AgWeatherNet Weekly Weather Outlook for Aug 7 to Aug 13, 2020

A slight chance for rain showers west of the Cascades around mid week

Craig Oswald, AgWeatherNet Field Meteorologist
Michelle Daughtrey, AgWeatherNet Intern

Discussion:

As the weekend approaches, a modest shortwave embedded in the mean northwest flow aloft is expected pass over the state tonight (Friday). This disturbance, paired with a plume of higher moisture air originating from the central Pacific, look to be enough to initiate a few light rain showers. Showers are to be mostly relegated to the Cascade crest as they develop over the course of the overnight and linger through Saturday morning. Greater shower activity can be expected through the northern half of the Cascade crest with portions that lie through the southern half of the state likely to remain dry. With this being said, a stray light rain shower or two can't be completely ruled out for lowland areas of western Washington, again, with any activity to be confined to the northern half as well as coastal areas of the region. Regions east of the Cascades are expected to see a slight increase in cloud cover tonight (Friday), but conditions are anticipated to remain dry.

Weather conditions are expected to turn dry statewide after Saturday and remain so through the first part of the week. Temperatures will continue to climb through the weekend and peak on Monday at slightly above seasonal as a weak ridge looks to begin moving across the state Saturday on the heels of the passing shortwave.

Models indicate another upper trough to move into the region from the northwest around the Tuesday night/Wednesday time frame. The primary effect of this will be to again cool temperatures to slightly below average for this time of year. Temperatures Wednesday and into the following weekend look to trend slightly cooler than seasonable. Precipitation is indicated in some models, but agreement across models and different model runs is inconsistent. The European model indicates a weaker trough developing and remining mostly to the north. This scenario keeps Washington state in a mostly zonal flow regime and dry. GFS and recent Canadian models indicate a much more pronounced trough with increased dynamical forcing initiating rain showers west to east throughout western Washington and high terrain areas of northern Washington (the Columbia Basin will likely remain dry however with only increased cloud cover and breezy conditions).

This information, paired with the prospect that the persistent high pressure centered over the central north Pacific will likely remain in place, directing higher moisture air into a plume guided to the Pacific Northwest by the jet stream, is making it seem that light rain showers are more possible than not on Wednesday. The chance for showers currently looks to be slight in lowland areas of western Washington with greater activity through the Cascades and Olympics. Upland and higher terrain areas of northern Washington can also possibly see a few light showers. Any showers that form will move into the western part of the state Wednesday and generally be scattered in nature. Again, the Colombia Basin and Palouse will likely remain dry with a small chance for a stray shower or two over the Blue Mountains. Most shower activity should be finished by Thursday with conditions turning dry and remaining so into the following Saturday.


8 to 14 Day Outlook  Aug 14, 2020 to Aug 20, 2020
  • Slightly cooler than average temperatures and near average precipitation are expected during the 8 to 14 day time frame.

Important Points about Next Week's Weather

South Central Washington
Weekend
  • Wind: Light W/NW wind Saturday and Sunday. Some gusts expected around 30 mph Saturday evening.
  • Precipitation: Dry conditions expected throughout the weekend.
  • High Temps: Low 80s Fri, mid 80s Sat, mid 80s Sun.
  • Low Temps: Upper 50s Fri night, mid 50s Sat night, mid 50s Sun night.
  • Sky Cover: Some clouds moving in Friday night with partly cloudy skies. Mostly sunny Saturday, clear Saturday night. Sunny and clear Sunday.
Next Week
  • Wind: Light W wind Monday through Tuesday, transitioning to W/SW Wednesday through Friday and continuing to be generally light through the day. However, gusts potentially reaching to 30 mph most evenings, with breezier conditions and gusts to 40 mph Wednesday.
  • Precipitation: Dry conditions expected throughout the week.
  • High Temps: Mid 90s Mon, low 90s Tue, mid 80s Wed, low 80s Thu.
  • Low Temps: Upper 50s Mon night, mid 50s Tue night, low 50s Wed night, mid 50s Thu night.
  • Sky Cover: Sunny and clear Monday and Tuesday. Partly cloudy with intermittent clear skies Wed and Thur.

