Here is my weekly weather quiz question for the last time. What is  “Radar Reflectivity?” Here is the correct answer. Radar Reflectivity is the sum of all backscattering cross-sections (e.g., precipitation particles) in a pulse resolution volume divided by that volume. The radar reflectivity can be related to the radar reflectivity factor through the dielectric constant term |K|^2, and the radar wavelength. 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 pressure trough (Shaded “U” shape with blue arrows) is continuing our rain chances. A frontal system has now moved east of us. An upper level ridge of high pressure, called an “Omega Block” because it is shaped like the Greek letter Omega, (Shaded “Arch” shape with blue arrows) takes over starting to clear us out late Monday and keeping the sunshine around for the rest of the workweek. A frontal system moves through Oregon next Sunday with another front right behind it and you know what that means, rainy weather.

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Air Quality Index:

Eugene-Springfield: The Air Quality Index is 12 in the Good category measuring Particulate Matter.

Oakridge: The Air Quality Index is 6 in the Moderate category measuring Particulate Matter.

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

Data courtesy of Lane Regional Air Protection Agency (LRAPA).

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Advisories: None At This Time.

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Eugene-Springfield Pollen Count:

Grass………. Low (0)

Trees………. High (358)

Last Counted: 3/24/16

Data Courtesy of Oregon Allergy Associates.

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Forecast for the Southern and lower Mid Willamette Valley including Eugene-Springfield and Albany-Corvallis:

• Mostly cloudy with showers and a slight (20%) chance of thunderstorms with small hail possible this evening, a good (50%) of showers and colder late tonight (0.10 in. of rain possible, more in storms),
• Mostly cloudy with a slight (20%) chance of AM showers, a (30%) chance of showers Monday afternoon (under 0.10 in. of rain possible), partly cloudy with patchy fog late Monday night and Tuesday AM, mostly sunny and a bit warmer in the afternoon, clear Tuesday night,
• Sunny and a bit warmer Wednesday, then clear at night.
• lows near 38 highs 54-63.
• Sunny and a bit warmer Thursday and Friday, mostly clear each night,
• Partly cloudy and a bit cooler with a slight (20%) chance of showers Saturday and Saturday night,
• Then a mix of clouds and sun with a (30%) chance of showers Sunday.
• highs 67-70 cooling to 63 Sunday lows 40-43. (seasonal averages high 58 low 38).

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Home Wood Heating Advisory:

Eugene-Springfield: GREEN – Burning is Allowed.

Oakridge: GREEN – Burning is Allowed.

*Note: Pellet stoves may be used anytime if they produce no visible emissions.

Advisory Courtesy of Lane Regional Air Protection Agency (LRAPA).

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Forecast for Roseburg:

• Mostly cloudy with showers likely (70%) this evening, rain and snow showers likely (70%) late tonight (0.10 in. of rain possible, snow level 3,000 ft. falling to 2,500 ft. late at night),
• Mostly cloudy with a (30%) chance of rain and snow showers Monday (under 0.10 in. of rain possible, snow level 2,000 ft. rising to 2,500 ft. in the afternoon), a slight (20%) chance of evening showers (under 0.10 in. of rain possible), partly cloudy late Monday night and Tuesday AM, sunny and a bit warmer Tuesday afternoon and Wednesday, then mostly clear at night.
• lows near 40 highs 55-69.
• Sunny and a bit warmer Thursday and Friday, clear both nights,
• Partly cloudy and a bit cooler with a slight (20%) chance of showers Saturday, a (30%) chance of showers Saturday night,
• Then mostly cloudy with a (30%) chance of showers Sunday.
• highs 70-73 cooling to 64 Saturday and Sunday lows near 43. (seasonal averages high 59 low 40).

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Forecast for The South Oregon Coast Including Coos Bay and North Bend:

• Mostly cloudy with coastal showers and a slight (20%) chance of thunderstorms this evening and showers late tonight while inland showers tonight (0.25 in. of rain possible, more in storms),
• Mostly cloudy with a good (50%) chance of showers and a bit warmer Monday (0.10 in. of rain possible), mostly cloudy in the evening, just partly cloudy late at night and Tuesday AM, sunny and a bit warmer Tuesday afternoon and Wednesday, clear both nights,
• Sunny and a bit warmer Wednesday, then clear Wednesday night.
• lows 43-46 highs 54-67.
• Sunny and a bit warmer Thursday and sunny and a bit cooler Friday clear both nights,
• Partly cloudy with a slight (20%) chance of showers and a bit cooler Saturday and Saturday night,
• Then mostly cloudy with a (30%) chance of showers Sunday.
• highs 69-58 lows 44-46. (seasonal averages high 54 low 42).

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Forecast for the Cascades in Lane County:

• Mostly cloudy with rain and snow showers this evening, snow showers late tonight (0.25 in. of rain possible, 1-3 in. of snow possible),
• Mostly cloudy with a good (50%) chance of AM snow showers, a good (50%) of snow showers and a bit warmer Monday afternoon, a slight (20%) chance of evening rain and snow showers, partly cloudy with a slight (20%) chance of rain and snow showers late Monday night,
• Just partly cloudy and warmer Tuesday, mostly clear at night,
• Sunny and a bit warmer Wednesday, then clear Wednesday night.
• snow level 2,500 ft. tonight and Monday, 3,000 ft. Monday night, 4,500 ft. rising to 5,500 ft. Tuesday, free air freezing level 6,000 ft. Tuesday night, 8,000 ft. Wednesday, then 9,000 ft. Wednesday night.
• lows 24-30 highs 37-49.
• Sunny and a bit warmer Thursday, mostly clear at night,
• Mostly sunny Friday, mostly clear Friday night,
• Partly cloudy with a slight (20%) chance of showers and a bit cooler Saturday and Saturday night,
• Then a mix of clouds and sun with a (30%) chance of rain and snow showers Sunday.
• free air freezing level 9,000 ft. Thursday, 10,000 ft. Thursday night through Friday night, snow level 7,500 ft. Saturday, 6,500 ft. Saturday night, then 5,500 ft. Sunday.
• highs 54-48 lows 32-34.

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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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