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 22 in the Good category measuring Ozone.

Oakridge: The Air Quality Index is 8 in the Good category measuring Particulate Matter.

Cottage Grove: The Air Quality Index is 20 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 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 in the evening, just mostly cloudy Saturday night,
• A mix of clouds and sun and a bit cooler Sunday with a slight (20%) chance of AM showers, a (40%) chance of showers and cooler in the afternoon and evening, partly cloudy with a slight (20%) chance of showers late Sunday night,
• Partly cloudy Monday, then mostly clear at night.
• lows 59-49 highs 76-74 warming to 78 Monday.
• Mostly sunny and warmer Tuesday, Wednesday, Thursday and Friday, mostly clear each night.
• highs 87-99 cooling to 93 Friday lows 56-60 (seasonal averages high 84 low 52)

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Eugene/Springfield Pollen Count:

Trees: Low- 2

Grass: High- 53

Reading as of: 7/24/15

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Forecast for the Umpqua Basin including Roseburg:

• Mostly clear this evening, partly cloudy with a (30%) chance of showers late tonight,
• Mostly cloudy and cooler with a (30%) chance of showers Saturday, a slight (20%) chance of showers in the evening, partly cloudy late Saturday night,
• Mostly cloudy in the AM, partly cloudy and cooler with a slight (20%) chance of showers Sunday afternoon and evening, partly cloudy late Sunday night and Monday AM, sunny and warmer Monday afternoon, then mostly clear Monday night
• lows 59-55 highs 86-78.
• Mostly sunny and a bit warmer Tuesday, mostly clear at night,
• Sunny and warmer Wednesday and, sunny and cooler Thursday, mostly clear both nights,
• Then mostly cloudy Friday.
• 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 this evening and mostly cloudy tonight at the shore with a good (50%) chance of showers late tonight while mostly clear inland this evening and partly cloudy with a (40%) chance of showers late tonight,
• Mostly cloudy and a bit cooler with a good (50%) chance of showers Saturday, just mostly cloudy Saturday night,
• Mostly cloudy with a slight (20%) chance of showers Sunday afternoon, partly cloudy in the afternoon, just partly cloudy Sunday night and Monday AM, sunny and a bit warmer in the afternoon, then mostly clear Monday night,
• lows 58-54 highs 65-68.
• Mostly sunny and a bit warmer Tuesday, Wednesday and Thursday (a bit cooler), mostly clear at night,
• Sunny Friday AM, then partly cloudy and a bit cooler Friday afternoon.
• highs 70-77 cooling to 68 Friday lows 56-58. (seasonal averages high 65 low 53)

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Forecast for the Cascades in Lane County:

• Partly cloudy with a slight (20%) chance of showers late tonight,
• Mostly cloudy with a (40%) chance of showers Saturday (under 0.10 in. of rain possible), a slight (20%) chance of showers in the evening, just mostly cloudy late Saturday night,
• A mix of clouds and sun with a slight (20%) chance of AM showers, a (30%) chance of showers and cooler Sunday afternoon, mostly cloudy with a (40%) chance of showers in the evening, a slight (20%) chance of showers Sunday night,
• A mix of clouds and sun with a slight (20%) chance of showers Monday AM, mostly sunny and warmer Monday afternoon, then mostly clear at night.
• snow level above 8,000 ft. tonight through Monday AM, then free air freezing level 11,000 ft. Monday night.
• lows 46-39 warming to 43 Monday night highs 62-57 warming back to 62 Monday.
• Mostly sunny and warmer Tuesday, Wednesday and Thursday, mostly clear each night.
• free air freezing level 12,000 ft. Tuesday, 13,000 ft. Tuesday night, 14,000 ft. Wednesday and Wednesday night, then 15,000 ft. Thursday through Friday.
• 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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