U.S. Air Quality

Extremely elevated AOD over Pacific NW; Critical fire weather over majority Minnesota /Oklahoma

Today's MODIS Terra RGB overlaid with AOD retrievals reveal much higher AOD over the Pacific NW compared to yesterday, thanks to the clearing out of cloud layers over Washington (top left). Raised AOD are not only plaguing the states with large wildfires, but also further south and east due to favorable atmospheric flow regimes. Much like yesterday, elevated AOD, mostly remnant smoke from the NW fires, was observed across the Central Plains through the Southeast states. Fortunately, Unhealthy (Code Red) PM2.5 air quality indices (AQI) were confined to smaller locations in north/central Washington and Oregon today, with wider regions of Unhealthy for Sensitive Groups (Code Orange) and Moderate (Code Yellow) along the periphery (top right, courtesy AIRNow). Code Orange and Yellow were also scattered across California, west Nebraska, Massachusetts, south Central Plains, and Southeast states.

Elsewhere, the Storm Prediction Center (SPC) issued a Critical Fire Weather alert today over eastern Minnesota, western Wisconsin and northern Iowa due to below normal rainfall conditions over past few weeks, a southward advancing cold front initiating gusty southwesterly winds, and extremely low relative humidity values (bottom left, courtesy SPC). Deep boundary layer mixing from a tightening pressure gradient near a low pressure system across southern Kansas and Oklahoma also caught the SPC's attention, as the team forecast a low-level jet (fast ribbon of winds in the lower troposphere) to form and further support fire weather in the already dry, drought-striken, region. According to wind observations at the Oklahoma City airport, a low-level jet was prevalent this afternoon, with measured wind gusts above 30mph (bottom right, courtesy NWS-KOKC).