National Weather Service Event Definitions

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WARM SEASON EVENTS	THRESHOLDS
SEVERE THUNDERSTORM WARNING	WINDS>=58 mph (or implied by damage), and/or HAIL >= 3/4 inch
TORNADO WARNING	Spotter Report and/or Radar Indicated and/or Environment Supported
FLASH FLOOD WARNING	Life/Property threat within 6 hours.
FLOOD WARNING	Life/Property threat within 6 to 12 hours.
FLOOD WARNING (MAIN STEM RIVER)	Life/Property threat beyond 12 hours.
URBAN & SMALL STREAM FLOOD ADVISORY	Inconvenience flooding 0 to 24 hours.
EXCESSIVE HEAT WATCH	Typically issued from 24 to 48 hours prior to the onset of a possible Excessive Heat Warning or Heat Advisory.
EXCESSIVE HEAT WARNING	Issued when the heat index will reach 110 for three or more hours. The warning will be continued overnight if the low temperature will drop no lower than 75 degrees.
HEAT ADVISORY	Issued when the heat index will reach 105 for three or more hours. The warning will be continued overnight if the low temperature will drop no lower than 75 degrees.
COLD SEASON EVENTS	THRESHOLDS
WINTER STORM WATCH	Issued when there is a likelihood a warning will eventually be issued. Watches are normally valid for possible events occurring 12 to 48 hours, but may be pushed to 6 hours if uncertainty still exists.
WINTER STORM WARNING	Heavy Snow 6" or more within 12 hours, or 8" within 24 hours. Warnings may also be issued for smaller amounts if there is significant blowing snow, low wind chills, sleet, freezing rain, etc.
HEAVY SNOW WARNING	Heavy snow 6" or more within 12 hours, or 8" within 24 hours. No other significant winter events such as blowing snow, low wind chills, sleet, freezing rain expected.
BLIZZARD WARNING (GROUND BLIZZARD WARNING)	Sustained winds or frequent gusts greater than or equal to 35 mph and falling or blowing snow with visibility less than 1/4 mile for greater at least 3 hours. Ground blizzard only deals with blowing snow.
ICE STORM WARNING	Ice accumulations of at least 1/4" expected.
WIND CHILL WARNING	Widespread wind chills of 35 degrees below zero or lower with winds greater than 10 mph. In some parts of southern Minnesota, the threshold may be 30 below.
WINTER WEATHER ADVISORY	Normally issued for weather which may cause inconvenience or require caution, and is occurring, imminent, or very likely. Issued for up to 6 inches of snow, freezing rain/drizzle, sleet, blowing snow, or a combination of weather elements. Typically issued for the upcoming 12 hour period, but sometimes extends to into the second 12 hour period.
WIND CHILL WATCH	Typically issued when wind chill values of -35 degrees with a 10 mph wind are possible 12 to 48 hours in the future.
WIND CHILL ADVISORY	Widespread wind chills of 25 degrees below zero or lower with winds at least 10 mph. In some parts of southern Minnesota, the threshold may be 20 below.
FREEZE WATCH	Typically issued when low temperatures of 32 degrees or colder will be possible in the next 12 to 48 hour period, during the growing season.
FREEZE WARNING	Low temperatures are expected to be 32 degrees or colder during the growing season
OTHER EVENTS	THRESHOLDS
HIGH WIND WATCH	Issued only if high wind warning criteria are likely to be met in the 12 to 48 hour period.
HIGH WIND WARNING	Sustained winds of at least 40 mph for 1 hour or more, or gusts to 58 mph or more.
AIR STAGNATION ADVISORY	Issued if MN Pollution Control Agency declares an air pollution episode.
CIVIL EMERGENCY MESSAGE	Any emergency declared by city, county or state emergency management. Most often associated with nuclear or other hazardous materials. Issued at the request of emergency management.
WIND ADVISORY	Sustained winds of 30 to 39 mph lasting for at least 1 hour.
DENSE FOG ADVISORY	Widespread visibilities less than 1/4 mile.
FREEZING FOG ADVISORY	Very light ice accumulation from freezing fog.
FROST ADVISORY	Formation of thin ice crystals on ground or other surfaces. Usually occurs with light wind. Frost may occur even though standard observing level temperatures (5 feet above ground) are in the mid to upper 30s. Issued only during growing season.