Here is my new weekly weather quiz question. What is “Zonal Flow ?”Please remember to post your answer as a comment by clicking on “no comments /comments” in the upper right hand portion of this page under the caption, then add your comment. The first person to post the correct answer will win a week of free personalized weather forecasts tailored to your needs. The answer has to be a comment to win. An email answer will not count. Good luck.

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An upper level low (Shaded “U” shape with blue arrows) continues an increased onshore flow that has cooled us down considerably. Weak high pressure (Shaded “Arch” shape with blue arrows) tries to take over, but low pressure quickly moves in. A weak frontal system  brings just a chance of some shower tonight through the weekend.

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Air Quality Index:

Eugene-Springfield: The Air Quality Index is 23 in the Good category measuring Ozone.

Oakridge: The Air Quality Index is 11 in the Good category measuring Particulate Matter.

Cottage Grove: The Air Quality Index is 22 in the Good category measuring Ozone.

Data courtesy of Lane Regional Air Protection Agency (LRAPA).

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Advisories: None at this time.

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Forecast for the Southern and lower Mid Willamette Valley including Eugene-Springfield and Albany-Corvallis:

• Mostly sunny this AM, partly cloudy this afternoon and evening, cloudy with a slight (20%) chance of showers late tonight,
• A mix of clouds and sun Saturday with a (40%) chance of AM showers, a bit cooler with a slight (20%) chance of showers Saturday afternoon, mostly cloudy with a slight (20%) chance of showers Saturday night,
• Mostly cloudy with a slight (20%) chance of showers Sunday AM, a (40%) chance of showers and cooler in the afternoon, a (30%) chance of showers Sunday evening, then partly cloudy with a slight (20%) chance of showers late Sunday night.
• highs 83-74 lows 57-52.
• Partly cloudy Monday AM, then mostly sunny and warmer Monday afternoon, Tuesday, Wednesday, and (a bit cooler) Thursday, mostly clear each night.
• highs 78-93 cooling to 90 Thursday lows 50-57 cooling to 55 Wednesday night. (seasonal averages high 84 low 52)

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Eugene/Springfield Pollen Count:

Trees: Low- 5

Grass: High- 55

Reading as of: 7/22/15

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Forecast for the Umpqua Basin including Roseburg:

• Sunny today, mostly clear this evening, partly cloudy late tonight,
• Mostly cloudy and cooler with a slight (20%) chance of showers Saturday, mostly cloudy with a slight (20%) chance of showers in the evening, partly cloudy late Saturday night,
• Mostly cloudy and cooler with a slight (20%) chance of showers Sunday afternoon and evening, then partly cloudy late Sunday night.
• highs 86-78 lows 59-55.
• Partly cloudy in the AM, sunny and warmer Monday afternoon, mostly clear Monday night,
• Mostly sunny and a bit warmer Tuesday, mostly clear at night,
• Then sunny and warmer Wednesday and cooler Thursday, clear at night.
• highs 85-96 cooling to near 90 Thursday lows 56-60. (seasonal averages high 86 low 57)

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Forecast for the South Oregon Coast including Coos Bay and North Bend:

• Partly cloudy with patchy coastal fog this AM, sunny this afternoon, partly cloudy this evening and mostly cloudy tonight at the shore while mostly clear inland this evening, mostly cloudy with a slight (20%) chance of light coastal rain or drizzle late tonight,
• Mostly cloudy and a bit cooler with a slight (20%) chance of showers Saturday, mostly cloudy in the evening, partly cloudy late Saturday night,
• Partly cloudy inland in the AM and mostly cloudy with a slight (20%) chance of showers  Sunday afternoon while a slight (20%) chance of coastal showers in the afternoon, then just partly cloudy Sunday night.
• highs 69-64 lows 57-54.
• Partly cloudy and a bit warmer Monday, mostly clear Monday night,
• Mostly sunny and a bit warmer Tuesday and Wednesday, mostly clear at night,
• Sunny and a bit warmer Wednesday, mostly clear at night,
• Then sunny and a bit cooler Thursday.
• highs 65-70 cooling back to 65 Thursday lows near 56. (seasonal averages high 65 low 53)

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Forecast for the Cascades in Lane County:

• Mostly sunny today, clouds increasing to partly cloudy with a slight (20%) chance of showers late tonight,
• A mix of clouds and sun with a (40%) chance of AM showers, a slight (20%) chance of showers and cooler Saturday afternoon, mostly cloudy a slight (20%) chance of showers Saturday night,
• A mix of clouds and sun with a slight (20%) chance of AM showers, (30%) chance of showers and cooler Sunday afternoon, then a slight (20%) chance of showers Sunday night.
• free air freezing level 13,000 ft. today, then snow level above 8,000 ft. tonight through Sunday night.
• highs 70-58 lows 46-42.
• A mix of clouds and sun Monday AM, then mostly sunny and warmer Monday afternoon, Tuesday, Wednesday and Thursday, mostly clear each night.
• free air freezing level 10,000 ft. Monday, 11,000 ft. Monday night, 13,000 ft. Tuesday, then 14,000 ft. Tuesday night and Wednesday, then 13,000 ft. Wednesday night and Thursday.
• highs 62-80 lows 43-50.

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**Because weather forecasting is a combination of science, intuition, and timing there can be no absolute guarantees that individual forecasts will be 100% accurate. Nature is in a constant state of flux and sudden unexpected weather events can happen.

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Get your local Eugene-Springfield and Lane County news on-line at eugenedailynews.com.

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