THE NEXT 2 WEEKS — Yes a Pattern Change is coming for the eastern US

IMAGE # 1 has two maps associated with it. The map on the left shows the jet stream map from December 15. Note the enormous trough in the jet stream situated along the West coast and western Canada. The Trough has dominated the weather pattern across the entire continent since the last week of November. A Trough in the jet stream this massive causes the e atmosphere to react by developing an equally strong and massive Ridge in the jet stream that is situated across the Eastern CONUS and extends into Eastern Canada. In addition, since the last week of November there has been deep and persistent large Upper LOW in the jet streams in Alaska that has been feeding energy down the West coast of North America. The result has been tremendous ran in and Mountain snows for the drought areas of the western CONUS, which has really helped with the severe drought areas in the Rockies, the Great Basin, and the West coast regions. But it has also produced an exceptionally mild and nearly snowless first half of December east of the Mississippi River along with exceptionally mild temperatures which you can see on the map on the right.

There are strong signs however of a significant pattern change coming which will begin to develop next week. The beginning of this pattern change has to do with the development of a strong blocking Pattern that is forming in Iceland and the United Kingdom which retrograde (move to the West) into Greenland starting next week. SEE IMAGE #2. This major development will cause the strong Ridge in the jet stream across the Eastern CONUS to begin to weaken at a steady pace. By the time we get to Christmas the strong Ridge in the jet stream across the Eastern CONUS will be dramatically flattened and weekend.

At the same time there will be a strong Ridge in the jet stream developing in Alaska which will expand north of Alaska into the Arctic region. This feature will help pull in Siberian arctic cold air from Siberia, across the Arctic and into central and southern Canada. The development of these two features will allow a major expansion of the deep cold air across Canada starting next week.

We can see the change in the temperatures by looking at the anomalies forecasted for the next 7 Days in the eastern CONUS . Notice that the Great Lakes and New England will finally see near normal temperatures for the middle of December.

In the week 2 forecast, the MJO stays in Phase 7 so the pattern change will be SLOW but steady. We are **NOT** looking at an Arctic outbreak at any point over the 15 days for the central and eastern Conus.

Let’s look at the 4 major North American Teleconnections. (A teleconnection is a type jet stream configuration that can / does have major impact on the weather patterns across a region). In North America there are four of them that we focus on. Some of them you may have heard of before. They are

The AO / Arctic oscillation/ The Polar Vortex
The NAO/ North American oscillation/ The Greenland Block
The EPO/ the Eastern Pacific Oscillation / Alaska- Siberia
The PNA / Pacific North America pattern / West Coast Ridge

In the eastern third of the country the ideal teleconnection pattern that you want for a sustained cold & winter storms are this combination
-AO /- NAO/ -EPO/ +PNA

The various models continue to show a strengthening Greenland Block weather pattern which will continue to alter the weather pattern across all of North America. The various models show that the Ridge in the eastern CONUS in week 2 will be completely destroyed or flattened. This in turn will allow the building up of Arctic air in southern Canada to begin to slowly push southward in the last week of December. Meanwhile, that deep Trough on the West coast is still in place. This means that weather systems will come out of the West Coast and the Rockies, track across the Plains, and Midwest, into the Northeast but the air mass will be substantially colder. This implies a much more winter-like pattern for these areas especially north of Interstate 70 during the last week of December.

Exactly what type of winter storms will occur in the last week of December, and what areas is impossible to know but in general the pattern looks quite promising for people who like snow and cold and ice for the central and eastern CONUS North of Interstate 70 in the last week of December