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 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
- Thunderstorm wind gusts of 58 mph or greater,
- AND/OR hail measuring 1" in diameter or larger.
Tornado Warning
- Tornado observed or indicated on radar.
Special Weather Statement
- Thunderstorm wind gusts of 40 to 57 mph,
- AND/OR hail less than 1" in diameter,
- AND/OR frequent to continuous lightning,
- AND/OR 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 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 overland flooding that is expected to persist for many hours.
Flood Advisory
- Nuissance flooding including river/stream flooding and/or ponding of water in a geographic area that warrants notification of the public but less urgent than a warning.
Special Weather Statement
- Heavy rainfall that is not 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 of 35 mph or higher,
- AND visibility less than 1/4 mile in snow and/or blowing snow for 3 hours or longer.
Ice Storm Warning
- Damaging ice accumulations of 1/4" or more.
Winter Storm Warning
- Snowfall of 4" or more in 12 hours or 6" or more in 24 hours,
- OR sleet accumulation of 1/2" or more in 24 hours.
Winter Weather Advisory
- Snowfall of at least 1" but less than 4" in a 12 hour period,
- AND/OR visibility reduced to 1/4 mile or less in blowing snow,
- AND/OR sleet accumulation of less than 1/2".
Freezing Rain Advisory
- Ice accumulations of less than 1/4".
Wind Chill Warning
- Wind chills of 25 below or colder are expected. In most cases a minimum wind speed of 10 mph should be occurring or forecast before a warning is issued.
Wind Chill Advisory
- Wind chills of 10 below to 24 below are expected. In most cases a minimum wind speed of 10 mph or more should be occurring or forecast before an advisory is issued.
Special Weather Statement
- Black ice,
- OR short-duration heavy snow bands.
See NWSI 10-513 WFO Winter Weather Products Specifications for additional information.
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High Wind Warning
- Sustained non-thunderstorm wind speeds of at least 40 mph for an hour or more,
- OR non-thunderstorm wind gusts of at least 58 mph regardless of duration.
Wind Advisory
- Sustained non-thunderstorm wind speeds between 30 and 39 mph for at least one hour,
- OR non-thunderstorm wind gusts of 40 to 57 mph for any duration.
Lake Wind Advisory
- Issued when sustained non-thunderstorm wind speeds reach 20 to 29 mph for at least one hour,
- OR non-thunderstorm wind gusts reach between 35 to 39 mph.
Freeze Warning
- Widespread temperatures are forecast to be 30ºF or below for 2 hours or more during the growing season. The beginning of the spring frost/freeze season and ending of the fall frost/freeze season is determined in conjunction with the University of Kentucky Agricultural Weather Center.
Frost Advisory
- Widespread frost during the growing season. The beginning of the spring frost/freeze season and ending of the fall frost/freeze season is determined in conjunction with the University of Kentucky Agricultural Weather Center.
Excessive Heat Warning
- Issued when the heat index is expected to reach around 110ºF or higher,
- AND the minimum heat index will remain around 75ºF or higher during a 48 hour period.
- A warning would also be appropriate if heat advisory criteria are expected to be reached for 4 consecutive days.
Heat Advisory
- Issued for heat index of around 105ºF
Dense Fog Advisory
- Widespread visibility 1/4 mile or less due to dense fog.
Dense Smoke Advisory
- Widespread visibility 1/4 mile or less due to dense smoke.
Dust Storm Warning
- Widespread visibility 1/4 mile or less due to blowing dust.
Blowing Dust Advisory
- Widespread visibility of between 1/4 mile and 1 mile.
Special Weather Statement
- Heat indices or wind chill 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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