AgWeatherNet Weekly Weather Outlook Monday Update for 10 May to 16 May 2021

Dry week with possible showers this weekend

Mark Ingalls, AgWeatherNet Intern

Synopsis:

Warmer temperatures are forecast this week thanks to a ridge of high pressure building over the region. Northwesterly flow at the surface and aloft may keep increased cloud cover over parts of Western Washington, otherwise mostly clear skies are expected. Wednesday, a shortwave trough transits British Columbia and may bring a few showers to mainly mountain regions north of US 2 and breezy conditions to typical windy spots statewide. A more zonal pattern following the shortwave should put a cap to the warming trend, with temperatures generally holding through Friday. Into the weekend, an upper level trough is expected to become the dominant weather feature bringing with it somewhat cooler temperatures and a chance of rain showers for some.

Discussion:

The Pacific Northwest is coming under the influence of an upper level ridge moving in from the Pacific Ocean. The region is forecast to lie on the east side of the ridge axis through Tuesday which will keep northwest flow aloft. This will continue to provide increased cloud cover for parts of Western Washington with more cloudiness closer to the coast and along mountain crests. Otherwise, look for partly cloudy skies.

Temperatures are expected to rise with the warming trend peaking Wednesday. This is when a shortwave trough is forecast to move across southern British Columbia, flattening the ridge and placing the region under more westerly flow. A few showers are possible but should be restricted mainly to mountain regions to the north of US Highway 2 (which runs from Everett to Spokane). Breezy conditions are expected from this trough in typical windy spots throughout Washington, including the Strait of Juan de Fuca, Kittitas Valley, Columbia Gorge, and Columbia Basin.

Temperatures Thursday and Friday are forecast to be similar to Wednesday thanks to modest onshore flow coming straight off the Pacific Ocean. Some low level stratus may linger under this regime, mainly west of Interstate 5, which would keep more mild temperatures closer to the coast. Otherwise, highs are expected to peak in the 70s along I-5 from Seattle southward with warmer Eastern Washington locations in the mid 80s.

Over the weekend, an upper level trough digging southward should replace the ridge. This would bring in increased cloud cover, cooler temperatures, locally breezy conditions, and a chance of rain showers. There is quite a bit of disagreement within the models with just how much rain the state can expect from this setup but given the ongoing dry trend it seems reasonable to favor the drier solution. Using that, rainfall will likely be light with some showers in Western Washington and mountainous parts of the state Saturday and Sunday.


Important Points About Next Week's Weather

South Central Washington
Remainder of the Week
  • Wind: Light and variable Tue, N and breezy Wed, NW with breezy areas Thu, becoming SW Fri.
  • Precipitation: Dry conditions expected.
  • High Temps: Near 80 Tue, mid 80s Wed-Fri.
  • Low Temps: Mid 40s Mon night, near 50 Tue night, low 50s Wed-Fri nights. Cooler in sheltered areas.
  • Sky Cover: Partly cloudy.
Weekend
  • Wind: SW and breezy Sat & Sun.
  • Precipitation: Dry conditions expected.
  • High Temps: Upper 70s Sat & Sun.
  • Low Temps: Upper 40s Sat & Sun nights. Cooler in sheltered areas.
  • Sky Cover: Partly to mostly cloudy.

North Central Washington
Remainder of the Week
  • Wind: Light and variable Tue, N with breezy areas Wed, NW and generally light Thu, becoming SW Fri.
  • Precipitation: Low chance of upslope showers Wed.
  • High Temps: Upper 70s Tue, near 80 Wed-Fri. Cooler in higher terrain.
  • Low Temps: Upper 40s Mon night, low 50s Tue-Fri nights. Cooler in higher terrain and sheltered areas.
  • Sky Cover: Partly cloudy Tue, mostly cloudy Wed, partly cloudy Thu-Fri.
Weekend
  • Wind: W and breezy Sat & Sun.
  • Precipitation: Chance of upslope showers.
  • High Temps: Mid 70s Sat, upper 70s Sun. Cooler in higher terrain.
  • Low Temps: Upper 40s Sat & Sun nights. Cooler in higher terrain and sheltered areas.
  • Sky Cover: Partly to mostly cloudy.

Eastern Washington
Remainder of the Week
  • Wind: Light and variable Tue, N and breezy Wed, NW with breezy areas Thu, becoming SW Fri.
  • Precipitation: Low chance of upslope showers north of Spokane Wed.
  • High Temps: Low 70s Tue, mid 70s Wed, upper 70s Thu-Fri. Warmer in the Lewis & Clark Valley.
  • Low Temps: Low 40s Mon night, mid 40s Tue night, upper 40s Wed-Fri nights. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Partly cloudy Tue, mostly cloudy Wed, partly cloudy Thu and Fri.
Weekend
  • Wind: SW and breezy Sat & Sun.
  • Precipitation: Chance of rain, mainly in upslope locations.
  • High Temps: Low 70s Sat & Sun. Warmer in the Lewis & Clark Valley.
  • Low Temps: Mid 40s Sat & Sun nights. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Partly to mostly cloudy.

Western Washington
Remainder of the Week
  • Wind: Light and variable Tue, NW and breezy through the strait Wed, W Thu, W with breezy areas Fri.
  • Precipitation: Chance of rain N of Everett Wed.
  • High Temps: Upper 60s Tue, near 70 Wed-Fri. Cooler in higher terrain and along the coast.
  • Low Temps: Mid 40s Mon night, near 50 Tue-Fri nights. Cooler in higher terrain.
  • Sky Cover: Partly to mostly cloudy. Increased cloud coverage closer to the coast.
Weekend
  • Wind: W with breezy areas Sat & Sun.
  • Precipitation: Chance of rain showers.
  • High Temps: Mid 60s Sat & Sun. Cooler in higher terrain.
  • Low Temps: Upper 40s Sat & Sun nights. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy.

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