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 46 in the Good category measuring Particulate Matter.

Oakridge: The Air Quality Index is 29 in the Good category measuring Particulate Matter.

Cottage Grove: The Air Quality Index is 44 in the Good category measuring Ozone.

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 IS IN EFFECT UNTIL 9 PM SUNDAY FOR THE EAST SLOPES OF THE NORTHERN OREGON CASCADES.
• A FIRE WEATHER WATCH IS IN EFFECT FOR GUSTY WINDS AND LOW HUMIDITY FROM SUNDAY AFTERNOON THROUGH SUNDAY EVENING FOR THE THE LOWER COLUMBIA BASIN OF OREGON.
• 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:

• Mostly clear tonight,
• Partly cloudy Sunday AM, mostly sunny and cooler in the afternoon, mostly clear in the evening, mostly cloudy late Sunday night,
• Mostly cloudy and cooler with a (30%) chance of showers Monday afternoon, a slight (20%) chance of evening rain, just mostly cloudy late at night,
• Mostly cloudy with a (30%) chance of rain Tuesday afternoon, then mostly cloudy with a good (50%) chance of rain Tuesday night.
• lows 54-49 highs 82-68.
• Cloudy with a good (50%) chance of AM rain, rain and a bit cooler Wednesday afternoon evening, showers likely (70%) late Wednesday night,
• Mostly cloudy with AM showers likely (70%), a bit warmer with a good (50%) chance of showers Thursday afternoon and evening, a slight (20%) chance of showers late at night,
• A mix of clouds and sun and a bit warmer Friday with a slight (20%) chance of AM showers,  partly cloudy Friday night,
• Then partly cloudy with a slight (20%) chance of showers Saturday afternoon.
• highs 65-74 lows 53-50. (seasonal averages high 78 low 48)

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Your Saturday College Football Forecasts:

Ducks vs Michigan State at Spartan Stadium, East Lansing, MI- Kickoff 5 PM PDT- (8 PM EDT): Partly cloudy 56 and cooling to 50 by the end of the game, Wind- NNE 5 mph.

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Forecast for the Umpqua Basin including Roseburg:

• Mostly clear this evening, partly cloudy late tonight,
• Sunny and cooler Sunday, partly cloudy in the evening, mostly clear late Sunday night,
• Partly cloudy Monday AM, increasing clouds to mostly cloudy and cooler in the afternoon and Monday night,
• Mostly cloudy with a slight (20%) chance of rain and a bit cooler Tuesday afternoon, cloudy with a slight (20%) chance of rain in the evening, then a (%) chance of showers late Tuesday night.
• lows 57-50 warming to 52 Tuesday night highs 86-70.
• Mostly cloudy and a bit cooler with AM rain likely (70%), rain Wednesday and in the evening, rain likely (70%) late Wednesday night and breezy,
• Cloudy with AM rain likely (70%) Thursday, partly cloudy and a bit warmer with a good (50%) chance of showers in the afternoon and evening, just partly cloudy Thursday night,
• Partly cloudy and warmer Friday through Saturday AM, then sunny and a bit warmer Saturday afternoon.
• highs 72-82 lows 55-52. (seasonal averages high 80 low 52)

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

• Partly cloudy this evening, mostly cloudy late tonight and Sunday AM, partly cloudy Sunday afternoon through Monday AM, mostly cloudy in the afternoon with a slight (20%) chance of afternoon coastal showers, a slight (20%) chance of evening inland rain while a slight (20%) chance of coastal rain Monday night,
• Mostly cloudy and a bit cooler with a (30%) chance of showers Tuesday afternoon, cloudy with a good (50%) chance of evening rain, showers likely (70%) late Tuesday night.
• lows 56-52 warming to 54 Tuesday night highs near 66.
• Rain and breezy Wednesday and Wednesday night,
• Mostly cloudy with AM rain Thursday, partly cloudy a good (50%) chance of showers and a bit warmer in the afternoon and evening, just mostly cloudy  late Thursday night,
• Partly cloudy Friday and Friday night,
• Then sunny Saturday.
• highs near 67 lows 57-55. (seasonal averages high 65 low 51).

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Forecast for the Cascades in Lane County:

• Mostly clear tonight,
• Mostly sunny, but cooler Sunday, partly cloudy Sunday night and Monday AM, mostly cloudy and a bit cooler in the afternoon, mostly cloudy with a slight (20%) chance of evening rain, just mostly cloudy and cooler Monday night,
• A mix of clouds and sun and cooler Tuesday with a slight (20%) chance of afternoon rain, partly cloudy with a slight (20%) chance rain in evening, then mostly cloudy with a good (50%) chance of rain late Tuesday night.
• free air freezing level 15,000 ft. tonight and Sunday, 14,000 ft. Sunday night, 11,000 ft. Monday AM falling to 9,000 ft. in the afternoon, snow level 7,000 ft. Monday night, 5,500 ft. Tuesday, then 6,500 ft. Tuesday night.
• lows 50-38 highs 72-54.
• Mostly cloudy and cooler with a good (50%) chance of rain Wednesday AM, rain and a bit warmer in the afternoon and evening, showers and breezy late Wednesday night,
• Mostly cloudy with AM showers, a good (50%) chance of showers and a bit warmer Thursday afternoon, a (40%) chance of evening showers, partly cloudy with a slight (20%) chance of showers late Thursday night,
• Partly cloudy and a bit warmer Friday with a slight (20%) chance of AM showers, then partly cloudy Friday night and Saturday.
• snow level 7,000 ft. Wednesday, above 8,000 ft. Wednesday night, 7,500 ft. Thursday, above 8,000 ft. Thursday night and Friday, free air freezing level 11,000 ft. Friday night, then 12,000 ft. Saturday.
• highs 50-59 lows near 43.

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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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