An atmospheric traffic jam will bring a wide variety of weather conditions to the northeastern United States this week, AccuWeather meteorologists say.
Parts of the region will be faced with building heat later this week while cooler air and showers target areas farther south. Additionally, smoke from ongoing Canadian wildfires will become trapped at higher levels of the atmosphere and lead to hazy conditions.
The normal west-to-east motion of weather systems has ground to a halt over much of the Eastern states. In the Southeast, a storm will form in place and create areas of flooding downpours and gusty thunderstorms, while a zone of high pressure and dry conditions will extend from the Midwest to the St. Lawrence Valley that borders southeastern Canada and the northeastern U.S.
Heat will build across the north, not the south, which is the opposite of what typically happens in a pattern such as the one taking place this week.
“This locked-up weather pattern will create plenty of heat from the Upper Midwest to much of [the Canadian provinces of] Ontario and Quebec,” AccuWeather Senior Meteorologist Dave Dombek said. Temperature departures from the historical average of 10, 15 even 20 degrees Fahrenheit are possible.
For example, temperatures will rise into the 80s by midweek in Caribou, Maine, then to record-challenging levels in the 90s on Thursday and Friday.
In this case, temperatures across the northern tier of the U.S. will end up being substantially higher than in more traditional warm spots like Washington, D.C., or Philadelphia as the week progresses. Highs in both cities and many others in the mid-Atlantic region will be in the 70s – or 5-15 degrees below the historical average.
“Part of the reason for the convoluted temperature pattern will be a light breeze from the Atlantic Ocean in the mid-Atlantic that will extend into some of the central Appalachians,” Dombek said. Since the breeze is originating from cooler waters that have temperatures in the 60s and 70s, it will hold temperatures back in the region.
Highs in New York City will be mainly in the 70s from Tuesday through Friday, but as the breeze from the Atlantic continues, more moisture will be added to the air in the form of higher humidity levels and eventually clouds.
Farther south in the mid-Atlantic, areas of rain will break out and mitigate temperatures even further, according to Dombek.
It is possible that where the flow of the Atlantic increases enough, in portions of the Delmarva Peninsula and the Carolinas, minor coastal flooding at times of high tide along with minor beach erosion could occur.
Regardless, poor beach weather is likely to develop in the mid-Atlantic due in part to the building surf. Stormy conditions with dangerous surf are possible farther south.
The building heat this week will occur in a part of Canada that has been dealing with numerous large forest fires. The fires are in highly remote areas and have been difficult to contain.
Cool air and some moisture last week benefited firefighting efforts, but with a resurgence of heat, there are concerns that more fires may erupt and spread.
The large fires have caused a significant amount of smoke at higher levels of the atmosphere to make the sun appear hazy, even though humidity levels have been low most of the time.
The hazy conditions will continue through this week since the flow of air higher in the atmosphere has stagnated.
“The air stagnation, even where no smoke reaches the ground, can also lead to poor air quality,” said AccuWeather Senior Meteorologist Matt Benz.
Normally, breezes near the surface would help to stir out pollutants generated by human activity, but in some areas, there will be very little wind to mix in fresh air. People with respiratory issues may want to limit their time spent outdoors, experts advise.
The zone of greatest air stagnation and potentially the poorest air quality may extend from portions of the Ohio Valley and lower Great Lakes region to parts of the central Appalachians and interior New England.
At this time, forecasters say there are no signs that any great movement of air needed to break up much of the pollutants and smoke at higher levels of the atmosphere will take place later this week into this weekend. However, some clouds and showers could reach into some of the parts of Canada where fires are burning.
As the moisture drifts northward, temperatures will ease back substantially across the northern tier of the Northeast and the southern tier of Canada. More humid conditions will also spread to the north.
With a somewhat more typical configuration in the atmosphere, traditional locations, such as Washington, D.C., may be warmer than northern tier locations beginning this weekend and lasting into next week.
Produced in association with AccuWeather
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