Weather / Air Quality
The heat gives us a break at the mid part of the week and then slowly builds back in as a cut off low spins away. For respiratory issues sufferers, the ozone has replaced dust and particulates in causing breathing difficulties. The ozone should return to a more normal range for this time of the year as clouds and cooler weather enter the picture this week.
Forecast Discussion: If the triple-digit heat came a little too early for you (104°F at Sky Harbor Friday and Saturday), take heart. Temperatures will "cool" to around 90°F by Wednesday as a trough of low pressure moves over Arizona. This trough will actually become cut off from the main flow, sitting over our area through next weekend as it eventually spins out and loses energy. This could eventually be good as far as wildfires go. Towards the end of the week, the low is expected to draw some moisture from the Gulf of Mexico into eastern Arizona. The mountains could see some showers next Saturday and Sunday. Regardless of the rain, the increased humidity should help reduce fire behavior. Ozone is the current topic of conversation. Yuma exceeded the 8-hour ozone health standard on Friday. Typically we'll see levels do the same in the Valley a day later. However, we were spared as the flow was more to the north-northeast rather than east-northeast. Unfortunately, Alamo Lake, Prescott, and Flagstaff all exceeded the standard on Saturday. Exceeding the ozone standard in those non-major-metropolitan areas is a classic case of ozone import from the west. Let's not forget that smoke from southern California may have played a role in enhancing the ozone development upstream. Looking forward, high clouds Sunday should keep ozone production down slightly. This may be just enough help to avoid exceeding the standard in Valley. Stronger winds develop Monday through Wednesday which should also help break up the invisible plume, decreasing the threat of elevated readings. Dust doesn't seem to be much of a concern for us this week, especially when moisture is drawn in later in the week.
May 19 Air Quality Forecast
Source: AIRNow, Weather Channel,