News & Events

Air Quality Alert for Saturday, June 30 (Code Orange)

Friday, June 29, 2012

Active children and adults, and people with lung disease, such as asthma, should reduce prolonged or heavy exertion outdoors.

Saturday’s Forecast: On Saturday expect hot and humid conditions once again as high climb right back into the 90s. Dew point temperatures look to remain in the mid 60s to low 70s range across the entire forecast region. Light winds early in the day will let PM 2.5 levels remain in the moderate range and climb slightly higher than Friday’s values. Mostly sunny skies through at least the mid-afternoon hours will boost Ozone levels to at least the high moderate range with some scattered Code Orange level concentrations. As we remain on the outer edge of an area of high pressure, the “ring of fire” scenario I have been discussing over the last few days will remain in play. The computer models have indicated a chance for another round of thunderstorms (much like early Friday morning) to move through the region.

No matter how strong or weak this storm cluster will be, it should not limit enough Ozone formation to reach Code Orange levels to issue another Action Day. Winds early in the day will continue to be mainly out of the northwest. After a period of light to nearly calm conditions, more of a southwesterly breeze will develop. The possibility that we could see some recirculation plus transport from already an already modified air mass in the Virginia/Washington DC area would also aid to the likelihood that Code Orange Ozone concentrations are probable.

Sunday’s Forecast: On Sunday, we will see a continuation of nearly similar conditions as Saturday. Clearing skies after the disturbance moves through late in the day on Saturday will lead to a rise in Ozone concentrations once again. This rise will likely be slower than on Saturday, but a longer duration of sunshine in the afternoon will allow concentrations to climb high enough to return to the Code Orange range. PM 2.5 levels will remain in the moderate range with little to no change in dew point temperatures to signify low level moisture remaining present over the region. Forecast highs will yet again reach the mid 90s as the heat wave continues on. Satellite imagery continues to analyze the atmosphere as containing smoke from the major wildfires out west. A growing wildfire on Massanutten Mountain in Shenandoah National Park (in western Virginia) has been sending smoke in the direction of Washington DC. Should transport bring any of the smoke into the forecast region, it may or may not impact both PM 2.5 and Ozone concentrations this weekend depending on if it remains higher aloft or is brought closer to the surface.

Extended Forecast: Drier conditions will evolve on Monday, reducing the chance for scattered showers or thunderstorms. A breezy northwesterly flow will gradually improve air quality conditions, though likely only improving into the moderate range. Temperatures will approach the 90 degree mark once again with ample sunshine forcing Ozone concentrations to the high moderate range. PM 2.5 levels should remain moderate as well, though slightly lower than on Sunday. The heat and humidity will remain for much of the week with forecast highs in the upper 80s to low 90s. A chance for showers in the middle of the week could help improve air quality conditions further along with a continuation of a northwesterly breeze, though moderate levels likely to still continue.