After days of an unhealthy amount of smoke from Canadian wildfires spreading across the Northern Plains and Midwest, there is some hope for relief over the weekend for the Lower 48 (contiguous United States, excluding Alaska and Hawaii).
However, the thickest smoke is expected to persist near its source in Canada, with the possibility of new plumes entering southern skies. Concerns about potential bursts of smoke next week remain high.
Air Quality Alerts and Caution for Eastern Iowa
Air quality alerts continue to be in effect for eastern Iowa until late Friday and nearby areas may also experience smoke pollution. The Iowa Department of Natural Resources has cautioned that compromised air quality could continue for several days.
While the smoke has not significantly affected air quality at ground level, smoke suspended at higher altitudes remains widespread, stretching from Quebec and Ontario through the Midwest and Great Lakes to the Mid-Atlantic and Northeast coasts.
Slow-Moving Low-Pressure System Circulating the Smoke
A slow-moving low-pressure system spinning between the Great Lakes and the Canadian Maritimes is responsible for circulating the smoke.
Similar steering currents are expected through the weekend until a high-pressure “heat dome” builds over eastern Canada, which will increase the fire threat in that region next week.
Code Orange and Code Red Conditions: Impacts and Trends
In recent conditions on Thursday, a plume of smoke from Canada resulted in a wide swath of Code Orange conditions, indicating unhealthy air for sensitive groups, from central North Dakota to northern Illinois.
Within this Code Orange zone, pockets of Code Red conditions, signifying unhealthy conditions for most people, were observed in Bismarck, North Dakota, and Davenport, Iowa.
Air quality improved in southern Minnesota, including Minneapolis, on Thursday following a Code Red day on Wednesday.
Since then, the main Code Red zones have been closer to the source of fires in Quebec and western Canada, where fires continue to rage.
Calgary has been experiencing Code Red conditions since Thursday afternoon.
The city has faced several waves of smoke pollution due to the record-breaking fire season in north-central Alberta and British Columbia.
The current smoke episode is the worst in about a month, with mid-May witnessing several days of Code Red and even more severe Code Purple conditions.
Quebec’s Code Red Conditions Extend to Bordering Regions
In Quebec, another blob of Code Red conditions persists, with Code Orange levels reaching as close as the international border with New York and New England.
Monitoring stations northwest of Montreal and near Ottawa reported Code Red levels on Friday.
Patchy Smoke and Poor Air Quality Outlook
Looking ahead, patchy areas of lowered visibility and smoke near ground level are likely from the Midwest to the Mid-Atlantic in the coming days.
Other patches of poor air quality may drop through the eastern Great Lakes and Ohio Valley.
Unhealthy Air Zone Moving into Northern New York and New England
Heading into Saturday, a zone of unhealthy air could move from southern Quebec into northern New York and parts of New England, with the highest concentration likely to remain near the international border.
Smoke at higher altitudes is expected to remain in areas where sunlight has already been obscured.
Much of eastern Canada and the northeast quadrant of the United States may experience milky skies throughout the weekend.
In the western region of Canada, winds are expected to eventually shift from the west, improving Calgary’s air quality. However, significant air quality issues are likely to persist in rural areas near the blazes.
Next week, fire threats are set to increase in Canada’s East as a large high-pressure heat dome dominates the region.
Much warmer than average conditions will expand across central Canada in the coming days before shifting eastward into next week.
Some locations may experience temperatures 20 or more degrees above average for several days, with the 80s and 90s likely in the icy Hudson Bay through eastern Canada and the Northeast United States.
Little rain is expected under the heat dome, although occasional lightning and ineffectual showers may occur.