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 Action Day
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Air Quality Index (AQI)
observed at 16:00 EDT
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Health Message: Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors. |
Note: Values above 500 are considered Beyond the AQI. Follow recommendations for the Hazardous category. Additional information on reducing exposure to extremely high levels of particle pollution is available here. |
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| Air Quality Index (AQI) |
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Moderate |
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Health Message: Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors. |
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| Air Quality Index (AQI) |
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Moderate |
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Health Message: Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors. |
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Forecast Discussion: FORECAST SUMMARY: Friday, September 22nd, 2017 through Monday, September 25th, 2017 Ozone: Ozone concentrations are expected to be mostly Moderate with scattered USG for the forecast period. PM-2.5: 24-hour Fine Particulate concentrations are also expected to be mostly Moderate through the forecast period. FORECAST DISCUSSION: Hot weather, more typical of mid-summer, looks to persist through the weekend and into the next week. Many records for daily high temperatures are being broken throughout the state. We are seeing a slow creep in air pollutant levels but not close to any Air Quality standards. The challenge for forecasting is that we have never had a threat of ozone this late in the year. If this were July, this would be an easy forecast to issue an Air Quality advisor. But in late September, the dynamics are different. One of the main ingredients for elevated ozone is a strong solar radiation presence. Heat, by itself, is not sufficient to generate ozone but it does work with solar radiation to preserve ozone in the lower levels of the atmosphere. With that said, the ozone models we use for guidance have been predicting high levels of ozone. In reality, we have not been seeing those levels. But numbers are increasing, albeit slowly. So, the question is if levels can rise to USG levels. Based on the projected wind patterns, I think the higher levels will stay over Lake Michigan and accumulate closer to the western side of the lake. Southeast Michigan may be a different story. Light winds will keep pollutants from dispersing and will accumulate locally. The main question is if the length of solar radiation exposure, with the shorter days, will be enough to push levels over USG. If it does, I believe it will isolated north of the Detroit area. Because I haven’t seen concentrations climbing at an alarming rate, I am inclined to keep the forecast at Moderate, observe the monitored values, and upgrade the forecast, as necessary. EXTENDED FORECAST: Air Quality is expected to be mostly Moderate to High-Moderate for the weekend into Monday with the possibility of scattered USG. Forecast updated by Jim Haywood: Friday, September 22nd, 2017 Next forecast update: Monday, September 25th, 2017 |
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AQI: Good (0 - 50)
AQI: Moderate (51 - 100)
AQI: Unhealthy for Sensitive Groups (101 - 150) 
AQI: Unhealthy (151 - 200) 
AQI: Very Unhealthy (201 - 300)
AQI: Hazardous (301 - 500)
National Parks/Monuments
Tribal Boundaries
