Thursday, May 15, 2008:  Fine Particulates (PM 2.5) – Code YELLOW    Ozone (O3) – Code GREEN

Regional Maximum PM 2.5 Concentrations:

Tuesday, May 13, 2008: Ozone (O3) – Code GREEN (46 AQI or 54 ppb) PM 2.5 – GREEN (21 AQI or 6.5 µg/m³) 

Short-Term Discussion:  A thin deck of cirrus clouds have spread over central Pennsylvania dimming the sun a bit.  To our west, clouds and showers are just beginning to enter the state.  These are associated with a disorganized cool front that will stall over the Commonwealth tomorrow.  We may see some showers from this system but it’s not real organized at the moment.  Thickening clouds should limit this afternoon’s ozone concentrations while fine-particulate concentrations have increased steadily.

Partly cloudy with a chance of a shower in spots overnight; temperatures will fall into the mid to upper 50s.  Partly cloudy Thursday with a chance of a shower and afternoon temperatures expected to climb back into the low to mid 70s.  There may be a few peaks of sunshine during the day as the cool front parked over us is rather weak.  We expect fine-particulate concentrations to linger in the code YELLOW (moderate) range while clouds should keep ozone concentrations in the code GREEN (good) range.

Extended:  Cloudy skies and showers remain in the extended forecast.  Northwesterly flow over the weekend will keep temperatures on the cool side.  The best chance of rain will occur on Friday with additional showers expected for Saturday afternoon lasting into Sunday.  Clouds should keep ozone levels in the good range through the extended period while fine-particulate concentrations will likely remain in the moderate range through Friday.