WEATHER TERMS BY THE SEASON


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SPRING/SUMMER WEATHER TERMS


It is very important to understand the difference between a severe weather WATCH and WARNING. WATCHES and WARNINGS are issued for Tornadoes, Severe Thunderstorms, or Flash Floods. The term WATCH implies that people should be alert for the possibility of severe weather , or flash flooding, and have a plan of action in case a storm threatens. When a WARNING is issued by the National Weather Service, this means that a tornado, severe thunderstorm, or flash flood has been detected by radar or observed by trained storm spotters (SKYWARN). These warnings are for short-fuse events that only last an hour or so. People in the path of the storm are expected to take action to protect life and property when the term WARNING is heard. Following is a list of watches/warnings/advisories that the NWS issues and the criteria used for issuing them:

FLASH FLOOD WATCH
Indicates that flash flooding is a possibility in or close to the watch area. Those in the affected area are urged to be ready to take action if a flash flood warning is issued or flooding is observed.
FLASH FLOOD WARNING
Signifies a dangerous situation where rapid flooding of rivers, small streams, or urban areas is imminent or is occurring. Very heavy rain that falls in a short time period can lead to flash flooding, depending on local terrain, ground cover, degree of urbanization, degree of man-made changes to river banks, and initial ground or river condition.
RED FLAG WARNING
A term used by fire-weather forecasters, to call attention to limited weather conditions of particular importance that may result in extreme burning conditions. A Red Flag Watch may be issued prior to the warning. The criteria for red flag events requires the combination of high to extreme fire danger and a critical fire weather pattern such as: dry lightning, low relative humidity, very dry and unstable air, and very strong/ shifting winds.
SEVERE THUNDERSTORM WATCH
Conditions are favorable for the development of severe thunderstorms in and close to the watch area. Watches are usually in effect for several hours, with 6 hours being the most common.
SEVERE THUNDERSTORM WARNING
Issued when a thunderstorm produces hail 3/4 of an inch or larger in diameter and/or winds equal or exceed 58 mph. Severe thunderstorms can result in the loss of life and/or property. Information in this warning includes: where the storm was, what towns will be affected and the primary threat associated with the storm. A very severe tstm wrng is issued for sustained winds over 75 mph in the 7-county Minneapolis/St. Paul area.
SEVERE WEATHER STATEMENT
Issued when the forecaster wants to follow up a warning with important information on the progress of severe weather elements.
SHORT TERM FORECAST (NOWCAST)
A short-term forecast designed to give specific, detailed forecast information for the next 1 to 6 hours on a county basis. Both severe and non-severe information is contained in these forecasts which are routinely issued several times per day, and more often during busy weather periods.
SPECIAL WEATHER STATEMENT
Issued when the forecaster wants to pass information on to the public about developing or approaching weather that is not expected to be severe, but nonetheless is significant.
TORNADO WATCH
Conditions are favorable for the development of tornadoes in and close to the watch area. Watches are usually in effect for several hours, with 6 hours being the most common.
TORNADO WARNING
Tornado is indicated by radar or sighted by storm spotters. It is very important the warning include where the tornado was and what towns will be in its path.
URBAN AND SMALL STREAM FLOOD ADVISORY
Alerts the public to flooding which is generally only an inconvenience (not life-threatening) to those living in the affected area. Issued when heavy rain will cause flooding of streets and low-lying places in urban areas. Also used if small rural or urban streams are expected to reach or exceed bankfull. Some damage to homes or roads could occur.


FALL/WINTER WEATHER TERMS

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Advisory Terminology


The following advisories will be used to ALERT the public of situations that may cause some inconvenience or difficulty to travelers or people who must be outdoors.

BLOWING SNOW ADVISORY
Widespread or localized blowing snow reducing visibilities to 1/4 mile or less with winds less than 35 mph.
FREEZING RAIN ADVISORY
Light ice accumulation (less than 1/4 inch) from freezing rain and/or freezing drizzle.
LAKE EFFECT SNOW ADVISORY
Lake-effect snow squalls are expected to accumulate to 3 to 6 inches in 12 hours over the southern Great Lakes region and up to 8 inches in 12 hours over the northern Great Lakes region.
SHORT TERM FORECAST (NOWCAST)
A short-term forecast designed to give specific, detailed forecast information for the next 1 to 6 hours on a county basis. Non-severe, advisory, and warning information is contained in these forecasts which are routinely issued several times per day, and more often in some events.
SLEET ADVISORY
Sleet accumulation expected that will remain under a 1/2 inch.
SNOW ADVISORY
Snowfall accumulation of 3 to 5 inches in a 12 hour period. May be used for 2 inch snowfalls if occurring at the beginning of the snow season or after a prolonged period between snow events. Some mountain locations have snow advisories issued for 4 to 7 inch accumulations in 12 hours.
SNOW AND BLOWING SNOW ADVISORY
Sustained wind or frequent gusts of 25 to 34 mph accompanied by falling and blowing snow, occasionally reducing visibility to 1/4 mile or less for three hours or more.
SPECIAL WEATHER STATEMENT
Issued when the forecaster wants to pass information on to the public about widespread, developing or approaching weather that is not expected to be severe, but nonetheless is significant.
WINTER WEATHER ADVISORY
Winter weather event having more than one predominant hazard (i.e. snow and ice, snow and sleet, or snow, ice and sleet) that meet advisory criteria listed above (3-5" of snow, glazing ice, etc.).


Warning Terminology


The following terms WARN the public of more serious winter weather situations that may cause impossible traveling conditions and could pose a threat to life and property.

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 1/4 mile for three hours or more. This is the most dangerous of the winter storm types.
HEAVY SNOW WARNING
Issued for snowfalls of 6 inches or more in 12 hours or less; or 8 inches or more in 24 hours or less (lesser amounts early or late in the season). Light winds (less than 10 mph) generally accompany these situations, with the primary hazard being heavy snow.
ICE STORM WARNING
Issued when damaging ice accumulations are expected during freezing rain situations; walking and driving becoming extremely dangerous. Ice accumulations are usually 1/4 inch or greater. Property damage can become widespread from the thickness of the ice.
LAKE EFFECT SNOW WARNING
Issued when accumulations of lake-effect snow squalls is expected to be 6 inches or more in 12 hours, or 8 inches in 24 hours in the southern Great Lakes region; and 8 inches in 12 hours or 10 inches in 24 hours over the northern Great Lakes region.
SHORT TERM FORECAST (NOWCAST)
A short-term forecast designed to give specific, detailed forecast information for the next 1 to 6 hours on a county basis. Non-severe, advisory, and warning information is contained in these forecasts which are routinely issued several times per day, and more often during busy weather periods.
SLEET WARNING
Sleet accumulation of 1/2 inch or more expected. This is a relatively rare event since sleet rarely falls by itself for extended periods without mixing or changing to other precipitation types.
SPECIAL WEATHER STATEMENT
Issued when the forecaster wants to pass information to the public about widespread, developing or approaching weather that is not expected to be severe, but nonetheless is significant.
WINTER STORM WATCH
Issued when conditions are favorable for the development of hazardous weather elements such as heavy snow and/or blizzard conditions, or significant accumulations of freezing rain or sleet. These conditions may occur singly, or in combination with others. Watches are usually issued 24 to 48 hours in advance of the event(s).
WINTER STORM WARNING
Winter weather event having more than one predominant hazard (i.e. heavy snow and blowing snow, snow and ice, snow and sleet, sleet and ice, or snow, sleet and ice) where local warning criteria is reached (usually 6" of snow or more, 1/4" ice, etc. and strong winds).


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