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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) along the coast will continue to send disturbances our way including this frontal system that will move through the Pacific Northwest by late Monday. That will keep us in a cooler and potentially wet weather pattern for the week. Yet another frontal system will move into Oregon by the end of next week.

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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:

• Mostly cloudy with a (30%) chance of evening showers, mostly cloudy late tonight (under 0.10 in. of rain possible).
• Mostly cloudy Monday AM, partly cloudy in the afternoon, mostly cloudy with a slight (20%) chance of rain late at night (under 0.10 in. of rain possible).
• A mix of clouds and sun Tuesday, partly cloudy in the evening, mostly cloudy late Tuesday night and Wednesday AM, a mix of clouds and sun in the afternoon, partly cloudy in the evening, then mostly cloudy late Wednesday night.
• lows 55-53 highs 77-83.
• Mostly cloudy Thursday AM, then partly cloudy Thursday afternoon through Saturday.
• Party cloudy with a slight (20%) chance of showers Saturday night and Sunday AM, then just partly cloudy Sunday afternoon.
• highs 82-77 lows 57-53. (seasonal averages high 82 low 50)

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Forecast for the Umpqua Basin including Roseburg:

• Mostly cloudy with a (30%) chance of scattered showers and a slight (20%) chance of thunderstorms early this evening, a (30%) chance of showers late this evening, mostly cloudy late tonight (under 0.10 in. of rain possible) and Monday AM, partly cloudy in the afternoon through Tuesday evening, mostly cloudy late at night.
• Cloudy Wednesday AM, then partly cloudy Wednesday afternoon and Wednesday night.
• lows 58-61 highs 81-85.
• Partly cloudy Thursday, partly cloudy with a slight (20%) chance of showers Thursday night and Friday, partly cloudy Friday night and Saturday, partly cloudy with a slight (20%) chance of showers Saturday night and Sunday AM, then just partly cloudy Sunday afternoon.
• highs near 83 lows 58-54 warming to 58 Friday 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 a slight (20%) chance of showers this evening, just mostly cloudy late tonight (under 0.10 in. of rain possible), mostly cloudy with patchy coastal fog Monday AM, a slight (20%) chance of rain in the afternoon, mostly cloudy Monday night with a slight (20%) chance of coastal rain late at night.
• Mostly cloudy with a slight (20%) chance of coastal rain Tuesday and Tuesday evening, then mostly cloudy Tuesday afternoon and night.
• lows 53-56 highs near 69.
• Mostly cloudy with a slight (20%) chance of rain Wednesday and Wednesday night.
• Mostly cloudy with a slight (20%) chance of AM rain, partly cloudy with a slight (20%) chance of showers Thursday afternoon, Thursday night and Friday partly cloudy Friday night and Saturday AM, mostly cloudy with a slight (20%) chance f .
• Partly cloudy Friday through Saturday AM, then mostly cloudy Saturday afternoon through Sunday AM, then just partly cloudy Sunday afternoon.
• highs 67-65 lows near 55. (seasonal averages high 66 low 53)

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Forecast for the Cascades of Lane County:

• Mostly cloudy with a good (50%) chance of thunderstorms this evening (0.50 in. of rain possible, more in storms), mostly cloudy late tonight.
• Mostly cloudy Monday AM, a mix of clouds and sun Monday afternoon, partly cloudy late Monday night. Partly cloudy Tuesday AM, mostly sunny in the afternoon, then partly cloudy Tuesday night through Wednesday night.
• free air freezing level 11,000 ft. tonight through Monday night, 12,000 ft. Tuesday, then 13,000 ft. Tuesday night through Wednesday night.
• lows 45-47 cooling to near 45 Wednesday night highs 67-70.
• Partly cloudy with a slight (20%) chance of showers Thursday afternoon through Sunday AM, then just partly cloudy Sunday afternoon.
• snow level 8,000 ft. Thursday through Sunday.
• highs 70-66 lows 48-44.

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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 Eugene Daily News.com.

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