AgWeatherNet Weekly Weather Outlook for August 23 to August 29, 2021

Dry and mild this week, possibly becoming warmer during the weekend

Mark Ingalls, AgWeatherNet Field Technician

Synopsis:

Temperatures in Washington are forecast to remain generally below average for much of the work week as weak upper level troughs cross the region from the Northwest. The North Pacific (the source region for the incoming disturbances) is currently relatively dry and cool. There is a low chance of rain in the mountains and northwestern quarter of the state Thursday and Friday. While there is a certain level of uncertainty regarding the weekend, ensemble guidance leans toward temperatures warming to near or just above average with the region remaining dry.

Discussion:

Monday brought the coolest temperatures seen in Washington for a while. Lows in parts of Eastern Washington even got below 40, including 37 at AgWeatherNet stations near Moxee and Davenport. For some locations in the state, this was the coldest morning since late May. While temperatures are likely to remain below average for much of the week, these readings are likely to be the coolest for a while.

A persistent ridge of high pressure located around 155 degrees west (the Washington Coast is around 122 degrees west) is likely to keep the general upper level flow pattern over the region as out of the northwest. This is expected to bring down several weak upper level troughs to keep the Pacific Northwest relatively cool during the work week. Highs in Eastern Washington are generally forecast in the mid 70s to mid 80s.

The frequent disturbances could keep breezy conditions in place in typical windy spots, such as the Columbia Gorge and Kittitas Valley. The may also bring periods of mostly cloudy conditions north of I-90, primarily Tuesday and Wednesday nights. A few locations in Eastern Washington may get into the 30s again Monday night, but temperatures this low will likely only be found in spots where strong nocturnal inversions are common. Tuesday night and beyond, look for lows in the 40s and 50s except cooler temperatures in higher elevations.

West of the Cascades, upper 60s to mid 70s are likely through Wednesday. The trough passing through on Thursday and Friday brings a little more moisture with it, producing a chance of rain in the Cascades and western lowlands generally north of Seattle. Precipitation values are forecast to be unimpressive with even the wettest spots staying under a quarter inch of rain. Increased cloud cover will cool daytime temperatures somewhat with many spots struggling to get above 70.

There is some uncertainty about what to expect this weekend. The general consensus brings the North Pacific ridge axis close enough to the Pacific Northwest to raise afternoon highs to near average for late August with lows above average. This means highs in the upper 80s in the Columbia Basin, low to mid 80s around Spokane, and mid to upper 70s for Western Washington lowlands that are away from the Pacific Ocean or Puget Sound. Model guidance indicates that a resumption of upper level troughing next week should keep temperatures near average to end August and meteorological summer.

Central Washington Heat Stress:
Note: This is an experimental forecast product that may undergo changes over the coming weeks. For questions or comments, please email Mark Ingalls.

Continued mild conditions should limit heat stress concerns both for agricultural workers as well as the fruit itself. During the work week, look for highs generally in the low 80s with a few spots of mid 80s in the warmest locations. Dew points are in for a slow rise, from the low 40s up toward the low 50s. With light winds and mostly clear skies, wet bulb globe temperatures should not get above 80, even in the warmest regions. Under this forecast, fruit skin temperatures are likely to remain below 110.


8 to 14 Day Outlook, August 30 to September 5, 2021
  • Near average temperatures and below average precipitation are favored for the period.

Important Points About This Week's Weather

South Central Washington
Remainder of the Week
  • Wind: N and light Tue, becoming W with breezy areas Wed-Fri.
  • Precipitation: Dry conditions expected.
  • High Temps: Low 80s Tue, mid 80s Wed, low 80s Thu-Fri.
  • Low Temps: Mid 40s Mon night, mid 50s Tue-Fri nights. Cooler in well sheltered areas.
  • Sky Cover: Partly cloudy, areas of haze.
Weekend
  • Wind: N and light Sat, variable with breezy areas Sun.
  • Precipitation: Dry conditions expected.
  • High Temps: Mid 80s Sat, upper 80s Sun.
  • Low Temps: Mid 50s Sat night, upper 50s Sun night. Cooler in well sheltered areas.
  • Sky Cover: Partly cloudy, areas of haze.

North Central Washington
Remainder of the Week
  • Wind: N and light Tue, becoming W with breezy areas Wed-Fri.
  • Precipitation: Dry conditions expected.
  • High Temps: Near 80 Tue, mid 80s Wed, low 80s Thu-Fri. Cooler in higher terrain.Near 80 Tue, mid 80s Wed, low 80s Thu-Fri. Cooler in higher terrain.
  • Low Temps: Upper 40s Mon night, upper 50s Tue night, low 60s Wed-Thu nights, upper 50s Fri night. Cooler in sheltered areas and higher terrain.
  • Sky Cover: Mainly partly cloudy with hazy periods. Mostly cloudy Tue & Wed nights.
Weekend
  • Wind: N and light Sat, variable with breezy areas Sun.
  • Precipitation: Dry conditions expected.
  • High Temps: Mid 80s Sat, upper 80s Sun. Cooler in higher terrain.
  • Low Temps: Mid 60s Sat & Sun nights. Cooler in sheltered areas and higher terrain.
  • Sky Cover: Mostly clear with hazy periods.

Eastern Washington
Remainder of the Week
  • Wind: N and light Tue, becoming W with breezy areas Wed-Fri.
  • Precipitation: Dry conditions expected.
  • High Temps: Mid 70s Tue, low 80s Wed, mid 70s Thu-Fri. Warmer in the Lewis & Clark Valley.
  • Low Temps: Upper 40s Mon night, near 50 Tue night, mid 50s Wed night, low 50s Thu night, mid 50s Fri night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Partly cloudy Tue, mostly cloudy Wed-Thu, partly cloudy Fri. Hazy periods.
Weekend
  • Wind: N and light Sat, SW and light Sun.
  • Precipitation: Dry conditions expected.
  • High Temps: Near 80 Sat, mid 80s Sun. Warmer in the Lewis & Clark Valley.
  • Low Temps: Low 50s Sat night, mid 50s Sun night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly clear, hazy periods.

Western Washington
Remainder of the Week
  • Wind: Light and variable Tue, W with breezy areas Wed, SW and light Thu, W with breezy areas Fri.
  • Precipitation: Chance of rain Thu & Fri.
  • High Temps: Mid 70s Tue, low 70s Wed, near 70 Thu, upper 60s Fri. Cooler in higher terrain.
  • Low Temps: Low 50s Mon night, mid 50s Tue-Wed nights, upper 50s Thu night, mid 50s Fri night. Cooler in higher terrain.
  • Sky Cover: Partly cloudy Tue-Wed, mostly cloudy Thu-Fri.
Weekend
  • Wind: N and breezy along the coast Sat, NW and breezy Sun.
  • Precipitation: Dry conditions expected.
  • High Temps: Mid 70s Sat, upper 70s Sun. Cooler in higher terrain and on the coast.
  • Low Temps: Upper 50s Sat & Sun nights. Cooler in higher terrain.
  • Sky Cover: Mostly clear.

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Washington State University