Medium Range Air Quality Outlook
Mid-Atlantic Region

Issued: Wednesday, July 9, 2014
Valid: July 10- 14, 2014 (Thursday-Monday)

Summary:

High pressure will move over the Great Lakes leaving the Mid-Atlantic mostly sunny with northerly flow while the southern Mid-Atlantic will experience rain and thunderstorms as a cold front stalls over NC. Air quality will be limited to the Good range for most locations. Sunny skies and northerly flow will remain in the northern Mid-Atlantic as the high pressure sits over the Great Lakes. The southern Mid-Atlantic will continue the rainy weather as the cold front will stall over NC. Air quality will remain in the Good range for Friday. The center of high pressure will move over New England on Saturday bringing easterly flow to the northern Mid-Atlantic. There is a slight chance of precipitation with partly cloudy skies. Air quality will remain in the Good range with the exception of scattered Moderate ozone in the northern half of the region. Sunday will have rain and thunderstorms later in the day as a cold front approaches from the west. The day will be mostly to partly sunny resulting in Moderate air quality. Monday will have all day rain and clouds reducing air quality to the Good range.

Discussion:

The weather forecast models are in good agreement for the medium range period. An upper level trough will pass through the area by Friday evening with a weak ridge immediately following behind. The models have come in slightly better agreement for the weekend with the exception of the discrepancies between minor shortwaves passing through the area. An upper level closed low will form over MB Saturday morning and will intensify and move eastward through the medium range period. By Monday, it will station north of the Great Lakes region. This will produce some potentially heavy rain for early next week yet it is still uncertain for this far out in the forecast.

A frontal boundary will stall over NC on Thursday as a center of high pressure moves in over the Great Lakes. The front will create rain and thunderstorms for most of the region but primarily in the southern Mid-Atlantic. Mostly cloudy skies and northerly flow will limit air quality to the Good range for Thursday.

The rain will continue in the southern Mid-Atlantic until late afternoon Friday as the cold front stalls over NC. The center of high pressure over the Great Lakes will allow northerly flow and partly to mostly sunny skies for the northern Mid-Atlantic. The southern Mid-Atlantic will have southerly transport aloft and mostly cloudy skies. Air quality will remain in the Good range for most locations.

By Saturday morning, the cold front will move to the NC/SC border as a stationary front. The center of high pressure will move eastward over New England resulting in easterly flow and mostly sunny skies for the northern Mid-Atlantic. The region should mostly stay dry with the exception of a slight chance for precipitation in the southern part of the region as the high will extend its associated ridge down through the region. Air quality will remain in the Good range for most locations with the exception of scattered Moderate ozone in the northern part of the region.

A cold front will approach from the west on Sunday as the stationary front in SC will now move northward as a warm front. There is a chance for rain later in the day as the cold front moves eastward. Most locations should have Good air quality although there will be scattered areas of Moderate ozone for locations receiving the most sunshine. By Monday, a pre-frontal trough will develop over the Mid-Atlantic as the cold front moves closer resulting in scattered rain and thunderstorms all day throughout the region. Air quality will be reduced to the Good range.

-Catena/Ryan