AgWeatherNet Weekly Weather Outlook for June 10 to June 16, 2020

Existing weather pattern continues into mid-July with seasonally cool temperatures and weak disturbances to bring periodic showers

Mark Ingalls, AgWeatherNet Intern
Michelle Daughtrey, AgWeatherNet Intern
Joe Zagrodnik, AgWeatherNet Postdoctoral Research Associate

Discussion:

Although the calendar reads mid-July, the large-scale weather remains in a late spring-like pattern that will continue to bring seasonally cool temperatures and occasional clouds/rain showers. High pressure usually becomes established in the Gulf of Alaska in mid-summer, but this year the high is centered farther south than normal, west of Oregon, leading to persistent cool onshore flow and a steady parade of weak weather systems arriving from the west-northwest. This pattern will continue over the next week, as several upper level disturbances tracking across southern British Columbia are expected to drag a few weak fronts across Washington. This should be enough to produce isolated thunderstorms in mountainous regions of the state most days, but incoming moisture will be limited so that lowlands in the eastern half of the state should remain dry with a few days of a low chance of rain for west side lowlands. Generally speaking, highs will be a little below average for the week with lows near average. Any rain that falls in the lowlands will be generally less than a tenth of an inch.

The main story over the weekend is a dry cold front that will cross the Pacific Northwest Saturday and Saturday night. Ahead of the front, many areas will see their warmest temperatures for the next seven days, with the Tri-Cities, Yakima, Wenatchee, and Moses Lake all expected to reach into the mid-90s. Dry is a fairly relative term in this instance. The front will have enough moisture to bring light rain showers to Western Washington and mountains across the state through Sunday, but it won't be enough to bring much of anything for eastern lowlands.

As the cold front crosses the Cascades, winds will ramp up on the lee side of the mountains. The strongest gusts will be seen in valleys that are down wind of mountain gaps, such as the Eastern Columbia Gorge and Kittitas Valley. There, gusts may reach to about 40 mph, but generally breezy conditions can also be expected for the Yakima Valley, Columbia Basin, and Palouse. Weaker, but still breezy, winds will linger into Sunday in the Columbia Gorge, along I-90, and on the Palouse.

Monday and Tuesday look mostly dry statewide before another weak disturbance starts coming in Tuesday evening. This system looks similar to Saturday's and will primarily be felt Wednesday. Precipitation will be light in the mountains and western half of the state. Those in eastern lowlands can expect breezy conditions to return as the disturbance crosses the Cascades. Some showers may linger in the Cascades and their western foothills Thursday.

Beyond Thursday there is lower confidence in the forecast, with some models indicating that enough of a ridge will build to bring drier and slightly warmer temperatures, while others suggest a continuation of onshore flow with additional chances for showers over the following weekend. There is no sign of any major pattern change, so we expect near or slightly below normal temperatures to persist into late July.

Drought conditions continue to persist in Central Washington, with the driest conditions being roughly along US 97 from Goldendale to Omak. For the water year, much of the US 97 corridor has observed precipitation values that are about half of climatological norms. At Yakima, 3.88 of precipitation have fallen, compared to the normal value of 7.50. This is the 5th lowest water year-to-date precipitation total for Yakima since records began in 1946. Central Washington is expected to miss out on most of this week's precipitation. In Seattle, a streak of high temperatures at-or-below normal has reached 13 days as of Thursday. It has been the coldest start to July since 2005 across much of Western Washington.


8 to 14 Day Outlook, July 17, 2020 to July 23, 2020
  • Slightly below 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/ SW flow through the weekend. A strong W breeze Sat night up to 30 mph at times.
  • Precipitation: Expected to remain dry throughout the weekend.
  • High Temps: Upper 80s Fri, mid 90s Sat, mid 80s Sun.
  • Low Temps: Low 50s Fri night, mid to low 50s Sat night, low 50s Sun night.
  • Sky Cover: Clear skies Fri, mostly clear Fri night, mostly sunny Sat, partly cloudy Sat night, partly cloudy Sun though Sun night.
Next Week
  • Wind: W/NW breeze throughout most of Mon and Tue. Wed breeze strengthens but continues the W/NW pattern. Thu and Fri return to a light W/NW breeze.
  • Precipitation: Dry conditions expected throughout the week in the region.
  • High Temps: Mid to low 80s Mon, upper 80s Tue, upper 80s Wed, low 90s Thu.
  • Low Temps: Mid 50s Mon night, upper 50s Tue night, upper 50s Wed night, low 60s Thu night.
  • Sky Cover: Clear skies are expected throughout the week.

