AgWeatherNet Weekly Weather Outlook for Feb 21 to Feb 27, 2020

A stormy weekend followed by a drying trend with seasonal temperatures

Mark Ingalls, AgWeatherNet Intern
Joe Zagrodnik, Postdoctoral Research Associate joe.zagrodnik@wsu.edu

Discussion:

After a rather uneventful week, an unsettled pattern returns to Washington this weekend. The first sign of the pattern change will be high clouds overspreading the state on Friday. The first round of showers could impact places like Forks and Neah Bay on the Olympic Peninsula as early as Friday evening. This will come in the form of lowland rain, with snow in the mountainous regions. This weak system continues eastward Saturday, with low chances of rain expanding to the lowlands east of the Puget Sound. This precipitation will be mainly north of Interstate 90, with greater chances closer to the Cascade Mountains and in northern portions of Puget Sound. Snow levels will start off Saturday around 2,500 to 3,000 feet, rising another 1,000 feet by the end of the day Saturday.

This weak system precedes the main story this weekend, which is a reasonably strong cold front that will bring precipitation chances to the entire state beginning Saturday night. Lowland rain and mountain snow are likely for the western half of Washington. Precipitation is also likely in and near the mountains east of the Cascade Crest, including cities like Yakima, Walla Walla, and Spokane. Columbia Basin cities like the Tri-Cities and Moses Lake have a lower chance of rain. Snow levels are expected to be low enough for several inches of snow on Snoqualmie, Stevens, and White Passes by Sunday.

Most of the east side of the state should become dry by the end of Monday, but a chance of rain will linger on the west side of the state with snow in the Cascades and Olympics. Models are showing a weak frontal passage Tuesday into Wednesday. This would mainly be a mountain snow event, but some light rain showers are possible in the lowlands statewide, possibly mixing with snow around Moses Lake, Ritzville, and Spokane.

Many westside locations saw their first completely sunny days of 2020 this week. On Tuesday, Seattle closed an 80 day stretch without a sunny day (defined as having 30% or less of the sky covered by clouds). On Wednesday, Sea-Tac Airport even recorded 0% cloud cover - a measurement that only occurred five times during 2019. Portland's airport also ended a similar streak on Wednesday, which lasted for 79 days.

The National Drought Mitigation Center continues to have moderate drought conditions listed for the Tri-Cities, Yakima, Moses Lake, and Wenatchee areas. This represents almost no change from last week and is thanks to lower precipitation values in this part of the state. So far this water year (which started October 1), Wenatchee has only recorded 2.52" of rain - half their normal water year-to-date value. Similar values can have been recorded at the other cities listed above.

While this drought represents the weakest drought category, some agricultural interests may experience negative impacts. Those who are most likely to be impacted are growers who do not source their water from any of the major rivers. Long range forecasts indicate that drought conditions should continue through the spring and may expand to include more of the Basin. On a positive note, snowpack across the state remains near-normal for this time of year. The snowpack situation should help to offset negative impacts from the drought that is in place in the Columbia Basin as many growers are able to irrigate with water pulled from area rivers.


Key Points:

  • Rain and mountain snow through the weekend.
  • Continued chances of rain statewide through the first half of the week with snow in the mountains.

Temperatures
  • Temps hovering near average statewide.

Precipitation
  • Widespread rain this weekend in Western Washington and near mountains in Eastern Washington, especially Sunday. Scattered showers in the Columbia Basin. Widespread mountain snow.
  • Chances of rain continue through Wednesday west of the Cascades, with chances of snow in the Cascades and Olympics.
  • Dry in most of Eastern Washington beginning Monday, though some areas may see showers Wednesday.

Wind
  • Breezy to windy conditions statewide on Sunday with a south to southwest flow.
  • Breezy conditions possible Monday, mainly along and west of Interstate 5, in the Columbia Basin, and on the Palouse.

8 to 14 Day Outlook Feb 27 to Mar 4, 2020
  • Near normal temperatures expected with a strong chance of below average precipitation.

Important Points about Next Week's Weather

South Central Washington
Weekend
  • Dry Friday and Saturday with rain possible Saturday. The best chance of rain is around Yakima and Walla Walla, with lower chances in the Columbia Basin. Snow in higher elevations. Breezy conditions Sunday. Partly cloudy to overcast.
  • Highs mid-40s to mid-50s with Saturday being the warmest.
  • Lows in the 30s.
Next Week
  • Rain showers possible Monday with a breeze. Dry Tuesday with another round of possible isolated rain showers Wednesday. Partly cloudy to overcast. Patchy morning fog.
  • Highs in the mid- to upper-40s.
  • Lows in the upper-30s to low-40s Monday. Mid-20s to low-30s for the rest of the week.

North Central Washington
Weekend
  • Mainly dry Friday and Saturday. Rain likely with upland snow Sunday. Pockets of freezing rain possible in some valleys. Partly cloudy to overcast.
  • Highs in the 40s. Colder in higher terrain.
  • Lows upper-20s to low-30s. Colder in higher terrain.
Next Week
  • Lingering lowland rain and mountain snow showers Monday, tapering off Tuesday. Another round of isolated light rain or snow is possible Wednesday with little-to-no accumulation. Partly cloudy to overcast.
  • Highs upper-30s to mid-40s. Colder in higher terrain.
  • Lows in the 20s. Colder in higher terrain.

Eastern Washington
Weekend
  • Dry Friday and Saturday with rain showers and breezy conditions Sunday. Clear Friday leading to most areas near overcast Sunday. Snow may mix with rain in some locations with little-to-no accumulation.
  • Highs mid-40s to low-50s.
  • Lows upper-20s to mid-30s Saturday morning. A few degrees warmer Sunday morning.
Next Week
  • Lingering light rain showers with snow possibly mixing in with little-to-no accumulation on Monday. Dry Tuesday with possible isolated light rain or snow showers Wednesday. Little-to-no snow accumulation expected. Partly cloudy to overcast with the clearest skies Tuesday.
  • Highs upper-30s to mid-40s.
  • Lows low-30s except upper-30s along the Snake River Monday. Otherwise low- to mid-20s.

Western Washington
Weekend
  • Low rain chances for the Olympic Peninsula Friday, expanding to include the entire coast plus the I-5 corridor north of Tacoma Saturday. Rain likely with gusty winds Sunday. All periods include mountain snow. Accumulations in the 3-8 inch range possible on the major Cascade passes Sunday. Partly cloudy to overcast.
  • Highs mid-40s to low-50s Friday, cooling slowly to all 40s by Sunday. Colder in higher terrain.
  • Lows near 40 Saturday except low- to mid-30s along the I-5 Corridor south of Olympia. Low- to mid-40s Sunday. Colder in higher terrain.
Next Week
  • Lingering rain and mountain snow showers Monday, becoming much more isolated Tuesday. Low rain chances on the Coast Wednesday and in the Columbia Gorge Thursday. Partly cloudy to overcast.
  • Highs in the 40s through the week, with the Puget Sound Region around 50 on Wednesday and Thursday. Colder in higher terrain.
  • Lows near 40 Monday morning. Otherwise, upper-20s to mid-30s with the warmest locations being near the ocean and Puget Sound. Colder in higher terrain.

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