An upper level high pressure ridge (“Arch” shaped shaded area with blue arrows in the jet stream over the Pacific Northwest) will keep us dry, but cool. An upper level trough of low pressure (the “U” shaped shaded area with blue arrows in the jet stream) will start changing our weather and help send a cold front our way Thursday.

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Advisories:  A FROST ADVISORY IS IN EFFECT FROM 1 AM TO 9 AM TODAY FOR THE NORTHERN OREGON COASTAL STRIP, THE COAST RANGE OF NORTHWEST OREGON, THE NORTHERN AND CENTRAL WILLAMETTE VALLEY (TO JUST NORTH OF ALBANY).

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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: Areas of patchy fog this AM, a mix of clouds and sun in the afternoon, mostly clear with patchy fog late tonight and early Monday AM, mostly sunny in the afternoon, mostly clear with patchy fog again late at night and Tuesday AM, a mix of clouds and sun in the afternoon, and partly cloudy Tuesday night highs 65-60 lows 35-33. Mostly sunny Wednesday, partly cloudy at night, partly cloudy Thursday and Thursday night with a slight (20%) chance of rain, mostly cloudy with a slight (20%) chance of rain Friday, and mostly cloudy with a good (50%) chance of rain Friday night and Saturday highs 63-59 lows 38-43.(seasonal averages highs 64 low 40)

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Forecast for the Umpqua Basin including, Roseburg:  Mostly cloudy this AM with patchy fog, partly cloudy this afternoon, mostly clear tonight, sunny Monday, and mostly clear and at night highs 62-64 lows 38-40. Sunny Tuesday, mostly clear Tuesday night, partly cloudy Wednesday and Wednesday night, mostly cloudy with a slight (20%) chance of  rain  Thursday through Friday, mostly cloudy Friday night and Saturday with a good (50%) chance of rain highs 70-74 cooling to 64 Thursday,  then to 59 Saturday lows 39-45. (seasonal averages high 69 low 44)

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Forecast for the South Oregon Coast including Coos Bay and North Bend: Mostly cloudy with patchy fog this AM,  partly cloudy this afternoon, mostly clear at night, sunny Monday, and mostly clear Monday night highs 59-63 lows 40-39. Mostly sunny Tuesday, mostly clear Tuesday night, partly cloudy Wednesday and Wednesday night, partly cloudy with a slight (20%) chance of rain Thursday through Friday, then mostly cloudy with a good (50%) chance of rain Friday night and Saturday highs 65-58 and back to near 60 Friday and Saturday lows 42-48. (seasonal averages high 63 lows 46).

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Forecast for the Cascades of Lane County:  A mix of clouds and sun today, and mostly clear tonight free  air freezing level  9,000 ft. today, 10,000 ft. tonight high 55 low 36. Mostly sunny Monday through Wednesday, mostly clear Monday night and Tuesday night, partly cloudy Wednesday night,  partly cloudy with a slight (20%) chance of rain Thursday and Thursday night,  mostly cloudy with a slight chance of rain Friday, a good (50%) chance rain Friday night, and rain likely (60%) Saturday free air freezing level 11,000 ft. Monday, 12,000 ft. Monday night, 13,000 ft. Tuesday through Wednesday night, a snow level above 8,000 ft Thursday and Thursday night, and  8,000 ft. through Saturday highs 60-64 cooling to  near 50 Saturday lows 38-33.

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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.