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) continues to control our weather. Another frontal system (Position shown is Wednesday) will keep our temperatures cooler than normal and keep the chance for rain with us also.

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Air Quality Index:

Eugene-Springfield: The Air Quality Index is 28 in the Good category measuring Particulate Matter.

Oakridge: The Air Quality Index is 8 in the Good category measuring Particulate Matter.

Cottage Grove: The Air Quality Index is 27 in the Good category measuring Particulate Matter.

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

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Advisories:

• AN AIR QUALITY ALERT HAS BEEN ISSUED UNTIL FURTHER NOTICE FOR CROOK, DESCHUTES, GILLIAM, GRANT, JEFFERSON, MONROE, SHERMAN, UMATILLA, UNION, WILLOWA, WASCO, WHEELER, BENTON AND COLUMBIA COUNTIES IN 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 cloudy tonight,
• A mix of clouds and sun with a slight (20%) chance of rain and a bit cooler Tuesday afternoon (under 0.10 in. of rain possible), mostly cloudy with a good (50%) chance of showers Tuesday night (under 0.10 in. of rain possible),
• A mix of clouds and sun Wednesday with a good (50%) chance of showers AM showers (under 0.10 in. of rain possible), partly cloudy and cooler with a slight (20%) chance of evening showers, just partly cloudy late Wednesday night,
• A mix of clouds and sun with a slight (20%) chance of showers Thursday, then partly cloudy with a (30%) chance of showers late Thursday night.
• lows 54-47 highs 75-70.
• Partly cloudy with a slight (20%) chance of showers Friday and in the evening, just partly cloudy late Friday night through Sunday night,
• Mostly sunny and and a bit warmer Monday AM (Labor Day), then partly cloudy in the afternoon.
• highs 72-80 lows near 48. (seasonal averages high 81 low 50)

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Forecast for the Umpqua Basin including Roseburg:

• Mostly clear this evening, partly cloudy with a slight (20%) chance of drizzle late tonight,
• Partly cloudy Tuesday, mostly cloudy with a slight (20%) chance of evening rain, a (30%) chance of showers late Tuesday night (under 0.10 in. of rain possible),
• Mostly cloudy with a (30%) chance of showers Wednesday (under 0.10 in. of rain possible), partly cloudy in the evening, mostly clear late Wednesday night,
• Partly cloudy Thursday, mostly clear in the evening, then partly cloudy late Thursday night.
• lows 55-58 cooling to 46 Thursday night highs 79-72.
• Partly cloudy with a slight (20%) chance of showers and Friday night,
• Then mostly sunny and  warmer Saturday, Sunday and Monday, mostly clear at night.
• highs 73-84 lows 49-53. (seasonal averages high 83 low 54)

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

• Partly cloudy with a (20%) chance of drizzle this evening, mostly cloudy with a (20%) chance of drizzle late tonight and Tuesday AM, partly cloudy with a slight (20%) chance of afternoon coastal rain (under 0.10 in. of rain possible), a bit cooler with a (30%) chance of evening rain, a (30%) chance of showers late Tuesday night (under 0.10 in. of rain possible),
• Mostly cloudy and a bit cooler with a (30%) chance of showers Wednesday (under 0.10 in. of rain possible), mostly clear in the evening, partly cloudy late Wednesday night,
• Mostly cloudy Thursday AM, sunny in the afternoon, mostly clear in the evening, then partly cloudy late Thursday night.
• lows 55-50 highs 69-64.
• Partly cloudy Friday, mostly clear at night,
• Mostly sunny and a bit warmer Saturday, mostly lear at night,
• Mostly sunny and a bit warmer Sunday and Monday (Labor Day), mostly clear Sunday night.
• highs 64-68 lows near 52. (seasonal averages high 66 low 52).

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Forecast for the Cascades in Lane County:

• Partly cloudy tonight and Tuesday, mostly cloudy with a good (50%) chance of evening rain, a good (50%) chance of showers late Tuesday night,
• A mix of clouds and sun and a bit cooler with a good (50%) chance of showers Wednesday, mostly cloudy with a slight (20%) chance of evening showers, partly cloudy and colder late Wednesday night,
• Partly cloudy and a bit cooler with a slight (20%) chance of showers Thursday afternoon and evening, just partly cloudy late Thursday night.
• free air freezing level 13,000 ft. tonight and Tuesday, snow level above 8,000 ft. Tuesday night and Wednesday, 7,500 ft. Wednesday night, then 6,500 ft. Thursday and Thursday night.
• lows 43-36 highs 63-55.
• A mix of clouds and sun with a (40%) chance of showers and a bit warmer Friday afternoon, partly cloudy with a (40%) chance of evening showers, just partly cloudy late Friday night,
• Partly cloudy and a bit warmer with a slight (20%) chance of showers Saturday afternoon and evening, then partly cloudy and warmer Saturday night through Monday (Labor Day).
• snow level 6,500 ft. Friday through Saturday, above 8,000 ft. Saturday night, free air freezing level 9,000 ft. Sunday, then 11,000 ft. Sunday night and Monday.
• highs 55-66 lows 38-40.

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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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