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Here is my weekly weather quiz question for you. Why are clouds white? It’s actually pretty easy. Please post your answer as a comment by clicking on “no 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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The jet stream shows a high pressure ridge (shaded “arch” shaped area with blue arrows) building over the Pacific Northwest. The  ridge will protect us at least through the end of the week when the computer models indicate a wet weather pattern may begin as another frontal system moves in. Remember that, particularly this time of the year, when it’s not raining it is usually fogging.

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Advisories:   A DENSE FOG ADVISORY IS IN EFFECT UNTIL NOON TODAY FOR THE I-5 CORRIDOR FROM THE PORTLAND AREA SOUTH THROUGH THE EUGENE-SPRINGFIELD AREA. AN AIR STAGNATION ADVISORY IS IN EFFECT UNTIL 4 PM TODAY FOR ALL OF THE I-5 CORRIDOR FROM PORTLAND SOUTH THROUGH EUGENE AND SPRINGFIELD.  AN AIR STAGNATION ADVISORY IS IN EFFECT UNTIL 4 PM SATURDAY FOR CENTRAL DOUGLAS COUNTY, INCLUDING ROSEBURG, AND EASTERN CURRY COUNTY, JOSEPHINE COUNTY,  JACKSON COUNTY, THE KLAMATH BASIN, AND CENTRAL AND EASTERN LAKE COUNTY.

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Here are your detailed forecasts. **

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Forecast for the Southern and lower Mid Willamette Valley including Eugene-Springfield and Albany-Corvallis: Mostly cloudy with patchy fog possibly dense again this AM, a mix of clouds and sun in the afternoon, partly cloudy in the evening, mostly cloudy with patchy fog again tonight and Friday AM, mostly cloudy with a slight (20%) chance of AM rain, a (30%) chance of afternoon rain, then mostly cloudy with a slight (20%) chance of rain Friday night highs 47-55 lows 34-38. Mostly cloudy with a (40%) chance of rain Saturday through Sunday night, then a mix of clouds and sun Monday through Wednesday highs 53-49 lows near 38-30. (seasonal  averages highs 48 low 34)

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Forecast for the Umpqua Basin including, Roseburg: Mostly cloudy with patchy fog this AM (some lingering until late AM) , partly cloudy this afternoon, partly cloudy tonight with patchy fog late tonight and Friday AM, mostly cloudy with a slight (20%) chance of rain Friday afternoon and night high 57-53 lows 36-40. Mostly cloudy with a good (50%) chance of rain Saturday, evening showers likely (60%), a good (50%) chance of showers Saturday night and Sunday,  a slight (20%) chance of showers Sunday evening and Monday,  just partly cloudy Monday night and Tuesday, then mostly cloudy Tuesday night and Wednesday highs near 52 lows 38-34. (seasonal averages high 52 low 35)

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Forecast for the South Oregon Coast including Coos Bay and North Bend:  Partly cloudy today and tonight, mostly cloudy with a (30%) chance of coastal rain Friday, a slight (320%) chance inland, a (30%) chance of rain Friday night highs 59-53 lows 42-44. Mostly cloudy with a (40%) chance of AM coastal rain Saturday then afternoon rain likely (60%),  a good (50%) chance of inland afternoon rain, cloudy with evening showers likely (60%), then a (40%) chance of showers late Saturday night, a (30%) chance of AM showers Sunday,  just mostly cloudy Sunday night, mostly cloudy with a  slight (20%) chance of showers Monday, partly cloudy Monday night, then just mostly cloudy Tuesday through Wednesday highs 50-54 lows 42-36. (seasonal averages high 53 low 40).

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Forecast for the Cascades of Lane County: A mix of clouds and sun today, partly cloudy tonight, more clouds and cooler with a (40%) chance of rain Friday afternoon (mainly North of Santiam Pass), a slight (20%) chance of rain and colder Friday night free air freezing level 10,000 ft. today and tonight, snow level falling from 7,000 ft. to 5,500 ft. Friday afternoon, and 5,000 ft. Friday night highs 56-44 lows 30-25. Mostly cloudy with a (40%) chance of rain and snow  showers Saturday and Saturday night, partly cloudy with a (40%) chance of rain and snow showers Sunday, a slight (20%) chance of rain and snow showers Sunday night, then a mix of clouds and sun Monday through Wednesday with partly cloudy nights snow level 4,000 ft. Saturday, 4,000 ft. Saturday  through Sunday night, then a free air freezing level of 6,000 ft. Monday and Monday night, 6,500 ft. Tuesday, 5,000 ft. Tuesday night, and 6,000 ft. Wednesday highs 36-42 lows 23-36.

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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.