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) will continue to slide through the Pacific Northwest. It already sent us a frontal system keeping us in clouds and a chance of showers. An upper level high pressure ridge will take over bringing back the sunshine Monday.

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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 5 in the Good category measuring Particulate Matter.

Cottage Grove: The Air Quality Index is 16 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:

• Partly cloudy with a slight (20%) chance of showers this evening, just mostly cloudy late tonight,
• Mostly cloudy with a slight (20%) chance of showers Sunday AM, a good (50%) chance of showers and a slight (20%) chance of thunderstorms in the afternoon (under 0.10 in. of rain possible, more in storms), a slight (20%) chance of showers late Sunday night (under 0.10 in. of rain possible),
• Mostly cloudy Monday AM, partly cloudy and warmer in the afternoon, mostly clear at night,
• Mostly sunny and warmer Tuesday, then mostly clear at night.
• lows 52-47 warming to 54 Tuesday night highs 74-88.
• Mostly sunny and warmer Wednesday, Thursday and Friday, mostly clear at night,
• Then mostly sunny and a bit cooler Saturday, mostly clear Saturday night.
• highs 98-100 cooling to 93 Saturday lows 58-55. (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:

• Partly cloudy tonight,
• Mostly cloudy in the AM, partly cloudy and cooler with a slight (20%) chance of showers Sunday afternoon and evening (under 0.10 in. of rain possible), partly cloudy late Sunday night,
• Partly cloudy Monday AM, sunny and warmer in the afternoon, clear Monday night,
• Sunny and warmer Tuesday, then clear Tuesday night.
• lows 53-58 highs 77-94.
• Sunny and warmer Wednesday, clear at night,
• Mostly sunny and hot Thursday with a slight (20%) chance of afternoon and evening thunderstorms, partly cloudy late Thursday night,
• Partly cloudy and cooler with a slight (20%) chance of thunderstorms Friday and Friday night,
• Then mostly sunny and a bit cooler with a slight (20%) chance of thunderstorms Saturday.
• highs 105-95 lows 63-66. (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, mostly cloudy late tonight,
• Mostly cloudy at the shore Sunday while mostly cloudy inland in the AM and partly cloudy with a slight (20%) chance of inland showers Sunday afternoon and evening, mostly cloudy Sunday night,
• Mostly cloudy Monday AM, sunny and a bit warmer in the afternoon, clear Monday night,
• Mostly sunny and a bit warmer Tuesday, then mostly clear Tuesday night.
• lows near 55 highs near 66.
• Sunny and a bit warmer Wednesday and Thursday (a bit cooler), clear Wednesday night and Thursday evening, partly cloudy late at night,
• Partly cloudy Friday and Friday afternoon,
• Then sunny Saturday.
• highs 74-70 warming to 73 Friday cooling to 67 Saturday 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 this evening, a slight (20%) chance of showers late tonight (under 0.10 in.of rain possible),
• Mostly cloudy with a slight (20%) chance of AM showers, a good (50%) chance of showers and a slight (20%) chance of thunderstorms and cooler Sunday afternoon and evening, a slight (20%) chance of showers late Sunday night,
• A mix of clouds and sun Monday AM, mostly sunny and warmer in the afternoon, mostly clear at night,
• Sunny and warmer Tuesday, then clear Tuesday night.
• snow level above 8,000 ft. tonight through Sunday night, free air freezing level 10,000 ft. Monday, 12,000 ft. Monday night, 13,000 ft. Tuesday, then 14,000 ft. Tuesday night.
• lows 42-36 warming to 50 Tuesday night highs 56-76.
• Sunny and warmer Wednesday, clear at night,
• Mostly sunny Thursday, partly cloudy Thursday night,
• Mostly sunny Friday AM, partly cloudy with a slight (20%) chance of afternoon and evening thunderstorms, just partly cloudy at night,
• Then mostly sunny and a bit cooler Saturday.
• free air freezing level 14,000 ft. Wednesday, 15,000 ft. Wednesday night  through Thursday night, snow level above 8,000 ft. Friday and Friday night, then free air freezing level 15,000 ft. Saturday.
• highs 84-80 lows near 55.

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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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