A chilly air mass is headed for parts of the northern, central and northeastern U.S at the height of summer early next week. Although the pattern bears a familiar resemblance to January’s brutally cold weather pattern, this deep pool of cool air is actually from the Gulf of Alaska, not necessarily the “Polar Vortex” we saw throughout the winter. There are many similarities though, so don’t be surprised as the news of this cool weather is reported next week and the “Polar Vortex” rears its ugly head. Several National Weather Offices, including State College, are already mentioning the term.

NOAA 6-10 Day Temperature Outlook

In parts of the Great Lakes and Upper Midwest many will need a jacket as highs are expected to remain in the 50s and 60s,  especially where there is considerable cloud cover.

Although the forecast calls for a cool down in the central U.S., this air mass should modify (warm) before it reaches the northeast. Regardless, below normal temperatures are expected to spread eastward and temperatures will range from 10 to as much as 20 degrees below normal. In fact, Wednesday morning’s lows could dip into the 40s in many parts of the Midwest.  Not your typical July weather!


So, the big question is why do we have the potential to set new record lows in the middle of summer? Part of the reason is chance, however, as Dr. Jeff Masters explains in his blog on Weather Underground, Japan’s typhoon Neoguri is playing a big role in the evolving pattern:

“….the large and powerful nature of this storm has set in motion a chain-reaction set of events that will dramatically alter the path of the jet stream and affect weather patterns across the entire Northern Hemisphere next week. Neoguri will cause an acceleration of the North Pacific jet stream, causing a large amount of warm, moist tropical air to push over the North Pacific. This will amplify a trough low pressure over Alaska, causing a ripple effect in the jet stream over western North America, where a strong ridge of high pressure will develop, and over the Midwestern U.S., where a strong trough of low pressure will form.”

What is most interesting about the pattern is not so much the forecast temperatures, but the similarities in the weather patterns seen over North America last winter that we are again seeing this summer. Many features are still prevalent in mid-July with low pressure over the Aleutians, a blocking hot ridge over the western U.S., a large cold low over the Great Lakes and a ridge over northeast Canada.

As we all know, weather patterns are cyclic so even though it is the same pattern we have seen since the winter things will eventually change.  Especially with El Nino forecast to develop by late summer or early fall.

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