AgWeatherNet Weekly Weather Outlook Monday Update for March 08 to March 14, 2021

Unsettled weather through Tuesday, clearing midweek

Mark Ingalls, AgWeatherNet Intern
Craig Oswald, AgWeatherNet Field Meteorologist

Synopsis:

Low pressure sliding down the West Coast is expected to continue to advect higher moisture air into the Pacific Northwest during the first half of the week. This will result in scattered rain and mountain snow showers, especially during the afternoon hours, through Tuesday. High pressure begins to spread over the region Thursday to bring drier conditions across Washington for the start of the weekend. Saturday afternoon rain and mountain snow chances increase again with a cold front crossing the state Saturday night into Sunday.

Discussion:

A robust upper low located off the Washington coast Monday morning continues to move southward. On the southern edge of the low there are a few weak shortwave disturbances moving into the state. Much like what was seen on Sunday, this combined with daytime heating and relatively low temperatures aloft, is expected to bring convective rain and mountain snow showers throughout the Pacific Northwest Monday and Tuesday, primarily in the afternoons and evenings. The highest chances of precipitation are in the mountains and west of the Cascades, with the lowest being in the Columbia Basin. With the convective nature of these showers, brief heavy rain, graupel, and small hail are possible at lower elevations. A few rumbles of thunder can't be ruled out, but very few of the showers will have lightning embedded within them.

By Wednesday, the low is expected to be making landfall on the coast south of San Francisco, taking shower activity with it. Behind the low, a ridge of high pressure builds across the Pacific Northwest to bring clearer skies and drier conditions. The ridge is expected to last through Friday and into Saturday.

The next round of rain may begin on the Olympic Peninsula as early as Saturday afternoon with a frontal boundary associated with a surface low pressure system moving into northern British Columbia from the west. This system should move eastward overnight and into the day Sunday, with rain and mountain snow showers even possible in the driest portions of the Columbia Basin. Heavy snow is possible with this event on mountain pass corridors, but there is considerable uncertainty so look for more details on that can be expected in the Friday outlook.

High temperatures this week are expected to be within a few degrees of average, but overnight lows may be consistently below average. This is especially true toward the end of the week when clearer skies are more likely. Below freezing temperatures are likely for much of the Eastern Washington lowlands most of the work week, with more sheltered areas such as around Naches, Moxee, and Winthrop possibly getting into the low- to mid-20s some nights. Light freeze conditions may also be seen in agricultural areas around the Puget Sound Region, especially for locations that are more than about 5-10 miles from the water.

Looking further ahead, by Sunday night upper air temperatures are indicated by some model guidance to be quite cold in association with the frontal passage. If guidance verifies, overnight low temperatures in the cold locations across fruit growing areas of Washington east of the Cascades have the potential to reach mid to upper teens. However, it is likely that stronger post frontal winds and residual cloud cover will greatly mitigate cold temperatures and inversion formation. Over night lows Sunday night and Monday night will likely remain within the low 20s. Please stay tuned for Fridays outlook where this topic will be reassessed with more up to date information.


Important Points About Next Week's Weather

South Central Washington
Remainder of the Week
  • Wind: Generally light & variable.
  • Precipitation: Isolated showers possible Mon-Tue.
  • High Temps: Mid 50s Tue-Thu, upper 50s Fri.
  • Low Temps: Near 30 Mon-Thu nights, low 30s Fri night.
  • Sky Cover: Decreasing clouds Tue, partly cloudy Wed-Fri.
Weekend
  • Wind: Generally S. Breezy to windy conditions possible Sun.
  • Precipitation: Chance of rain showers Sun.
  • High Temps: Near 60 Sat, upper 50s Sun.
  • Low Temps: Mid 30s Sat & Sun nights.
  • Sky Cover: Partly cloudy Sat, mostly cloudy to overcast Sun.

North Central Washington
Remainder of the Week
  • Wind: Generally light & variable.
  • Precipitation: Isolated rain and mountain snow Mon-Tue, highest chance in the mountains.
  • High Temps: Near 50 Tue-Thu, low 50s Fri. Cooler in higher terrain.
  • Low Temps: Upper 20s Mon-Thu nights, near 30 Fri night. Cooler in higher terrain and sheltered valleys.
  • Sky Cover: Partly to mostly cloudy Mon-Wed, clear Thu, partly cloudy Fri.
Weekend
  • Wind: Generally S. Breezy to windy conditions possible Sun.
  • Precipitation: Chance of rain and mountain snow Sun.
  • High Temps: Mid 50s Sat, low 50s Sun. Cooler in higher terrain.
  • Low Temps: Low 30s Sat & Sun nights. Cooler in higher terrain.
  • Sky Cover: Partly to mostly cloudy.

Eastern Washington
Remainder of the Week
  • Wind: Generally light & variable Mon-Tue. W with breezy areas Thu, SW and light Fri.
  • Precipitation: Isolated rain and mountain snow Mon-Wed.
  • High Temps: Upper 40s Tue, near 50 Wed-Fri. Warmer in the Lewis & Clark Valley.
  • Low Temps: Upper 20s Mon-Thu nights, near 30 Fri night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly cloudy Mon-Wed, partly cloudy Thu-Fri.
Weekend
  • Wind: Generally S. Breezy to windy conditions possible Sun.
  • Precipitation: Chance of rain and mountain snow Sun.
  • High Temps: Mid 50s Sat, near 50 Sun. Warmer in the Lewis & Clark Valley.
  • Low Temps: Low 30s Sat & Sun nights. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Partly cloudy Sat, mostly cloudy Sun.

Western Washington
Remainder of the Week
  • Wind: Generally light & variable except breezy on the coast Mon-Tue.
  • Precipitation: Isolated rain and mountain snow showers Mon-Wed.
  • High Temps: Low 50s Tue, near 50 Wed & Thu, low 50s Fri. Cooler in higher terrain.
  • Low Temps: Mid 30s Mon-Thu nights, upper 30s Fri night. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy Mon-Tue, partly cloudy Wed, mostly cloudy Thu-Fri.
Weekend
  • Wind: Widespread breezy to windy conditions possible. Generally W Sat, S Sun.
  • Precipitation: Chance of rain and mountain snow beginning Sat PM.
  • High Temps: Low 50s Sat, upper 40s Sun. Cooler in higher terrain.
  • Low Temps: Upper 30s Sat night, mid 30s Sun night. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast.

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Washington State University