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  • Issuance 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.

 

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

  • Nuisance 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.

 

  • Watches are issued when forecaster confidence in meeting criteria reaches 50% and are typically issued in the 12 to 72 hour time frame before the onset of wintry conditions.
  • Warnings/Advisories are issued when forecaster confidence in meeting criteria reaches 80% and are typically issued within 24 hours of the onset of wintry conditions.

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 Watch/Warning

  • Snowfall of 4-6" or more in 12 hours or 6-8" or more in 24 hours, depending on location,
 
  • OR sleet accumulation of 1/2" or more in 24 hours.

Snow Squall Warning

  • Snow squalls reducing the visibility to 1/4 statute miles or less,
  • AND sub-freezing ambient road temperatures or plunging temperatures sufficient to produce flash freezes,
  • AND gusty winds and blowing snow.

Winter Weather Advisory

  • Snowfall of 2-4" in a 12 hour period, depending on location,
  • Ice accumulations of less than 1/4",
  • AND/OR visibility reduced to 1/4 mile or less in blowing snow,
  • AND/OR sleet accumulation of less than 1/2".

Wind Chill Watch/Warning

  • Wind chills of 25 below or colder are expected for 3 hours or more with wind speeds greater than 5 mph.

Wind Chill Advisory

  • Wind chills of 10 below to 24 below are expected for 3 hours or more with wind speeds greater than 5 mph.

Special Weather Statement

  • Black ice,
  • OR short-duration heavy snow bands/squalls.

See NWSI 10-513 WFO Winter Weather Products Specifications for additional information.

 

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 46 to 57 mph for any duration.

Freeze Warning

  • Widespread temperatures are forecast to be 32ºF or below for 2 hours or more during the growing season.

Frost Advisory

  • Widespread frost during the growing season.

Excessive Heat Warning

  • Issued when the heat index is expected to reach around 105ºF or higher for a period of at least 2 hours.
  • 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 equal to 100ºF and less than 105ºF for a period of at least 2 hours.

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.

 

Fire Weather Watch (typically issued 24 to 72 hours out) / Red Flag Warning (typically issued within 24 hours)

  • West Virginia
    • 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.
  • Ohio
    • Sustained 20-foot wind speeds or gusts of 15 mph or greater,
    • AND minimum relative humidity of 25% or less,
    • AND 10-hour fuel moisture values of 8% or less.
    • The above criteria must be met for at least 2 consecutive hours.
  • Kentucky
    • 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.
  • Virginia
    • Sustained 20-foot wind speeds of 20 mph or greater,
    • AND minimum relative humidity of 30% or less,
    • AND 10-hour fuel moisture values of 7% or less.

See NWSI 10-401 Fire Weather Services Product Specification for additional information.