I will be posting the maps for my final update of the winter forecast for Canada later this evening.

I have increased confidence that the El Nino this winter will be of moderate strength, instead of weak.

The maps will be kept up through Wednesday.

Also, I will discuss the potential snowfall for parts of eastern Canada coming Thursday night into Saturday. Right now, it looks like minor accumulations over parts of Ontario, with the best potential for 10 cm or more coming over Quebec, especially north and west of the St. Lawrence Valley. Lake effect behind the storm will be minimal as well.

Here is the link to my preliminary winter 2009/2010 forecast that I made back on October 20th. You can use this to see where some adjustments were made based on the latest computer modeling and current, observed conditions.

My final forecast update for the winter of 2009/2010

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The overall weather pattern across North America will be undergoing a slow, but significant change through the course of this week, just as we have been talking about for several weeks now.

Here is some of what will be going on between now and the first week of December.......

1. A major trough amplification across Ontario and the Great Lakes during the middle of the week will lead to a large area of light snow over northwestern and northern Ontario Wednesday and Wednesday night.

2. As upper level energy coming in from the northwest merges with this first trough, it will strengthen the whole system and lead to a surface storm development over the interior Northeast U.S. Thursday night and into Friday.

This development should produce a band of steady snow from interior Southwestern Ontario up into northeastern Ontario on Friday as colder air changes the rain to snow. Some accumulation is possible, but to early to pinpoint.

3. As the surface storm continues to intensify Friday night and Saturday, we will see the steadier snow spreading from northeastern Ontario up into Quebec and perhaps northern New Brunswick. Computer models are still is disagreement on the where the overall trough sets up, and that will have big implications on where specifically the best accumulations (likely under 20 cm) will be. A dry slot will also come into play Friday night and Saturday, which could cut into potential accumulations.

4. Lake effect snow. Tough call on that, as it will be a close call as to whether it will be cold enough, but we may see some bands setting up in the typical areas inland andsoutheast of Huron and Georgian Bay Friday night or Saturday.

Looking farther ahead........

The first two days of December look unseasonably cold over the southern U.S. plains, while chilly and moist conditions will impact the Southeast U.S. and up along the East Coast. California should stay dry, while Alaska will continue to climb out of the deep freeze. Prairies look dry and mild, while more snow could impact southern and eastern Ontario.

It looks like cold air will set up shop over eastern and Atlantic Canada, along with the eastern U.S. through the end of the first week of December, while the warming trend will continue over BC, the Yukon Territory and Alaska. It will also be a drier pattern (finally!) over southern BC and the Pacific Northwest.

During this time the Arctic Oscillation will be going negative, which normally supports the idea of much colder air coming southward into southern Canada and the U.S. So we may not be cold enough over the eastern and central U.S., including eastern Canada. Also, we may be too mild over the Prairies.

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My final update of the Winter forecast will be released this week.

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Note: I will try to answer the questions in the comment section later tonight.

This is my latest interpretation of the European Long Range Model output for North America that goes out through the third week of December. This model is only released to our in-house computer system each Friday.

Mean pattern for the week of Nov. 3-Dec. 6

--Temperatures back above normal over Alaska and precipitation near normal.
--Colder, but noticeably drier pattern over BC and the Pacific Northwest.
--Dry, but seasonably cold across the southern Prairies.
--Most of the western United States, including the Rockies colder compared to normal. Much colder than normal over the Southwest and into the southern Rockies.
--Above-normal precipitation from California through the southern and central Rockies. Good for ski country!
--Chilly and wet across the southern Plains.
--Temperatures slightly above normal with near-normal precipitation over Ontario and Quebec.
--Temperatures close to normal over the eastern United States, with near- to above-normal rainfall.
--Temperatures and precipitation close to normal over Atlantic Canada.

The week of Dec. 7-13

--Relatively dry and mild over most of Alaska.
--Possible charge of Arctic air coming southward through the Prairies and into the High Plains of the United States. Typical upslope snow from Alberta through eastern/central Colorado.
--Precipitation below normal from BC through the Pacific Northwest, but temperatures slightly colder than normal.
--Southern branch storm track suppressed farther south from southern California to the Gulf Coast states and then off the Middle Atlantic coast. Could lead to some winter precipitation events from the southern Plains through the Ohio Valley and parts of the Northeast/Middle Atlantic region.
--Cold pattern over Ontario and Quebec. Dry over the north and near-normal precip. over the south.
--Below-normal temperatures and precipitation over Atlantic Canada.
--Warm over Florida.

The week of Dec. 14-20

Looks like a -AO and -NAO type pattern

--Above-normal temperatures from the North Pole to Greenland.
--Stormy over the Aleutians.
--Precipitation and temperatures close to normal over BC and the Pacific Northwest.
--Cold pattern from the Prairies down through the midsection of the United States.
--Drier in California.
--Turning stormier over eastern Canada, Northeast United States and into the Maritimes. Temperatures near to slightly below normal.
--Cold over the Great Lakes with some lake-enhanced snowfall.

Have a great weekend!

