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 and has sent a frontal system into Oregon that will keep our temperatures cooler than normal and keep the chance for rain with us.

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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 12 in the Good category measuring Particulate Matter.

Cottage Grove: The Air Quality Index is 29 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:

• Mostly cloudy with a slight (20%) chance of showers this evening, a good (50%) chance of showers late tonight (0.10 in. of rain possible),
• Mostly cloudy with a good (50%) chance of showers Wednesday (under 0.10 in. of rain possible), partly cloudy and cooler Wednesday night,
• Partly cloudy with a slight (20%) chance of showers Thursday afternoon, just partly cloudy Thursday night and Friday, a slight (20%) chance of showers and thunderstorms Friday evening, then just partly cloudy at night.
• lows 55-45 highs 72-70.
• Partly cloudy Saturday AM, sunny in the afternoon, then partly cloudy Saturday night through Monday (Labor Day) continuing through Tuesday.
• highs 74-79 cooling to 50 lows 47-50. (seasonal averages high 80 low 50)

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Forecast for the Umpqua Basin including Roseburg:

• Partly cloudy this evening, mostly cloudy with a good (50%) chance of showers late tonight (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,
• Mostly cloudy Thursday AM, sunny in the afternoon, mostly clear in the evening, partly cloudy with a slight (20%) chance of showers late at night,
• Mostly cloudy Friday AM, partly cloudy with a slight (20%) chance of afternoon thunderstorms, a slight (20%) chance of evening showers, just partly cloudy Friday night.
• lows 57-48 highs near 72.
• Then mostly sunny and  warmer Saturday, Sunday and Monday (Labor Day), mostly clear Saturday night and Sunday night, then partly cloudy Monday night and a bit cooler Tuesday.
• highs 78-84 cooling to near 80 Tuesday lows 52-55. (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 coastal showers tonight while a good (50%) chance of inland showers late (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 with a slight (20%) chance of AM coastal rain Thursday, sunny in the afternoon, mostly clear in the evening, partly cloudy with a slight (20%) chance of showers late Thursday night,
• Mostly cloudy in the AM, partly cloudy Friday afternoon, partly cloudy with a slight (20%) chance of evening showers,  just partly cloudy at night.
• lows 55-49 highs near 65.
• Sunny and a bit warmer Saturday, mostly clear in the evening, partly cloudy at night,
• Mostly sunny and a bit warmer Sunday and Monday (Labor Day), mostly clear Sunday night, partly cloudy Monday night and Tuesday.
• highs 66-68 lows 52-54. (seasonal averages high 66 low 52).

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Forecast for the Cascades in Lane County:

• Partly cloudy with a slight (20%) chance of evening showers, mostly cloudy with a good (50%) chance of showers late tonight (0.10 in. of rain possible),
• A mix of clouds and sun and a bit cooler with a good (50%) chance of showers Wednesday (0.10 in. of rain possible), mostly cloudy with a slight (20%) chance of evening showers, partly cloudy and cooler late Wednesday night,
• Mostly sunny and a bit cooler Thursday, partly cloudy with a slight (20%) chance of evening showers, just partly cloudy late Thursday night,
• A mix of clouds and sun Friday with a (40%) chance of showers and a slight (20%) chance of thunderstorms and a bit warmer in the afternoon, partly cloudy with a good (50%) chance of evening showers and a slight (20%) chance of thunderstorms, then just partly cloudy late Friday night.
• snow level above 8,000 ft. tonight, 8,000 ft. falling to 7,500 ft. Wednesday afternoon, 6,000 ft. Wednesday night, 6,500 ft. rising to 7,000 ft. Thursday afternoon, then 6,500 ft. Thursday night, 6,000 ft. Friday, then 6,500 ft. Friday night.
• lows 44-35 warming to 38 Friday night highs 55-57.
• Partly cloudy and a bit warmer Saturday through Monday AM (Labor Day), mostly sunny in the afternoon, then partly cloudy Monday night and a bit cooler Tuesday.
• free air freezing level 8,000 ft. Saturday, 9,000 ft. Saturday night, 11,000 ft. Sunday through Monday, 12,000 ft. Monday night, then 11,000 ft. Tuesday.
• highs 57-66 cooling to 62 Tuesday lows 40-44.

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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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