Smoke invaded the D.C. area yet again Tuesday and could get worse

While most days the smoke has remain higher in the atmosphere, some of Tuesday’s smoke — brewed by fires in Quebec — also made it to the surface. The same happened last Thursday from wildfires in New Jersey. In addition to offering an occasional whiff of acrid air, the smoke has also raised health concerns.

Where wildfire smoke is hitting the U.S. the hardest — and when it will end

Parts of the region are seeing Code Orange air quality, indicating hazardous air for sensitive groups, with a few nearing Code Red, signifying unhealthy air for some members of the general public.

You might also notice a tickle in your throat and hazy views. Reagan National Airport saw its visibility drop to 5 miles Tuesday afternoon.

Clean Air Partners — which provides air quality forecasts for the Washington-Baltimore region — is predicting code orange conditions for Washington on Wednesday, and code red for Baltimore. Code red conditions are predicted to reach Washington on Thursday.

Where did the smoke come from?

Most of the smoke in our skies now is from wildfires in Quebec. Storms bringing lightning but not a lot of rain to the already parched region set off many of the larger blazes. Others were started by human means.

A cold front that swept through Quebec on Monday caused winds to increase and shift, which boosted smoke production as fires grew.

The D.C. area has also seen smoke from western Canada, Nova Scotia and New Jersey in recent weeks. We’re still getting some smoke from western Canada.

Where is the smoke the worst?

Air quality Tuesday afternoon in the immediate Washington region is mainly Code Yellow to Code Orange on official EPA stations. Code Orange is unhealthy for sensitive groups, such as the very young and elderly, or people with cardiovascular conditions.

“That is extremely rare these days,” wrote Ryan Stauffer, a NASA research scientist, in a text message. “The Washington-Arlington-Alexandria region has not had a Code Orange for PM2.5 outside of July 4 since Nov. 25, 2016.”

The Purple Air website — a network of unofficial stations — has shown the region spiking as high as low-end Code Red. Local air quality index (AQI) values of 150 to 175 have been common on these stations.

Code Red is unhealthy for the general population, with sensitive groups feeling more serious effects. Code Red begins at 150, while Code Orange starts at 100.

Similar conditions are ongoing up and down the Northeast urban corridor and westward into the Great Lakes and Ohio Valley. Even Code Purple conditions — 200-plus AQI, very unhealthy for everyone — have been relatively widespread across parts of New York, Pennsylvania and into parts of New England.

Will the smoke get worse?

Fires in Quebec continue to push smoke southward, and the general pattern that drives it this way is set to persist.

Areas of thicker smoke to our north should drift in this general direction over at least the next few days, although some of the smoke may shift eastward out to sea.

With a stalled area of low pressure east of Maine set to hang around and even intensify its grip for a time, wind patterns may better align the smoke plumes with our region Wednesday into Thursday. The image above shows dense smoke low in the atmosphere headed south.

“Tomorrow could be even worse, especially toward the evening if some model forecasts end up correct,” wrote Stauffer.

Like all things weather-related, confidence decreases with time. The air flow pattern bringing smoke into the region appears set to persist into at least the weekend and perhaps beyond.

The low-level wind trajectories seen lately in the D.C. and broader Mid-Atlantic regions — frequently coming from the north — are unusual this time of year. Without the fires, it would be quite pleasant for June. If winds return to a more typical summer direction out of the south, much of the lower-level smoke should disperse.

However, high-altitude winds from the jet stream may continue to carry smoke from Canada toward the central and eastern United States for many weeks to come. So at least some haze in the sky from Canadian smoke may make regular appearances, filtering sunshine, even if it doesn’t make it down to ground level very often, where it is potentially harmful.