AgWeatherNet Weekly Weather Outlook for Feb 28 to Mar 5, 2020

A trifecta of low pressure systems to impact Washington through the period

Craig Oswald, Field Meteorologist, 509-786-9256
Mark Ingalls, AgWeatherNet Intern
Joe Zagrodnik, Postdoctoral Research Associate

Discussion:

A series of three surface cyclones, ranging from modest to strong, look to bring precipitation to Washington over the course of the outlook period. The first of these disturbances looks to be a very modest surface cyclone that will impact the southern coast of British Columbia Friday night. This is expected to bring rain and mountain snow to western Washington, as well as generally showery and scattered precipitation to northern and far eastern Washington. Central and south central parts of the state may see a light rain shower or two Saturday but will likely remain dry through most locales. Snow levels are expected to drop into the 2800ft range Friday night with this activity and a few inches of snow can be expected for the passes during the overnight and day Saturday. Conditions look to trend dry statewide Saturday night with some breaks in cloud cover making Sunday an enjoyable day for any outdoor recreation. However, Monday morning looks to see showers move back in from the west, so definitely take advantage of the pleasant conditions Sunday if you can!

The disturbance moving through on Monday appears to be another Clipper like system originating over northern British Columbia and moving southeast into southern Saskatchewan in conjunction with a broad, low amplitude trough sweeping across the Pacific Northwest from the northwest. This disturbance again looks to bring most of its impacts to western Washington where light rain and light to moderate mountain snow look to prevail through the Cascades and Olympics. Regions east of the Cascades are expected to again see only light scattered precipitation, most of which will likely be found through upland areas of northern Washington and along the Idaho border. Any such activity is anticipated in the Tuesday time frame with conditions trending dry for regions east of the Cascades Wednesday and remaining so for Thursday.

Conditions look to remain a bit more wet west of the Cascades. Some light and scattered shower activity will likely cling onto the area through the first part of the week. It looks as if there will be a brief dry window late Wednesday but this will be short lived as a more significant low pressure system looks to crash into the shores of northern British Columbia. The long precipitation band associated with the systems strong cold front is expected to start bringing light to moderate rain and mountain snow back into western Washington from the northwest sometime around Thursday morning. An increase in southwest wind can also be expected with conditions becoming quite blustery. Once the cold front passes, temperatures are anticipated to dip below average through the state, but desperately cold temperatures that may bring concerns for bud kill are not expected.

Finally, for interest, the windstorm of Sunday, February 23 was one of the stronger ones the Columbia Basin has seen in a while. Rattlesnake Mountain adjacent to the Hanford Site (not Rattlesnake Mountain near Issaquah) recorded a peak wind gust of 82 mph. A few AgWeatherNet sites recorded wind gusts above 60 mph, with the strongest being at Prescott.N north of Walla Walla. That 66.8 mph gust was the strongest recorded there since November 2015. The Vantage station also had its strongest gust since the November 2015 storm, coming in at 56.8 mph. Pomeroy.E in Garfield County got up to 64.2 mph that following Monday. That, however, wasn't even the strongest gust recorded at that station during 2020. On the west side, Sea-Tac recorded a 48 mph gust on February 23 which was the second strongest of the winter season in what has been a relatively benign year for windstorms on the west side of the state.


Key Points:

  • Rainy for western Washington, while mostly dry to scattered precip for eastern Washington
  • A few inches of snow at pass levels for most days of the period
  • A more significant disturbance to move in from the northwest around Thursday

Temperatures
  • Temps wavering between slightly above and slightly below normal

Precipitation
  • Rain type precip expected in all lowland areas
  • Snow for parts of upland northern Washington and the Cascades/Olympics

Wind
  • Breezy Saturday with winds from the W/SW and some gusts into the 35 mph range through the Basin/Palouse and Puget Sound areas
  • W/SW winds again increasing Monday afternoon with more gusts in the 35 mph range
  • Winds to remain somewhat elevated and breezy through much of the week

8 to 14 Day Outlook - Mar 6, 2020 to Mar 12, 2020
  • Near to slightly above average temperatures and near average precipitation are expected during the 8 to 14 day time frame.

