AgWeatherNet Weekly Weather Outlook for November 22 to November 28, 2021

Building ridge to dominate conditions, but rain and mountain snow remain in the forecast

Mark Ingalls, AgWeatherNet Field Technician

Synopsis:

An incoming system is expected to bring low elevation rain and mountain snow into Tuesday. Aside from some lingering showers in the mountains, the daytime hours of Wednesday appear mainly dry before a new front comes ashore that evening. A building ridge across the Southwestern United States will change the trajectory of incoming systems to out of the west-southwest, bringing in warmer air and higher snow levels. Persistent rainfall and high elevation snow is possible for at least a portion of the state this weekend, but small variations in eventual positioning will make big differences on impacts, especially in Eastern Washington.

Discussion:

The Pacific Northwest sat under the influence of an upper level ridge over the weekend, bringing areas of low clouds and fog to low elevations with sunny skies elsewhere. This is being eroded Monday morning as a new disturbance moves onshore. Look for rain and mountain snow showers to spread across the Cascades overnight and into Tuesday. Snow levels are forecast to be below pass level with mountain travel expected to be difficult through Tuesday.

Wednesday, a strong upper level ridge is expected to build into the Western United States. Expect dry conditions throughout Washington during the day, but a new storm system begins coming ashore that evening, moving east overnight and into Thursday. Under the influence of this ridge, the general storm trajectory is likely to shift from out of the northwest to out of the west or southwest. These storms will be warmer than the Monday-Tuesday system with snow levels above pass level expected.

Models are pointing toward a moderate atmospheric river event this weekend, but significant differences remain on its timing and position. If the moisture plume aims directly at Washington and Oregon, rain and high elevation snow can be expected statewide. That said, there is a significant chance that the plume will be aimed more toward Vancouver Island, which would keep much of the lowland areas in Eastern Washington dry. Furthermore, if this solution verifies, look for another round of inversion-induced fog, low clouds, and cold temperatures, particularly in the Columbia Basin and Yakima Valley.


8 to 14 Day Outlook, November 29 to December 5, 2021
  • Above 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 Mon, W and breezy Tue, S and light Wed-Thu, S with breezy areas Fri.
  • Precipitation: Chance of rain Mon night & Thu night.
  • High Temps: Low 50s Tue, upper 40s Wed-Thu, upper 50s Fri.
  • Low Temps: Mid 30s Mon night, low 30s Tue-Wed nights, low 40s Thu-Fri nights.
  • Sky Cover: Mostly cloudy with areas of fog.
Weekend
  • Wind: Light and variable.
  • Precipitation: Slight chance of rain.
  • High Temps: Low 50s Sat-Sun. Cooler in inversion conditions.
  • Low Temps: Low 40s Sat-Sun nights. Cooler in inversion conditions.
  • Sky Cover: Mostly cloudy, areas of fog.

North Central Washington
Remainder of the Week
  • Wind: Light and variable Mon, W and breezy Tue, S and light Wed-Thu, S with breezy areas Fri.
  • Precipitation: Chance of rain/snow Mon night, rain and mountain snow Thu-Fri.
  • High Temps: Near 50 Tue, mid 40s Wed-Thu, low 50s Fri. Cooler in higher terrain.
  • Low Temps: Low 30s Mon-Wed nights, mid 30s Thu-Fri nights. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast.
Weekend
  • Wind: Light and variable.
  • Precipitation: Chance of rain and mountain snow.
  • High Temps: Low 50s Sat-Sun. Cooler in higher terrain.
  • Low Temps: Upper 30s Sat-Sun nights. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast.

Eastern Washington
Remainder of the Week
  • Wind: Light and variable Mon, W and breezy Tue, S and light Wed-Thu, S with breezy areas Fri.
  • Precipitation: Chance of rain/snow Mon night-Tue, chance of rain and mountain snow Thu night-Fri.
  • High Temps: Near 40 Tue-Wed, low 40s Thu, upper 40s Fri. Warmer in the Lewis & Clark Valley.
  • Low Temps: Low 30s Mon night, mid 20s Tue night, upper 20s Wed night, mid 30s Thu-Fri nights. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly cloudy to overcast with areas of fog.
Weekend
  • Wind: Light and variable.
  • Precipitation: Chance of rain and mountain snow.
  • High Temps: Near 50 Sat-Sun. Warmer in the Lewis & Clark Valley.
  • Low Temps: n the Lewis & Clark Valley.Mid 30s Sat-Sun nights. Warmer i
  • Sky Cover: Mostly cloudy to overcast with areas of fog.

Western Washington
Remainder of the Week
  • Wind: W with breezy areas Tue, SE and generally light Wed-Thu, light and variable Fri.
  • Precipitation: Rain and mountain snow showers.
  • High Temps: Upper 40s Tue-Wed, near 50 Thu, low 50s Fri. Cooler in higher terrain.
  • Low Temps: Mid 40s Mon night, near 40 Tue night, low 40s Wed night, upper 40s Thu night, mid 40s Fri night. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast.
Weekend
  • Wind: Generally S with breezy areas.
  • Precipitation: Rain and mountain snow.
  • High Temps: Mid 50s Sat-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