AgWeatherNet Weekly Weather Outlook Monday Update for April 19 to April 25, 2021

Sunny and warm through Wednesday, becoming more active for the weekend

Mark Ingalls, AgWeatherNet Intern
Craig Oswald, AgWeatherNet Field Meteorologist

Synopsis:

The ridge of high pressure over the West Coast is expected to rebuild following an upper disturbance slipping into the Great Basin through Tuesday. In most of the state, this will result in sunny skies and seasonably warm temperatures. Thursday, northwest upper level flow becomes stronger with an increase in clouds (especially west of the Cascades) while a surface cold front clips the eastern half of the state. Friday into Saturday, the ridge pushes eastward to bring a closed low and southwest flow over the Pacific Northwest, bringing the first chance of widespread shower activity in a couple weeks.

Discussion:

Mostly sunny skies are expected throughout much of Washington through Wednesday and through Friday east of the Cascades under a ridge of high pressure. Along the coast, light onshore winds are likely to bring in some low level stratus, possibly extending to the I-5 corridor during the morning hours. Otherwise, look for light winds in most locations with some areas in Eastern Washington likely dipping below freezing Monday night.

A warming trend begins Tuesday for the eastern half of the state with highs reaching the upper 70s by Thursday. Overnight lows will also slowly rise, but there is a risk for frost in many sheltered areas. For further details, please see the Spring Frost Program in the sidebar on this website. West of the Cascades, highs will remain steady with some areas reaching above 70 Tuesday and Wednesday.

Flow aloft becomes stronger and northwesterly Thursday which is likely to increase cloud cover throughout the region with a few upslope showers in mountainous areas. Snow levels are expected to be above 5000 feet, so travel impacts in the mountains will be limited if any. Increased cloud cover should bring cooler daytime temperatures to the I-5 corridor. A shortwave trough and another cold surge moving south along the Canadian Rockies into Montana and the Upper Midwest is likely to send another northeasterly cold front through Eastern Washington on Thursday. With the continental origin of this frontal boundary, this will be another dry disturbance with the largest impact being breezy to windy northeast winds. A modest drop in temperatures is expected Friday.

A pronounced southwesterly wind shift in the upper levels late Friday will help to maintain higher moisture air throughout the state. And paired with an approaching cold front, widespread rain is anticipated to reach the coast Friday evening and move eastward across Washington through Saturday. Snow levels behind the front are currently expected to drop to around 4500 feet which may bring some snow to the higher passes. Rain is expected Saturday in Western Washington lowlands, with shower activity possible in Eastern Washington. On Sunday, there is a chance of convective showers in the postfrontal environment west of the Cascades along with some leftover shower activity to the east. Model guidance suggests that this active weather pattern will continue into the first half of next week with continue chances for precipitation statewide.


Important Points About Next Week's Weather

South Central Washington
Remainder of the Week
  • Wind: NE with breezy areas Tue, W Wed, NW with breezy areas Thu, S and light Fri.
  • Precipitation: Dry conditions expected.
  • High Temps: Low 70s Tue, mid 70s Wed, upper 70s Thu, mid 70s Fri.
  • Low Temps: Low 30s Mon night, mid 30s Tue night, low 40s Wed night, mid 40s Thu night, upper 40s Fri night. Cooler in sheltered areas.
  • Sky Cover: Clear to partly cloudy through Fri.
Weekend
  • Wind: W and breezy Sat, S Sun.
  • Precipitation: Chance of rain showers Sat & Sun.
  • High Temps: Low 70s Sat, upper 60s Sun.
  • Low Temps: Upper 40s Sat night, mid 40s Sun night.
  • Sky Cover: Mostly cloudy.

North Central Washington
Remainder of the Week
  • Wind: NE with breezy areas Tue, W Wed, NW with breezy areas Thu, S and light Fri.
  • Precipitation: Low chance of upslope showers Thu.
  • High Temps: Near 70 Tue, mid 70s Wed & Thu, low 70s Fri. Cooler in higher terrain.
  • Low Temps: Mid 30s Mon night, upper 30s Tue night, low 40s Wed-Thu nights, mid 40s Fri night. Cooler in higher terrain and sheltered areas.
  • Sky Cover: Clear to partly cloudy.
Weekend
  • Wind: W and breezy Sat, S Sun.
  • Precipitation: Chance of rain and high elevation snow.
  • High Temps: Upper 60s Sat, mid 60s Sun. Cooler in higher terrain.
  • Low Temps: Mid 40s Sat-Sun nights. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy.

Eastern Washington
Remainder of the Week
  • Wind: NE with breezy areas Tue, W Wed, NW with breezy areas Thu, S and light Fri.
  • Precipitation: Low chance of showers Thu.
  • High Temps: Mid 60s Tue, near 70 Wed-Thu, mid 60s Fri. Warmer in the Lewis & Clark Valley.
  • Low Temps: Near 30 Mon night, low 30s Tue night, upper 30s Wed night, mid 30s Thu night, upper 30s Fri night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Partly cloudy.
Weekend
  • Wind: W and breezy Sat, S Sun.
  • Precipitation: Chance of rain.
  • High Temps: Mid 60s Sat, near 60 Sun. Warmer in the Lewis & Clark Valley.
  • Low Temps: Near 40 Sat night, upper 30s Sun night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly cloudy.

Western Washington
Remainder of the Week
  • Wind: Light and variable Tue & Wed, W with breezy areas Thu, S with breezy areas Fri.
  • Precipitation: Chance of rain and mountain snow Thu.
  • High Temps: Near 70 Tue-Wed, mid 60s Thu-Fri. Cooler in higher terrain.
  • Low Temps: Upper 40s Mon-Fri nights. Cooler in higher terrain.
  • Sky Cover: Partly cloudy Mon-Wed, mostly cloudy Thu-Fri.
Weekend
  • Wind: S Sat, becoming W Sun.
  • Precipitation: Rain and mountain snow.
  • High Temps: Upper 50s Sat & Sun. Cooler in higher terrain.
  • Low Temps: Upper 40s Sat & Sun nights. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast.

Washington State University