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. The weather will be near-perfect for the Lane County Fair with just a slight chance of showers Friday night through Sunday evening as the Fair continues.

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Air Quality Index:

Eugene-Springfield: The Air Quality Index is 22 in the Good category measuring Ozone.

Oakridge: The Air Quality Index is 10 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 clear tonight,
• Mostly sunny Friday AM, partly cloudy in the afternoon and evening, cloudy with a slight (20%) chance of showers late Friday night and Saturday AM, a mix of clouds and sun and 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 slight (20%) chance of showers Sunday evening, then just partly cloudy late Sunday night.
• lows 52-57 cooling back to 52 Sunday night highs 83-75.
• Partly cloudy Monday AM, then mostly sunny and warmer Monday afternoon, Tuesday, Wednesday, and (a bit cooler) Thursday, mostly clear each night.
• highs 80-93 cooling to 90 Thursday lows 52-55. (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:

• Mostly clear tonight,
• Sunny Friday, mostly clear in the evening, mostly cloudy with occasional rain and drizzle late Friday night and Saturday AM, cooler with a slight (20%) chance of showers in the afternoon, partly cloudy in the evening, mostly cloudy late Saturday night,
• Partly cloudy Sunday AM, mostly cloudy and cooler in the afternoon, then partly cloudy late Sunday night.
• lows 56-59 highs 83-88.
• Mostly sunny and warmer Monday, mostly clear Monday night,
• Then sunny and a bit warmer Tuesday, Wednesday and (cooler) Thursday, clear each night.
• highs 83-94 lows 57-60. (seasonal averages high 86 low 57)

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

• Partly cloudy at the shore this evening and mostly cloudy with patchy coastal fog late tonight while mostly clear inland,
• Cloudy with patchy coastal fog Friday AM and partly cloudy in the afternoon while sunny inland, partly cloudy in the evening and mostly cloudy Friday night at the shore while mostly clear inland in the evening, mostly cloudy with a slight (20%) chance of light rain and drizzle late Friday night and Saturday AM, mostly cloudy and a bit cooler in the afternoon, partly cloudy in the evening, mostly cloudy late Saturday night and Sunday, then partly cloudy Sunday night.
• lows near 56 highs near 68.
• Mostly sunny Monday and Tuesday, mostly clear at night,
• Sunny and a bit warmer Wednesday, mostly clear at night,
• Then mostly sunny Thursday.
• highs near 68 lows near 56. (seasonal averages high 65 low 53)

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Forecast for the Cascades in Lane County:

• Mostly clear tonight,
• Mostly sunny Friday, clouds increasing to partly cloudy in the evening, mostly cloudy late Friday night,
• A mix of clouds and sun with a slight (20%) chance of showers and cooler Saturday, mostly cloudy a slight (20%) chance of showers Saturday night,
• A mix of clouds and sun with a slight (20%) chance of showers and a bit cooler Sunday, then just partly cloudy Sunday night.
• free air freezing level 12,000 ft. tonight and Friday, 13,000 ft. Friday night, then snow level above 8,000 ft. Saturday through Sunday night.
• lows 43-46 cooling back to 43 Sunday night highs 72-58.
• Partly cloudy Monday AM, then mostly sunny and warmer Monday afternoon, Tuesday, Wednesday and Thursday, mostly clear each night.
• free air freezing level 9,000 ft. Monday, 10,000 ft. Monday night, 12,000 ft. Tuesday, then 13,000 ft. Tuesday night through Thursday.
• highs 62-78 lows 42-45.

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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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