FORECAST SUMMARY:
Wednesday August 4th, 2021, through Friday, August 6th, 2021
Ozone: 8-hour average Ozone concentrations are expected to be Good to Low Moderate.
PM-2.5: 24-hour average Fine Particulate concentrations are also expected to range from Good to High Moderate.
FORECAST DISCUSSION:
A gradual warm-up begins on Thursday as we return to a southerly air flow and more typical August temperatures and humidity. Wildfire smoke continues to be a major issue. Fortunately, most of the surface smoke has stayed on the west side of Lake Michigan, but the Upper Peninsula is experiencing Wednesday morning hourly concentrations in the USG range. As such, I’ve bumped the U.P. forecast up to USG.
The forecast models are still holding our ozone in the Good to Moderate range for the remainder of the work week. However, the fires and smoke look to hang around for the foreseeable future. The smoke models are indicating a southerly drift of the U.P. smoke into the Upper Lower Peninsula, during Wednesday, but I am not yet seeing that reflected in the monitors.
The smoke forecast models look to keep most of the surface smoke west of Lake Michigan. It is anticipated that the heavier Michigan smoke, currently in the U.P., may drift southward and affect the Upper Lower Peninsula for the remainder of today and tomorrow. That said, I think the overall 24-hour average will settle in the High Moderate range. As southerly flow picks up during Wednesday, that smoke cloud should begin to be pushed to the northeast.
While that should clear out the current smoke by late Thursday, by Friday morning, I expect the old smoke cloud that has been over the Ohio Valley to move back north on the southerly return air flow. That smoke cloud should be thinner and more elevated, but some could still mix down during daytime convection.
The weekend looks to be very warm and humid with the chance of showers. The question is whether enough elevated smoke will help reduce ozone formation and whether there be enough clouds/showers from a stalled frontal boundary to the north to thwart ozone production. Either way, I think a forecast update on Friday will be necessary to nail down these possibilities.
EXTENDED FORECAST:
Air Quality is expected to be Good increasing to Moderate going into the weekend.
Forecast updated by Jim Haywood: Wednesday, August 4th, 2021