Criteria

NWS Raleigh Products & Services Guide

NWS Watch, Warning, and Advisory Quick Reference
New One Inch Hail Warning Criteria

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Hazardous Weather

To accomplish our mission, we use a three-tiered approach (READY…SET…GO!!) to disseminate information about hazardous weather. This approach is based on the amount of time leading up to a weather event.

Ready, Set, Go, Watch and Warning Strategy

Referring back to our mission statement, the main focus of the NWS is the protection of life and property. Our number one priority is issuing statements and products that prepare and alert you to upcoming hazardous weather. The following section details these products in terms of the three-tiered approach. Note the VTEC and the WMO code used for each type of statement.

Outlooks (Get Ready!!)

The National Weather Service issues outlooks if the potential for hazardous weather exists in the next three to seven-day period. While still too far in advance to warrant a detailed watch, an outlook highlights potential hazards and explains possible threats.

OUTLOOKS

EXAMPLES

HAZARDOUS WEATHER OUTLOOK
VTEC: NONE
WMO: FLUS42 KRAH

Issued daily to highlight any hazardous weather within the next seven days. Broken down into day one (current day and night), and days two through seven, it highlights the potential for such events as critical severe thunderstorms, flooding, winter storms, high wind, dense fog, heat, cold, and critical fire weather. Forecast confidence at the outlook phase of the forecast can range from 30% to near 100%.

Watches (Get Set!!)

The NWS issues watches up to 48 hours in advance of the onset of potentially hazardous weather. This allows people time to plan for the protection of lives and property. A watch means that conditions are favorable for the development of certain phenomena, but the conditions are not yet occurring or imminent. During a watch, people are advised to continue with their normal activities, but are made aware that hazardous weather may approach.

WATCHES	CRITERIA
SEVERE THUNDERSTORM WATCH VTEC: SV.A WMO: WWUS64 KWNS	Issued by the Storm Prediction Center when conditions are favorable for the development of thunderstorms which contain winds of at least 58 mph (50 kts) and/or hail 1 inch (2.5 cm) or larger
TORNADO WATCH VTEC: TO.A WMO: WWUS64 KWNS	Issued by the Storm Prediction Center when conditions are favorable for thunderstorms to produce tornadoes
WATCH COUNTY NOTIFICATION VTEC: SV.A or TO.A WMO: WWUS62 KRAH PIL: WCNRAH	Issued by the local NWS office outlining the counties within the forecast and warning area included in the current Severe Thunderstorm or Tornado Watch. Issued immediately following the official watch issued by the Storm Prediction Center.
FLASH FLOOD WATCH VTEC: FF.A WMO: WGUS62 KRAH PIL: FFARAH	Potential for short duration, flash flooding resulting from heavy rain typically associated with thunderstorms or tropical squalls producing rainfall rates 1 to 2 inches per hour or greater. Also issued for potential dam failures when a large release of water is possible.
FLOOD WATCH VTEC: FA.A WMO: WGUS62 KRAH PIL: FFARAH	Conditions are favorable for slower developing flooding from long duration rains typically not exceeding one inch per hour. Typically issued for slower developing spring floods.
RIVER FLOOD WATCH VTEC: FL.A WMO: WGUS62 KRAH PIL: FFARAH	Issued for river forecast points when river flooding is possible and flooding is not expected to begin within the next 24 hours. Issued primarily when river flood forecasts are solely based on forecast heavy rainfall 24 to 48 hours in the future.
WINTER STORM WATCH VTEC: WS.A WMO: WWUS42 KRAH PIL: WSWRAH	Potential for a blizzard, heavy snowfall or ice storm within 18 to 48 hours. Issued when there is a 50% confidence or greater of at least 3 inches of snow, ½ inch (13 mm) of sleet and/or a ¼ inch (6 mm) of ice.
FREEZE WATCH VTEC: FZ.A WMO: WWUS72 KRAH PIL: NPWRAH	Potential for the first freeze of the fall season or for a late spring freeze within 18 to 24 hours. Product is discontinued for the season following the first fall "killing" freeze.
HIGH WIND WATCH VTEC: HW.A WMO: WWUS72 KRAH PIL: NPWRAH	Conditions are favorable for development of sustained winds of 40 mph (35 kt) or greater and/or gusts of 58 mph (50 kt) or greater within 24 to 48 hours
EXCESSIVE HEAT WATCH VTEC: HT.A WMO: WWUS72 KRAH PIL: NPWRAH	Potential for heat index values of 110 degrees or hotter within 24 to 48 hours. Also issued during prolonged heat waves when the heat index is near 110ºF.
FIRE WEATHER WATCH VTEC: FW.A WMO: WWUS82 KRAH PIL: RFWRAH	Dangerous fire behavior possible within the nest 24-36 hours based on weather conditions and dry fuels. Generally wind gusts 20 mph or greater, minimum humidity 25% or lower and dry fuels. Coordinated with the NC Division of Forestry.

Warnings/Advisories (GO!!)

Warnings are issued when potentially hazardous or life-threatening weather is occurring or imminent. This is the cue to immediately implement plans to protect life and property.

