Mid-Atlantic Medium Range Air Quality Outlook, Issued Monday, September 6, 2010

Medium Range Air Quality Outlook
Mid-Atlantic Region

Issued: Monday, September 6, 2010
Valid:  September 7-11 (Tuesday-Saturday)

Note:  This discussion can also be found on the Web at:
http://www.meteo.psu.edu/~wfryan/medium-range-outlook.txt

Summary:

Warm and more humid with moderate air quality Tuesday then a sharp cold front during the day Wednesday with
good air quality thereafter.

Discussion:

Note:  This will be the last Medium Range Air Quality Outlook discussion for the 2010 season.
Discussions will begin again May 1, 2011.

The forecast models, and the HPC guidance, continue to trend toward a faster frontal passage on Wednesday.
A quick look at the 12 UTC models corroborates that timing with the cold front expected to be just west of the
I-95 Corridor by 1200 UTC on Wednesday with sufficient ooomph to push it quickly through the mid-Atlantic
later in the afternoon.

Surface high pressure is moving over the northern mid-Atlantic this morning and will be oriented roughly
on a line from well east of the New Jersey coast to western NC by Tuesday morning.  This will allow for south
to southwest winds overnight, increasing during the day on Tuesday.  Temperature forecasts for Tuesday remain
in the upper 80's F, and, with steady winds expected, the threat of high ozone levels is much reduced.  At this time,
moderate ozone is expected for Tuesday.  PM will struggle upward along with humidity but only scattered locations
will reach the moderate range.

With a faster cold frontal passage forecast for Wednesday, good air quality is expected for locations west of I-95.
Winds will be very strong from the west and a much drier air mass will move in behind the front.  There is still a chance that
locations east of I-95, seeing the front arrive later, may inch into the lower moderate range for ozone.
As PM is a 24-hour average, all locations will see a significant drop in PM behind the front which will keep
PM levels good.

Cool, dry weather with strong NW winds Thursday and Friday will continue good air quality.  A warming trend
begins Saturday but good air quality continues.

-Ryan

William F. Ryan
Department of Meteorology
The Pennsylvania State University