Here is my new weekly weather quiz question. What is a “Back-building thunderstorm?” 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) that has been controlling our weather will be replaced by high pressure (Shaded “Arch” shape with blue arrows) and that means the rain goes away again, but not quite yet. The low will move southward through Oregon bring the chance of showers and thunderstorms today, then the high pressure takes over for most of the long Labor Day Holiday Weekend with the exception of Sunday. Weather will be good, but chilly for the Duck game Saturday evening. There is a slight chance of a shower or thunderstorm, though, for the Beaver game this evening.

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Air Quality Index:

Eugene-Springfield: The Air Quality Index is 26 in the Good category measuring Particulate Matter.

Oakridge: The Air Quality Index is 7 in the Good category measuring Particulate Matter.

Cottage Grove: The Air Quality Index is 24 in the Good category measuring Particulate Matter.

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

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Advisories:

• 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:

• A mix of clouds and sun today with a slight (20%) chance of AM showers, a (40%) chance of showers and a slight (20%) chance of thunderstorms this afternoon, partly cloudy with a slight (20%) chance of showers and thunderstorms this evening, partly cloudy late tonight and Saturday AM, mostly sunny and warmer in the afternoon, partly cloudy Saturday night,
• A mix of clouds and sun with a slight (20%) chance of showers Sunday afternoon, mostly cloudy in the evening, then partly cloudy late Sunday night.
• highs 70-75 lows 45-50.
• Partly cloudy in the AM, mostly sunny and a bit warmer Monday afternoon (Labor Day), partly cloudy Monday night through Wednesday AM, mostly sunny in the afternoon, mostly clear at night,
• Mostly sunny Thursday AM, then partly cloudy and a bit cooler in the afternoon.
• highs 77-83 lows 48-53. (seasonal averages high 80 low 49)

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Your College Football Weather Forecast:

Friday – Beavers vs Weber State – Reser Stadium- Kickoff: 5 pm (PDT)

Forecast: Temperature near 70 and falling, A mix of clouds and sun, slight chance of afternoon and evening showers and thunderstorms, then just partly cloudy, wind: N 5-10 mph. Remember, after the sun goes down it will get chilly. Dress appropriately.

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Saturday- Ducks vs Eastern Washington – Autzen Stadium- Kickoff: 5 pm (PDT)

Forecast: Temperature near 70 and falling, mostly sunny late in the afternoon then partly cloudy in the evening and at night, wind: W 5-10 mph. Remember, after the sun goes down it will get chilly. Dress appropriately.

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Forecast for the Umpqua Basin including Roseburg:

• Mostly cloudy with a slight (20%) chance of showers this AM, a (30%) chance of showers and a slight (20%) chance of afternoon thunderstorms, partly cloudy with a slight (20%) chance of showers and thunderstorms this evening, mostly cloudy with a slight (20%) chance of showers late tonight,
• Partly cloudy and warmer Saturday afternoon, mostly clear Saturday night,
• Partly cloudy and  warmer Sunday, then partly cloudy at night.
• highs 70-78 lows 48-54.
• Partly cloudy in the AM, sunny Monday afternoon (Labor Day), clear Monday night,
• Mostly sunny and a bit warmer Tuesday and Wednesday, mostly clear at night,
• Then sunny and a bit warmer Thursday.
• highs 82-87 cooling to 85 Thursday lows 50-53. (seasonal averages high 82 low 54)

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

• Mostly cloudy with a slight (20%) chance of showers this AM, partly cloudy with a slight (20%) chance of showers and isolated thunderstorms this afternoon, partly cloudy in the evening with a slight (20%) chance of showers, just partly cloudy late tonight and Saturday, mostly clear in the evening, then partly cloudy Saturday night through Sunday night.
• highs 64-66 lows 52-54.
• Partly cloudy in the AM, sunny Monday afternoon (Labor Day), clear at night,
• Mostly sunny Tuesday and Wednesday, mostly clear at night,
• Then sunny and a bit warmer Thursday.
• highs 65-70 lows 54-56. (seasonal averages high 66 low 52).

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Forecast for the Cascades in Lane County:

• A mix of clouds and sun today with a slight (20%) chance of AM showers, showers and a slight (20%) chance of thunderstorms this afternoon (0.25 in. of rain possible, more in storms), mostly cloudy with a good (50%) chance of showers and a slight (20%) chance of thunderstorms in the evening, partly cloudy with a good (50%) chance of showers late tonight,
• Then partly cloudy and with a slight (20%) chance of showers and warmer Saturday, partly cloudy Saturday night through Sunday night.
• snow level 6,500 ft. today and tonight, 5,500 ft. Saturday, free air freezing level 9,000 ft. Saturday night, 10,000 ft. Sunday, then 11,000 ft. Sunday night.
• highs 52-64 lows 37-40.
• Partly cloudy in the AM, mostly sunny and warmer Monday afternoon (Labor Day), mostly clear Monday night,
• Mostly sunny and a bit warmer Tuesday, Wednesday and Thursday, mostly clear each night.
• free air freezing level 9,000 ft. Monday, 12,000 ft. Monday night, then 13,000 ft. Tuesday through Thursday.
• highs 64-70 lows 43-48.

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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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