FORECAST SUMMARY: Monday, September 11, 2023, through Friday, September 15, 2023

Ozone: 8-hour average Ozone concentrations will remain Good through Thursday with scattered Moderates possible Friday

PM-2.5: 24-hour average Fine Particulate levels are expected to be mostly Good with only a few low Moderate readings possible.

FORECAST DISCUSSION:The start of this forecast period favors clouds and rain as a low-pressure area and associated boundary pass through the state. Upper-level energy and cooler temperatures keep rain around Tuesday, but precipitation will be more scattered in nature. High pressure moves in from the west Wednesday drying conditions out and clearing skies. The coolest temperatures are projected Wednesday into Thursday morning with the center of the high overhead. Highs Wednesday struggle to reach out of the 50s across the northern portion of the state; further south readings in the low-middle 60s are expected. Thursday morning lows dip down into the 30s across the north with 40s elsewhere.

Regarding ozone this week, clouds Monday and Tuesday, northerly winds late Monday through Thursday, and cooler conditions hamper ozone development keeping readings Good. The high-pressure area tracks east of the state Friday, and southerly winds bring warmer temperatures back into the region. Plenty of sunshine is anticipated as well, and the combination of sunshine and warmer air may lead to increases in ozone. However, considering the time of year a significant development is not expected and ozone concentrations should not reach higher than low-Moderate in southern and/or western locations.

Wildfire smoke models are not showing any substantial plumes the next few days; therefore, we do not expect wildfire smoke to influence PM2.5 conditions this week. Our expectation for PM2.5 is that increased moisture Monday into Tuesday may allow for low Moderate readings, generally across the southern portion of the state, otherwise, Good levels are expected. Light winds Wednesday and Thursday morning may allow for hourly concentrations in the Moderate range during the morning hours, but increases should mix out and decrease during the day allowing for 24-hour averages to be mostly Good. Southerly winds developing Friday may bring in some scattered low Moderate readings across the southern portion of the state.

EXTENDED FORECAST: Extended models show a continuation of dry conditions and warmer temperatures for the start of the weekend. Pollution levels may reach low Moderate during this period.

Next Forecast Update: Friday, September 15, 2023