Monsoon Cool Down and Decent Air Quality, Week of July 15

Staff Writer, Nathaniel Diaz

Weather / Air Quality
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Today's Air Quality

Forecast Discussion: Forecast models did very well with Sunday's storms in regards to timing and location. Areas in the southeast Valley are cleaning up this morning after severe weather rolled through the area. Reports of hail, downed trees, winds in excess of 60 mph and over an inch of rain in less than an hour came in as the storm moved west. Typically after a storm like that, the Valley is tapped of energy and the following day is a down-day. However, models are in agreement that we could see another round Monday afternoon. They differ slightly on whether storms move through the Valley or skirt metro area to the north and south, merging again in western Maricopa County. There could be isolated downpours, hazardous lightning, damaging winds, and hail. This will be the last chance for rain until next Sunday or Monday as the monsoon high moves to northern California. Much drier air moves into Arizona by Wednesday. Expect middle Moderate ozone levels through Wednesday. PM10 levels should be back in the Good range following Sunday's rain event and any subsequent precipitation on Monday.

Source: AIRNow, Weather Channel

Instant Summer, Just Add Heat and Ozone

Staff Writer, DB Holmes
Weather / Air Quality
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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.

May 19 Air Quality Forecast

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.

Source: AIRNow, Weather Channel,

Ozone Concern and Triple Digit Heat for the Desert Valley

Staff Writer, DB Holmes

Weather / Air Quality
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Phoenix should have a quiet weather weekend as winds are subdued and temperatures remain hot. Ozone rose but now the westerly winds will pick up the smoke from the California wildfires. People with respiratory issues should take note.

Here is the rest of the forecast:

Forecast Discussion: Ozone levels soared into the upper Moderate range across the forecast area on Thursday, and that was without the help of southern California wildfire smoke. Now that the flow has switched out of the west, the likelihood of smoke-enhanced ozone affecting Arizona increases. In fact, locations north of the Valley (Prescott, Flagstaff) could see elevated concentrations the next several days. Locally, Valley concentrations will remain in the upper part of the Moderate range through Sunday. Winds will increase Sunday afternoon as another trough of low pressure approaches the region. This should break up the invisible daily plume of ozone, effectively lowering concentrations. PM10 levels should also remain in the Good range the next several days, increasing Sunday through early next week with stronger winds. Expect daytime temperatures to reach 102-104°F Friday through Sunday, decreasing Monday. Unfortunately, no rain is in the forecast for at least another 2 weeks.

Source: AIRNow 

Desert Heat with a Hint of Chicago Wind; Where's Our Spring Rains?

Staff Writer, DB Holmes

Weather / Air Quality
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Phoenix will still have breezy conditions throughout the ten day forecast but Sunday through Tuesday will see the winds kick up again. No precipitation in sight.

Forecast Discussion: Winds out of the east this morning are gusting 30 mph at times. There are no significant visibility reductions being reported at Valley monitoring sites, but there is some haze out there. This is likely a combination of long-range dust transport and wildfire smoke that has entered the Phoenix Metro area from the Skunk Fire, burning about 100

Tomorrow's Air Quality Forecast

miles to the east. Wildfire smoke does contain ozone precursors, so an increase in ozone production today is possible, but the smoke will be well dispersed and be gaining lift with the heating of the day. Overall, the wildfire smoke seems to be having minimal impacts on our current air quality. Wind speeds start to drop off later this afternoon when the pressure gradient relaxes. There have been brief periods of elevated PM-10 at some sites today due to the gusty winds, but generally PM-10 will still range from the upper Good to lower Moderate range today. As high pressure makes its way over us tomorrow and Friday, much lighter winds and above average temps around 100 degrees are expected. Ozone at this time may reach lower Moderate levels under clear skies and light westerly flow, while PM levels register in the Good category.

Southwest U.S. Long Range Weather Forecast
16th-19th. Fair, warmer.
20th-23rd. Scattered showers.
24th-27th. Changeable skies: mixed cloud, sun, possible shower. Cool temperatures.
28th-31st. Possible showers again.

Last year's May 14th Statistics:

High Temp:	101.7F
Low Temp:	69.8F
Average Temp:	87F
Dewpoint:	36.7F
Wind Speed:	4.1 Knots

Source: AIRNow, Weather Channel, Farmer's Almanac,   

Last of April's Hours Don't Bring May Flowers

Staff Writer, DB Holmes

Weather / Air Quality

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Phoenix is going to be hot in the beginning of this week but temperatures will be tapering off into the mid to upper 80's by next weekend. Watch out for more wind associated with low pressure systems making their way down the jet stream.

Forecast Discussion: Daytime highs in Phoenix will warm to the middle 90s through Tuesday with high pressure moving through the region. We will see ozone levels edge up each day, reaching the middle Moderate range by Tuesday, ahead of the next disturbance on Wednesday. The mid-week system will bring cooler air, dropping afternoon highs into the upper 80s. This wave will be lacking moisture, so no rain is expected for the deserts. Winds may exceed 15-20 mph at times. We'll be watching the models of changes to speeds and directions of the wind which could result in some blowing dust. For now, it doesn't appear to be a big dust-maker for the Phoenix area.

Source: AIRNow, Weather Channel