Important Points about Next Week's Weather

South Central Washington
Weekend
  • A chance of light rain showers Saturday, otherwise mostly dry. Breezy conditions starting Friday evening and lasting through the daytime hours Saturday. Also breezy Sunday, but the wind won't be quite as strong. Clear to mostly cloudy.
  • Highs near 60 Friday, mid 50s Saturday and Sunday.
  • Lows in the upper 30s Saturday morning, low 30s Sunday morning.
Next Week
  • Possible rain showers throughout the area Tuesday and in the Yakima Valley Thursday, otherwise dry. Partly cloudy to overcast.
  • Highs in the mid 50s Monday and Tuesday, mid to upper 50s Wednesday and Thursday.
  • Lows in the mid 30s Monday morning, low 40s Tuesday morning, and mid to upper 30s Wednesday and Thursday mornings.

North Central Washington
Weekend
  • Low chance of light lowland rain and mountain snow possible beginning Friday night, lasting through Saturday. Precipitation values will be low (if any), with the highest chances closer to the Cascade Crest. Clear to mostly cloudy.
  • Highs near 50 Friday and mid 40s Saturday and Sunday. Cooler through higher terrain.
  • Lows in the low 30s Saturday morning, and upper 20s Sunday morning. Cooler through higher terrain.
Next Week
  • Dry Monday with scattered light lowland rain and mountain snow showers Tuesday, with isolated mountain snow lingering into Wednesday. Another chance of rain and mountain snow comes Thursday. Little to no snow accumulation expected. Clear to mostly cloudy.
  • Highs in the mid 40s Monday and Tuesday, upper 40s Wednesday and Thursday. Cooler through higher terrain.
  • Lows in the upper 20s Monday morning, low 30s Tuesday morning, and upper 20s Wednesday and Thursday mornings. Cooler through higher terrain.

Eastern Washington
Weekend
  • Scattered light rain and snow showers Friday night through Saturday, trending dry Saturday night and remaining dry Sunday. Greater chances for precip near the Idaho border. Little to no snow accumulations. Clear to mostly cloudy.
  • Highs in the mid 50s Friday, low 40s Saturday and Sunday.
  • Lows in the mid 30s Saturday morning, and upper 20s Sunday morning.
Next Week
  • Dry Monday with scattered light rain showers Tuesday, with a greater chance again near the Idaho border. Trending dry Tuesday night and remaining so through the period. Clear to mostly cloudy.
  • Highs in the low 40s Monday, mid 40s for the remainder of the period.
  • Lows in the upper 20s Monday morning, mid 30s Tuesday morning, and near 30 Wednesday and Thursday mornings.

Western Washington
Weekend
  • Light rain showers and light to moderate mountain snow. Several inches of snow expected by the end of the weekend at pass levels. Trending dry through Sunday with a few scattered showers remaining. Foggy at times. Partly sunny to overcast.
  • Highs in the low 50s Friday, mid 40s Saturday, and upper 40s Sunday. Much cooler throughout the mountains.
  • Lows in the upper 30s Saturday morning, low 30s Sunday morning. Much cooler throughout the mountains.
Next Week
  • Return of light rain and light to moderate mountain snow showers Monday morning and remaining through the beginning of the week. Brief dry period likely before a more significant disturbance moves in around Thursday. Patchy fog at times. Mostly cloudy to overcast.
  • Highs in the upper 40s Monday and Tuesday, and low 50s Wednesday and Thursday. Much cooler throughout the Cascades.
  • Lows in the upper 30s Monday and Tuesday mornings, and low 50s Wednesday and Thursday mornings. Much cooler throughout the Cascades.

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