AgWeatherNet Weekly Weather Outlook for October 4 to October 10, 2021

Active week ahead but remaining dry in arid parts of Washington

Mark Ingalls, AgWeatherNet Field Technician

Synopsis:

A weak cold front is forecast to move across Washington on Tuesday and Wednesday, bringing rain showers to the mountains as well as lowlands west of the Cascades. Temperatures are likely to cool significantly following the frontal passage with many Eastern Washington locations getting near or below freezing for the remainder of the work week. Western Washington dries out Thursday before another weak front moves through on Friday. Arid portions of the state will again remain dry, but this front should be the start of a wet weekend for Western Washington and the mountains. Sunday, a more robust disturbance approaches the state, extending the chance of rain to include the entire state.

Discussion:

An upper level trough is expected to dive south into the Pacific Northwest on Tuesday, bringing with it a cold front. As this sweeps across Washington, it is forecast to bring rain to the mountains as well as lowlands in the western half of the state. Little moisture will make it into Eastern Washington lowlands, but the effects of this cold front will still be felt in the form of much cooler temperatures. Snow levels are even expected to drop low enough that some of the higher passes may see some snow, though little if any accumulation is expected along routes like US 2 and US 12. Breezy conditions can be expected Tuesday and Wednesday in typical windy spots such as Cascade mountain gaps.

Cool temperatures aloft combined with ample moisture in the postfrontal environment should keep rain showers in place for the Cascades and points west on Wednesday. Most of Eastern Washington has a risk of frost Thursday through Saturday mornings. For Western Washington, only the greater Portland/Vancouver area and the coast are expected to get into the low 60s with highs in the 50s or cooler elsewhere. Highs in Eastern Washington lowlands will range from the mid 50s on the Palouse to mid 60s around the Tri-Cities.

Thursday is expected to be dry statewide, but another disturbance moves into the region perhaps as early as Friday. Look for similar conditions out of this event, namely rain in the mountains and Western Washington (with snow possibly mixing in at some of the higher mountain passes), breezy conditions in typical windy spots throughout the state, and dry conditions in arid regions. A more robust disturbance may move in on Sunday to bring higher precipitation values to areas already seeing rain as well as a low chance of showers to parts of Washington that will have thus far remained dry.

Model consensus shows continuing unsettled weather for next week with cool and wet conditions. It is far too early to discuss timing beyond Sunday, but it appears possible that the whole state will get wetting rain during this period. This time of year, many folks are wondering about first freeze dates. For the convenience of readers, the following table provides data for select cities in Washington:

First Freeze Climatology
City Record Earliest 30-year Average Record Latest
Bellingham Sep 21 (1955) Oct 25 Nov 23 (1962)
Pullman Aug 24 (1908) Sep 26 Nov 6 (1937)
Seattle Oct 16 (1946) Nov 17 Dec 24 (1999)
Spokane Sep 10 (1895) Oct 9 Nov 11 (1944)
The Dalles Sep 17 (1965) Oct 22 Nov 22 (1984)
Tri-Cities Sep 12 (1921) Oct 16 Nov 19 (1947)
Vancouver Sep 13 (1970) Nov 4 Dec 23 (1939)
Walla Walla Sep 17 (1965) Oct 29 Dec 13 (1968)
Wenatchee Sep 27 (1972) Oct 21 Nov 23 (1965)
Yakima Sep 13 (1970) Oct 5 Nov 3 (2015)


8 to 14 Day Outlook, October 11 to October 17, 2021
  • Below average temperatures and above average precipitation are favored for the period.

Important Points About This Week's Weather

South Central Washington
Remainder of the Week
  • Wind: SW with breezy areas Tue-Wed, light and variable Thu, W with breezy areas Fri.
  • Precipitation: Dry conditions expected.
  • High Temps: Low 70s Tue, mid 60s Wed, low 60s Thu-Fri.
  • Low Temps: Mid 40s Mon-Tue nights, mid 30s Wed-Fri nights. Cooler in sheltered areas.
  • Sky Cover: Partly cloudy.
Weekend
  • Wind: SW with breezy areas Sat, W and breezy Sun.
  • Precipitation: Low chance of rain Sun.
  • High Temps: Mid 60s Sat & Sun.
  • Low Temps: Mid 40s Sat & Sun nights.
  • Sky Cover: Partly cloudy.

North Central Washington
Remainder of the Week
  • Wind: SW with breezy areas Tue-Wed, light and variable Thu-Fri.
  • Precipitation: Chance of mountain showers Tue-Wed & Fri.
  • High Temps: Low 70s Tue, low 60s Wed-Fri. Cooler in higher terrain.
  • Low Temps: Mid 40s Mon night, low 40s Tue night, mid 30s Wed-Fri nights. Cooler in higher terrain and sheltered areas.
  • Sky Cover: Mostly cloudy Tue, partly cloudy Wed-Fri.
Weekend
  • Wind: SW with breezy areas Sat, W and breezy Sun.
  • Precipitation: Chance of rain Sun.
  • High Temps: Mid 60s Sat, low 60s Sun. Cooler in higher terrain.
  • Low Temps: Low 40s Sat & Sun nights. Cooler in higher terrain.
  • Sky Cover: Partly cloudy Sat, mostly cloudy Sun.

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

Western Washington
Remainder of the Week
  • Wind: SW with breezy areas Tue-Wed, light and variable Thu-Fri.
  • Precipitation: Rain Tue, Wed, and Fri.
  • High Temps: Upper 50s Tue, mid 50s Wed, upper 50s Thu-Fri. Cooler in higher terrain.
  • Low Temps: Near 50 Mon night, upper 40s Tue night, mid 40s Wed-Fri nights. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy Tue-Wed, partly cloudy Thu, mostly cloudy Fri.
Weekend
  • Wind: S and light Sat, W with breezy areas Sun.
  • Precipitation: Rain showers.
  • High Temps: Upper 50s Sat, mid 50s Sun. Cooler in higher terrain.
  • Low Temps: Upper 40s Sat & Sun nights. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast.

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Washington State University