Good to moderate air quality expected

Weather Forecast: Issued on Wednesday, October 22, 2014

The main weather factors affecting air quality indices during the next several days include:

Wednesday:
- a low pressure trough over the Atlantic coast is forecast to cause continuing cloudiness with scattered precipitation over eastern Ontario, and a high pressure ridge over northern Ontario is forecast to cause sunny skies over northern regions and partly sunny skies over southern and central regions, with north to northeasterly winds and generally seasonal temperatures in the forecast regions
-the continuing northerly flow is resulting in low air pollutant concentrations and air quality indices continuing in the good category

Thursday:
-the low is forecast to remain near the Atlantic coast and the ridge is forecast to be over northern Ontario and the central Great Lakes region. Partly or mostly sunny skies are expected, except for continuing cloudiness and scattered precipitation over eastern Ontario
-winds are forecast to be light and northerly, except for southwesterly winds developing over the northwestern forecast regions near the axis of the high pressure ridge
-the continuing northerly flow over most regions is forecast to result in low air pollutant concentrations and air quality indices continuing in the good category

Friday:
-similar conditions are expected with the Atlantic low causing cloudiness and scattered precipitation over eastern Ontario and the ridge causing partly or mostly sunny skies over most other regions, except for cloudiness spreading eastward over the northern regions ahead of a low pressure trough that is forecast to move over northwestern Ontario
-winds are forecast to be light and northwesterly over most regions, except for south to southwesterly winds over the northwestern forecast regions, and temperatures are forecast to be near or above seasonal values
-concentrations of air pollutants are not expected to increase significantly, and air quality indices are forecast to continue to be in the good category

Air Quality Forecast:
Air quality indices are forecast to be generally in the good category across the province during the next several days, due to low concentrations of air pollutants.

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Smog, comprised of Ozone (O3) and/or Fine Particulate Matter (PM2.5), is primarily a summer phenomenon, occurring mostly in southern Ontario; however, PM2.5 can elevate smog levels during all months of the year. For this reason, the ministry reports the AQI hourly, seven days a week; and continues to provide air quality forecasts daily.