AgWeatherNet Weekly Outlook for February 26 to March 04, 2021

Active pattern continues with drier conditions east of the Cascades

Mark Ingalls, AgWeatherNet Intern
Joe Boomgard-Zagrodnik, AgWeatherNet Postorctoral Research Associate

Synopsis:

Wind and precipitation will taper off for much of Washington Friday night as a weak ridge moves over the region. Upslope light rain and snow showers remain possible in the Cascades and Blues Saturday with snow levels around 2000-3000 feet, but this will be nothing like the extreme snow totals seen Thursday and Friday. A weak warm front crosses the state Sunday to bring light rain showers to Western Washington and increased precipitation chances in the mountains. Much of Eastern Washington should remain dry with this frontal passage. Monday, a cold front comes ashore to bring more west side and mountain precipitation. Some light showers are also possible in the Okanogan and Palouse, but the Columbia Basin and Yakima Valley look to remain dry. Westerly flow keeps rain chances in place for Western Washington and snow in the mountains through much of the work week. Another round of rain showers is possible around and north of Spokane Wednesday, otherwise expecting dry weather with a warming trend for Eastern Washington lowlands to end the forecast period.

Discussion:

The disturbance producing heavy snowfall in the mountains and strong winds for parts of the state will continue to move eastward toward Boise by Friday night. As the sun sets, windy conditions should relax as vertical mixing ceases. The mountains should transition from consistent snow to light upslope showers by Saturday morning. A weak upper level ridge is expected to keep the rest of the state precipitation free during the day Saturday.

Ridging will only last about a day as another series of 3-4 weather systems will attempt to reach Washington State from Sunday through mid-week. Compared with recent storm systems these are expected to be relatively weak systems, with most precipitation occurring west of the Cascades and minor impacts to travel in the passes. However, snow levels will generally remain below pass level.

This next series of weather systems will begin with a weak warm front from Saturday night into Sunday. This brings with it increasing clouds and a chance of rain showers for Western Washington with somewhat increased mountain snow and a modest uptick in wind for the Columbia Basin and Spokane area. Compared to other recent disturbances, this one should pass without much fanfare. Monday, a weakening cold front is expected to push across the state, bringing more rain west of the mountains, snow in the mountains, and wind in the Columbia Basin. This one may be wet enough to produce some drizzle in the Columbia Basin plus light rain showers around Spokane and Pullman.

Cool, westerly flow is expected to keep unsettled conditions in place over the region through Wednesday. On the ground, this will look much the same as the impacts from Sunday's warm front with some rain showers in Western Washington, snow in the mountains, and perhaps a few upslope showers in the Okanogan highlands. Breezy conditions can be expected to continue in the Columbia Basin, on the Palouse, and around Spokane under this pattern.

By Thursday morning, a ridge is expected to build over the western US which will transition the Pacific Northwest into a warmer southerly flow regime. With the southerly flow will also come a surge subtropical moisture with a southerly-orientated atmospheric river looking like a possibility by the end of next week. Models disagree on the strength and timing of this event, with some in a stronger system by Thursday and others keeping the storm offshore until the weekend with warm and dry weather across the state by the end of the week. We should have a better idea of how this storm will play out by Monday's outlook.

Lowland temperatures are expected to remain steady through the weekend before starting a slow climb for the work week. The warmest parts of the Columbia Basin may even have highs in the 60s toward Thursday with mid 50s possible for much of the I-5 corridor near and south of Seattle. Snow levels are generally expected to remain in the 2500-3500 foot range.

Drought conditions in Central Washington continue to slowly improve. In this week's update of the National Drought Monitor, severe drought (D2 out of 5) conditions were dropped for much of the Yakima Valley. This narrowed area now only includes Mattawa, Prosser, and the SR 14 corridor from Maryhill to Plymouth. The Yakima Valley is now considered to have moderate drought (D1 out of 5) conditions, along with the Tri-Cities, Moses Lake, and Goldendale.


