Medium Range Air Quality Outlook
Mid-Atlantic Region

Issued: Saturday, August 1, 2015
Valid: August 2-6, 2015 (Sunday – Thursday)

Summary:

Moderate air quality will be the rule for most of the medium range period. An upper level low over James Bay on Monday will move slowly east and several weak frontal boundaries will cross the mid-Atlantic. The day of most interest will be Monday as temperatures return to the 90’s F although strong winds should ventilate the region enough to keep peak concentrations in the Moderate range.

Discussion:

The forecast models have been consistent over the past several runs leading to higher confidence in both the weather and air quality forecasts through the medium range.

An upper level closed low will be centered west of James Bay early Monday and remain in place through Tuesday before slowly moving eastward to southern QC on Wednesday. As the low opens and moves further east Thursday, zonal flow will set up. This pattern is consistent with generally Good to Moderate air quality in the mid-Atlantic.

Surface high pressure over WV, with a coastal front over eastern NC will result in light westerly winds, mostly sunny skies and Moderate levels of both ozone and particles in the mid-Atlantic. By Monday, winds will shift to the southwest and increase in strength. Temperatures will rise to the low 90’s F and dew points to the upper 60’s F. This pattern is conducive to both ozone and fine particle formation. However, steadily increasing winds will keep air quality in the Moderate range.

A weak cold front will reach the I-95 Corridor on Tuesday morning. Although weak, this boundary will bring a drier air mass and steady westerly winds, along with deep vertical mixing. As a result, particle concentrations are likely to drop to the Good range while ozone concentrations will decrease but remain in the Moderate range.

The frontal boundary dissipates over the southern mid-Atlantic on Wednesday with another frontal passage expected early Thursday morning. Clouds, particularly south of the Mason Dixon Line, and a chance of showers on Wednesday will bring Good to low Moderate air quality. A cooler and slightly drier air mass after the front passes Thursday will keep air quality in the Good to low Moderate range.

-Ryan