AgWeatherNet Weekly Weather Outlook for October 18 to October 24, 2021

Generally unsettled weather pattern continuing

Mark Ingalls, AgWeatherNet Field Technician

Synopsis:

Look for generally dry conditions through Tuesday before a cold front on Wednesday kicks off the next series of showery weather. Rain and mountain snow is expected for most of Washington, though precipitation chances are quite low in the Columbia Basin and Yakima Valley. On Thursday, a strong disturbance offshore is expected to start bringing rain to the coast with that rain spreading eastward Friday. Weaker systems are forecast to cycle through the region Saturday and Sunday, keeping rain showers in place. With a more southwesterly flow pattern, snow levels are likely to be higher through the weekend, with snow possibly making it down to pass level on Stevens Pass and the North Cascades Highway.

Discussion:

A lull in activity will bring dry conditions to the Pacific Northwest through the day Tuesday. Clear to partly cloudy skies will allow for a chilly morning Tuesday but by afternoon clouds begin moving in along the coast. Rain showers associated with an incoming cold front move ashore by Tuesday evening. This crosses the Cascades to bring showers into Eastern Washington on Wednesday.

Rain and mountain snow in the postfrontal environment linger west of the Cascades on Thursday as a very strong low pressure system associated with the remnants of Tropical Storm Namtheun moves northward well offshore. This storm has the potential to produce hurricane-force winds near its center, but models are keeping the center west of 135 degrees west (the coast is about 124 degrees west).

On Friday, a cold front associated with the strong low is forecast to bring widespread rain to Washington. In addition, windy conditions with gusts reaching as high as 50 mph are possible along the Coast and in the San Juan Islands. Breezy conditions are likely elsewhere as the front moves through. At the upper levels, a large trough located to the west of the region is forecast to bring in air from out of the southwest, raising snow levels so that they should be above pass level except perhaps at Stevens Pass and on the North Cascades Highway through the weekend.

Shortwave disturbances embedded within the mean flow around the upper level trough keep rain and periodically breezy conditions in the Pacific Northwest through the weekend. Some models are showing a strong low in the region, but there is a lot of uncertainty as to the position and timing of this storm. Either way, this creates a chance of a widespread wind event on Sunday or Monday.

Precipitation values in Western Washington over the next week are currently forecast to range from as low as half an inch in the Olympic rain shadow (encompassing Sequim and the San Juan Islands) to possibly exceeding five inches on the windward side of the Olympics. East of the Cascades, the Tri-Cities may see around a quarter inch of rain, with values nearing an inch and a half in the Blue Mountains and highland areas north of Spokane. This should help to improve the drought gripping the region, though improvement may be limited around the Columbia Basin and Yakima Valley.


8 to 14 Day Outlook, October 25 to October 31, 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: Light and variable Tue, SW and breezy Wed, light and variable Thu, SW with breezy areas Fri.
  • Precipitation: Chance of rain Wed, rain likely Fri.
  • High Temps: Mid 60s Tue-Wed, near 70 Thu, low 60s Fri.
  • Low Temps: Upper 30s Mon night, mid 40s Tue-Wed night, upper 40s Thu night, mid 40s Fri night.
  • Sky Cover: Partly cloudy Tue, mostly cloudy Wed-Fri.
Weekend
  • Wind: SW and light Sat, SW and possibly windy Sun.
  • Precipitation: Chance of rain through the weekend.
  • High Temps: Low 60s through the weekend.
  • Low Temps: Mid 40s through the weekend.
  • Sky Cover: Mostly cloudy to overcast through the weekend.

North Central Washington
Remainder of the Week
  • Wind: Light and variable Tue, SW and breezy Wed, light and variable Thu, SW with breezy areas Fri.
  • Precipitation: Rain likely Wed, Thu night, and Fri.
  • High Temps: Mid 60s Tue, low 60s Wed-Thu, upper 50s Fri. Cooler in higher terrain.
  • Low Temps: Upper 30s Mon night, mid 40s Tue night, low 40s Wed night, upper 40s Thu night, low 40s Fri night. Cooler in higher terrain.
  • Sky Cover: Increasing clouds Tue, mostly cloudy Wed-Fri.
Weekend
  • Wind: SW and light Sat, SW and possibly windy Sun.
  • Precipitation: Rain and high elevation snow likely through the weekend.
  • High Temps: Mid 50s through the weekend. Cooler in higher terrain.
  • Low Temps: Mid 40s through the weekend. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast through the weekend.

Eastern Washington
Remainder of the Week
  • Wind: Light and variable Tue, SW and breezy Wed, light and variable Thu, SW with breezy areas Fri.
  • Precipitation: Chance of rain Wed, rain likely Fri.
  • High Temps: Mid 60s Tue, low 60s Wed, mid 60s Thu, near 60 Fri. Warmer in the Lewis & Clark Valley.
  • Low Temps: Mid 30s Mon night, low 40s Tue night, upper 30s Wed night, mid 40s Thu night, near 40 Fri night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Partly cloudy Tue, mostly cloudy to overcast Wed-Fri.
Weekend
  • Wind: SW and light Sat, SW and possibly windy Sun.
  • Precipitation: Rain showers through the weekend.
  • High Temps: Mid 50s through the weekend. Warmer in the Lewis & Clark Valley.
  • Low Temps: Low 40s through the weekend. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly cloudy to overcast through the weekend.

Western Washington
Remainder of the Week
  • Wind: E and generally light Tue, S and breezy Wed, E with breezy areas Thu, S with breezy areas Fri. Elevated winds along the coast.
  • Precipitation: Rain and high elevation snow Tue night-Fri.
  • High Temps: Low 60s Tue, near 60 Wed, mid 60s Thu, mid 50s Fri. Cooler in higher terrain.
  • Low Temps: Low 40s Mon night, near 50 Tue-Fri nights. Cooler in higher terrain.
  • Sky Cover: Increasing clouds Tue, mostly cloudy to overcast Wed-Fri.
Weekend
  • Wind: S and breezy Sat, SE and possibly windy Sun. Elevated winds along the coast.
  • Precipitation: Rain and high elevation snow.
  • High Temps: Mid 50s through the weekend. Cooler in higher terrain.
  • Low Temps: Mid 40s through the weekend. Cooler in higher terrain.
  • Sky Cover: Overcast through the weekend.

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Washington State University