FORECAST SUMMARY:
Monday, September 21st, 2020 through Friday, September 25th, 2020
OZONE: 8-hour average Ozone concentrations are expected to be mostly Good; some Moderates are possible late in the week.
PM-2.5: 24-hour average Fine Particulate concentrations will range from upper Good to middle Moderate.
FORECAST DISCUSSION:
Weak disturbances may bring a few periods of precipitation to the northern portion of the state; however, most areas will be dominated by high pressure providing dry conditions and moderating temperatures through the week. Another item to note, wildfire smoke has returned which will again provide a hazy look to the sky.
Air quality this past weekend was Good for both ozone and fine particulate aside from two monitors in the southeast that reached low Moderate for fine particulate. For Monday and Tuesday, winds will be from a southerly direction, but surface and upper level temperatures look to remain low enough (along with earlier sunset this time of year), where ozone will stay generally Good. Smoke forecast models show the plume staying “elevated” the next few days; therefore, it should not have a negative impact on fine particulate. With lighter southerly winds, fine particulate will range from upper Good to low Moderate.
By mid-week, west/southwesterly winds continue with high pressure to our east. Making the forecast a bit challenging is uncertainty on how the smoke over the region will play out as the week progresses. Models show the plume reaching closer to the ground and this is something we will keep an eye on. Considering there is no real air mass change this week, we would expect fine particulate to increase into the Moderate range, especially across the southern portion of the state. Ozone may also increase into low-Moderate.
Similar conditions continue through Friday and more widespread Moderate pollution levels are a good possibility. By Saturday, temperatures as the surface and upper levels increase and coupled with plenty of sunshine, conditions look more conducive for ozone development. While it is late in the ozone season, it’s not out of the question to see elevated ozone in September; therefore, we will be updating the forecast Friday to detail expected pollution levels for the weekend.
EXTENDED FORECAST:
Extended forecast models show the next chance for widespread precipitation comes with a storm system passing late Saturday into Sunday. Good pollution levels should return early next week.