Canada / USA — No doubt you thought Friday was a pretty fantastic day. In fact, Id give it the big ol Top 10 weather day of the year stamp of approval. When its in the 70s/near 80, humidity is low, and the sun is shining its pretty tough to beat (I know it was pretty brutal dragging myself into the cave of a weather office we have here). But perhaps you looked up, scratched your chin, and said hmm I would have thought the sky would have been more blue today. I know I did and because Im a huge nerd I went straight to the satellite imagery. And there was the answer.
Usually when you have a hot and humid air mass thats been stagnant for a day or two (as is typically the case in July) the air gets more and more hazy. Particulates can add up, pollution can accumulate, and water vapor becomes dense in the air. With all those factors combined, the summer sky is rarely as brilliant as it is in the middle of winter. And Im sure youve also noticed that after a strong front passes through, the sky looks a lot brighter the next morning. Thats because all of those additives to the normal atmosphere have been swept away for the time being. We had one of those fronts move through on Thursday night, with excellent results. A beautiful air mass in place when we awoke on Friday!
There was hardly a cloud in the sky on Friday, as high pressure built into the region. But if you glanced up, you probably noticed how opaque the heavens above looked. Thats typically something you see after days of muggy and steamy weather. So what gives?
MODIS image over the Northeast on Friday, with the most dense area of smoke circled. Courtesy: NASA
Above is an image captured by MODIS (Moderate Resolution Imaging Spectroradiometer) aboard NASAs Terra satellite. While there are only a few scattered cumulus clouds across the region (mainly across more mountainous terrain) you do immediately notice that big hazy gray area that is very thick across New York State, and to a lesser extent across New England. That whole area is a batch of smoke from wildfires in Canada! And it traveled thousands of miles to turn our skies a milky gray. This particular batch was extremely thick over the Great Lakes yesterday (see below).
Wildfire smoke over the Great Lakes on July 24th, 2014. Courtesy: NASA
The majority of those fires, particularly the ones >1,000 hectares in size, are burning across far western Canada in British Columbia, the Northwest Territories, and Alberta. There are also several large fires that continue to burn in Washington State and Oregon in the U.S.. As they continue to burn their byproducts, namely smoke, have been picked up by the general west-east jet stream winds. Waves of smoke have been blown across the country over the last couple of weeks, varying in intensity/thickness.
In the above image from NOAA, you can see how this area of wildfires in the Boreal forests of Canada can affect so many people at the same time. Its a pretty amazing example of how everything in weather (and on this planet) is connected. The constantly blowing and shifting winds have brought smoke all over North America, and it is especially dense (as you might imagine) near the source region.
The general flow over the next couple of days will remain conducive for more waves of smoke to glide their way across North America, and possibly into our skies here in New England.
Its not likely that this problem will go away anytime soon. The jet stream has been locked into a very particular pattern for months now, leading back into last year. In general, it keeps returning to a high-amplitude setup with a large trough digging across the central/eastern U.S. and an equally large ridge pushing well northward across the western U.S. and into Canada. There have been several days where highs have topped 100º in western Canada this summer! This pattern will strengthen again early next week as another unusually comfortable and cool air mass will dive across the east and heat will soar northward back into the fire zone.