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    Brett Anderson

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    Pattern Change Later This Week

    January 7, 2014; 3:46 PM ET

    Several record low temperatures were set earlier this morning over the eastern U.S. and parts of southern Ontario as the coldest air mass in years has arrived.

    As expected, heavy lake-effect snow has been pounding some areas of Ontario and New York state and will continue to do so tonight and into Wednesday.

    The main Lake Huron/Georgian Bay snow band ended up a little farther north into the Parry Sound area on Tuesday as the westerly flow had a slightly more southerly component to it than what was expected from yesterday. This particular band should start to drift more toward the south into tonight as the wind ever so slightly veers more westerly or just north of due west. If this happens, then the heavier snow would likely get back into the Bracebridge and Gravenhurst areas of Ontario.

    Here is an updated lake-effect snow map effective Tuesday p.m. through Wednesday.

    As you can see, we also brought higher snow amounts into the Buffalo/Niagara region as the northern edge of the main Lake Erie band broke away and spread the snow farther north on Tuesday. The same thing also happened in the Watertown, N.Y., and Thousand Islands region, though the band has consolidated back to the south as of this writing.

    Lake-effect snow will wind down off Lake Erie midday Wednesday but not until Wednesday night east of Georgian Bay and Lake Ontario.

    Westerly winds will begin to ease a bit late tonight and the core of the Arctic air will begin to lift northeast into Quebec overnight. So while it will still be very cold with low AccuWeather RealFeel temperatures, it will not be quite as bad as last night in Ontario and points south.

    Pattern change

    Yes, you read that correctly. A significant pattern change will take place the second half of this week across North America as the polar vortex lifts back toward the Arctic and the eastern Pacific ridge breaks down.

    All of this will lead to a significant warm-up late this week in the East with plain rain and possible ice into parts of eastern Canada.

    In the West, the strong, persistent east Pacific high pressure ridge, which has been blocking storms from coming inland across BC will collapse and open the door to several storms and fronts over the next six days or so.

    The storm system Friday and Saturday in particular will likely tap into subtropical moisture and could bring over 100 mm of rain Vancouver Island with lesser amounts on the lower mainland. Higher elevation ski areas in western BC have been in a snow drought and should get some relief over the next week.

    However, there are indications that the east Pacific ridge will rebound after Jan. 16 or so, bringing a return to the drier and milder conditions in BC, while potentially sending more cold air down from the Arctic and into the Prairies and eastern Canada through Jan. 22.

    The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com

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