Air Quality Action Day has been declared for Susquehanna Valley on Friday, Aug 24

Friday, Aug 24: 117 AQI Unhealthy for Sensitive Groups Ozone
80 AQI Moderate Particle Pollution (2.5 microns)

Extended Forecast
Saturday, Aug 25: 102 AQI Unhealthy for Sensitive Groups Ozone
78 AQI Moderate Particle Pollution (2.5 microns)
Current Conditions as of 1 PM on Thursday: You may have noticed that the weather this morning and so far this afternoon seem to be quite similar to yesterday. That is indeed the case as the trend in the weather this week has been for similar conditions to repeat themselves, with only a slight change. That slight change each day has been morning patchy fog becoming mostly sunny skies by late morning, temperatures rising a degree or two higher than the previous day, and Ozone and PM 2.5 concentrations climbing higher and higher. The threat for Code ORANGE conditions will continue into at least Friday before becoming more scattered Code ORANGE to moderate over the weekend. *** Friday’s Forecast: On Friday, the broken record of the weather this week once again repeats itself with patchy morning fog quickly burning off to provide mostly sunny skies under an area of high pressure. The trend for rising temperatures and air quality concentrations will continue as well. Forecast highs should climb into the mid to upper 80s, which is slightly above normal for late August. The high moderate to Code ORANGE Ozone concentrations from Thursday will continue to slowly become more modified on Friday, climbing higher into the Code ORANGE level. Nearly calm winds all week have allowed for these concentrations to slowly become more modified each day due to a lack of vertical mixing that we would see on days with a strong afternoon breeze. It has been several days since we have had a frontal passage or increased precipitation threat to also allow for this period of stagnation to occur. PM 2.5 concentrations have also been slowly climbing, but have and will continue to remain moderate with low moisture levels present. Dew point temperatures will remain in the lower 60s as a result of the low moisture. An increasing chance for stronger easterly flow on Saturday may be able to help us reverse the trend from this week. *** Extended Forecast: Saturday appears to begin a tricky forecast period as we may see a wide range of conditions across the region that will impact the air quality forecast for the next several days. An area of low pressure is likely to develop off the coast and approach the coast line. This system will provide a chance for some showers along with cloud cover for a portion of the east coast. High clouds may extend far enough to the west to cover the entire forecast region. If they stay more to the east, ample sunshine again on Saturday may create high moderate to Code ORANGE concentrations for the locations in the region furthest to the west. More eastward sites would likely see more moderate concentrations. Easterly flow associated with this system may bring stronger onshore flow to provide more mixing than we have experienced over the last several days. I believe at this point the current air mass over the region is modified enough that it will take some time to improve air quality greatly. While conditions may become more moderate over the weekend, our next best threat for precipitation and a change in the air mass will come in the Monday/Tuesday timeframe. The outcome of current Tropical Storm Isaac will play a role in air quality conditions for the middle to latter half of next week. The computer models do not have a solution yet as to exactly where Isaac will track and make landfall or if the system will stall out over the Southeast vs. jet back out to sea and off to the northeast. — Roble

This forecast is brought to you by the Pennsylvania Department of Environmental Protection (PA DEP) and the Air Quality Partnership of the Susquehanna Valley.

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