AgWeatherNet Weekly Weather Outlook for June 28 to July 4, 2021

Extreme heat drawing to a close but above average temperatures continue

Mark Ingalls, AgWeatherNet Intern

Note: In observation of Independence Day, next week’s AgWeatherNet Outlook will be issued on Tuesday instead of Monday.

Synopsis:

Monday is bringing another day of extreme heat to most locations in Washington. The surface trough responsible for drawing heat into the western half of the state will move eastward overnight resulting in marine flow west of the Cascades and cooler temperatures Tuesday. Some areas may also experience low clouds with more widespread cloud cover in the morning. East of the Cascades, Tuesday is likely to be the hottest day before the surface trough continues eastward Wednesday bringing in moderated temperatures and breezy areas. Since the Pacific Northwest will continue to be under the influence of an upper level ridge producing south to southwesterly flow aloft, temperatures are forecast to remain above average (except along the coast) and precipitation is not expected.

Discussion:

Monday started with a thermal trough situated along the coast and a closed low moving north offshore. The pressure gradient resulting from these drove winds out of the east into Western Washington bringing extreme temperatures all the way to the coast. The trough is moving slowly eastward with areas to the west of it beginning to enjoy onshore flow and much cooler conditions but the Puget Sound Region is likely to see its hottest day of the week. By evening, the trough is forecast to be nearing Interstate 5. Tuesday morning, the marine push should have made it clear to the Cascades with low clouds possible along the coast and in the southwest interior.

As the trough passes into Eastern Washington, Tuesday will likely be the hottest day of the week there. It remains possible that a new all-time high for Washington state is set. The current value is 118 set in 1961 at Ice Harbor Dam and 1928 near present-day Vernita Bridge. Highs above 110 will be common In the southeastern quarter of the state both Monday and Tuesday with most lowland areas elsewhere above 100. Some readings around 120 are possible in typical warm spots near the Tri-Cities.

Tuesday night into Wednesday the thermal trough continues east allowing the marine push will make it through the remainder of the state. Wednesday will look similar to Tuesday to the west of the Cascades, but for Eastern Washington a slow cooling trend will begin. Still, this places the Columbia Basin, Yakima Valley, and surrounding areas above 100 with a few readings above 110. Breezy westerlies are expected through the mountain gaps and in the Columbia Basin are likely Wednesday as cross-state pressure gradients tighten behind the thermal trough. Locally strong winds may last into Thursday.

Look for much of the same Thursday through Independence Day as the Pacific Northwest sits under the influence of an upper level ridge to the east. Some monsoonal moisture may be injected into mountainous regions in the far southeastern part of the state, otherwise dry conditions are forecast with above average temperatures. Off and on low clouds along the Coast will probably keep them cooler. These clouds may make it a couple dozen miles inland some mornings, but should clear out by afternoon.


8 to 14 Day Outlook, July 5 to July 11, 2021
  • Above average temperatures and below average precipitation are favored for the period.

Important Points About Next Week's Weather

South Central Washington
Remainder of the Week
  • Wind: Becoming W Tue night, breezy areas Wed & Thu.
  • Precipitation: Dry conditions expected.
  • High Temps: Mid 110s to near 120 Tue, low 110s Wed, upper 100s Thu, mid 100s Fri.
  • Low Temps: Near 80 Mon night, mid 70s Tue-Wed night, low 70s Thu-Fri nights.
  • Sky Cover: Mostly clear.
Weekend
  • Wind: Generally SW, breezy Sun.
  • Precipitation: Dry conditions expected.
  • High Temps: Mid 100s Sat-Sun.
  • Low Temps: Low 70s Sat-Sun nights.
  • Sky Cover: Mostly clear.

North Central Washington
Remainder of the Week
  • Wind: Becoming W Tue night, breezy areas Wed & Thu.
  • Precipitation: Dry conditions expected.
  • High Temps: Mid to upper 110s Tue, mid 110s Wed, upper 100s Thu, mid 100s Fri. Cooler in higher terrain.
  • Low Temps: Low 80s Mon-Tue nights, upper 70s Wed night, low 70s Thu-Fri nights. Cooler in higher terrain and sheltered areas.
  • Sky Cover: Mostly clear.
Weekend
  • Wind: Generally SW, breezy Sun.
  • Precipitation: Dry conditions expected.
  • High Temps: Mid 100s Sat & Sun. Cooler in higher terrain.
  • Low Temps: Low 70s Sat-Sun nights. Cooler in higher terrain and sheltered areas.
  • Sky Cover: Mostly clear.

Eastern Washington
Remainder of the Week
  • Wind: Becoming W Tue night, breezy areas Wed & Thu.
  • Precipitation: Dry conditions expected.
  • High Temps: Around 110 Tue, upper 100s Wed, mid 100s Thu, near 100 Fri. Hotter in the Lewis & Clark Valley.
  • Low Temps: Low 70s Mon night, mid 70s Tue-Wed nights, near 70 Thu-Fri nights. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly clear.
Weekend
  • Wind: Generally SW, breezy Sun.
  • Precipitation: Dry conditions expected.
  • High Temps: Near 100 Sat & Sun. Hotter in the Lewis & Clark Valley.
  • Low Temps: Near 70 Sat & Sun nights. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly clear.

Western Washington
Remainder of the Week
  • Wind: Generally W, breezy periods through the Strait.
  • Precipitation: Dry conditions expected.
  • High Temps: Low 90s Tue, mid 80s Wed-Fri. Cooler in higher terrain and on the coast.
  • Low Temps: Upper 60s Mon night, mid 60s Tue night, low 60s Wed-Fri nights. Cooler in higher terrain.
  • Sky Cover: Mostly clear except low clouds along the coast. Some interior areas may see low clouds in the mornings.
Weekend
  • Wind: Generally W, breezy periods through the Strait.
  • Precipitation: Dry conditions expected.
  • High Temps: Upper 80s Sat-Sun. Cooler in higher terrain and on the coast.
  • Low Temps: Low 60s Sat-Sun nights. Cooler in higher terrain.
  • Sky Cover: Mostly clear except low clouds along the coast. Some interior areas may see low clouds in the mornings.

Like us on Facebook at https://www.facebook.com/AgWeatherNet
Follow us on Twitter at https://www.twitter.com/AgWeatherNet
Washington State University