Medium Range Air Quality Outlook
Mid-Atlantic Region

Issued: Monday, June 9, 2014
Valid: June 10 – June 14, 2014 (Tuesday-Saturday)

Summary:

Tuesday and Wednesday will be characterized as mostly cloudy all day with a chance of rain due to the stalling of a warm front over the region. Ozone will reduce to the Good range while PM2.5 will increase to the Moderate range due to warm air advection. Thursday and Friday will both have a greater chance of convection and precipitation as the front travels through the region. The air quality will improve both days, yet PM2.5 will still remain in the low Moderate. As the surface low brings its cold front through the region on Saturday morning, sun will shine for the greater part of the day increasing ozone concentrations. Air quality will be in the Moderate range.

Discussion:

There is high confidence in the weather forecast models for the upcoming days. All the models are in agreement that a deep trough in the Southern Plains will move slowly eastward and weaken, crossing the region on Friday. Give or take some minor discrepancies, the NAM, ECMWF, and GFS all show very similar predictions at the surface, 850 mb, and 500 mb. On Tuesday, however, the ECMWF calls for less precipitation, which would lead to an increase in air pollutants.

A surface stationary/warm front will slowly move northward through the region on Tuesday creating humid conditions and mostly cloudy skies. There will be afternoon rain in the northern part of the region, and we expect better air quality to the north. An upper level ridge, however, will keep most of the Mid-Atlantic dry. Mostly cloudy skies and limited mixing will easily bring PM2.5 into the low/mid Moderate range for Tuesday. Scattered regions of Moderate ozone are expected as well.

The surface warm front will inch northward on Wednesday leaving the Mid-Atlantic region in the warm sector with temperatures and dew points rising to above average. The upper level ridge, still in place, should reduce the chance of rain, but there will still be localized showers and thunderstorms on Wednesday. PM2.5 will stay in the Moderate range, while ozone will be reduced to the high Good range.

By Thursday, the surface warm front will move southward over Maryland. The weather forecast models all agree that there will be significant divergence aloft over the entire region. With enough sun, and plenty of moisture in place, this combination will destabilize the atmosphere, and increase chances for convection and rain. There is a high chance for rain and thunderstorms all day Thursday. Ozone will remain in the Good range, while southerly flow and warm air advection aloft will keep PM2.5 in the Moderate range.

A good chance for rain and thunderstorms will continue on Friday as a trough extends over the Mid-Atlantic. There lies a good chance that convection will become organized over the prefrontal trough running parallel to I-95 Corridor. The air quality will improve bringing ozone and PM2.5 concentrations to the Good range. The low will carry its cold front through the region on Saturday leaving early morning showers and sunshine for most of the day. Air quality will reach the Moderate range.

-Catena/Ryan