Good to moderate air quality expected

Weather Forecast: Issued on Friday, March 27, 2015

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

Friday:
-an upper level trough over southern Ontario is causing cloudiness and scattered precipitation over some regions of southern and eastern Ontario, while a strong high pressure ridge spreading southward over the Great Lakes region is causing clearing skies over northern and central regions with north to northwesterly winds and decreasing temperatures
-the northerly flow of cooler and dry air is expected to result in low pollutant concentrations and air quality indices in the good category

Saturday:
-the high is forecast to remain over the Great Lakes region and to cause sunny skies
-winds are forecast to be light and north to northwesterly over most regions, except becoming westerly over northern regions
-temperatures are forecast to be significantly cooler than seasonal values for late March
-air pollutant concentrations are expected to remain low in the cool and dry northerly flow, and air quality indices are forecast to remain in the good category

Sunday:
-the high is forecast to move southeastward over the eastern US while a low pressure trough is forecast to move eastward over the central Great Lakes region
-mostly sunny skies are expected over central and eastern regions, while increasing cloudiness is expected over southern and northern regions with scattered precipitation possible over northern regions
-continuing cool temperatures are forecast and increasing and gusty southwesterly winds are forecast to develop over all of the forecast regions
-pollutant concentrations are not expected to increase significantly and air quality indices are forecast to remain in the good category

Air Quality Forecast:
Air quality indices are forecast to be mostly in the good category during the next several days across the province.

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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.