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    Brett Anderson

    Weather Pattern Set to Change

    10/10/2012, 9:10:56 AM

    The record dry spell across the Pacific Northwest and BC will finally come to an end Friday.

    A large, blocking high pressure system has been fairly persistent over the eastern Pacific since late summer, acting as a block and directing storms and rainfall away from the region.....


    590x393_10091840_amp


    However, by the end of this week that high pressure area will finally break down, allowing the westerlies to return, which will send Pacific storms back into the region.....


    590x393_10091842_bre


    The first storm will arrive Friday followed by at least two or three more storms. Actually, the storm coming later Sunday into Monday could produce heavy rainfall from the Coastal Mountains and Cascades on west as tropical moisture from the central Pacific could be tapped.

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    Weak storm will bring narrow band of snow......


    590x393_10091848_sn


    A weak, clipper-type storm will track across central Ontario and Quebec later Wednesday night through Thursday night and will bring a narrow band of wet snow just north of the low pressure track. Any accumulations will likely be under 5 cm. Montreal should get light rain out of this, while Quebec City could get some wet snow mixed with rain, though I do not think it will stick in the valley.

    South of the storm track southwesterly winds will bring a brief warm-up before a second cold shot arrives.......


    590x393_10091851_nex


    Cold shifts back West late next week......

    It looks like the cold air from the north could set up shop across western Canada late next week as a large trough (pocket of cold air aloft) builds in. The GFS ensemble model temperature anomaly forecast below for the following Saturday (Oct. 20) shows the cold air in the west.......


    590x486_10091854_picture-40


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    New ECMWF seasonal forecast for the upcoming winter was released yesterday. Here are some highlights from it....

    1. Does not show a strengthening El Nino into this winter, rather near-neutral to barely weak El Nino. This has been a consistent trend lately among models.

    2. Much different winter for Alaska as it looks much drier and milder in the west and just dry in the east, but seasonable in terms of temps.

    3. The model does not show any below-normal temperatures for the winter across 99% of the land mass of North America. The exception is coastal southwestern BC and the Aleutians, which is probably more of a reflection of the below-normal sea surface temperatures.

    4. Continued mild across much of northeast Canada.

    5. No surprise... above-normal temperatures for far northern Canada.

    6. Room for cold blasts in western Canada, including the Prairies, though the model is forecasting near-normal temps.

    7. With milder temps we can also expect more snow over far northern Canada.

    8. Still looking dry for most of BC, though the model is not as excited about it as the previous runs.

    9. Slightly wetter than normal from the U.S. Middle Atlantic through the St. Lawrence Valley, which can mean more rain or snow. Keep in mind the precipitation forecast has a fairly low skill level, so take it with a grain of salt.

    10. The model has trended warmer this winter for the Southwest and central Plains.

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

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