AgWeatherNet Weekly Weather Outlook Monday Update for January 04 to January 10, 2021

Repeated frontal passages to keep rain and snow chances in Washington for most of the week

Mark Ingalls, AgWeatherNet Intern
Craig Oswald, Field Meteorologist

Synopsis:

The frontal passage responsible for bringing rain and mountain snow to the state during the day Monday will continue eastward overnight. Behind the front, snow levels are expected to drop below pass level as precipitation tapers off. Tuesday should start off dry, but a shortwave trough is expected to reach the region during the afternoon hours, spreading rain and mountain snow east across Washington Tuesday evening through Wednesday. Some lingering showers are possible in the Cascades Wednesday night and Thursday as a separate yet small upper disturbance moves into northern Oregon, promoting unsettled conditions. Another front moves into the Pacific Northwest on Friday with the low pressure center skirting northwest Washington and bringing more chances of rain and mountain snow with lingering showers for parts of the state Saturday. Sunday should be dry, except in Western Washington and the Cascades.

Discussion:

Monday started off with a warm front lifting rain and mountain snow north through Washington state, followed by a cold front pushing more precipitation eastward. The warm front rose snow levels in many mountain locations to above 4,000 feet but following the cold front they are expected to drop again to the 2,000-2,500 foot range. Precipitation should taper off heading into the evening hours, with some lingering postfrontal showers in Western Washington and the mountains. A few inches of extra snow are possible in the Cascades during the postfrontal activity, but most of Monday’s accumulation will result from snow that fell during the day.

A ridge of high pressure slides across the state Monday night and Tuesday morning to provide a brief drying period before an upper level trough brings a surface cold front across the state beginning that afternoon. Precipitation from this front will begin on the coast and move eastward into the day Wednesday with a few showers even possible in the Columbia Basin. This should be mainly a snow event for the major Cascade passes, and temperatures may be cool enough to produce snow east of the Cascades generally north of Connell. Another round of postfrontal showers are expected in the wake of this front in and west of the Cascades on Wednesday. A small upper disturbance anticipated to move across northern Oregon Wednesday will also help provide forcing for sustained scattered precipitation across the southern one third of Washington.

Dry conditions look to be in the cards for nearly all Washington locations on Thursday thanks to a quickly passing ridge, but Friday brings in another system to spread rain and mountain snow across the state into Saturday. Modest rainfall values are again expected in the Columbia Basin with some additional snow in the Cascades. Northern reaches of the Columbia Basin as well as the Palouse may also see a bit of mixed precipitation, especially toward the evening hours, before trending dry through the overnight.


Important Points About Next Week's Weather

South Central Washington
Remainder of the Week
  • Wind: Mainly S Mon-Wed, breezy Mon & Tue. N/NE Thu & Fri.
  • Precipitation: Rain tapering off Mon PM. Rain chances Tue night-Wed night and Fri night.
  • High Temps: Near 50 Mon & Tue, upper 40s Wed & Thu, low 40s Fri.
  • Low Temps: Mid 30s Mon night, upper 30s Tue night, mid 30s Wed night, low 30s Thu & Fri nights.
  • Sky Cover: Mostly cloudy Mon, partly cloudy Tue, mostly cloudy Wed, partly cloudy Thu, mostly cloudy Fri.
Weekend
  • Wind: Generally S.
  • Precipitation: Generally S.
  • High Temps: Low 40s Sat & Sun.
  • Low Temps: Low 30s Sat night & Sun night.
  • Sky Cover: Mostly cloudy.

North Central Washington
Remainder of the Week
  • Wind: Mainly S Mon-Wed, breezy Mon & Tue. N/NE Thu & Fri, breezy Fri.
  • Precipitation: Mountain rain/snow showers possible through the week. Lowland rain tapering off Mon night, likely Tue night tapering off Wed, chance of lowland rain and AM snow Fri.
  • High Temps: Mid 40s Mon & Tue, low 40s Wed & Thu, near 40 Fri. Cooler in higher terrain.
  • Low Temps: Near 30 Mon night, low 30s Tue & Wed nights, near 30 Thu & Fri nights. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy Mon-Wed, partly cloudy Thu, mostly cloudy Fri.
Weekend
  • Wind: Generally S/SE/E (dependent on terrain).
  • Precipitation: Chance of showers Sat.
  • High Temps: Upper 30s Sat & Sun. Cooler in higher terrain.
  • Low Temps: Upper 20s Sat night & Sun night. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy.

Eastern Washington
Remainder of the Week
  • Wind: Mainly S Mon-Wed, breezy Mon & Tue. N/NE Thu & Fri, breezy Fri.
  • Precipitation: Rain tapering off Mon. Rain/snow likely Tue night-Wed night.
  • High Temps: Low 40s Mon & Tue, near 40 Wed & Thu, upper 30s Fri. Warmer in the Lewis & Clark Valley.
  • Low Temps: Near 30 Mon night, low 30s Tue & Wed night, upper 20s Thu & Fri night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly cloudy to cloudy.
Weekend
  • Wind: Generally S/SE/E (dependent on terrain).
  • Precipitation: Rain and possible snow Sat.
  • High Temps: Mid 30s Sat & Sun. Warmer in the Lewis & Clark Valley.
  • Low Temps: Upper 20s Sat night & Sun night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly cloudy to cloudy.

Western Washington
Remainder of the Week
  • Wind: Generally S through Wed. Breezy in areas Mon & Tue. E Thu & Fri, widespread breezy areas Fri.
  • Precipitation: Rain and mountain snow showers through Wed night, resuming Thu night.
  • High Temps: Upper 40s Mon & Tue, near 50 Wed, upper 40s Thu & Fri. Cooler in higher terrain.
  • Low Temps: Near 40 Mon night, low 40s Tue night, near 40 Wed-Fri nights. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast.
Weekend
  • Wind: Generally S. Breezy on the Coast and in the NW Interior.
  • Precipitation: Rain and mountain snow showers possible.
  • High Temps: Upper 40s Sat & Sun. Cooler in higher terrain.
  • Low Temps: Upper 30s Sat & Sun nights. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast.

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