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) will be replacing the high pressure ridge (Shaded “Arch” shape with blue arrows). That means an increased onshore flow that will cool us down considerably. It looks like rather pleasant weather for the Lane County Fair that begins today and continues through Sundaybut there will be just a slight chance of showers Saturday and Sunday.

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Air Quality Index:

Eugene-Springfield: The Air Quality Index is 19 in the Good category measuring Ozone.

Oakridge: The Air Quality Index is 13 in the Good category measuring Particulate Matter.

Cottage Grove: The Air Quality Index is 19 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 cloudy this AM, mostly sunny and a bit cooler this afternoon, partly cloudy this evening, mostly cloudy late tonight and Thursday AM, mostly sunny and a bit warmer in the afternoon, partly cloudy Thursday night,
• Mostly sunny in the AM, then partly cloudy Friday afternoon and at night.
  highs 80-85 lows 53-58.
• Partly cloudy with a slight (20%) chance of AM showers, a mix of clouds and sun Saturday afternoon, partly cloudy in the evening, mostly cloudy with a slight (20%) chance of showers late Saturday night through Sunday evening, just partly cloudy Sunday night,
• Then mostly sunny and warmer Monday and Tuesday, mostly clear Monday night.
• highs 86-82 warming back to 86 Tuesday lows 58-54. (seasonal averages high 84 low 52)

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Forecast for the Umpqua Basin including Roseburg:

• Partly cloudy this AM, sunny and a bit cooler this afternoon, partly cloudy this evening, mostly cloudy late tonight and Thursday AM, sunny and a bit warmer Thursday afternoon, mostly clear Thursday night,
• Sunny and a bit warmer Friday, then mostly clear Friday night.
• highs 83-89 lows 56-58.
• Partly cloudy with a slight chance of AM showers, partly cloudy and a bit cooler Saturday afternoon, partly cloudy Saturday night,
• Partly cloudy  a bit cooler and with a slight (20%) chance of showers Sunday and in the evening, partly cloudy late Sunday night,
•  Mostly sunny and warmer Monday, mostly clear Monday night,
• Then sunny and a bit warmer Tuesday.
• highs 87-84 warming to 92 Tuesday lows near 60. (seasonal averages high 86 low 57)

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

• Mostly cloudy this AM, sunny this afternoon, mostly cloudy tonight,
• Mostly cloudy Thursday AM, sunny in the afternoon, mostly clear with patchy coastal fog late Thursday night,
• Patchy coastal fog Friday AM and just partly cloudy Friday afternoon , while sunny inland, partly cloudy Friday night.
• highs near 65 lows near 56.
• Mostly cloudy with a slight (20%) chance of AM showers, partly cloudy Saturday afternoon and evening, mostly cloudy at night,
• Mostly cloudy Sunday AM, partly cloudy with a slight (20%) chance of showers Sunday afternoon, just partly cloudy through Monday AM, sunny Monday afternoon, mostly clear at night,
• Then mostly sunny Monday and Tuesday, mostly clear Monday night.
• highs near 65 lows near 56. (seasonal averages high 65 low 53)

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Forecast for the Cascades in Lane County:

• A mix of clouds and sun this afternoon and Thursday, partly cloudy at night,
• Mostly sunny Friday, then mostly clear Friday night.
• free air freezing level 12,000 ft. today and tonight, 11,000 ft. Thursday, 13,000 ft. Thursday night and Friday, then 12,000 ft. Friday.
• highs near 72 lows 42-47.
• Mostly sunny in the AM, partly cloudy Saturday afternoon, partly cloudy with a slight (20%) chance of showers late Saturday night through Sunday evening, just partly cloudy at night and Monday AM, then mostly sunny Monday afternoon and Tuesday, mostly clear Monday night.
• free air freezing level 12,000 ft. Saturday and Saturday night, 11,000 ft. Sunday, 12,000 ft. Sunday night, 11,000 ft. Monday, then 12,000 ft. Monday night and Tuesday.
• highs 72-68 warming to 75 Tuesday lows 47-42 warming to 75 Monday night.

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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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