When will the air quality improve in the Midwest, Northeast?
Poor air quality as a result of smoke from the record-setting wildfires in Canada plagued the Midwest and Northeast this past week, but some relief has arrived ahead of the early parts of the Fourth of July holiday weekend.
A change in wind direction across different layers of the atmosphere will be responsible for the relief from the dangerously smoky air, but experts caution that the return of an air mass with higher humidity and thunderstorms will replace one hazard with several others.
The concentration of smoke increased over the Midwest and Northeast in recent days due to a flow of air out of the north as a departing low pressure system was replaced by high pressure. While skies typically clear as pressure rises, the shift in wind direction provided the perfect opportunity for the wildfire smoke to be funneled south into the region.
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On Friday morning, air quality alerts from the National Weather Service were in effect across more than a dozen states from Iowa to Rhode Island. Plume Labs, an AccuWeather-owned air quality company, was reporting pollution from the smoke was in the 'unhealthy' to 'very unhealthy' range in cities such as Chicago, Detroit and Pittsburgh.
By early Sunday morning, these alerts were confined to northern Lower Michigan and eastern Upper Michigan.
Rather than coming from the north, the wind has shifted more westerly and even southerly, allowing the smoke to clear some and the plume to move out of the Great Lakes and part of the interior Northeast.
"A storm moving eastward across the Midwest and into the Northeast this weekend has allowed some of the worst smoky conditions to disperse," said AccuWeather Senior Meteorologist Alex Sosnowski.
That dispersion of smoke would be good news for those with outdoor plans over the weekend ahead of the upcoming Fourth of July holiday. However, forecasters warn that it will not be like flipping a switch and going from polluted to clean air and a bright blue sky.
"Since the coverage of the smoke is so extensive and humidity levels are likely to climb, the air is unlikely to become pristine, and some haze will persist," said Sosnowski.
Despite the prospects of some lingering haze early this week, air quality should markedly improve. AccuWeather forecasters expect the air quality index to settle in the code yellow or 'moderate' range for most areas, meaning the vast majority of the population would not have to limit time spent outdoors. However, pockets of smoke that settle into deeper valleys may take longer to disperse, keeping air quality in a more unhealthy range for a longer amount of time there.
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Additionally, residents in the Midwest and Northeast will likely have to dodge some showers and thunderstorms from the pesky, slow-moving storm system. While any given day will not be a washout, any storms that do roll through will produce downpours and dangerous lightning due to the expected abundance of moisture in the atmosphere.
As the summer goes on, the eastern U.S. may not be done with the smoke or poor air quality yet.
"With the likelihood that forest fires will continue in southern Canada deep into the summer, occasional plumes of smoke can head south into the northern U.S.," added Sosnowski. "The next opportunity for that could come as early as [this] week."
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