Winter Weather Advisory

Issued for a winter weather event in which there is more than one of the following: snow, sleet, and ice (freezing rain), and one of the advisory criteria is met but does not exceed warning criteria. In addition, a winter weather advisory will be issued for an all-snow event if the advisory criteria is met but does not exceed the warning criteria. The advisory criteria is 3 inches of snow and/or sleet expected in a 12 hour period, or a trace of ice accumulation.  An advisory may still be warranted if lesser accumulations will significantly impact mass transit and/or utilities.

Freezing Rain Advisory
Issued when a trace of ice accumulation is expected from freezing rain and/or drizzle, but not to exceed 1/2 inch.

Wind Chill Advisory
Issued when wind chill values will reach -15°F to -24°F.

 



National Weather Service
WFO-Upton
175 Brookhaven Ave. Bldg. NWS-1
Upton, NY 11973

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Page last modified: May 9th, 2010
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