AgWeatherNet Weekly Weather Outlook for Mar 6 to Mar 12, 2020

A few weak weather systems interspersed with dry conditions

Mark Ingalls, AgWeatherNet Intern
Joe Zagrodnik, Postdoctoral Research Associate

Discussion:

The recent period of pleasant, spring-like weather is coming to an end as a low-pressure system centered in Southeast Alaska is pushing a weakening cold front across the Pacific Northwest. Rain and mountain snow are expected throughout the state resulting from this, with higher precipitation values along and west of the Cascades. Precipitation that began Thursday should continue off and on in the west side of the state through Sunday. Snow levels will be below pass level, leading to a few inches of snow over the weekend on major passes like Snoqualmie. Most of the state will see some precipitation over the weekend, but totals will be relatively light (a few tenths of an inch at most) except in the mountains.

East of the Cascades, many locations can expect showers starting Friday afternoon or evening. This should last overnight with a few possible lingering showers Saturday around Yakima and the Tri-Cities. Closer to the Idaho state line, precipitation may extend into the afternoon. The highest chance of rain from this event on the east side will be approximately along and east of a line near Boardman, Oregon, the Tri-Cities, Ritzville, and Republic. Throughout the weekend, high temperatures should be in the 40s to low-50s in low elevation areas statewide.

Things begin to clear out Sunday east of the Cascades and Monday on the west side with a warming trend across Washington starting on Monday. The next round of precipitation arrives as a chance rain and mountain snow on Tuesday. Right now, it looks as though this will be restricted to mountainous areas as well as lowlands west of the Cascades.

It appears that another rainmaker (again with mountain snow) will impact the Pacific Northwest later next week. This will likely bring with it more moisture than Tuesday's storm, with precipitation likely west of the Cascades and a chance of showers in the east. We intend to provide more specifics on this system in our Monday update to the outlook.

As conditions continue to warm into Spring, seasonal allergies are becoming more of an issue throughout the region. The largest contributors to airborne pollen across Washington are currently trees, especially Cedar/Juniper. If you are experiencing allergy issues, expect that to continue to some extent through the week.

February brought wide variations in rainfall across Washington. This geographic variability was especially evident in Eastern Washington. Both Yakima and Wenatchee got right around a tenth of an inch of rain for the entire month, with ranks as the 7th and 6th driest Februaries respectively. Meanwhile, Walla Walla and Lewiston recorded over 2" of rain, which rank within the top 10 wettest Februaries on record for those places.

This difference helps to demonstrate why rivers draining the Blue Mountains experienced extreme flooding earlier in the month while the Yakima River only minorly flooded in some areas. It also helps to provide context for the ongoing moderate drought conditions impacting parts of the Inland Northwest. West of the Cascades, variation from climatological norms wasn't quite as extreme. Many cities were near climatological norms, but Olympia did experience its 10th driest February on record.


Key Points:

  • Rain and mountain snow through the weekend.
  • Periodic chances of rain for Western Washington Tuesday through Thursday and in Eastern Washington Thursday.

Temperatures
  • Temps below average this weekend.
  • Warming trend beginning Monday with temperatures rising to near or above average by midweek.

Precipitation
  • Widespread rain this weekend statewide, with the lowest chances being around Yakima and Wenatchee. Widespread mountain snow.
  • Chances of rain resume west of the Cascades Tuesday, extending east of the state Thursday.

Wind
  • Breezy conditions possible midweek.

8 to 14 Day Outlook March 12 to 18, 2020
  • Slight chance of below normal temperatures with normal precipitation values.

Important Points about Next Week's Weather

South Central Washington
Weekend
  • Chance of rain showers begins Friday evening, especially near and east of the Tri-Cities. This ends Saturday with clearing skies into Sunday. Partly cloudy to overcast.
  • Highs in the 50s Friday, upper-40s to mid-50s Saturday and Sunday.
  • Lows in the 30s Saturday morning and 20s Sunday morning.
Next Week
  • Dry conditions until a chance of rain forms Thursday. Clear to mostly cloudy.
  • Highs starting in the upper-40s to mid-50s Monday, rising to upper-50s to low-60s by Wednesday. Returning to upper-40s to mid-50s Thursday.
  • Lows in the mid-20s to mid-30s.

North Central Washington
Weekend
  • Chance of rain and upland snow Friday night into Saturday with the best chance east of Republic. Clearing skies into Sunday. Partly cloudy to overcast.
  • Highs in the mid-40s to low-50s Friday, cooling to 40s Saturday and Sunday. Colder in higher terrain.
  • Lows upper-20s to low-30s Saturday morning, 20s Sunday morning. Colder in higher terrain.
Next Week
  • Dry conditions until a chance of rain forms Thursday. Clear to mostly cloudy.
  • Highs mid-40s to low-50s Monday, rising to all 50s by Wednesday. Returning to mid-40s to low-50s Thursday. Colder in higher terrain.
  • Lows in the 20s Monday and Tuesday with 30s for Wednesday and Thursday. Colder in higher terrain.

Eastern Washington
Weekend
  • Rain showers start Friday, becoming widespread overnight and into the day Saturday. Snow may mix with rain in some areas during the coldest hours. Patchy fog Sunday morning, otherwise clearing. Partly cloudy to overcast. Little to no snow accumulation expected.
  • Highs mid-40s to low-50s Friday, upper-30s to mid-40s Saturday and Sunday.
  • Lows upper-20s to mid-30s Saturday morning. A few degrees warmer Sunday morning.
Next Week
  • Dry conditions until a chance of rain forms Thursday. Clear to mostly cloudy.
  • Highs in the 40s Monday, rising to the mid-40s to low-50s by Wednesday. Cooler Thursday.
  • Lows in the mid-20s to mid-30s.

Western Washington
Weekend
  • Chance of rain and mountain snow through the weekend, with the best chance Saturday. Accumulations in the 1-4 inch range possible on the major Cascade passes Sunday. Partly cloudy to overcast.
  • Highs mid-40s to low-50s. Colder in higher terrain.
  • Lows in the 30s. Colder in higher terrain.
Next Week
  • Dry Monday before another chance of rain showers with mountain snow moves in Tuesday and Wednesday. Precipitation likely Thursday. Partly cloudy to overcast.
  • Highs in the mid-40s to mid-50s. Colder in higher terrain.
  • Lows in the 30s to near 40 with the warmest locations being near the ocean and Puget Sound. Colder in higher terrain.

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