AgWeatherNet Weekly Weather Outlook for March 19 to March 25, 2021

Active week ahead with multiple systems from the northwest expected

Mark Ingalls, AgWeatherNet Intern
Joe Boomgard-Zagrodnik, AgWeatherNet Postdoctoral Research Associate
Craig Oswald, AgWeatherNet Field Meteorologist

Special note:

AgWeatherNet is providing daily spring frost forecasts. This service is aimed at tree fruit growers in Central Washington and will be available to the public online under the Spring Frost Program section at weather.wsu.edu. AgWeatherNet thanks WSTFA for financially supporting the Spring Frost Program.

Synopsis:

Unsettled weather is expected to last in the Pacific Northwest through the weekend with higher chances of showers in Western Washington and mountainous regions and snow levels ranging as low as 1500 feet, and up to 3000+ feet. Windy conditions are expected throughout the Columbia Basin and surrounding areas Saturday. With northwesterly flow aloft chances of rain and mountain snow will remain most days in and west of the Cascades with even a low chance of showers in the Columbia Basin Monday thanks to an upper disturbance. Toward the end of the forecast period it appears a stronger frontal boundary will cross the state in the Wednesday to Thursday time frame, but guidance remain inconsistent on timing of this system.

Discussion:

Low pressure centered off the coast Friday morning was providing showery conditions in and west of the mountains during the day. Some of these showers were fairly strong, and a couple tornado warnings were even issued by the National Weather Service in Seattle for along the coast north of Aberdeen for possible waterspouts coming onshore. Overnight, the low is expected to transition into more of an upper level trough as it passes over Washington.

Shower activity is expected to decrease in Western Washington with the trough axis crossing the Cascades Saturday morning. The exception to this is the Puget Sound Convergence Zone, which is expected to fire up during the afternoon. Models indicate that PSCZ precipitation should start around the latitude of Everett before slipping south toward northern King County before dissipating after sunset. A few convective showers are possible in Eastern Washington under the trough, but the main impact will be strong winds in the Columbia Basin and in the greater Spokane area. Gusts may reach above 40 mph at times, with the highest winds being in exposed areas such as open fields and ridgetops.

Widespread rain and mountain snow moves back into Western Washington from the northwest during the day Sunday, with shower activity reaching east of the Cascades overnight and into Monday. Snow levels are expected to be below pass level for most of this event, allowing for perhaps more than six inches of snow for the major mountain passes. Plan for adverse travel conditions in the mountains Sunday and Sunday night.

Ridging begins to build over the Pacific Northwest Monday but with a modest amount of moisture embedded within it isolated to scattered rain and snow showers are expected to continue in mountainous areas and Western Washington. Arid regions of the state should remain dry until Wednesday when an upper disturbance crossing British Columbia flattens out the ridge to provide a chance for isolated convective showers in Eastern Washington. More widespread yet scattered rain showers can be expected by Wednesday evening and into the overnight before trending dry.

Northwesterly flow aloft will continue to close out the week with a ridge rebuilding by the following weekend.


8 to 14 Day Outlook, March 26 to April 01, 2021
  • Near average temperatures and below average precipitation are favored for the period.

Important Points About Next Week's Weather

South Central Washington
Weekend
  • Wind: Generally SW, windy Sat with gusts to 40+ mph.
  • Precipitation: Isolated light rain afternoons through the weekend.
  • High Temps: Upper 50s Sat, mid 50s Sun.
  • Low Temps: Mid 30s Fri night, low 30s Sat night, mid 30s Sun night.
  • Sky Cover: Partly to mostly cloudy.
Next Week
  • Wind: S becoming W & breezy Mon, W Tue & Wed, becoming SW and windy Thu.
  • Precipitation: Low chance of light rain Mon & Wed.
  • High Temps: Upper 50s Mon & Tue, Near 60 Wed & Thu.
  • Low Temps: Mid 30s Mon night, upper 30s Tue-Thu nights.
  • Sky Cover: Partly to mostly cloudy.

North Central Washington
Weekend
  • Wind: Generally W, breezy in the basin Sat.
  • Precipitation: Low chance of light rain and mountain snow.
  • High Temps: Mid 50s Sat, near 50 Sun. Cooler in higher terrain.
  • Low Temps: Mid 30s Fri-Sun nights. Cooler in higher terrain.
  • Sky Cover: Partly cloudy Sat, mostly cloudy Sun.
Next Week
  • Wind: S becoming W & breezy in the Basin Mon, W Tue & Wed, becoming SW and windy in the Basin Thu.
  • Precipitation: Chance of rain and mountain snow Mon & Wed.
  • High Temps: Mid 50s Mon-Thu. Cooler in higher terrain.
  • Low Temps: Low 30s Mon night, mid 30s Tue-Thu nights. Cooler in higher terrain.
  • Sky Cover: Partly to mostly cloudy.

Eastern Washington
Weekend
  • Wind: Generally SW. Windy Sat with gusts to 40 mph.
  • Precipitation: Low chance of rain in the afternoons, low chance of rain/snow Sun night.
  • High Temps: Low 50s Sat, upper 40s Sun. Warmer in the Lewis & Clark Valley.
  • Low Temps: Low 30s Fri night, near 30 Sat night, low 30s Sun night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly cloudy.
Next Week
  • Wind: S becoming W & breezy Mon, W Tue & Wed, becoming SW and windy Thu.
  • Precipitation: Chance of rain Mon, Wed, & Thu.
  • High Temps: Near 50 Mon, low 50s Tue-Thu. Warmer in the Lewis & Clark Valley.
  • Low Temps: Upper 20s Mon night, low 30s Tue night, mid 30s Wed-Thu night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly cloudy Mon, partly cloudy Tue, mostly cloudy Wed-Thu.

Western Washington
Weekend
  • Wind: S becoming W Sat and with breezy areas on the Coast/Strait.
  • Precipitation: Rain & mountain snow.
  • High Temps: Near 50 Sat, upper 40s Sun. Cooler in higher terrain.
  • Low Temps: Upper 30s Fri night, mid 30s Sat-Sun nights. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast.
Next Week
  • Wind: SW Mon-Tue becoming W for Wed-Thu. Periodically breezy areas, mainly on the Coast, along the Strait, and in the South Sound.
  • Precipitation: Rain and mountain snow through the week. Likely Mon, low chance Tue, chance Wed-Thu.
  • High Temps: Near 50 Mon, low 50s Tue-Thu. Cooler in higher terrain.
  • Low Temps: Low 30s Mon night, mid 30s Tue-Thu nights. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast.

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