AgWeatherNet Weekly Outlook for October 12 to October 18, 2020

Regional rain and wind event Tuesday followed by calming conditions

Mark Ingalls, AgWeatherNet Intern
Joe Zagrodnik, AgWeatherNet Postdoctral Research Associate

Synopsis:

The last of this set of frontal systems is expected cross Washington overnight Monday into Tuesday, bringing rain and strong winds to much of the state. Cooler temperatures and lowered snow levels will follow this front, but by the time that happens much of the precipitation will have ended. Wednesday begins a stretch of drier conditions for most, with a ridge of high pressure building offshore through the end of the week. High temperatures are expected to remain within a few degrees of average through the weekend, with the northeast quarter of the state possibly getting below freezing some nights.

Discussion:

Light rain showers in Western Washington are possible through Monday, primarily in and near the Cascades and Olympics. Breezy conditions should prevail through the day in the Columbia Basin and adjacent valleys, but things in that part of the state should remain dry during the daytime hours. A potent frontal system is forecasted to begin impacting the region Monday night. This is associated with a low pressure system that is expected to have a minimum central pressure below 995 mb as it makes landfall in the midsection of Vancouver Island. The track and intensity of this low suggests a moderate windstorm is possible Tuesday afternoon.

Rain from this front could begin falling on the Coast as early as Monday evening as it quickly progresses eastward to bring rain to the I-5 Corridor overnight and much of Eastern Washington by sunrise. Look for rainfall values in the Western Washington lowlands to range from a half inch to an inch, with Eastern Washington lowlands possibly seeing from a tenth of an inch near the Tri-Cities to half an inch in the northern Columbia Basin and on the Palouse.

The front is expected to cause winds to shift from generally southerly to westerly, and with that shift will also come an increase in velocity. By Tuesday morning, the strongest winds should be in the South Sound, Strait of Juan de Fuca, and Bellingham areas, with gusts reaching to 50 mph in spots. As it passes into Eastern Washington and beyond during the afternoon hours, the strongest winds will move into the Columbia Basin and Palouse where gusts to 60 mph are possible. Exposed locations such as ridgetops, and treeless areas will see the worst conditions.

A light breeze is possible for the Columbia Basin, Palouse, and Strait of Juan de Fuca areas Wednesday, but this will only come with gusts to 25 mph at times. Lingering showers are also possible, but these will be limited to the Cascades generally north of Interstate 90. High temperatures will remain within a few degrees of average following the frontal passage, except in higher elevations where things will be much cooler compared to average.

Temperatures reaching below freezing are possible in some valleys north of Spokane Wednesday morning, spreading to include most of the northeast quarter of the state and the Palouse Thursday morning. Both lows and highs begin to rise Friday as the ridge offshore continues to build, but nocturnal inversions could keep some valleys north of US 2 getting below 32 through the weekend. Dry conditions are expected through the weekend, though some models are trying to bring another storm system into the region during that period. Models should have this resolved with more consensus by the Friday outlook, so a more certain forecast will be provided then.


Important Points About Next Week’s Weather

South Central Washington
Remainder of the week
  • Wind: Southerly through Tue AM, becoming westerly through Thu, then light and variable. Breezy Mon, windy Tue with gusts to 60 mph in spots, breezy Wed.
  • Precipitation: Rain showers possible Mon night & Tue. Otherwise dry.
  • High Temps: Low 70s Mon, mid 60s Tue & Wed, near 60 Thu, mid 60s Fri.
  • Low Temps: Low 50s Mon night, mid 40s Tue night, near 40 Wed night, mid 40s Thu night & Fri night.
  • Sky Cover: Partly cloudy to overcast Mon-Tue. Clear to partly cloudy Wed-Fri.
Weekend
  • Wind: Southerly through the weekend. Breezy conditions possible Sat & Sun.
  • Precipitation: Low chance of showers during the weekend, dependent on storm track.
  • High Temps: Mid 60s Sat & Sun.
  • Low Temps: Mid 40s Sat night & Sun night.
  • Sky Cover: Partly to mostly cloudy Sat-Sun.

North Central Washington
Remainder of the week
  • Wind: Southerly through Tue AM, becoming westerly through Thu, then light and variable. Breezy Mon, windy Tue with gusts to 60 mph in the Basin, breezy Wed.
  • Precipitation: Rain showers possible Mon night & Tue. Otherwise dry.
  • High Temps: Mid 60s Mon-Thu, upper 60s Fri. Cooler in higher terrain.
  • Low Temps: Mid 40s Mon night-Thu night, near 50 Fri night. Cooler in higher terrain.
  • Sky Cover: Partly cloudy to overcast Mon-Tue. Clear to partly cloudy Wed-Thu. Partly to mostly cloudy Fri.
Weekend
  • Wind: Southerly through the weekend. Breezy conditions possible Sat & Sun.
  • Precipitation: Low chance of showers during the weekend, dependent on storm track.
  • High Temps: Mid 60s Sat-Sun. Cooler in higher terrain.
  • Low Temps: Mid 40s Sat night & Sun night. Cooler in higher terrain.
  • Sky Cover: Partly to mostly cloudy.

Eastern Washington
Remainder of the week
  • Wind: Southerly through Tue AM, becoming westerly through Thu, then light and variable. Breezy Mon, windy Tue with gusts to 60 mph in spots, breezy Wed.
  • Precipitation: Rain showers possible Mon night & Tue. Otherwise dry.
  • High Temps: Near 60 Mon & Tue, upper 50s Wed & Thu, near 60 Fri. Warmer in the Lewis and Clark Valley.
  • Low Temps: Mid 40s Mon night, upper 30s Tue night, low 30s Wed night, mid 30s Thu night, upper 30s Fri night. Warmer in the Lewis and Clark Valley.
  • Sky Cover: Partly cloudy to overcast Mon-Tue, clear to mostly cloudy Wed-Fri. Patchy morning fog Wed-Fri.
Weekend
  • Wind: Southerly through the weekend. Breezy conditions possible Sat & Sun.
  • Precipitation: Low chance of showers during the weekend, dependent on storm track.
  • High Temps: Low 60s Sat & Sun. Warmer in the Lewis and Clark Valley.
  • Low Temps: Upper 30s Sat night & Sun night. Warmer in the Lewis and Clark Valley.
  • Sky Cover: Partly to mostly cloudy Sat & Sun.

Western Washington
Remainder of the week
  • Wind: Southerly through Tue AM, becoming westerly through Thu, then light and variable. Breezy Mon, windy Tue with gusts to 50 mph in spots.
  • Precipitation: Showers Mon, mainly near mountains. Rain Mon night & Tue. Leftover showers possible Wed, mainly near mountains. Dry Thu, low chance of showers Fri.
  • High Temps: Near 60 Mon-Fri. Cooler in higher terrain.
  • Low Temps: Near 50 Mon night & Tue night. Mid 40s Wed night & Thu night. Near 50 Fri night. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast Mon-Wed. Partly to mostly cloudy Thu & Fri.
Weekend
  • Wind: Southerly through the weekend. Locally breezy conditions possible Sat & Sun.
  • Precipitation: Low chance of showers during the weekend, dependent on storm track.
  • High Temps: Near 60 Sat & Sun. Cooler in higher terrain.
  • Low Temps: Near 50 Sat night & Sun night. Cooler in higher terrain.
  • Sky Cover: Partly to mostly cloudy Sat & Sun.

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Washington State University