Tornado and Thunderstorm Advisories

Blizzard warning – a blizzard warning means that there will be gusts of wind greater than thirty-five miles per hour, along with heavy snowfall and reduced visibility. The length of time for a blizzard is at least three hours. As mentioned, there are no temperature criteria. You can issue a Winter storm watch for blizzard conditions if you expect such a storm to happen within 12 to 48 hours.

Lake effect snow warning – this is usually a warning used for regions where lake effect snows are possible. The expectation is of at least six inches of snow in twelve hours or less. Alternatively, it could mean eight inches of snow in twenty-four hours or less. The warning is given when this precipitation is imminent or highly likely.

Snow squalls warning – this is an intense winter storm of limited duration with the expectation of at least moderate snowfall according to radar. Expect reduce visibility of less than one fourth mile, white out conditions, lightning, extreme temperature drops, and strong surface winds.

The National Weather Service no longer uses sleet warnings, sleet advisories, snow advisories, blowing snow advisories, blowing and drifting snow advisories, or extreme cold watches or warnings. They have also deprecated lake effect advisories and watches as well as blizzard watches and freezing rain advisories. These have largely simplified the winter storm advisories.

TORNADO AND THUNDERSTORM ADVISORIES

These are watches and warnings related to spring through fall weather and related to severe storms in the continental regions.

Tornado watch – this means there are favorable conditions for the development of either severe thunderstorms or tornadoes. They are often valid for between five and eight hours.

Particularly dangerous tornado watch – this indicates favorable chances for very destructive storms or tornadoes. They are commonly issued when a major tornado outbreak could happen or when there is the potential for violent category tornadoes.

These are valid for longer periods of time than regular watches and often involve a wider swatch of the country.

Tornado warning – this indicates Doppler radar detection of rotation or the siting of a tornado by special spotters or by law enforcement. These are often issued for thirty minutes that can extend for as long as an hour. You do not need to have a tornado watch in order to have a tornado warning.

Particularly dangerous tornado warning – this indicates a large and severe tornado has been confirmed and is moving through an area that has already been warned. It is often a reissuance of a prior tornado warning and can be a situation where a severe tornado has already damaged property and is expected to do similar damage as it moves along.

Tornado emergency – this is an unofficial warning issued to heavily populated areas when severe F5 tornadoes are headed toward these areas. They have been issued in the past when severe tornadoes have damaged areas like Oklahoma City, Greensburg Kansas, and Tuscaloosa, Alabama. This is the highest level of tornado warning alerts possible. It indicates the greatest potential for loss of human life because major metropolitan areas are involved.

Severe thunderstorm watch - what this means is that the conditions are right for a severe thunderstorm to develop. This means the potential for high winds, hail, and significant rain as well as tornadic activity. They are valid for up to eight hours in the future.

Particularly dangerous situation severe thunderstorm watch – these are issued for a longer period of time and severe thunderstorm watches and usually involve a larger area. It also means that conditions are right for severe thunderstorm activity and isolated tornadoes. It is reserved for thunderstorm activity over a larger area as well.

Severe thunderstorm warning – this indicates a known thunderstorm on Doppler radar or one that has been sighted by spotters. You can expect hail that is one inch in diameter or larger, damaging winds in excess of fifty-eight miles per hour, and heavy rains. The total duration of these warnings is thirty minutes to an hour. You do not need

a watch in order to have a warning. These can be upgraded to tornado warnings, depending on the situation. Lightning is possible but is not a requirement to have this type of warning.

Particularly dangerous situation severe thunderstorm warning – this is similar to other particularly dangerous situation warnings in that it usually indicates a larger area is involved and also indicates the possibility of fatalities and significant property damage to a larger swath of a state or part of the country. You might expect winds greater than eighty miles per hour or hail greater than three inches in diameter.

Severe thunderstorm emergency – this is a high end thunderstorm warning sometimes issued when a severe storm is bearing down on a large metropolitan area or other heavily populated area. A warning of this type was first issued in 2019 when a thunderstorm approached Cheyenne, Wyoming. Clear criteria for this emergency have not yet been established.

Significant weather advisory – this is issued when a severe storm is expected that is not as strong as one would issue in a severe thunderstorm warning. It usually means that you have detected a storm on Doppler radar or that one has been spotted; however, the hail is not as large and the winds are not as strong as you would see in a severe thunderstorm warning.

Severe weather statement – this is simply a revision warning to help the public understand the storm in greater detail. It could indicate that you are canceling a prior warning or that you have heard of specific damage in a certain area. It could also mean that you are allowing a warning to lapse.

Flash flood watch – this indicates favorable conditions for other urban flooding or flash flooding within the next thirty-six hours, although it is often issued about twentyfour hours in advance of any expected flood.

Particularly dangerous flash flood watch – this indicates extremely high levels of flooding and often span multiple counties or an entire state. As you have noted, when a watch or warning indicates that it is particularly dangerous, it often means that a larger area is involved, although it could mean that a more severe situation is pending.