North Central Washington
Weekend
  • Wind: W/SW flow with breezy conditions Sat & Sat night. Gusts to 30 mph possible during that period.
  • Precipitation: Mountain showers possible Sat, otherwise dry.
  • High Temps: Upper 80s Fri, mid 90s Sat, mid 80s Sun. Cooler in higher terrain.
  • Low Temps: Upper 50s Fri night, mid 50s Sat and Sun night. Cooler in higher terrain.
  • Sky Cover: Partly cloudy Fri and Fri night, becoming partly to mostly cloudy Sat. Returning to partly cloudy Sun.
Next Week
  • Wind: Generally W flow through the week. Breezy conditions possible Wed
  • Precipitation: Mountain showers possible Wed-Fri, possible stray lowland shower Thu. Otherwise dry.
  • High Temps: Mid 80s Mon, upper 80s Tue-Thu. Cooler in higher terrain.
  • Low Temps: Mid 50s Mon night, near 60 Tue-Thu night. Cooler in higher terrain.
  • Sky Cover: Clear to partly cloudy Mon-Tue, partly to mostly cloudy Wed-Thu.

Eastern Washington
Weekend
  • Wind: W/SW flow with breezy conditions Sat & Sat night. Gusts to 30 mph during that time period.
  • Precipitation: Showers possible in the Blues Sat, otherwise dry.
  • High Temps: Near 80 Fri, near 90 Sat, mid 70s Sun.
  • Low Temps: Mid 50s Fri-Sat night, near 50 Sun night.
  • Sky Cover: Clear to partly cloudy through the weekend.
Next Week
  • Wind: Generally W/SW flow with breezy conditions possible Wed.
  • Precipitation: Dry through the week.
  • High Temps: Mid 70s Mon, near 80 Tue-Thu.
  • Low Temps: Low 50s Mon night, mid 50s Tue-Thu night.
  • Sky Cover: Clear to partly cloudy through the week.

Western Washington
Weekend
  • Wind: Light and generally S/SW yet variable. Becoming breezier Sat night with winds shifting W. Sun carrying out the same pattern.
  • Precipitation: Dry conditions expected until system rolls in Sat from the W bringing scattered showers across the peninsula and to the Cascades. Conditions begin to clear up to start the week.
  • High Temps: Mid 70s Fri, low 70s Sat, low 70s Sun. Much cooler through the Cascades and Olympics.
  • Low Temps: Low 50s Fri night, low to mid 50s Sat night, low 50s Sun night. Much cooler through the Cascades and Olympics.
  • Sky Cover: Mostly cloudy in the mornings. Becoming partly sunny to sunny Fri afternoon. Mostly cloudy Sat. And partly cloudy most of Sun.
Next Week
  • Wind: Mostly light onshore flow yet variable. Flow shifting to a N pattern Mon night and similarly throughout the weeknights. Offshore to low expected Tue. Winds expected to remain light and breezy throughout the week and carrying out the onshore to Northerly to offshore pattern.
  • Precipitation: Chance for light showers in the Cascades and on the Peninsula Mon. Otherwise dry conditions expected.
  • High Temps: Mid 70s Mon, mid 70s Tue, low 70s Wed, mid 70s Thu. Much cooler through the Cascades and Olympics. Cooler near the coast.
  • Low Temps: Low 50s Mon night, mid 50s Tue night, mid 50s Wed night, mid to high 50s Thu night. Much cooler through the Cascades and Olympics.
  • Sky Cover: Partly cloudy to mostly sunny throughout the week.

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