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Check out my latest Eugene Daily News Weather Or Not Column Remember What Don Essig Always Says. Really?

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No winner this week. Here is my new weekly weather quiz question for the last time. What is a “wall cloud?” Here is the correct answer. A wall cloud is a localized, persistent, often abrupt lowering from a rain-free base. Wall clouds can range from a fraction of a mile up to nearly five miles in diameter, and normally are found on the south or southwest (inflow) side of the thunderstorm. When seen from within several miles, many wall clouds exhibit rapid upward motion and cyclonic rotation. However, not all wall clouds rotate. Rotating wall clouds
usually develop before strong or violent tornadoes, by anywhere from a few minutes up to nearly an hour. Wall clouds should be monitored visually for signs of persistent, sustained rotation and/or rapid vertical motion. “Wall cloud” also is used occasionally in tropical meteorology to describe the inner cloud wall surrounding the eye of a tropical cyclone, but the proper term for this feature is eyewall. 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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Advisories:

There is a Blue-Green Algae warning that continues for Dexter Reservoir and Dorena Reservoir, and now Fern Ridge Reservoir has been added to the list. Water monitoring has confirmed the presence of blue-green algae that can produce toxins, state public health officials said. The algae levels are likely associated with dangerous cyanotoxin concentrations in the water that can be harmful to humans and animals. Swallowing or inhaling water droplets, as well as skin contact with water, should be avoided according to the authorities.

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An upper level low (“U” shape with blue arrows) has moved to the north away from us.  Now the upper airflow is moving from the south producing the chance of showers and thunderstorms as the upper low rides north. A weak frontal system is sliding through Oregon with cooler temperatures behind it. Another upper level low will move in along the coast continuing the normal to cooler than normal temperatures. The Eugene Celebration runs through Sunday and so far the weather is looking not too bad. Look for cooler temperatures with just a slight chance of a shower Sunday AM and a (40%) chance of showers in the afternoon.

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The Grass Pollen Count is listed as Absent at 0 and Tree pollen is Absent at 0 as of 8/22/13 according to Oregon Allergy Associates.

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

• Cloudy this AM, a mix of clouds and sun this afternoon, partly cloudy this evening, mostly cloudy late tonight.
• Mostly cloudy with a slight (20%) chance of showers Sunday AM, a (40%) chance of showers in the afternoon, a slight (20%) chance of evening showers, partly cloudy late Sunday night.
• A mix of clouds and sun Monday, partly cloudy in the evening, then mostly cloudy with a slight (20%) chance of rain late at night.
• highs 78-80 lows 55-52.
• Mostly sunny Wednesday AM, a mix of clouds and sun in the afternoon, mostly cloudy in the evening, partly cloudy late Wednesday night.
• A mix of clouds and sun Thursday, partly cloudy at night, mostly sunny Friday AM, then a mix of clouds and sun in the afternoon.
• highs near 80 lows near 53. (seasonal averages high 82 low 51)

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Forecast for the Umpqua Basin including Roseburg:

• Mostly cloudy with patchy fog this AM, mostly cloudy with more patchy smoke in the afternoon, mostly cloudy with areas of smoke tonight and Sunday AM, a (40%) chance of AM showers, a (30%) chance of showers and a slight (20%) chance of thunderstorms in the afternoon and evening, partly cloudy late Sunday night through Monday evening, then mostly cloudy late Monday night.
• highs 83-76 warming to 80 lows near 58.
• Mostly cloudy with a slight (20%) chance of rain Tuesday through Wednesday, then partly cloudy Wednesday night through Friday.
• highs 82-84 lows 55-58 cooling to 54 Thursday night. (seasonal averages high 84 low 55)

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

• Mostly cloudy with patchy fog and areas of drizzle this AM, mostly cloudy in the afternoon and at night with patchy fog late at night.
• Mostly cloudy Sunday with patchy fog and a slight (20%) chance of showers, partly cloudy at night and Monday AM, mostly cloudy in the afternoon, then mostly cloudy with a slight (20%) chance of rain late Monday night.
• highs 69-66 lows 57-52 warming to 55 Monday night.
• Mostly cloudy with a slight (20%) chance of rain Tuesday through Wednesday evening, partly cloudy late Wednesday night, partly cloudy with a slight (20%) chance of showers Thursday and Thursday night, then just partly cloudy Friday.
• highs near 67 lows near 55. (seasonal averages high 66 low 53)

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Forecast for the Cascades of Lane County:

• A mix of clouds and sun today with a slight (20%) chance of showers this afternoon, partly cloudy in the evening, mostly cloudy at night.
• Cloudy with a good (50%) chance of showers Sunday, mostly cloudy in the evening with a slight (20%) chance of showers, then mostly cloudy late Sunday night.
• A mix of clouds and sun Monday, partly cloudy with a slight (20%) chance of rain late Monday night.
• snow level above 8,000 ft. today through Sunday night, free air freezing level 11,000 ft. Monday and Monday evening, then snow level above 8,000 ft. late Monday night.
•  highs 65-60 warming to 66 Monday lows near 45.
• Partly cloudy with a slight (20%) chance of rain Tuesday AM, partly cloudy in the afternoon and Tuesday night, a mix of clouds and sun Wednesday afternoon, partly cloudy Wednesday night. Partly cloudy with a slight (20%) chance of showers Thursday afternoon and evening, then partly cloudy Friday.
• snow level above 8,000 ft. Tuesday AM, free air freezing level 12,000 ft. Tuesday afternoon, 12,000 ft. rising to 13,000 ft. at night, 13,000 ft. Wednesday and  Wednesday night and Thursday AM, snow level above 8,000 ft. in the afternoon and evening, free air freezing level 12,000 ft. late Thursday night, then 12,000 ft. rising to 13,000 ft. Friday.
• highs 66-70 lows near 46.

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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 Eugene Daily News.com.

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