Guide to public weather forecasts: special weather bulletins
Note: All Special Weather Statements and Weather Summary Bulletins can be found at Weather.gc.ca
Special Weather Statement
The purpose of the Special Weather Statement bulletin is to explain weather situations that may not be adequately described in the Public Forecast Bulletin or Watches/Warnings.
Examples of when a Special Weather Statement would be used are:
To express uncertainty when there is a reasonable chance that a weather event has more impact than currently implied by the Public Forecast Bulletin (or a reasonable chance that warnings will be issued for this event). An example of this would be an approaching weather system which has a history of producing numerous severe thunderstorms; or an intense winter storm which could produce heavy snowfall overnight, creating dangerous conditions for the morning commute.
To highlight significant weather that may affect major events with heightened media attention. For example, snow and cold wind chills for the Grey Cup.
To highlight significant weather in cases for which a warning is not normally issued. For example, widespread fog with near-zero visibilities for regions that rarely encounter such conditions.
To give a broader scope to a local weather event. For example: “Blizzard conditions have developed in Montana. Although extreme southern Saskatchewan may be brushed by the storm, it will generally remain south of the international border.”
To highlight and explain unusual weather such as cold air (cold core) funnels, waterspouts, and dust devils.
To highlight and report the unusual durationof a specific weather phenomenon, for example, days with/without rain.
Ultimately, Special Weather Statements are intended to advise the media and the public of not so common, inconvenient, or unusual weather conditions, or for the longer term potential development of hazardous weather conditions.
Note: Special weather statements are not ended, but are left to self-expire after 7 hours. They can, however, be ended if needed for technical reasons or when it makes sense to.
Weather Summary Bulletin
This is a post-event summary of a significant weather event, for example, an intense winter storm that produced heavy snowfalls. Following the storm (and sometimes even midway through the storm) the snow amounts measured in various locations across the affected region will be included in the Weather Summary Bulletin.
The Bulletin is issued as needed, often at the end of an event. Updates to the Bulletin are also issued as needed.