Air Quality Forecast for Friday, August 31

Friday, August 31, 2007

Action Day?:  No

Temperature:  Low 80s

Fine Particulates (PM 2.5) – Code YELLOW

Ozone (O3) – Code GREEN

Short-Term Discussion: Hazy with a stray shower possible Friday morning. Temperatures will only fall into the mid 60s overnight. Clouds will slowly begin to clear and humidity levels will gradually decrease as a cool front works its way across the region. Afternoon temperatures should reach the low 80s with an outside chance of a stray shower or thunderstorm during the day. Fine-particulate concentrations should decrease on Friday but still remain in the lower code YELLOW (moderate) range while clouds and northerly winds should restrict ozone concentrations to the code GREEN (good) range.
 
Extended: The models continue to predict a nice start to the Labor Day weekend. Temperatures should fall back into more seasonable ranges (low 80s) with lower humidity for Saturday and Sunday. A ridge of high pressure will eventually slide eastward causing winds to turn out of a more southerly direction on Monday and Tuesday. This will cause temperatures and humidity levels to rise. Air-quality levels should be in the good range to start this weekend then gradually work their way back into the moderate range early next week.

Air Quality Forecast for Thursday, August 30

Thursday, August 30, 2007

Action Day?:  No

Temperature: Mid to Upper 80s

Fine Particulates (PM 2.5) – Code YELLOW

Ozone (O3) – Code YELLOW

Short-Term Discussion: Hazy with patchy fog Thursday morning and temperatures only falling into the mid 60s. Clouds will increase as a slow moving cool front approaches the area late tomorrow night giving us a slight chance of rain. Afternoon temperatures will reach the mid to upper 80s. Thursday’s fine-particulate concentrations should increase into the upper code YELLOW (moderate) range. Ozone concentrations may be limited by late afternoon clouds but could reach the code YELLOW (moderate) range in some areas.
 
Extended: Models continue to indicate a rain-free Labor Day weekend. An approaching cool front will work its way off shore on Friday and in its wake more seasonable temperatures and lower humidity will be in place for Saturday and Sunday. Southerly flow will return early next week as a ridge of high pressure sets up over the Southeast. Air-quality levels should remain mostly in the good range for the first half of the weekend then creep up into the moderate range next week.

Air Quality Forecast for Wednesday, August 29

Wednesday, August 29, 2007

Action Day?:  No

Temperature:  Mid 80s

Fine Particulates (PM 2.5) – Code YELLOW

Ozone (O3) – Code GREEN

Short-Term Discussion: Areas of fog early Wednesday morning with temperatures expected to bottom out near 60 degrees. Becoming mostly sunny and more humid with light southeasterly winds and afternoon temperatures expected to reach the mid 80s. Fine-particulate concentrations should push into the code YELLOW (moderate) range while ozone will remain in the upper code GREEN (good) range.
 
Extended: We expect several days of warm and humid weather prior to the arrival of a weak cool front late Thursday night. The forecast models do not depict this as an overly strong front at the moment with only spotty showers expected Thursday night and Friday. Ozone and fine-particulate concentrations should remain in the moderate range prior to this frontal passage. A ridge of high pressure is then forecast to pass over the Northeast lowering temperatures and humidity levels for the start of the Labor Day weekend.

Air Quality Forecast for Tuesday, August 28

Tuesday, August 28, 2007

Action Day?:  No

Temperature: Low 80s

Short-Term Discussion: On Tuesday, expect mostly sunny skies to once again be the rule as our area of high pressure, which was off to our north on Monday, begins to slide east. This slide east will help allow the winds to turn from out of the north to out of the east. As a result, temperatures should remain in the low 80s. Air quality levels should also remain low thanks to the maritime air mass moving into the region. This air mass will be relatively void of precursor pollutants, resulting in ozone and fine particulate levels hovering in the good (GREEN) range.
 
Extended: Over the next couple days, expect the warm and humid conditions to remain locked in over the region. Why? Well, we will have two main players on the weather field across the Northeastern US. A high pressure system combined with a cold front pressing through the Midwestern US will help create a southwesterly flow across the region, resulting in an increase in temperatures and dewpoint temperatures across the region. This “heat” should only last Wednesday into possibly Thursday though. The cold front pushing through the Midwest should eventually reach our region in the Thursday / Friday time frame. As it passes through, expect another round of showers to break out across the region. On the backside of the front, an area of high pressure will build in across the northern Midwest and Great Lakes regions. As a result, expect northerly flow to prevail for a couple of days, allowing a cooler and drier air mass to build southward as we head into the holiday weekend. By the end of the weekend, this high should be off to our east, which, in turn, should allow conditions to return to seasonable levels. Overall, we expect the air quality to be the highest in the Tuesday to Wednesday time frame this week. Air quality will begin to be on the downswing on Thursday as the cold front passes through the region. Expect levels to hit rock bottom on Friday into Saturday as the cooler and drier air mass arrives. Levels at this time should be in the good range.

