Mid-Atlantic Medium Range Air Quality Discussion, Issued Friday, August 4, 2017

Mid-Atlantic Medium Range Air Quality Discussion, Issued Friday, August 4, 2017
Medium Range Air Quality Outlook  Mid-Atlantic Region

Issued: Friday, August 4, 2017
Valid: August 5-9, 2017 (Saturday-Wednesday)


After several weeks of hot weather and wild swings in local and regional air quality, we will enter a quiet, cleaner period that will persist into next week. A large upper level trough with a series of embedded disturbances will keep temperatures below average and air quality in the Good to Moderate range across the mid-Atlantic.

Weather Model Discussion:

The standard set of 0600 UTC numerical model forecasts were consulted for this discussion. While there are some differences in the finer grain aspects of the forecasts, the models are in good overall agreement with the result that forecast confidence is higher than average through the medium range. A broad trough over the northern US with embedded short wave disturbances will push frontal boundaries, with rain and cloudiness, through the mid-Atlantic on Saturday and again on Monday. Between frontal passages, a dry and cool air mass will limit any significant build up of pollutants.


A cold front will reach the I-95 Corridor Saturday morning with precipitation expected to accompany its passage. The air mass will gradually become cooler and much less humid behind the front. The cleaner air will be in place across most of the mid-Atlantic by Saturday afternoon. The combination of clouds, precipitation and an entering clean air mass will make for only a Slight risk of poor air quality in the mid-Atlantic on Saturday.

Sunday will be a very pleasant day across the region weather-wise. High pressure moves over Virginia. Temperatures and dew points will be below normal with plentiful sunshine.

Regional ozone concentrations will be quite low in the dry post-frontal air mass but sunny skies will allow ozone to accumulate later in the day. With a clean start, the risk of high ozone on Sunday will remain Slight. Particles concentrations will remain low due to the very dry air mass.

A warm front pushes north through the mid-Atlantic on Monday with rain likely. The associated cold front is expected to reach the I-95 Corridor Tuesday morning with high pressure building over PA on Wednesday. Rain will keep the mid-Atlantic in the Slight risk category on Monday. Expect a slow rise in pollutants on both Tuesday and Wednesday with a Marginal risk by Wednesday.