Here is my weekly weather quiz question for the last time. What is “Rayleigh Scattering?” Here is the correct answer. Rayleigh Scattering: Changes in directions of electromagnetic energy by particles whose diameters are 1/16 wavelength or less. This type of scattering is responsible for the sky being blue. 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 high (Shaded “Arch” shape with blue arrows) is going to weaken and a trough of low pressure (Shaded “U” shape with blue arrows) will slowly take over sending a cold front to the Pacific Northwest.

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Air Quality Index:

Eugene-Springfield: The Air Quality Index is 35 in the Good category measuring Particulate Matter.

Oakridge: The Air Quality Index is 28 in the Good category measuring Particulate Matter.

Cottage Grove: The Air Quality Index is 42 in the Good category measuring Particulate Matter.

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

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Advisories:

• A RED FLAG WARNING IS IN EFFECT FOR GUSTY WINDS AND LOW HUMIDITY FROM 2 PM UNTIL 9 PM TODAY FOR THE EAST SLOPES OF THE NORTHERN OREGON CASCADES AND THE CENTRAL OREGON MOUNTAINS.
• A HEALTH ADVISORY CONTINUES FOR SUNSET BAY STATE PARK BEACH LOCATED IN COOS COUNTY FOR HIGHER-THAN-NORMAL FECAL BACTERIA WHICH CAN RESULT IN DIARRHEA, STOMACH CRAMPS, SKIN RASHES, UPPER RESPIRATORY INFECTIONS AND OTHER ILLNESSES. DIRECT CONTACT WITH THE WATER – ESPECIALLY BY CHILDREN AND THE ELDERLY, WHO MAY BE VULNERABLE TO WATERBORNE BACTERIA – SHOULD BE AVOIDED IN THIS AREA UNTIL THE ADVISORY IS LIFTED. VISITORS SHOULD AVOID WADING IN NEARBY CREEKS, POOLS OF WATER ON THE BEACH, OR IN DISCOLORED WATER AND STAY CLEAR OF WATER RUNOFF FLOWING INTO THE OCEAN.
• A HEALTH ADVISORY CONTINUES FOR UPPER KLAMATH LAKE AND AGENCY LAKE DOWN TO KENO DAM, LOCATED JUST NORTH OF KLAMATH FALLS ALONG HIGHWAY 97 IN KLAMATH COUNTY. WATER MONITORING BY THE USGS HAS CONFIRMED THE PRESENCE OF BLUE-GREEN ALGAE TOXINS WHICH CAN BE HARMFUL TO HUMANS AND ANIMALS. SWALLOWING, INHALING OR SKIN CONTACT WITH WATER DROPLETS SHOULD BE AVOIDED.

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

• Partly cloudy tonight,
• Mostly cloudy and cooler with a (30%) chance of showers Monday afternoon and evening, just mostly cloudy late at night,
• Cloud cover increasing to cloudy with a (30%) chance of rain and a bit cooler Tuesday afternoon (under 0.10 in. of rain possible), then mostly cloudy with a good (50%) chance of rain Tuesday night (under 0.10 in. of rain possible),
• Rain and a bit cooler Wednesday and in the evening, then showers likely (70%) late Wednesday night.
• lows 48-53 highs 69-63.
• Mostly cloudy with showers likely (70%) and a bit warmer Thursday, a (30%) chance of showers at night,
• AM clouds, a mix of clouds and sun and a bit warmer Friday with a slight (20%) chance of showers, just partly cloudy Friday night,
• A mix of clouds and sun with a slight (20%) chance of showers and warmer Saturday and Sunday afternoon, mostly cloudy with a slight (20%) chance of showers Sunday night.
• highs 69-79 lows 52-54. (seasonal averages high 78 low 47)

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Forecast for the Umpqua Basin including Roseburg:

• Mostly clear tonight,
• Partly cloudy with a slight (20%) chance of rain Monday afternoon (under 0.10 in. of rain possible), clouds increasing clouds to mostly cloudy with a slight (20%) chance of evening rain, just mostly cloudy Monday night (under 0.10 in. of rain possible),
• Mostly cloudy with a slight (20%) chance of rain and a bit cooler Tuesday afternoon (under 0.10 in. of rain possible), a (30%) chance of rain Tuesday night (under 0.10 in. of rain possible),
• Then mostly cloudy and a bit cooler with rain Wednesday and Wednesday night.
• lows 52-50 warming to 55 Wednesday night highs 73-70.
• Mostly cloudy with AM showers likely (70%) Thursday, a good (50%) chance of showers in the afternoon and evening, just mostly cloudy Thursday night,
• Partly cloudy and warmer Friday through Saturday evening, mostly clear Saturday night,
• Sunny in the AM, then partly cloudy with a slight (20%) chance of showers Sunday afternoon.
• highs 75-82 lows 53-56. (seasonal averages high 80 low 52)

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

• Partly cloudy tonight and Monday AM, mostly cloudy in the afternoon with a (30%) chance of showers (under 0.10 in. of rain possible), mostly cloudy with a slight (20%) chance of evening rain, just mostly cloudy Monday night,
• Mostly cloudy with a (40%) chance of rain Tuesday afternoon (under 0.10 in. of rain possible), cloudy with a good (50%) chance of evening rain, coastal rain late at night while inland rain likely (70%) late Tuesday night (under 0.10 in. of rain possible),
• Then mostly cloudy with rain Wednesday and Wednesday night.
• lows near 53 highs near 65.
• Cloudy with AM showers Thursday, partly cloudy a good (50%) chance of showers in the afternoon and evening, mostly cloudy with a (30%) chance of showers late Thursday night,
• Mostly cloudy with a slight (20%) chance of showers Friday AM, partly cloudy Friday afternoon through Saturday evening, mostly cloudy late Saturday night,
• Then mostly cloudy with a slight (20%) chance of showers Sunday afternoon.
• highs 67-65 lows near 56. (seasonal averages high 65 low 51).

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Forecast for the Cascades in Lane County:

• Mostly clear and cooler tonight,
• A mix of clouds and sun Monday, mostly cloudy with a slight (20%) chance of evening showers, just partly cloudy and colder late Monday night,
• A mix of clouds and sun Tuesday AM, increasing clouds to mostly cloudy and a bit cooler in the afternoon, mostly cloudy with a (40%) chance of rain Tuesday night,
• Mostly cloudy and cooler with rain Wednesday and in the evening, then showers late Wednesday night.
• free air freezing level 14,000 ft. tonight, 10,000 ft. Monday, snow level 6,500 ft. Monday night, 7,000 ft. Tuesday, 6,500 ft. Tuesday night, then 7,000 ft.Wednesday and Wednesday night.
• lows 40-34 warming to 38 Wednesday night highs 54-47.
• Mostly cloudy with showers and a bit warmer Thursday, a (40%) chance of showers Thursday night,
• AM clouds, a mix of clouds and sun and a bit warmer with a slight (20%) chance of showers Friday, then just partly cloudy Friday night through Sunday.
• snow level above 8,000 ft. Thursday through Friday, free air freezing level 12,000 ft. Friday night and Saturday, then 13,000 ft. Saturday night and Sunday.
• highs 53-67 lows 42-44.

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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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