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MAFOR Sheets

Coded MAFOR forecasts are broadcast by the US Coast Guard in the US and by Canadian Coast Guard Radio in Canada.

Here is the MAFOR Sheet for your use.

Thunder Bay Coast Guard Radio Weather Reports for Lake Superior and Lake Huron

As of 26 June 2008, Environment Canada changed the weather broadcast format and MAFOR code to include more information. Thunder Bay Coast Guard Radio Weather on continuous VHF weather channels adopted this new expanded format which includes extended weather information for Lake Superior, Lake Huron and Georgian Bay. In addition to the regular Notices to Mariners the weather broadcast is in 4 different formats:

Plain language – covers “Today, tonight, tomorrow and tomorrow night” for each lake section. This replaces the previous 24 hour forecast “with an outlook to the next 24 hours”.

MAFOR – this is part of the extended format. Instead of covering just a 24 hour period as in the past, it now gives broadcast codes in different time formats – up to 48 hours if needed. The most common time periods given are 30, 39 and 45 hours. It still remains important for the beginning of the forecast period to be known to give validity to the code. Unfortunately, there is some discrepancy here because sometimes the beginning time of the code is given as EDT and other times as UTC (Universal TimeCoordinated) and it is then necessary to convert to EDT.

Wave heights – this is no longer part of the plain language broadcast but is in a

separate format for each of the lake sections concerned.

Extended forecast – this is also new covering the 3 days after the plain language

forecast. For example if the plain language forecast covers Tuesday and

Wednesday, the extended forecast will cover Thursday, Friday and


Report by Ron & Bonnie Dahl

4/18/2014 JM