Throughout the week of May 29th, a large wildfire in Nova Scotia, Canada has burned thousands of acres and sent smoke and poor air quality into the skies of the Northeast. The size of this fire is rare for Nova Scotia, let alone the smoke transported into the Northeast. Let’s take a look into the weather that caused this wildfire to spawn, why the smoke has taken an unusual path, and when it will end.

NASA Satellite View of the Wildfire. May 29th, 2023. 

Image - Satellite View of Wildfire

Video - Wildfire producing smoke and transporting to the Northeast 

The wildfire initially developed on Saturday, May 27th. As of Thursday, June 1st, 18,173 hectares or 44,906 acres have burned. The wildfire has destroyed at least 200 homes and forced the evacuation of more than 21,000 people. The cause of the wildfire is still unknown, but the weather leading up to and during it has certainly been a significant factor.

Nova Scotia and other parts of Eastern Canada have seen unusually dry conditions this spring. A strong and persistent high-pressure system has remained stationary over Eastern Canada, causing storm systems to track further inland and to the north. This has led to very little rain and well above-average temperatures. 

These precipitation departures in excess of 100mm (>3.9in) below the average are some of the driest conditions during April and May on record for Nova Scotia and New Brunswick. This combination with above-average temperatures, as well as trees and grasses gaining foliage, have led to a tinder box in this area.  

Once the fire started spreading, there was nothing stopping it from growing quickly. Gusty winds in excess of 40mph have helped fuel this fire and transported it into the mid-levels atmosphere, which has then transported it to the Northeast.

Why has the smoke traveled to the Northeast? 

The center of a high-pressure system is located in the Northeast. This means coastal Canada and the East Coast are seeing northeast winds (fueled in part by the cool Atlantic Ocean), which are transporting the smoke to millions of people and major Eastern Cities. 

The wind pattern around the High pressure is indicated by the blue arrow. The warm colors show warmer and drier weather. The fire emoji is where the fire is centrally located. 

While the smoke is being transported to the Northeast in the middle of the atmosphere, winds at the surface are much weaker, thus not allowing the smoke to move out of the Northeast. This lack of mixing in the atmosphere has caused smokey skies, which has degraded air quality substantially. The OpenSnow surface smoke and upper-level smoke maps have been highlighting this transport throughout the week. 

The National Weather Service has issued several Air Quality Alerts for code orange, meaning that, “air pollution concentrations within the region may become unhealthy for sensitive groups.” You can see these clearly on the OpenSnow Air Quality Map, which takes in PurpleAir data.  

This is not the only smoke the Northeast has seen this spring. Several large wildfires in the Canadian Provinces of Alberta and Saskatchewan have been burning since April, which have filled the skies with smoke in Canada, the Great Lakes, and the Northeast. These fires have transported smoke into the upper part of the atmosphere, which has caused hazy skies, and no direct air quality issues. The smoke from Nova Scotia is staying at the surface, which is causing the current air quality issues. 

When will this end?

The likely end of wildfire smoke is in the forecast with a change in the weather pattern expected this weekend around Saturday and Sunday, June 3rd and 4th. A storm disturbance moving in from Canada will interact with another disturbance moving up the Atlantic Ocean.

The models are giving strong signals of a storm system developing and stalling out over the Northeast and Eastern Canada next week. This would move widespread light to moderate rain, and cool temperatures (40s and 50s F) into the region. The forecast still remains a bit uncertain due to the reliance on the storm disturbance over the Atlantic Ocean.

This widespread rain will likely put out these wildfires and give some much needed precipitation to Eastern Canada and areas of the Northeast. Locally heavier rain is possible, so flash flooding is going to be a concern, especially for some areas that were heavily impacted by the wildfire. Less vegetation and severe burns can prevent water from entering the soil, and create flash flooding. 

This storm system will even bring a chance of snow for the highest peak in the Northeast, Mount Washington. Cold temperatures will mix down to the surface from the upper parts of the atmosphere. Check out the forecast at Mount Washington next week. 

Wildfire season is just getting underway and has started early in an unusual way for Canada and parts of the US. Keep a tab on the OpenSnow smoke maps for the latest prediction that can help plan your summer adventures to have good air quality and clean lungs!

Zach Butler