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The North American pattern change that has been talked about recently is indeed coming, but it will take some time. The pattern will begin to undergo changes starting around the 25th, but the overall reversal of the pattern might take until the 2nd or 3rd of December. To be honest, about 80% of Canada will still be fairly mild by late November standards through the 28th.

The main changes to this pattern will be a turn to milder weather over Alaska, a drier pattern over British Columbia and the Pacific Northwest, and a turn to colder weather over eastern North America, but I do not see any Arctic air getting down into most of southern Canada or the lower 48 anytime before the 1st of the month.

It does appear that the first shot of Arctic air could eventually be directed toward Quebec, Labrador and New Brunswick sometime during the first week of December.

In the meantime..........

--Looks like at least another three storms coming into BC and the Pacific Northwest through next week. Expect more heavy rain and wind at the coast and big snow accumulations in the Cascades, Coastal Range and BC Rockies. Snow levels in SW BC will fall again to 3,000 feet Friday morning then all the way down to 1,000 feet on Saturday as another storm plows inland. Snow levels will go back upward to near 2,000 feet Saturday evening. Whistler has a new November snowfall record already, and by the time this month is over this new record could be one that holds for many decades.

--Expect another round of strong west to southwest winds coming down off the Rockies into the western Prairies Friday night and into Saturday.

--The change from October to November has been incredible across the Prairies. In Calgary, for instance, October 2009 was 3.5 degrees C below normal with an average temperature of +1.5 C.
November, which should normally be much colder than October, is averaging 4.2 C above normal with an average temperature of 2.8 C!!! Seems like we are going backwards in time, doesn't it?

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UPDATE

Whistler/Blackcomb ski area in SW British Columbia just set a new November snowfall record! So far this month, there has been 418 cm or 164 inches of snow on the mountains. 56 cm or 22 inches of new snow in the past 24 hours.

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I wanted to post this yesterday, but I ran out of time. Anyway, this visible satellite image of western Canada, which was taken Tuesday (yesterday), clearly shows how the changing topography across western Canada impacts the weather during a strong southwesterly flow of very moist air.

The satellite image below is a close-up of southern British Columbia and extends into western Alberta.

Keep in mind that there was a strong, southwesterly wind (lower left to upper right) flow across the region.

What do we see?

1. Note the more textured cloud cover over central Vancouver Island (far left) and along the Coastal Range, which runs almost right up along the mainland coast of western British Columbia. These textured clouds indicate higher cloud tops that are producing heavier precipitation. As the southwesterly winds ram up against the higher elevations over central Vancouver Island (Insular Mountains) and again into the Coastal Range, the air is forced to rise, which cools the air particles and leads to condensation, causing precipitation.

These areas received the heaviest precipitation (rain or snow depending on elevation), as they usually do in this situation.

2. Note how the clouds break up over the Strait of Georgia, which is between Vancouver Island and the coast of Mainland British Columbia. Why is that? Well, the air is descending off the higher terrain of interior Vancouver Island and also the Olympic Range of northwestern Washington state. As the air descends, it begins to warm up and dry out, otherwise known as downsloping. These winds can be strong as well, since they are getting a gravitational boost coming down off the higher terrain.

As this air comes back into the higher terrain of the Coastal Range just north and east of Vancouver, it is forced to rise again and the cooling/condensation process starts all over.

3. Note the large area of clear skies and broken clouds over south-central British Columbia. This is the interior plateau, but it is actually a relatively low valley area that extends from Prince George in the north to Kamloops and Kelowna in the south. The air coming into this large valley is descending off the Coastal Range. This region gets much less rain and snow compared to the coast during the year. A totally different climate.

4. As you go farther east, the air runs into the Canadian Rockies and is lifted once again, resulting in widespread snowfall across the mountains.

5. Once you go east into Alberta, the elevations drop quickly as you approach Edmonton and Calgary, and we can see the evidence of that as the cloud shield is sharply cut off along the eastern edge of the mountains. On Tuesday, we had record high temperatures around Edmonton, while very strong, chinook winds (warm and dry) in excess of 100 km/h swept through parts of southern Alberta as the wind really gets a ton of downward momentum coming off the high Rockies and into the prairie.

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Western ski areas getting the snow.......

At Whistler/Blackcomb in British Columbia, the snow levels have dropped to about 2,000 feet at this time but will begin to rise back to 3,000 feet Thursday morning then 3,500 feet by Thursday afternoon as milder air comes in with the next major precipitation producer tonight and through tomorrow. The middle and upper slopes should get dumped on with more snow. So far, there has been 98 cm, or 38 inches, of snow in the past 48 hours at Whistler. There has been 362 cm, or 141 inches, of snow so far this season and we may be headed for a record November monthly snowfall at the resort. Stay tuned!

Other ski areas have been getting snow, but not as much......

Sun Peaks, BC...... 17cm or 6.6 inches past 24 hrs.
Big White, BC....... No new snow, but it is open with good conditions
Sunshine Village, AB......... 14 cm or 6 inches past 24 hrs with 97 cm or 38 inches on the ground.
Lake Louise, AB.......... 12 cm or 5 inches past 24 hrs with 87 cm or 34 inches on the ground.

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