Criteria may be adjusted in certain circumstances to take into account the expected impact of an event. For example, a Winter Weather Advisory may be issued for less than an inch of snow if it will occur at a peak travel time, such as around the normal morning commute time, and thus potentially have a significant impact.
Severe Thunderstorm Warning
- Radar or satellite indicate and/or reliable reports of thunderstorms with:
- Wind gusts equal to in excess of 58 mph
- AND/OR hail size of 1 inch (U.S quarter size) in diameter or larger.
Tornado Warning
- Radar indication and/or reliable reports of tornado or developing tornado.
Special Weather Statement
- Strong thunderstorms that approach, or expected to approach severe criteria.
- A strong thunderstorm contains one or combination of the following events:
- Wind gusts of 40 to 57 mph
- Hail less than 1 inch in diameter
- Frequent to continuous lightning
- Landspouts that are not anticipated to threaten lives and/or property
- Funnel clouds not expected to become a tornado threat
See NWSI 10-511 WFO Severe Weather Products Specification for additional information.
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Flash Flood Warning
- Life or property-threatening, short-term rapid onset flooding is imminent or occurring. This can include flooding due to heavy rainfall or due to a dam or levee break.
Flood Warning
- Flooding due to potentially damaging river level rises,
- OR damaging overland flooding that is expected to persist for many hours.
Flood Advisory
- Nuisance flooding due to river level rises and minor overland flooding and/or ponding of water that warrants notification of the public but less urgent than a warning.
Special Weather Statement
- Heavy rainfall that is expected to cause hazardous travel conditions but is not expected to cause flooding.
See NWSI 10-922 WFO Hydrologic Products Specification for additional information.
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Blizzard Warning
- Sustained wind or frequent gusts greater than or equal to 35 mph accompanied by falling
- AND/OR blowing snow, frequently reducing visibility to less than ¼ mile for 3 hours or more.
Ice Storm Warning
- Ice accumulation of of ¼" or more on an elevated horizontal flat surface.
Snow Squall Warning
- Heavy snow and gusty winds reducing visibility to ¼ mile or less with sub-freezing ambient road surfaces
- AND/OR plunging temperatures behind an arctic front sufficient to produce flash freezes, along with a significant reduction in visibility from falling and/or blowing snow
- AND at least a risk for a flash freeze.
Winter Storm Warning
- Heavy snow accumulation of 4" or more within 48 hours or less
- AND/OR sleet accumulation of ½" or more
- AND/OR mixed precipitation with at least one winter hazard type (blizzard, freezing rain, sleet, or snow) meeting or exceeding warning criteria
- OR high impact frozen precipitation outside of the normal winter season or during a critical situation (standard criteria not being met, but impacts are expected to be unusually significant).
Winter Weather Advisory
- Snow accumulations of between 1 and 4", or impacts expected with 1" or less of snow
- AND/OR Freezing rain accretions less than ¼" on an elevated horizontal flat surface
- AND/OR Sleet accumulation less than ½"
- AND/OR Black ice causing widespread slick roads and/or numerous accidents
- AND/OR Blowing snow that reduces visibilities to ¼ mile or less.
Special Weather Statement
- Black ice,
- OR short-duration heavy snow bands below warning criteria.
See NWSI 10-513 WFO Winter Weather Products Specifications for additional information.
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Blowing Dust Warning
- Widespread synoptically driven blowing dust reducing visibilities to ¼ mile or less
- AND winds of 25 mph or greater usually required
- AND generally for a duration of longer than 90 minutes.
Blowing Dust Advisory
- Widespread synoptically driven blowing dust reducing visibilities to 1 mile or less but greater than ¼ mile
- AND winds of 25 mph or greater usually required
- AND generally for a duration of longer than 90 minutes.
Dust Storm Warning
- Dust storm reducing visibility to ¼ mile or less, with sudden reduction in visibility
- AND winds of 25 mph or greater usually required
- AND typically localized and brief in duration.
Dust Advisory
- Dust reducing visibility to 1 mile or less but greater than ¼ mile, with sudden reduction in visibility
- AND winds of 25 mph or greater usually required
- AND typically localized and brief in duration.
Excessive Heat Warning
- Maximum heat index around 110ºF or higher
- AND the minimum heat index will remain around 75ºF or higher
- AND conditions persist for at least 48 hours;
- OR Heat Advisory criteria is to be met for 4 consecutive days.
Heat Advisory
- Maximum heat index of around 105ºF or higher for up to 3 consecutive days.
Extreme Cold Warning
- Air temperatures or wind chill values reaching or exceeding the county-level warning criteria (displayed below).
Cold Weather Advisory
- Air temperatures or wind chill values reaching or exceeding the county-level warning criteria (displayed below).
Freeze Warning
- Minimum shelter temperature to be under 30ºF for 2 hours or more during the growing season. The beginning and end of the growing season are determined in conjunction with the University of Kentucky Agricultural Weather Center.
Frost Advisory
- Widespread frost during the growing season. The beginning and end of the growing season are determined in conjunction with the University of Kentucky Agricultural Weather Center.
High Wind Warning
- Sustained non-thunderstorm wind speeds of at least 40 mph for 1 hour or more
- OR non-thunderstorm wind gusts of 58 mph or greater for any duration.
Wind Advisory
- Sustained non-thunderstorm wind speeds of 30 and 39 mph for at least 1 hour
- OR non-thunderstorm wind gusts of 40 to 57 mph for any duration.
Lake Wind Advisory (for Lake Cumberland, Laurel Lake, and Cave Run Lake only)
- Sustained non-thunderstorm wind speeds of 20 to 29 mph for at least 1 hour
- OR non-thunderstorm wind gusts of 35 to 39 mph.
Dense Fog Advisory
- Widespread fog reducing visibility to ¼ mile or less
- OR localized fog reducing visibility to ¼ mile or less producing major impacts.
Dense Smoke Advisory
- Widespread smoke reducing visibility to ¼ mile or less
- OR localized smoke reducing visibility to ¼ mile or less producing major impacts.
Freezing Fog Advisory
- Freezing fog producing light ice accretion and slippery conditions.
Special Weather Statement
- Heat indices, wind chill or air temperature values near "advisory" level for an hour or two,
- OR local areas of dense fog, dense smoke or other hazards that are below advisory criteria.
See NWSI 10-515 WFO Non-Precipitation Weather Products Specification for additional information.
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Red Flag Warning
- Sustained 20-foot wind speeds of 15 mph or greater
- AND minimum relative humidity of 25% or less
- AND 10-hour fuel moisture values of 8% or less.
Special Weather Statement
- Low confidence or borderline red flag conditions:
- Critically low relative humidity values
- Near criteria wind gusts
- Marginal 10-hour fuel moistures
See NWSI 10-401 Fire Weather Services Product Specification for additional information.
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