AgWeatherNet Weekly Outlook for November 06 to November 12, 2020

Active weather continues for most of the next week

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

Synopsis:

This week looks to be dominated by repeated upper level troughs that are expected to bring a few shots of precipitation. Rainfall will end Friday as low pressure moves south into California. Behind this system, dry flow out of the north will keep things cool in Washington ahead of a trough dropping in from British Columbia Saturday into Sunday. The trajectory of this trough looks to keep precipitation chances limited mainly to mountainous areas of the state where it should fall mostly as light snow. A ridge extending northeast from the North Pacific will build on Monday with dry conditions before it is superseded by a trough moving south along the Pacific Coast from SE Alaska to bring widespread precipitation with snow levels around 1500 to 2000 feet. Dry conditions Wednesday are expected to be ended by an upper disturbance Thursday. This is expected to bring more wet conditions ahead of a significant surface cyclone that looks to start moving into the Pacific Northwest as early as Thursday night.

Discussion:

As the low that brought copious amounts of rain to Washington Thursday and Friday moves south into California, surface high pressure in British Columbia will keep winds out of the north. This may be breezy at times through Saturday, with the strongest winds being in and downwind of valleys that drain the Fraser Plateau (including the Okanogan Valley, San Juan County, and western Whatcom County). Temperatures will remain around 0 to 5 degrees below average through Saturday, except southeast of a line from the Tri-Cities to Spokane where highs may approach 10 degrees below average.

The next trough is expected to move south from interior British Columbia Saturday into Sunday. Unlike similar features that come from the west or northwest, this will not have much moisture embedded within it, thanks in part, to its origins from the Canadian Arctic. Still, cooler temperatures aloft could help showers form, mainly in and near mountainous portions of Washington. Snow levels during this event will be low, perhaps down to around 2000 feet, but precipitation values should be light.

Monday an opportunistic ridge stretching northeast from the North Pacific will briefly build over the area, keeping things dry with northerly flow aloft. This should be fairly short-lived as the next trough rapidly moves south from near Anchorage late Sunday to reach Washington as early as Monday evening. Its trajectory gives it access to plenty of moisture from the ocean. Most of this system’s precipitation should come Monday night into Tuesday. With snow levels around 1500 to 2000 feet at times, the three major Cascade passes should see winter travel conditions. This may even be enough to drop some snow in Spokane and on the Palouse overnight Tuesday into Wednesday morning.

Another period of relative calm for most of Washington is in the cards for Wednesday with only leftover showers expected in far eastern and far southwestern portions of the state. A shortwave trough comes in on Thursday, and current indications are that this one will be drier than the one preceding it (though not quite as dry as the feature from the previous Saturday/Sunday). If this pans out, rain and mountain snow would be widespread for most points in the state except for in and near the Columbia Basin. Guidance indicates that this shortwave will be moving ahead of a more significant system that currently looks to bring widespread rain and snow throughout the state beginning as early as Thursday night along the coast and lasting through much of Friday.

A few places in Washington set new daily rainfall records when data was taken by the National Weather Service. For Thursday, November 5, the Richland Airport recorded 0.70 inches beating the old record of 0.48 inches set in 1991. Friday morning, COOP statons in Kennewick, Ritzville, and at Whitman Mission reported daily record rainfall rates. These sites report rainfall for the previous 24 hours up to around 7 am, so most of the rain reported by these sites likely fell on the 5th. Kennewick's record of 0.64 inches is especially interesting as it tripled the old record (0.21 in. set in 2006). That station has a period of record extending back to 1894.


8 to 14 Day Outlook, November 13 to November 19, 2020
  • Below average temperatures and above average precipitation are favored for the period.

Important Points About Next Week’s Weather

South Central Washington
Weekend
  • Wind: N/NW, breezy conditions Fri & Sun with gusts to 30 mph.
  • Precipitation: Rain ending by Fri night, otherwise dry except in Cascade foothills Sun.
  • High Temps: Near 50 Sat, mid 40s Sun.
  • Low Temps: Mid 30s Fri & Sat night, mid 20s Sun night.
  • Sky Cover: Decreasing clouds Fri night, partly cloudy Sat, mostly cloudy Sun.
Next Week
  • Wind: S/SW, breezy Tue.
  • Precipitation: Rain showers possible Tue & Thu.
  • High Temps: Mid 40s Mon, near 50 Tue, mid 40s Wed & Thu.
  • Low Temps: Mid 30s Mon night, low 30s Tue-Thu night.
  • Sky Cover: Partly cloudy Mon, mostly cloudy Tue, partly cloudy Wed, mostly cloudy Thu.

North Central Washington
Weekend
  • Wind: N, locally breezy Fri.
  • Precipitation: Upslope rain/snow showers possible Sat night and Sun.
  • High Temps: Near 50 Sat & Sun. Cooler in higher terrain.
  • Low Temps: Near 30 Fri & Sat night, low 20s Sun night. Cooler in higher terrain.
  • Sky Cover: Decreasing clouds Fri night, partly cloudy Sat, mostly cloudy Sun.
Next Week
  • Wind: S/SW, breezy Tue, mainly in the Basin.
  • Precipitation: Chance of rain and mountain snow Mon night, Tue, Wed night, and Thu. Rain may mix with snow in lowland areas during the overnight hours.
  • High Temps: Mid 40s Mon, near 50 Tue, mid 40s Wed & Thu. Cooler in higher terrain.
  • Low Temps: Mid 20s Mon night, near 30 Tue night, low 30s Wed & Thu night. Cooler in higher terrain.
  • Sky Cover: Partly cloudy Mon, partly to mostly cloudy Tue-Thu.

Eastern Washington
Weekend
  • Wind: N/NW, breezy conditions Fri & Sun with gusts to 25 mph.
  • Precipitation: Rain ending Fri night, possibly a stray shower Sun.
  • High Temps: Upper 40s Sat, low 40s Sun. Warmer in the Lewis & Clark Valley.
  • Low Temps: Low 30s Fri night, near 30 Sat night, low 20s Sun night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly cloudy to overcast.
Next Week
  • Wind: S/SW, breezy Tue.
  • Precipitation: Chance of snow Mon night, chance of rain/snow Tue, chance of snow Tue night & Wed night, chance of rain/snow Thu.
  • High Temps: Near 40 Mon, low 40s Tue, near 40 Wed & Thu. Warmer in the Lewis & Clark Valley.
  • Low Temps: Upper 20s Mon night, mid 20s Tue-Thu night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly cloudy to overcast.

Western Washington
Weekend
  • Wind: N wind, locally breezy Fri & Sun with gusts to 30 mph.
  • Precipitation: Upslope showers possible in and near the Cascades and Olympics.
  • High Temps: Upper 40s Sat & Sun. Cooler in higher terrain.
  • Low Temps: Near 40 Fri night, upper 30s Sat & Sun night. Cooler in higher terrain.
  • Sky Cover: Partly to mostly cloudy Fri & Sat, partly cloudy Sun.
Next Week
  • Wind: S and breezy Mon and Tue. Light and variable Wed. S and locally breezy Thu.
  • Precipitation: Rain and mountain snow likely Mon night, chance of rain and mountain snow Tue, Tue night, chance of rain in SW WA Wed, chance of rain and mountain snow Wed night, and Thu.
  • High Temps: Mid 40s Mon, upper 40s Tue-Thu. Cooler in higher terrain.
  • Low Temps: Near 40 Mon night-Thu night. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast.

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