Air Quality Forecast for Monday, August 27

Monday, August 27, 2007

Action Day?:  No

Temperature:  Mid 80s

Short-term Discussion: Some clouds and lingering showers possible early on Monday but skies should begin to clear and humidity levels should decrease as northerly winds become established. Afternoon temperatures are expected to reach the mid 80s. Monday’s ozone and fine-particulate concentrations should both remain in the upper code GREEN (good) range.
 
Extended: More seasonal weather is in store for us next week with some isolated showers possibly lingering into Monday. Southerly flow will reestablish itself by the middle of the week bringing us another bout of warm weather but nothing too drastic. The models are suggesting more fall-like weather across the Northeast for the start of the Labor Day weekend. Air-quality levels should remain in the moderate range for most of next week.

Air Quality Forecast for Friday, August 24

Friday, August 24, 2007

Action Day?:  No

Temperature: Mid to upper80s

Fine Particulates (PM 2.5) – Code YELLOW

Ozone (O3) – Code GREEN

Short-Term Discussion: Mostly cloudy with patchy fog, low 68. Becoming partly sunny and humid, high 87. Fine-particualte concentrations should reach the code YELLOW (moderate) range while ozone concentrations will remain in the code GREEN (good) range.

Extended: Very warm and humid over the next several days. A cool front will cross the region on Sunday. Air-quality levels should remain in the moderate range.

Extended Weekend Forecast

Date	8/24/2007	8/25/2007	8/26/2007	8/27/2007
Ozone	GREEN	YELLOW	GREEN	GREEN
PM	YELLOW	YELLOW	YELLOW	GREEN

Air Quality Forecast for Thursday, August 23

Thursday, August 23, 2007

Action Day?: No

Temperature: Low 80s

Short-Term Discussion: Mostly cloudy Thursday morning with temperatures falling into the lower 60s. Skies will gradually begin to clear a bit during the afternoon. Humidity levels should increase as the day progresses and afternoon temperatures could rise into the low 80s if clouds break earlier than expected and rain showers don’t develop later in the afternoon. Thursday’s fine-particulate concentrations should reach the code YELLOW (moderate) range while ozone levels will remain in the code GREEN (good) range.

Extended: Warm air currently situated over the Midwest will work its way over the eastern seaboard. A frontal system will eventually cross the region later this weekend. The models are giving slightly different indications when this will happen but the front should cross the region by late Sunday or early Monday. Air-quality levels will most likely remain in the moderate range over the next several days.

Air Quality Forecast for Wednesday, August 22

Wednesday, August 22, 2007

Action Day?:  No

Temperature: Mid 60s

Short-Term Discussion: Cloudy, cool with left over showers to start out Wednesday morning. Any rain should eventually taper off during the day with temperatures slowly rising from the upper 50s in the morning to mid 60s by the afternoon. Easterly winds, rain and clouds should keep Wednesday’s ozone and fine-particulate concentrations in the code GREEN (good) range.

Extended: The frontal system that has been lingering over the region will begin to lift out over the next several days. Warm and muggy temperatures will eventually return though this will be tempered by the chance of thunderstorms. Another cool front will cross the region later this weekend bringing another opportunity for rain before cooler and drier air filters in for Sunday and Monday. Expect ozone and fine-particulate concentrations to remain mainly in the good range for the next day or so though concentrations could reach moderate levels by Friday.

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Air Quality Forecast for Tuesday, August 21

Tuesday, August 21, 2007

Action Day?:  No

Temperature: Near 70

Short-Term Discussion: On Tuesday, expect mostly cloudy skies to persist for much of the day as we still contend with a stalled out frontal system to our south. In addition, thanks to the cooler air to the north, warmer air to the south couplet, rain is likely to continue to fall at times throughout the day. This rain is also likely to be heavy at times as the best dynamics remain across Pennsylvania. Thanks to the area of high pressure to our north, temperatures will remain a bit on the cool side, with highs ranging around the 70 degree mark. Air quality levels will also remain rather low. During the day, we expect easterly winds to prevail. Onshore flow like this tends to clean out the higher air pollutants and shift them west. Therefore, we expect PM 2.5 levels to range in the good (GREEN) range. As is the case with many rain events, ozone will stay confined to the good (GREEN) category.

Extended: For the rest of the week, we notice that conditions will be getting progressively warmer and possibly even drier as the frontal system, which plagued our weather early in the week, finally moves off to the north. The heaviest rain should fall on Tuesday as the main tropical flow combines forces with the frontal system to our south. For the most part, Wednesday should be a transition day. The model guidance is still conflicting on the exact timing of when the warm air advection will commence across the region. This all has to do with the timing of the frontal passage as it passes off to our north. We do think that this will definitely happen by Thursday. Therefore, expect much warmer and more humid conditions to return to the region at this time. As the temperatures warm, we will have to be concerned once again with the air quality across the region. Ozone and PM 2.5 levels will likely be on the increase as the weather conditions become more favorable for higher air pollution. Depending on how bad conditions get, we could be issuing another round of Air Quality Action Days for the region. This warm and more humid air mass will be in place across the region until the next frontal system passes through the region on Sunday. At this time, we expect another round of showers to break out across the region before passing off to our east and allowing a seasonably cool and dry air mass to return early next week. We will continue to keep our eyes open for the developing air quality situation later this week.