North Central Washington
Weekend
  • Wind: Mostly W/NW and generally light yet becoming breezier through the day. Evening winds becoming particularly breezier through the Basin with some gusts to around 30 mph.
  • Precipitation: A few light rain showers near the Cascade crest Friday night. Dry conditions elsewhere with dry conditions expected through the weekend.
  • High Temps: Near 80 Fri, mid 80s Sat, mid 80s Sun. Cooler in high terrain.
  • Low Temps: Mid 50s Fri night, mid 50s Sat night, mid 50s Sun night. Cooler in high terrain and deep valleys.
  • Sky Cover: Becoming mostly cloudy Friday night. Skies to clear with mostly sunny and clear conditions Saturday. Sunny and clear Sunday.
Next Week
  • Wind: Mostly W yet variable and light while maintaining a pattern of breezy evenings, especially through the Basin. Becoming breezy with SW winds Wednesday with gusts to 40 mph possible through the Basin. Shifting to W/NW and light Thursday while becoming breezy again in the evening.
  • Precipitation: Dry early in the week with a chance for a few scattered and light rain showers in upland/high terrain areas Wednesday. Dry Thursday.
  • High Temps: Low 90s Mon, upper 80s Tue, mid 80s Wed, low 80s Thu. Cooler in high terrain.
  • Low Temps: Upper 50s Mon night, mid 50s Tue night, mid 50s Wed night, low 50s Thu night. Cooler in high terrain and deep valleys.
  • Sky Cover: Mostly sunny and clear early in the week. Becoming partly cloudy Wednesday. Skies clearing again by Thursday with mostly sunny and clear skies.

Eastern Washington
Weekend
  • Wind: Light and generally W/SW throughout the weekend. Gusts not to exceed 30 mph.
  • Precipitation: Dry conditions expected throughout the weekend.
  • High Temps: Low 70s Fri, upper 70s Sat, low 80s Sun.
  • Low Temps: Low 50s Fri night, near 50 Sat night, low 50s Sun night.
  • Sky Cover: Clouds building in Friday night with partly cloudy skies. Partly cloudy Saturday. Sunny and clear Sunday.
Next Week
  • Wind: Generally light S/SW but variable wind throughout the week. Becoming breezier by the evening with some gusts approaching 30 mph. Breezier Wednesday with gusts reaching 35 mph.
  • Precipitation: Dry conditions expected through the week aside from a low chance for a stray light rain shower over the Blue Mtns Wednesday.
  • High Temps: Mid 80s Mon, mid 80s Tue, upper 70s Wed, mid 70s Thu.
  • Low Temps: Mid 50s Mon night, mid 50s Tue night, low 50s Wed night, around 50 Thu night.
  • Sky Cover: Sunny and clear Monday and Tuesday. Partly cloudy Wed and Thu.

Western Washington
Weekend
  • Wind: Generally light and variable through the weekend while becoming slightly breezier by the evening. Breezier near the coast.
  • Precipitation: Scattered rain showers along the northern half of the Cascade crest Friday night and into Saturday morning. Lower chance for a few light scattered rain showers throughout lowland areas as well, again in the northern half of the region. Becoming dry region wide through Saturday afternoon.
  • High Temps: Mid 70s Fri, mid 70s Sat, low 80s Sun. Much cooler through the Cascades and Olympics.
  • Low Temps: Mid 50s Fri night, near 50 Sat night, low 50s Sun night. Much cooler through the Cascades and Olympics.
  • Sky Cover: Mostly cloudy Friday night with clouds slowly clearing through the weekend. Partly cloudy Saturday and sunny skies expected by Sunday.
Next Week
  • Wind: Mostly light and variable while continuing to become slightly breezier by the evening hours. Breezy Wednesday with some gusts near 25 mph possible. Breezier near the coast.
  • Precipitation: Dry early in the week. Chance for light and scattered rain showers to move in from the west Wednesday. Again becoming dry region wide by Thursday.
  • High Temps: Mid 80s Mon, upper 70s Tue, upper 70s Wed, upper 70s Thu. Much cooler through the Cascades and Olympics.
  • Low Temps: Low 50s Mon night, low 50s Tue night, near 50 Wed night, low 50s Thu night. Much cooler through the Cascades and Olympics.
  • Sky Cover: Sunny and clear skies Monday with clouds slowly building in Tuesday. Partly sunny by Wednesday and remaining so for the rest of the period.

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