Here is my weekly weather quiz question for the last time. What is “Zonal Flow ?” Here is the correct answer. Zonal Flow is large-scale atmospheric flow in which the east-west component (i.e., latitudinal) is dominant. The accompanying meridional (north-south) component often is weaker than normal. Compare with meridional flow. I’ll have a new weekly weather quiz question for you starting Monday. 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) tried to take over, but low pressure quickly moves in. A weak frontal system  brings just a chance of some showers through the whole weekend.

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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 8 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:

• A mix of clouds and sun today with a (40%) chance of AM showers, a bit cooler with a slight (20%) chance of showers this afternoon (under 0.10 in. of rain possible), mostly cloudy with a slight (20%) chance of showers this evening, just mostly cloudy late tonight,
• 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.
• highs 76-74 warming to 78 Monday lows 52-49.
• 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 cloudy and cooler with a (30%) chance of showers today, a slight (20%) chance of showers this evening, partly cloudy late tonight,
• 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
• highs 86-78 lows near 55.
• 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:

• Mostly cloudy and a bit cooler with a good (50%) chance of showers today, just mostly cloudy tonight,
• 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,
• highs 65-68 lows near 55.
• 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:

• Mostly cloudy with a (40%) chance of showers today (under 0.10 in. of rain possible), a slight (20%) chance of showers this evening, just mostly cloudy late tonight,
• 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, partly cloudy with 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. today through Monday AM, then free air freezing level 11,000 ft. Monday night.
• highs 62-57 warming back to 62 Monday lows 42-39 warming to 43 Monday night.
• 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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