Here is my weekly weather quiz question for the last time. What is a “Nocturnal Inversion?” Here is the correct answer. A Nocturnal Inversion: Used interchangably with Radiational Inversion; a temperature inversion that develops during the night as a result of radiational cooling of the surface. Because the immediate surface (lower Boundary Layer) cools much more rapidly during radiational cooling conditions than the air just above (upper Boundary Layer), a temperature inversion can be created overnight, but typically erodes quickly after sunrise. ( Note: Inversion means the reverse of normal. Instead warm air is above cooler air.) 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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An upper level low (Shaded “U” shape with blue arrows) is sending more moisture our way. A frontal system moved into the Pacific Northwest bringing another round of rain Friday and yet another storm moved through today.  A frontal system approaches the coast next Tuesday for more precipitation.

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Air Quality Index:

Eugene-Springfield: The Air Quality Index is 8 in the Good category measuring Particulate Matter.

Oakridge: The Air Quality Index is 14 in the Good category measuring Particulate Matter.

Cottage Grove: The Air Quality Index is 12 in the Good category measuring Particulate Matter.

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

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Advisories:

• A FROST ADVISORY IS IN EFFECT FROM 2 AM UNTIL 8 AM SUNDAY FOR THE SOUTH CENTRAL OREGON COAST AND THE CURRY COUNTY COAST.

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

• Mostly cloudy with showers likely (70%) and a slight (20%) chance of evening thunderstorms (small hail possible), a good (50%) chance of showers late tonight (under 0.10 in. of rain possible),
• A good (50%) chance of showers Sunday AM, showers likely (70%) in the afternoon (0.10 in. of rain possible, small hail possible) and a bit cooler, evening showers likely (70%) with possible small hail, a good (50%) chance of showers late Sunday night,
• A mix of clouds and sun and a bit warmer with a good (50%) chance of showers Monday, mostly cloudy with a good (50%) chance of showers Monday night and Tuesday, then partly cloudy with a slight (20%) chance of showers Tuesday night.
• lows 32-35 highs 43-46.
• Just mostly cloudy and a bit warmer Wednesday, cloudy with a good (50%) chance of showers Wednesday night,
• Mostly cloudy with rain likely (60%) and a bit warmer Thursday, a (30%) chance of showers at night,
• A mix of clouds and sun and just a bit cooler Friday, partly cloudy with a slight (20%) chance of showers Friday night,
• Then mostly cloudy with a (30%) chance of rain Saturday.
• highs 48-52 lows 40-38. (seasonal averages high 49 low 35)

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Home Wood Heating Advisory:

Eugene-Springfield: GREEN – Burning is allowed.

Oakridge: YELLOW – Caution is Advised.

*Note: Pellet stoves may be used anytime if they produce no visible emissions.

Advisory Courtesy of Lane Regional Air Protection Agency (LRAPA).

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Forecast for Roseburg:

• Mostly cloudy with a (40%) chance of rain and snow showers tonight (under 0.10 in. of rain possible, snow level 2,000 ft.),
• Cloudy with a (30%) chance of AM rain and snow showers, rain and snow showers likely (60%) and a bit cooler Sunday afternoon (under 0.10 in. of rain possible, 1 in.of snow possible, snow level 1,500 ft.), evening rain and snow showers likely (60%), a good (50%) chance of rain and snow showers late Sunday night (under 0.10 in. of rain possible, 1 in. of snow possible, snow level 2,000 ft. falling to 1,500 ft),
• Mostly cloudy with a good (50%) chance of rain and snow showers Monday (snow level 1,500 ft.) and Monday night (snow level 2,500 ft. falling to 2,000 ft. late at night),
• Mostly cloudy and a bit warmer with a (40%) chance of rain and snow showers Tuesday, a good (20%) chance of evening rain and showers, then a slight (20%) chance of rain and snow showers late Tuesday night.
• lows 30-38 highs 45-47.
• Mostly cloudy and a bit warmer with a slight (20%) chance of rain Wednesday, a (40%) chance of rain Wednesday night,
• Cloudy with a (30%) chance of rain and a bit warmer Thursday, a slight (20%) chance of showers at night,
• Just partly cloudy  and a bit cooler Friday, then mostly cloudy with a slight (20%) chance of showers late Friday night and Saturday.
• highs 52-55 cooling back to 52 Saturday lows 40-37. (seasonal averages high 51 low 37)

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Forecast for The South Oregon Coast Including Coos Bay and North Bend:

• Mostly cloudy with a good (50%) chance of coastal showers and a slight (20%) chance of thunderstorms tonight while a good (50%) chance of inland showers and a slight (20%) chance of thunderstorms this evening and a good (50%) chance of showers, snow showers and a slight (20%) chance of thunderstorms late tonight inland (snow level 2,000 ft.),
• Cloudy with a good (50%) chance of coastal showers and a slight (20%) chance of thunderstorms Sunday AM and showers likely (60%) with a slight (20%) chance of thunderstorms in the afternoon while a good (50%) chance of showers, snow showers and a slight (20%) chance of thunderstorms inland in the AM snd showers, snow showers likely (60%) in the afternoon (snow level 1,500 ft. with no accumulation expected), mostly cloudy with evening coastal showers likely (60%) and a good (50%) chance of showers late at night while inland rain and snow showers Sunday night,
• Mostly cloudy with a good (50%) chance of showers Monday (snow level 2,000 ft.), a (30%) chance of evening showers, showers likely (60%) Monday night,
• Then mostly cloudy and a bit warmer with a good (50%) chance of showers Tuesday and Tuesday night.
• lows 36-45 highs 48-52.
• Mostly cloudy and a bit warmer with a slight (20%) chance of rain Wednesday, cloudy with a good (50%) chance of rain Wednesday night and Thursday, mostly cloudy with a slight (20%) chance of rain at night,
• Just partly cloudy Friday, then becoming mostly cloudy with a slight (20%) chance of showers Friday night and Saturday.
• highs near 55 lows 48-42. (seasonal averages high 52 low 40).

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Forecast for the Cascades in Lane County:

• Cloudy with snow showers diminishing and colder late tonight (1-3 in. of snow possible),
• Mostly cloudy with snow showers increasing again and cooler Sunday (1-2 in. of snow possible), evening snow showers likely (70%), a good (50%) chance of show showers late Sunday night (1-3 in. of snow possible),
• Mostly cloudy and a bit warmer with a good (50%) chance of snow showers Monday, a (40%) chance of snow showers Monday night,
• A good (50%) chance of snow showers and a bit warmer Tuesday, then a slight (20%) chance of snow showers Tuesday night.
• snow level at the surface tonight through Tuesday, then 3,000 ft. Tuesday night.
• lows 17-20 highs 20-30.
• Just mostly cloudy and a bit warmer Wednesday, a good (50%) chance of rain and snow Wednesday night,
• Cloudy and a bit warmer with a good (50%) chance of rain and snow Thursday, a (40%) chance of showers Thursday night,
• A mix of clouds and sun and a bit warmer Friday, mostly cloudy with a slight (20%) chance of showers at night,
• Then mostly cloudy with a (30%)  chance of rain or snow Saturday.
• free air freezing level 3,500 ft. Wednesday, snow level 3,500 ft. Wednesday night, 4,000 ft. Thursday and Thursday night, free air freezing level 5,500 ft. Friday, then snow level 5,500 ft. Friday night and Saturday.
• highs 34-36 lows near 26.

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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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