The 8-Day Hazardous Weather Briefing at New York Metro Weather is a feature meant to put you ahead of any hazardous weather well in advance of its occurrence. Our forecasters use a carefully calculated scale to measure the risk of the following hazards (these may change or disappear from the briefing by season). The risk areas and associated categories below give you a reference as to how and why our forecasters are issuing risk areas.
In a general sense, Slight Risk is meant to signify unusual but manageable weather risk. Enhanced Risk is meant to signify a more organized unusual or severe weather risk that requires area Moderate risk is meant to signify unusual weather risk that requires preparation. High Risk is meant to categorize highly unusual, impactful, and extremely hazardous weather.
Slight Risk (15% probability of occurrence within 25 miles of any point)
This risk category is meant to signify the manageable potential for unusual or hazardous weather. Typically, this refers to things such as the potential for a few scattered severe thunderstorms, the possibility of torrential rain or lightning. These are lower confidence risk areas that are meant to signify the potential.
Enhanced Risk (25% probability of occurrence within 25 miles of any point)
This risk category is meant to carry more weight than the slight risk, with more confidence in an organized weather event. An organized line of strong thunderstorms, rising confidence in a high wind/flooding event, or risk of hazardous roadways during wintry precipitation.
Moderate Risk (40% probability of occurrence within 25 miles of any point)
This risk category is more rarely used, and signifies a heightened chance for unusual severe or damaging weather conditions that will require preparation. This risk category also signifies a more organized or concentrated risk of that said weather risk. For instance, an organized or dangerous severe weather event, a blizzard or significant snowfall, or flooding.
High Risk (60% risk of occurrence within 25 miles of any point)
Used extremely rarely, this risk category is meant to signify an extremely heightened chance of hazardous weather, with much higher than normal chances of damage or adverse impacts from that weather hazard. An extreme severe thunderstorm event, blizzard, high confidence in flooding or high wind events causing damage, or significantly impactful wind event are all examples.
Categories, hazards and criteria:
Snow 4″/8″/12″: The risk of snow accumulating to the specified amount within 25 miles of the specified location.
Hazardous Roads: The risk of roads becoming hazardous for driving or transportation; i.e flooding, debris, accumulated snow or ice with expected delays or travel impacts.
High Winds: Risk of non-thunderstorm related high-wind gusts over 45 miles per hour.
Wind Chill: The risk of wind chill values falling below -10 F for more than 3 hours.
Heavy Rain: The risk of heavy rain impacting travel or transportation and causing other imminent hazards.
Flooding: The risk of impact from flooding including coastal flooding, flash flooding, river flooding, etc which may be associated with hazardous conditions including flooded or impassable roads, threat of damage to property, threat to life and well being.
Dense Fog: Probability of decreased visibility or hazardous travel due to thick and dense fog. No visibility requirements for a risk area.
Heat: Probability of Heat Index (Air Temp + Humidity) exceeding 90 F.
Severe Storms: Risk of any severe weather (wind gusts over 55mph, hail over 0.75″ diameter, or tornadoes) within 25 miles of a point (wind, hail, tornadoes).
Tropical: The risk of tropical weather impacts including but not limited to tropical rains, storm surge, or tropical storm force winds.
Fire Danger: The risk of fire danger, owing to low humidity and high winds and the potential for rapid brush or wildfire spread.
Ice Accretion: The risk of 0.05″ or greater of ice accretion on any surface.