8 to 14 Day Outlook, March 05 to March 11, 2021
  • Below average temperatures and near average precipitation are favored for the period.

Important Points About Next Week's Weather

South Central Washington
Weekend
  • Wind: SW, breezy areas Sun.
  • Precipitation: Dry conditions expected.
  • High Temps: Low 50s Sat, mid 50s Sun.
  • Low Temps: Mid 30s Fri-Sun nights.
  • Sky Cover: Decreasing clouds Fri night, clear to partly cloudy Sat, partly cloudy Sun.
Next Week
  • Wind: Generally S/SW, breezy areas Mon-Wed.
  • Precipitation: Isolated showers Mon, otherwise dry.
  • High Temps: Low 50s Mon-Tue, mid 50s Wed, upper 50s Thu.
  • Low Temps: Mid 30s Mon-Thu nights.
  • Sky Cover: Partly to mostly cloudy Mon, partly cloudy Tue, mostly cloudy Wed-Thu.

North Central Washington
Weekend
  • Wind: W/SW, breezy areas in the Basin Sunday.
  • Precipitation: Upslope rain/snow showers possible Sat night, otherwise dry.
  • High Temps: Mid 40s Sat, upper 40s Sun. Cooler in higher terrain.
  • Low Temps: Near 30 Fri-Sat nights, mid 30s Sun night. Cooler in higher terrain.
  • Sky Cover: Partly cloudy Sat, mostly cloudy Sun.
Next Week
  • Wind: Generally S/SW, breezy areas in the Basin Mon-Wed.
  • Precipitation: Low chance lowland rain Mon, Wed, & Thu. Upslope rain/snow showers Mon-Thu.
  • High Temps: Mid 40s Mon-Tue, upper 40s Wed, near 50 Thu. Cooler in higher terrain.
  • Low Temps: Low 30s Mon-Tue nights, mid 30s Wed-Thu nights. Cooler in higher terrain.
  • Sky Cover: Partly to mostly cloudy Mon-Thu.

Eastern Washington
Weekend
  • Wind: NW Sat, SW with breezy areas Sun.
  • Precipitation: Dry conditions expected.
  • High Temps: Near 40 Sat, low 40s Sun. Warmer in the Lewis & Clark Valley.
  • Low Temps: Mid 20s Fri night, upper 20s Sat night, low 30s Sun night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Decreasing clouds Fri night, partly cloudy Sat, mostly cloudy Sun.
Next Week
  • Wind: Generally S/SW, breezy areas in the Basin Mon-Wed.
  • Precipitation: Low chance of rain Mon & Wed night.
  • High Temps: Mid 40s Mon, low 40s Tue, upper 40s Wed, near 50 Thu. Warmer in the Lewis & Clark Valley.
  • Low Temps: Near 30 Mon night, low 30s Tue-Thu nights. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly cloudy Mon-Thu.

Western Washington
Weekend
  • Wind: Generally light and variable Sat, S with breezy areas Sun.
  • Precipitation: Rain showers ending Fri night, resuming Sat night. Mountain snow showers all weekend.
  • High Temps: Upper 40s Sat, near 50 Sun. Cooler in higher terrain.
  • Low Temps: Mid 30s Fri night, near 40 Sat-Sun nights. Cooler in higher terrain.
  • Sky Cover: Decreasing clouds Fri night, partly cloudy Sat, increasing clouds Sat night, overcast Sun.
Next Week
  • Wind: S becoming W and with breezy areas Mon. S and widespread breezy Tue-Wed. Becoming E Thu and breezy on the coast/near mountain gaps.
  • Precipitation: Rain and mountain snow showers through the week.
  • High Temps: Near 50 Mon-Wed, mid 50s Thu. Cooler in higher terrain.
  • Low Temps: Near 40 Mon-Tue nights, low 40s Wed-Thu nights. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast.

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Washington State University