AgWeatherNet Weekly Weather Outlook for July 26 to August 1, 2021

Return to warmer conditions across Washington this week

Mark Ingalls, AgWeatherNet Intern

Synopsis:

Generally southwesterly flow is forecast to keep temperatures above average in most areas through midweek. In Western Washington, some low clouds may make it as far as I-5 in the Southwestern Interior and Northwester part of the state. Some monsoon moisture may make it into far Southeast Washington through Wednesday, but this will largely be confined to Oregon. Beginning Thursday, a building ridge over the Rocky Mountains will turn this flow to be more out of the south. This will cut off the low morning clouds in most of Western Washington and usher in a new heatwave. Friday and Saturday are likely to be the hottest days before the ridge begins to erode Sunday and temperatures cool a few degrees.

Discussion:

A low-amplitude ridge centered over Central Montana is forecast to keep temperatures in the Pacific Northwest above average to start the week. Flow aloft will be out of the southwest, pulling some monsoon moisture into the region. Most of the rain and thunderstorms resulting from this will be limited to Eastern Oregon, but far Southeast Washington may also benefit. In Western Washington, this flow pattern will allow low morning clouds to make it as far as I-5, especially in the Southwest Interior and through the Strait of Juan de Fuca.

Thursday, the ridge strengthens over the Rocky Mountains, turning upper level flow more southerly and initiating Washington's next heatwave. Whatever monsoon moisture reaching into the state will be cut off by this change, as well as the low morning clouds for Western Washington (except perhaps along the coast). This heatwave is not likely to be as extreme as the one seen at the end of June, but temperatures in the 90s are possible in the Southwest Interior and the Columbia Basin is forecast to reach to around 105.

Friday and Saturday should be the hottest day this week. Sunday, the ridge begins to erode as an upper level low approaches Southeast Alaska. Temperatures should moderate somewhat for Sunday but remain above average. Models indicate that shortwave disturbances embedded within the mean flow may bring some shower activity to start next week, but confidence in this pattern isn't all that high yet.

Exceptional drought (D4/4) has spread to cover almost all of Washington south and east of a line from Goldendale to Moses Lake to Newport. Last week's National Drought Monitor update didn’t see any other significant changes, leaving Yakima in extreme drought (D3/4), Vancouver in severe drought (D2/4), Bellingham and Tacoma in moderate drought (D1/4), and abnormally dry (D0/4) conditions elsewhere. Spokane has yet to see five inches of precipitation this year, which is about half of the year-to-date average. The Tri-Cities remain below two inches so far in 2021, just above a third of the year-to-date average.

For most of Washington, average temperatures begin to slowly fall this week. The Coast, Olympic Peninsula, and Northwest Interior have to wait for another week for this to happen. That part of the state receives the most influence from the Pacific Ocean, which is slower to respond to the changing seasons.


8 to 14 Day Outlook, August 2 to August 9, 2021
  • Above average temperatures and near average precipitation are favored for the period.

Important Points About This Week's Weather

South Central Washington
Remainder of the Week
  • Wind: Generally SW and light.
  • Precipitation: Dry conditions expected.
  • High Temps: Mid 90s Tue, upper 90s Wed, low 100s Thu, mid 100s Fri.
  • Low Temps: Low 70s Mon night, near 70 Tue night, upper 60s Wed night, low 70s Thu-Fri nights.
  • Sky Cover: Partly cloudy Tue-Wed, mostly clear Thu-Fri. Hazy periods.
Weekend
  • Wind: Light and variable Sat, SW and breezy Sun.
  • Precipitation: Dry conditions expected.
  • High Temps: Mid 100s Sat, near 100 Sun.
  • Low Temps: Low 70s Sat night, near 70 Sun night.
  • Sky Cover: Mostly clear, hazy periods.

North Central Washington
Remainder of the Week
  • Wind: Generally SW and light.
  • Precipitation: Dry conditions expected.
  • High Temps: Upper 90s Tue-Wed, low 100s Thu, mid 100s Fri. Cooler in higher terrain.
  • Low Temps: Near 70 Mon-Tue nights, low 70s Wed night, mid 70s Thu-Fri nights. Cooler in higher terrain and sheltered areas.
  • Sky Cover: Mostly clear, hazy periods.
Weekend
  • Wind: Light and variable Sat, NW and breezy Sun.
  • Precipitation: Dry conditions expected.
  • High Temps: Mid 100s Sat, near 100 Sun. Cooler in higher terrain.
  • Low Temps: Mid 70s Sat night, near 70 Sun night. Cooler in higher terrain and sheltered areas.
  • Sky Cover: Mostly clear, hazy periods.

Eastern Washington
Remainder of the Week
  • Wind: Generally SW with breezy areas during the afternoon.
  • Precipitation: Isolated T-Storms Tue-Wed, mainly S of Pullman.
  • High Temps: Mid 90s Tue-Wed, near 100 Thu, low 100s Fri. Warmer in the Lewis & Clark Valley.
  • Low Temps: Mid 60s Mon-Fri nights. Warmer in the Lewis and Clark Valley.
  • Sky Cover: Partly Cloudy Tue-Wed, mostly clear Thu-Fri. Hazy periods.
Weekend
  • Wind: Light and variable Sat, SW and breezy Sun.
  • Precipitation: Dry conditions expected.
  • High Temps: Low 100s Sat, upper 90s Sun. Warmer in the Lewis & Clark Valley.
  • Low Temps: Upper 60s Sat night, mid 60s Sun night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly clear, hazy periods.

Western Washington
Remainder of the Week
  • Wind: Generally light and variable except NW and breezy along the coast and through the strait.
  • Precipitation: Dry conditions expected.
  • High Temps: Near 80 Tue, mid 80s Wed-Fri. Cooler in higher terrain and along the coast.
  • Low Temps: Near 60 Mon-Fri nights. Cooler in higher terrain.
  • Sky Cover: Mostly clear, hazy periods. AM low clouds possible, mainly along the coast.
Weekend
  • Wind: Generally light and variable except NW and breezy along the coast and through the strait.
  • Precipitation: Dry conditions expected.
  • High Temps: Mid 80s Sat & Sun. Cooler in higher terrain and along the coast.
  • Low Temps: Near 60 Sat & Sun nights. Cooler in higher terrain.
  • Sky Cover: Mostly clear, hazy periods.

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Washington State University