Mon, May 10, 2021: A quiet day across Minnesota. Patchy clouds continue over most the state with surface winds northerly at 10mph with gusts to 20mph. The cool temperatures and clouds have created Green (Good) AQI values across all of Minnesota. Expect that trend to continue overnight. Tuesday there are two areas of concern. First is the possibility of minor stagnation across northern Minnesota. Weather models develop and stall an area of high pressure across Northern Minnesota moving roughly from Lake of the Woods to Northome to Hibbing Tuesday. Surface winds near and under the low will be calm and depending on how slowly the high stalls there may be an opportunity for some stagnation of particulate matter. So far the CMAQ and other air quality guidance does not have any major increase of particulate matter, so stuck with upper level Green (Good) conditions statewide, though trends in northern Minnesota will need to be watched with this threat. Further to the south the second issue is the concentration of smoke moving in from Ontario and Manitoba. The HRRR smoke model has been pretty bullish about smoke concentration over southern MN tomorrow with values as high as 20 micrograms per cubic meter. That being said, the observations in the area that the HRRR currently has smoke has been considerably lower than modeled. Therefore, raised the values for PM tomorrow a bit in southern Minnesota, but still ended up on the higher end of Green (Good) AQI in these areas. Another factor playing into this is the weather models (especially the Euro) have a mixing depth Tuesday afternoon of nearly 3km. This all leads to the thinking that conditions will be Good (Green) across all of Minnesota, but this will be another scenario to monitor during the day Tuesday. Through the end of the week the high will depart but Minnesota still remains under modest surface flow. This may allow the AQI to climb some days, but generally forecasting Green (Good) through Wednesday for all of Minnesota.