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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 you might want to take an umbrella because there will be a good chance of showers with a slight  chance of a thunderstorm 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:

• Mostly cloudy with isolated evening showers, just mostly cloudy late tonight.
• Mostly cloudy with a slight (20%) chance of showers Sunday AM, a good (50%) chance of showers and a slight (20%) chance of thunderstorms in the afternoon (under 0.10 in. of rain possible, more in storms), a (30%) chance of evening showers, mostly cloudy late Sunday night.
• Mostly cloudy Monday AM, a mix of clouds and sun in the afternoon, partly cloudy in the evening, mostly cloudy with a slight (20%) chance of rain late at night.
• Mostly cloudy Tuesday AM, a mix of clouds and sun in the afternoon with a slight (20%) chance of showers, then just mostly cloudy Tuesday night.
• lows 56-53 highs 75-80.
• Mostly cloudy Wednesday AM, partly cloudy in the afternoon and evening, mostly cloudy late Wednesday night.
• Mostly cloudy Thursday AM, then partly cloudy in the afternoon through Tuesday.
• highs 82-78 lows near 55. (seasonal averages high 82 low 51)

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Forecast for the Umpqua Basin including Roseburg:

• Mostly cloudy with patchy fog this evening, a slight (20%) chance of thunderstorms late tonight.
• Mostly cloudy with a (30%) chance of showers and a slight (20%) chance of thunderstorms Sunday, a slight (20%) chance of evening showers, partly cloudy late Sunday night and Monday, mostly cloudy Monday night through Tuesday night.
• lows 60-55 highs 76-84.
• Mostly cloudy Wednesday AM, partly cloudy with a slight (20%) chance of rain in the afternoon, then partly cloudy Wednesday night through Saturday.
• highs 82-85 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 coastal showers tonight while a slight (20%) chance of thunderstorms inland late tonight.
• Mostly cloudy with a slight (20%) chance of AM coastal showers and a slight (20%) chance of thunderstorms late Sunday afternoon while a (30%) chance of showers and a slight (20%) chance of thunderstorms inland Sunday, partly cloudy with a slight (20%) chance of evening showers inland, just mostly cloudy at night, 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 rain late.
• Mostly cloudy with a slight (20%) chance of rain Tuesday afternoon, then mostly cloudy Tuesday night.
• lows 54-52 warming to 55 Tuesday night highs 66-69.
• Mostly cloudy Wednesday AM, partly cloudy with a slight (20%) chance of rain in the afternoon and evening, partly cloudy late Wednesday night.
• Partly cloudy with a slight (20%) chance of showers Thursday and Thursday night.
• Partly cloudy Friday through Saturday AM, then mostly cloudy Saturday afternoon.
• highs 69-66 lows near 55. (seasonal averages high 66 low 53)

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Forecast for the Cascades of Lane County:

• Mostly cloudy with a slight (20%) chance of isolated showers tonight.
• Cloudy with a (40%) chance of showers Sunday AM, mostly cloudy with showers likely (70%) and a slight (20%) chance of thunderstorms in the afternoon and evening (0.25 in. of rain possible, more in storms), mostly cloudy late Sunday night.
• Mostly cloudy with a slight (20%) chance of  AM showers, a mix of clouds and sun Monday afternoon, partly cloudy Monday night.
• A mix of clouds and sun Tuesday, then partly cloudy at night.
• snow level above 8,000 ft. tonight through Monday, free air freezing level 12,000 ft.  Monday evening, then snow level above 8,000 ft. late Monday night, free air freezing level 13,000 ft. Tuesday, then 12,000 ft. Tuesday night.
•  lows 47-45 warming back to 47 Tuesday night highs 65-68.
• Partly cloudy Wednesday and Wednesday night. Partly cloudy with a slight (20%) chance of showers Thursday afternoon and evening, partly cloudy at night. Partly cloudy with a slight (20%) chance of showers Friday afternoon and evening, partly cloudy late at night and Saturday.
• free air freezing level 12,000 ft. Wednesday through Thursday AM, snow level above 8,000 ft. in the afternoon and evening, free air freezing level 12,000 ft. late Thursday night and Friday AM, snow level above 8,000 ft. Friday afternoon and evening, then free air freezing level 12,000 ft. late Friday night and Saturday.
• highs 70-66 lows 46-48.

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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 Eugene Daily News.com.

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