Markham, ON - Today's weather equation: Vancouver's Rain + St. John's Fog = ??

If you live in the Greater Toronto Area, you are experiencing the equation. By the way, the equation's answer is Toronto's January Thaw.

Believe it or not, January Thaws in Toronto is a usual thing. According to weather records, Toronto had experienced January Thaws ever since 1937. Since 1937, all Januaries had temperature above 0 C at some point and time, all with the exception of the year 1977.

This year's unusualness was that the January Thaw lasted way longer. This year it lasted (so far) for half a week. In addition, the 2008 Warm Wave is the first Warm Wave to have overnight temperature above 10 C during nighttimes. In additions, daily high records are broken. In Toronto, for example, the daily high of today (15 C), broke the old record of 6 C set back in 1965.

The warm wave was brought to us earlier in the week by the return southernly flow from the Pacific Ocean. However, sorry to disappoint you, a return arctic flow of air is coming back into Southern Ontario sooner or later. The clash between this arctic air and this pacific air is creating a monster storm, now sitting over Michigan and parts of Ohio and Missouri. In this case, the warm air flow and the cold air flow is so strong, that there were reports of severe thunderstorm along the cold front. Significant rotations were reported yesterday near 19:00 CST. The rotations later became tornadoes, swiping through Missouri. There are 25 reported tornadoes.

Back in Canada, Environment Canada issued a tornado watch to Sarnia, Essex County, and Windsor this morning. It is one of the rare cases. It is extremely rare, if not, it had never happened before, for tornado watches to be issued in January for any part of Canada.

This cold front that brought severe thunderstorms and tornadoes will enter our area later tonight. Thunderstorms will bring flash flooding to many low lying areas in the GTA, especially across Humber River (flooding sensitive area). Rainfall accumulation could go up to 25 mm. Colder arctic air is expected to pour in with a northwesterly winds of 50 km/h, gusting up to 80 km/h. Temperature will reach its high early tomorrow morning, peaking at 10 C, then rapidly falling to an afternoon high of only 2 C. Lake effect flurries later in the night.

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