FORECAST SUMMARY: Monday, June 19, 2023, through Tuesday, June 20, 2023

PM-2.5: 24-hour average Fine Particulate concentrations are expected to be mostly Moderate.

OZONE: 8-hour average ozone concentrations are expected to be mostly Good increasing to Moderate.

FORECAST DISCUSSION: Smoke levels held in the Moderate range during Sunday and ozone remains the secondary pollutant of concern in the Good to Moderate range.  Not much has changed with the short and long range forecast.  High pressure persists over the region with extremely dry conditions and high fire danger. Easterly winds persist with daytime high temperatures in the upper 80’s and approaching 90.  Relative humidity remains in the 20-30% range.

There is still a thick layer of smoke, aloft, which is dimming the sun and giving us gray rather than blue skies.  At the surface, fine particulate readings have been mostly in the 20-30 ug/m3 range, which is Mid-to-High Moderate.  The smoke models are predicting an improvement with a slight lowering of those numbers today and tomorrow. 

While ozone numbers have been behaving during this high smoke episode, we are in the time of year where the threat of elevated ozone is the highest.  The lower numbers we have been seeing may be partially due to the smoke layer aloft which has been dimming the amount of sun reaching the surface and reducing photochemical conversion of surface pollutants.  The ozone models are predicting that our numbers will remain in the Good to Moderate range for the next couple of days, and I am not seeing anything to challenge that conclusion.

Dry conditions are predicted to persist, at least into the weekend.  Hopefully we will see some scattered shower potential, by the weekend.

Due to the unpredictable nature of smoke, I will be updating this forecast Tuesday morning.

EXTENDED FORECAST: Air Quality should be generally Moderate through the week.

Forecast updated by: Jim Haywood: Monday, June 19, 2023

Next Forecast update: Tuesday, June 20, 2023