FORECAST SUMMARY: Monday, April 17, 2023, through Monday, April 24, 202323

OZONE: 8-hour average Ozone concentrations are expected to be mostly Good through the forecast period.

PM-2.5: 24-hour average Fine Particulate will range primarily Good with only small chances for Moderate.

FORECAST DISCUSSION:

The weather conditions from last week caused increases in both Ozone and Fine Particulate, warranting our first Action Day this season for ozone along the western lakeshore and in the southeast on Friday. USG ozone concentrations were seen at two southwest lakeshore monitors, and one southeast location. Clouds moved in early enough Saturday to keep western and central areas Moderate for ozone, however, further east sunshine prevailed longer, and a handful of monitors reached low-end USG. Fine particulate also increased with daily averages in the 20’s at several locations. The highest concentrations were Friday and Saturday in the southeast and one monitor reach just over the USG threshold on Saturday. The airmass over the region was a “dirty” airmass and increases in pollution were experienced in neighboring states as well. Smoke also prevailed over the region; however, more research would be needed to determine if smoke played a role in increased pollution levels.

The new week began with a cold front Sunday which ended the summer-like conditions, ushering in colder than normal temperatures and snow showers. Low pressure just north of the region dominates Monday and Tuesday with cool northerly winds and scattered snow showers. High pressure settles in briefly Wednesday before the next weather system brings a warm front north Thursday and then an associated cold front Friday. A quick temperature warmup Thursday allows precipitation to fall as rain, but another cool down is expected for the end of the week.

Good pollution levels should prevail Monday and Tuesday thanks to stronger winds with a northerly component. Weak high pressure sliding south of the state Wednesday could allow for increases in fine particulate to the low Moderate range, but ozone should remain Good. Warmer conditions move in Thursday, along with stronger winds and chances for precipitation. Fine particulate may remain low Moderate; however, ozone should average mostly Good. Precipitation may linger into Friday as the system tracks east. Fine particulate may remain Moderate in the southeast; otherwise, pollution levels will be Good.

EXTENDED FORECAST:

Extended models show high pressure settling in from the north during the second half of the weekend. Conditions will dry out as the weekend progresses, and temperatures will fall to below seasonable levels. Air quality readings are expected to be mostly Good during the weekend into early next week.

NEXT FORECAST UPDATE: Monday, April 24, 2023