WARNINGS	CRITERIA
SEVERE THUNDERSTORM WARNING VTEC: SV.W WMO: WUUS52 KRAH PIL: SVRRAH	Thunderstorm winds 58 mph (50 kts) and/or hail 1 inch (2.5 cm) or greater
TORNADO WARNING VTEC: TO.W WMO: WFUS52 KRAH PIL: TORRAH	A tornado has been spotted or detected on radar
FLASH FLOOD WARNING VTEC: FF.W WMO: WGUS52 KRAH PIL: FFWRAH	Short duration (usually less than six hours), flash flooding resulting from storms with rainfall rates of 1 to 2 inches per hour or greater. Also issued when a dam has failed or when a dam failure is imminent.
FLOOD WARNING (AREAL/COUNTY) VTEC: FA.W WMO: WGUS42 KRAH PIL: FLWRAH	Long duration (slow to evolve), flooding resulting from steady stratiform rain with rates typically less than 1 inch per hour. Most common during long duration spring rains resulting in widespread flooding.
RIVER FLOOD WARNING VTEC: FL.W WMO: WGUS42 KRAH PIL: FLWRAH	River flooding is occurring or is forecast for a point. Normally issued when flooding is forecast within 24 hours based on accumulated rainfall, but may also be issued when there is a high confidence in a heavy rain event.
WINTER STORM WARNING VTEC: WS.W WMO: WWUS42 KRAH PIL: WSWRAH	Snow accumulations 3 inches or greater in 12 hours (4 inches or more in 24 hours); Freezing rain accumulations ¼ inch (6 mm) or greater; Sleet accumulations ½ inch (13 mm)or more. Issued when there is at least a 60% forecast confidence of any one of the three criteria being met.
BLIZZARD WARNING VTEC: BZ.W WMO: WWUS42 KRAH PIL: WSWRAH	Winds 35 mph (30 kts) AND falling and/or blowing snow reducing visibility to less than ¼ mile (1.2 km) for at least three hours
ICE STORM WARNING VTEC: IS.W WMO: WWUS42 KRAH PIL: WSWRAH	Freezing rain accumulations ¼ inch (6 mm) or greater resulting in significant, widespread power outages, tree damage and dangerous travel. Issued only in those rare instances where just heavy freezing rain is expected and there will be no "mixed bag" precipitation meaning no snow, sleet or rain.
WIND CHILL WARNING VTEC: WC.W WMO: WWUS42 KRAH PIL: WSWRAH	Wind chill -15ºF or lower with wind speeds 10 mph (9 kt) or greater
FREEZE WARNING VTEC: FZ.W WMO: WWUS72 KRAH PIL: NPWRAH	When temperatures will be at or below 32ºF over a large area for a significant time during the growing season
HIGH WIND WARNING VTEC: HW.W WMO: WWUS72 KRAH PIL: NPWRAH	Non-convective sustained wind speeds 40 mph (35 kt) and greater and/or frequent wind gusts 50 mph (43 kt) and greater or any winds gusts 57 mph (50 kt) and greater
EXCESSIVE HEAT WARNING VTEC: HT.W WMO: WWUS72 KRAH PIL: NPWRAH	Heat Index of 110ºF or greater for any duration
RED FLAG / FIRE WEATHER VTEC: FW.W WMO: WWUS82 KRAH PIL: RFWRAH	Dangerous fire behavior expected within 12-24 hours based on weather conditions and dry fuels. Generally wind gusts 20 mph (17 kt) or greater, minimum humidity 25% or lower and dry fuels. Coordinated with the NC Division of Forestry.

Advisories are issued for weather events that are expected to have a significant, but somewhat less overall impact.

ADVISORIES	CRITERIA
FLOOD ADVISORY VTEC: FA.Y WMO: WGUS82 KRAH PIL: FLSRAH	Localized flooding resulting from heavy rain. Water may start to threaten homes and businesses, and minor flooding of roads is possible
WINTER WEATHER ADVISORY VTEC:WS.Y WMO: WWUS42 KRAH PIL: WSWRAH	Snow accumulations 1-3 inches; Any freezing rain accumulations less than ¼ inch; Any sleet accumulations less than ½ inch. Winter Weather Advisories are issued in any one of the three criteria are forecast to be met
WIND CHILL ADVISORY VTEC: WC.Y WMO: WWUS72 KRAH PIL: WSWRAH	0ºF to -14ºF with wind speeds 10 mph (9 kt) or greater
FROST ADVISORY VTEC: FR.Y WMO: WWUS72 KRAH PIL: NPWRAH	When frost is expected during the growing season
WIND ADVISORY VTEC: HW.Y WMO: WWUS72 KRAH PIL: NPWRAH	Non-convective sustained wind speeds 31-39 mph (27-34 kt); frequent wind gusts 40-45 mph (35-39 kt); any wind gusts 46-57 mph (40-50 kt)
HEAT ADVISORY VTEC: HT.Y WMO: WWUS72 KRAH PIL: NPWRAH	Heat Index of 105ºF to 109ºF for 3 hours or more. Can also be issued for lower values 100ºF to 104ºF for heat lasting several consecutive days
DENSE FOG ADVISORY VTEC: FG.Y WMO: WWUS72 KRAH PIL: NPWRAH	Fog reducing visibilities to a ¼ mile (0.4 km) or less
DENSE SMOKE ADVISORY VTEC: SM.Y WMO: WWUS72 KRAH PIL: NPWRAH	Smoke reducing visibilities to a ¼ mile (0.4 km) or less and/or smoke expected to cause travel hazards. Could be localized or widespread

For current severe weather outlooks, watches and warnings nationwide, please reference the Storm Prediction Center webpage.