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 will move through for your Saturday.  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 13 in the Good category measuring Particulate Matter.

Oakridge: The Air Quality Index is 28 in the Good category measuring Particulate Matter.

Cottage Grove: The Air Quality Index is 21 in the Good category measuring Particulate Matter.

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

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Advisories:

• A WINTER WEATHER ADVISORY IS IN EFFECT UNTIL NOON TODAY FOR THE NORTHERN OREGON CASCADES AND THE CASCADES IN LANE COUNTY.

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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%) this AM, showers likely (60%) with a slight (20%) chance of thunderstorms and a bit cooler this afternoon (0.25 in. of rain possible, more in storms), a good (50%) chance of showers tonight (under 0.10 in. of rain possible) and Sunday AM, a slight (20%) chance of showers and thunderstorms in the afternoon (under 0.10 in. of rain possible) and a bit cooler, a slight (20%) chance of evening showers, just mostly cloudy Sunday night,
• Mostly cloudy and a bit warmer with a (40%) chance of showers Monday, then cloudy with a good (50%) chance of showers at night.
• highs 49-43 warming to 45 Monday lows 32-35.
• Mostly cloudy with a good (50%) chance of showers and a bit warmer Tuesday and Tuesday night,
• Cloudy with a slight (20%) chance of showers and a bit warmer Wednesday and Wednesday night,
• A good (50%) chance of rain and a bit warmer Thursday, a (40%) chance of rain at night,
• Then a mix of clouds and sun and just a bit warmer Friday.
• highs 46-52 lows 38-40 cooling back to 38 Thursday night. (seasonal averages high 49 low 35)

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Home Wood Heating Advisory:

Eugene-Springfield: GREEN – Burning is allowed.

Oakridge: GREEN – Burning is allowed.

*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 and a bit cooler with rain and snow showers and a slight (20%) chance of thunderstorms today (0.15 in. of rain possible, 1-2 in. of snow possible, snow level 1,500 ft. rising to 2,500 ft. in the afternoon), a (40%) chance of rain and snow showers and a slight (20%) chance of thunderstorms this evening, a slight (20%) chance of thunderstorms and snow showers late tonight (under 0.10 in. of rain possible, evening snow level 2,500 ft.),
• Mostly cloudy with a (30%) chance of rain and snow showers and a slight (20%) chance of thunderstorms a bit cooler Sunday (under 0.10 in. of rain possible, snow level 600 ft. rising to 2,000 ft. in the afternoon, a (30%) chance of rain and snow  rain and snow showers Sunday night (under 0.10 in. of rain possible),
• Partly cloudy with a slight (20%) chance of rain and snow showers Monday, mostly cloudy with a slight (20%) chance of rain and snow showers Monday night.
• highs near 46 lows 32-36.
• Cloudy with a (40%) chance of rain and snow showers Tuesday, mostly cloudy with a slight (20%) chance of evening showers, a slight (20%) chance of rain and snow showers late Tuesday night,
• Mostly cloudy and a bit warmer with a slight (20%) chance of rain Wednesday and Wednesday night,
• Cloudy with a (30%) chance of rain Thursday, mostly cloudy with a (30%) chance of rainThursday night,
• Then just mostly cloudy Friday.
• highs 47-52 lows 38-42. (seasonal averages high 51 low 37)

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

• Mostly cloudy and a bit cooler today with showers and a slight (20%) chance of coastal thunderstorms this afternoon while inland showers, snow showers and a slight (20%)  chance of thunderstorms and a bit cooler this afternoon (, 0.20 in. of rain possible, AM snow level 2,000 ft.), a good (50%) chance of coastal showers with a slight (20%) chance of thunderstorms tonight while a good (50%) chance of inland showers and a slight (20%) chance of thunderstorms late tonight (snow level 2,000 ft. late),
• Mostly cloudy with a good (50%) chance of coastal showers and a slight (20%) chance of thunderstorms Sunday while snow showers and a slight (20%) chance of thunderstorms inland in the afternoon (snow level 1,500 ft. rising to 2,000 ft. in the afternoon), mostly cloudy with a (40%) chance of showers late Sunday night,
• Partly cloudy with a slight (20%) chance of showers Monday, then a (30%) chance of showers Monday night.
• highs 48-50 lows 36-42.
• Cloudy with a good (50%) chance of showers Tuesday, mostly cloudy with a (30%) chance of showers Tuesday night,
• Mostly cloudy and a bit warmer with a slight (20%) chance of rain Wednesday and Wednesday night,
• Cloudy and a bit cooler with a good (50%) chance of rain Thursday, mostly cloudy with a (30%) chance of rain at night,
• Then just mostly cloudy and a bit warmer Friday.
• highs 50-54 cooling to 52 Thursday warming to 55 Friday lows 44-48. (seasonal averages high 52 low 40).

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Forecast for the Cascades in Lane County:

• Mostly cloudy and a bit cooler with snow showers today (1-4 in. of snow possible), snow showers likely (70%) this evening, a good (50%) chance of snow showers and colder late tonight (1 in. of snow possible),
• Mostly cloudy with a (30%) chance of snow showers and cooler Sunday and Sunday night,
• Mostly cloudy with a (40%) chance of snow showers Monday, then cloudy with a good (50%) chance of snow showers Monday night.
• snow level 2,500 ft. today, then at the surface tonight through Monday night.
• highs 30-24 lows 17-19.
• Mostly cloudy with a good (50%) chance of snow showers and a bit warmer Tuesday and Tuesday night,
• A mix of clouds and sun with a slight (20%) chance of snow and a bit warmer Wednesday, a slight (20%) chance of rain and snow Wednesday night,
• Cloudy and a bit warmer with a (40%) chance of rain and snow Thursday, mostly cloudy with a (40%) chance of rain and snow Thursday night,
• Then a mix of clouds and sun and a bit warmer with a slight (20%) chance of rain and snow showers Friday.
• snow level at the surface Tuesday, 2,500 ft. Tuesday night and Wednesday, 3,500 ft. Wednesday night, 4,000 ft. Thursday, 4,500 ft. Thursday night, then 5,000 ft. Friday.
• highs 30-38 lows 22-27.

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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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