Guide to Environment Canada Marine Weather Forecasts

Forecast Issue Times and Valid Periods

Regular Marine Forecast

The regular marine forecast is issued two to four times daily. The number of forecasts and the issue times are determined regionally. The period of coverage is from the forecast issue time out to midnight of the second day of the stated forecast period. Each day of this two-day period is referred to as Day 1 and Day 2 (See Table 1).

Extended Marine Forecast

The extended marine forecast is issued twice a day, and the issues times are determined regionally. The period of coverage begins after midnight of Day 2 and extends out to midnight of the fifth day of the stated forecast period. Each day of this extended three-day period is referred to as Day 3, Day 4, and Day 5 (See Table 1).

Wave Height Forecast

For waters where wave height forecasts are issued, the wave height forecast is issued two times daily. The issue times are determined regionally, but issue-times are usually the same as, or shortly after, the regular marine forecast issue time. The period of coverage is from the forecast issue time out to midnight of the second day of the stated forecast period. Each day of this two-day period is referred to as Day 1 and Day 2 (See Table 1).

Technical Marine Synopsis

The technical marine synopsis is issued with the regular marine forecast, and its time period of coverage corresponds to the time period of coverage of the regular marine forecast.

Marine Weather Statement

A marine weather statement is a non-scheduled bulletin that is issued on an “as needed” basis. It is used in special circumstances to describe the synoptic situation or potentially high impact marine weather expected to occur beyond the period of coverage of the regular marine forecast. This type of marine weather statement is issued at the forecaster’s discretion.

Table 1.  Definition of the Periods of Coverage Associated with the Regular Forecast (Day 1 and Day 2) and the Extended Forecast (Day 3, Day 4, and Day 5).
Forecast TermsCorresponding Valid Time Period (local time)Remarks
TodayIssuing time to 5:59 p.m. 
Tonight

6:00 p.m. – 5:59 a.m.

or

issue time to 05:59 a.m.

When a forecast is issued after 6:00 p.m., valid time for the phrase Tonight covers from the time of issue to 5:59 a.m. the next day
Day 26:00 a.m. – 11:59 p.m.Identified using the name of day
Day 312 midnight – 11:59 p.m.Identified using the name of day
Day 412 midnight – 11:59 p.m.Identified using the name of day
Day 512 midnight – 11:59 p.m.Identified using the name of day


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