Thursday, July 13, 2017

Odd Summer Temperature Contrast Causing Havoc-Strewn Weather Wisconsin To New England

Lightning strikes the tarmac of O'Hare airport in Chicago
as that region shared in the severe weather along a stalled
weather front from Wisconsin to New England. 
Almost always in mid-summer, there's not much of a temperature constrast on either side of a cold or warm front.

Unlike in the winter, there's no grand pushes of cold air from Canada to feed these dramatic contrasts. So in the summer, when a cold front goes through, the temperature might drop just a few degrees. Or not at all.  

Not this time.

An unusual push of very cold air for this time of year pushed southwestward from Greenland, where there was some big time almost record breaking snows.

The front has pushed down through Quebec, where snow fell last night in the northeastern part of the vast province.

The front has settled down into the Great Lakes through southern New England, where it is stalling out and doing battle with the usual intense heat and humidity of summer across most of the rest of the nation.

The result is some very bad weather that's been going on for the past couple of days in numerous spots. This bad weather will continue for a few more days -- though here in Vermont we seem to be escaping almost all of it.

Here in New England, the chill north of the front is being enhanced by east and northeast winds that are bringing even cooler, more damp air in from the North Atlantic.

In northern New England, including northern Vermont, high temperatures won't get out of the 60s today. The same is probably true for Friday.  Normally, afternoon temperatures are in the low 80s this time of year.

Near the coast, the shift is even more dramatic. At mid-afternoon today, the temperature in Boston should only be around 60 degrees with a raw east wind.

Justt 50 miles or so south of Boston, on the other side of the front, Providence, Rhode Island is forecast to be at 88 degrees at the same time. Quite a difference.

Such a sharp temperature contrast is a recipe for strong storms and heavy rain near and just south of the frontal boundary, and that's what's been happening.
Torrential thunderstorms caused flash flooding in
Belmont, Massachusetts Wednesday. 

The front yesterday and today extended to the western Great Lakes. The nearly stationery front, and heavy storms along it, caused terrible flooding Wednesday in Wisconsin and northern Illinois.

Severe thunderstorms struck parts of southern New England on Wednesday, too.

Today, flash flood watches are up for a broad area from Indiana to western New York.

A particularly heavy batch of rain was over the western third of New York as of mid-morning, and flash flood warnings were up for a big area that included Buffalo and Rochester.

The weather boundary won't be going too far any time soon. It will become more diffuse, becoming more like a summertime weather front with not so big temperature contrasts.

Still it will remain a focus for rounds of showers and thunderstorms through next week as weak disturbances ride along the boundary, making it waver back and forth, north and south.

Here in Vermont, that means an almost daily chance of showers through next Tuesday. It's hard to pick out exactly when it will rain and how hard during this period. At this point, I don't see anything extreme coming for the Green Mountain State, but it's something to watch.

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