Severe weather terminology (Canada)

This article describes **severe weather terminology** used by the Meteorological Service of Canada, a branch within Environment and Climate Change Canada. The article primarily describes various weather warnings, and their criteria. Related weather scales and general weather terms are also addressed in this article. Some terms are specific to certain regions.

## Warning categories
Severe weather bulletins are issued as a watch or a warning, depending on the risk or severity of the event.

***Watches** are issued when conditions are favourable for the development of severe weather, but the occurrence, location, and/or timing is still too uncertain to issue a warning. The target lead time for severe thunderstorm watches is typically six hours before the event, whereas watches for winter events have a target lead time of 12 to 24 hours in advance. Watches are intended to raise awareness of the public to the potential for hazardous weather conditions, and typically serve as a lead-up to a warning.
***Warnings** are issued when severe weather is either imminent or occurring. Warnings for synoptic scale events such as snowstorms are issued with an ideal lead time of at least six, and up to 24 hours. Severe thunderstorm warnings and tornado warnings, by their nature, will typically be issued with very little lead time. Weather warnings are usually issued for regular forecast regions affected. Severe thunderstorm and tornado warnings, however, might be issued specifically for smaller warning or "sub-regions" within the regular forecast area where available. 
***Advisories** are issued in a similar format to that of an official warning. Unlike warnings, however, these types of bulletins describe exceptional weather events that are generally not considered hazardous, such as frost.
* **Blowing Snow Advisory** – Issued when blowing snow caused by winds of at least  is expected to reduce visibility to  or less for at least 3 hours. This advisory is only issued south of the tree line.
* **Fog Advisory** – Issued when low visibility caused by fog is expected for at least six hours. Advisory criteria for Newfoundland and Labrador, Nova Scotia, New Brunswick, and Prince Edward Island is low visibility caused by fog that lasts at least eighteen hours.
* **Freezing Drizzle Advisory** – Issued when freezing drizzle is expected to last for at least eight hours.
* **Frost Advisory** – Issued during the growing season in southern portions of Canada (except British Columbia) where formation of frost is expected due to surface temperatures falling to near  in the overnight hours.
* **Weather Advisory** – A message that can be used for any situation for which there is no other alert that effectively describes the conditions expected. Typically used to alert the public about conditions favourable for cold-core funnel clouds.

### Special Weather Statements
A Special Weather Statement is usually issued in two circumstances:
* A warning or watch is not warranted because the expected conditions are less menacing than those necessary to meet warning criteria.
* A warning or watch is not yet practical to be issued, usually due to a high degree of uncertainty of timing, occurrence and/or location of the hazardous conditions.

A Tropical Cyclone Information Statement consists of three sections:

* **Section 1 –** The storm’s current position, strength, motion, and central pressure.
* **Section 2** – Reported severe weather threats, expected impacts (rainfall, wind, storm surge), and a summary of land watches and warnings issued by the Canadian Hurricane Centre or regional Storm Prediction Centres.
* **Section 3** – Summary of marine warnings issued by regional Storm Prediction Centres, reported severe weather and expected impacts.

### Thunderstorm Outlooks
Thunderstorm Outlooks are issued by each regional Storm Prediction Centre for their respective regions, typically starting in May and ending in September. Thunderstorm Outlooks are issued for every province and territory except Nunavut.

This product remains experimental, and as such, there is no official spot to find the product. They are typically found on official Environment and Climate Change Canada Twitter accounts for the respective provinces.

## Related weather scales as defined by Environment Canada 
### Enhanced Fujita Scale
The **Enhanced Fujita Scale** (EF) is a scale for rating tornado intensity based on the damage on human-built structures and vegetation. While the United States adopted the Enhanced Fujita Scale in 2007, Environment Canada continued to use the original Fujita Scale to assess tornado intensity until April 18, 2013, when the agency adopted the Enhanced Fujita Scale. Tornadoes exceeding F2/EF2 intensity are rare in Canada, although some tornadoes, such as the Edmonton Tornado in 1987, have been as strong as F4. The only F5/EF5 tornado recorded in Canada to date was the Elie, Manitoba tornado in 2007.

### Saffir-Simpson Hurricane Scale
The **Saffir-Simpson Hurricane Scale** is used by the Canadian Hurricane Centre for hurricanes affecting the East Coast of Canada. The Scale ranges from Category 1, the weakest, to Category 5, the strongest with sustained winds exceeding .

## See also
* List of severe weather phenomena
* Environment and Climate Change Canada
* Meteorological Service of Canada
* Severe weather terminology (Japan)
* Severe weather terminology (United States)

## References
## External links
* Land warning definitions by Meteorological Service of Canada

* Marine warning definitions in Canada

*Canadian Weather warnings in real time