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Here is my new weekly weather quiz question. In the Fall the leaves change colors and fall from the trees. What causes the leaves to change colors? 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 trough of low pressure ( “U” shaped area) swinging through the Pacific Northwest with another one following behind it. A frontal system moved through the area bringing a mixture of sunshine  and wet weather. A weak, short lived high pressure ridge (small “Arch” shape moving over us) will stop the rain temporarily. We’ll see another frontal system move in Tuesday followed by another Wednesday and Wednesday night. It’s been a long time coming, but a high pressure ridge (“arch” shape shown at the end of the jet stream movie) will build in late in the week warming us up a bit so it will feel more like Spring. It’s about time. It still looks like the rain will still hang around though.

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Advisories:   NONE AT THIS TIME.

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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 this AM with a slight (20%) chance of isolated showers, a mix of clouds and sun this afternoon, cloudy with a (40%) chance of evening rain, rain likely (60%) late tonight (0.10 in. of rain possible), showers likely (60%) Tuesday, a (40%) chance of rain Tuesday night, mostly cloudy Wednesday AM, a mix of clouds and sun Wednesday afternoon with a good (50%) chance of rain, mostly cloudy with a slight (20%) chance of showers Wednesday night highs 55-60 lows 40-43. Partly cloudy with a slight (20%) chance of showers Thursday, mostly cloudy with a good (50%) chance of showers Thursday night through Friday night, (30%) Saturday, a slight (20%) chance of showers Saturday night, then a slight (20%) chance of showers Sunday highs 64-55 lows near 42. (seasonal  averages high 58 low 37)

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Forecast for the Umpqua Basin including, Roseburg:  Mostly cloudy with a slight (20%) chance of showers this AM (snow level 3,000 ft.), mostly cloudy with a good (50%) chance of rain this evening, rain late tonight, rain Tuesday,  rain likely (60%) Tuesday night, a (30%) chance of rain Wednesday, then partly cloudy Wednesday night highs 55-66 lows 42-45. Partly cloudy Thursday, mostly cloudy with a slight (20%) chance of showers and warmer Wednesday, just partly cloudy Wednesday night and Thursday, mostly cloudy with a slight (20%) chance of rain Thursday night,  a (40%) chance of rain Friday, a (30%) chance of showers Friday night through Saturday night, then partly cloudy with a slight (20%) chance of showers Sunday highs 68-55 lows 45-36. (seasonal averages high 61 low 39)

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Forecast for the South Oregon Coast including Coos Bay and North Bend: Cloudy with a slight (20%) chance of showers this AM, cloudy with a good (50%) chance of evening rain, then rain likely (60%) late tonight, rain Tuesday, rain likely (60%) Tuesday night, a (30%) chance of rain Wednesday, then just partly cloudy Wednesday night highs 54-61 lows 44-47. Partly cloudy with a slight (20%) chance rain Thursday, a (30%) chance Thursday night, a (40%) chance of rain Friday, a (40%) chance of showers Friday night, (30%) Saturday and Saturday night, then partly cloudy with a slight (20%) chance of showers Sunday highs 62-52 lows 45-40. (seasonal averages high 56 low 42).

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Forecast for the Cascades of Lane County: Mostly cloudy this AM, partly cloudy with a slight (20%) chance of  rain and snow showers today with afternoon sun breaks, a good (50%) chance of snow and rain this evening, snow tonight, rain and snow Tuesday (1-4 in. of snow possible), rain Tuesday night (1-3 in. of snow possible, 0.50 in. of rain possible), AM rain likely (60%), a (40%) chance of rain Wednesday afternoon, and a (30%) chance of showers Wednesday night snow level 3,500 ft. today, 3,000 ft. falling to 2,500 ft. late tonight, 2,500 ft. rising to 3,000 ft. Tuesday, 5,000 ft. rising to 7,000 ft. late Tuesday night, then  8,000 ft. Wednesday, and 7,000 ft. Wednesday night highs 37-50 lows 28-35. Partly cloudy with a (20%) chance of showers Thursday, mostly cloudy with a good (50%) chance of showers Thursday night, a good (50%) chance of rain and snow showers Friday, a (40%) chance of showers Friday night, then mostly cloudy with a (40%) chance of rain and snow showers Saturday, and a (30%) chance Saturday night and Sunday snow level 6,000 ft. Thursday  and Thursday night, 5,500 ft. Friday, 4,500 ft. Friday night,  3,500 ft. Saturday, 3,000 ft. Saturday night, and 3,500 ft. Sunday highs 50-40 lows near 32.

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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.