AgWeatherNet Weekly Weather Outlook for Apr 17 to Apr 23, 2020

A slightly warmer, yet unsettled outlook period

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

Discussion:

After a couple of chilly nights this past Wednesday and Thursday, minimum temperatures look to trend warmer for the upcoming weekend and week. Precipitation can also be expected for certain parts of the state Saturday, mid week, and again at the end of next week as we enter a different flow pattern that looks to bring unsettled weather to the Pacific Northwest for the next week or two.

A persistent ridge continues to take up residence over the north Pacific while a shortwave embedded in the northwesterly flow downstream of the ridge axis looks to bring a few scattered rain showers to the state. Showers look to be focused through upland and mountain areas of northern Washington, western Washington as a whole, and areas along the Idaho border. South central and interior parts of the state will likely remain mostly dry, however, the chance for a passing shower or two are certainly possible. Isolated lightning and thunder may also be observed with any scattered rain shower activity.

Early next week appears to be dry and warm statewide. However, a robust jet and associated strong surface cyclone will be moving east across the north Pacific. The persistent ridge over the north Pacific that has provided mostly dry weather the past week or two looks to finally break down. This will place the Pacific northwest into a more zonal flow regime and an active weather pattern beginning mid week. The aforementioned strong surface cyclone moving east across the north Pacific is expected to move into Alaska from the south. Subsequently, its band of frontal type precipitation looks to move into British Columbia and the Pacific Northwest from the west beginning Wednesday. This is anticipated to bring widespread light to moderate rain showers over western Washington and the Cascades. Widespread light rain showers can be expected for most of eastern Washington as well.

There looks to be a brief break from precipitation Thursday and Thursday night (western Washington will likely cling to at least scattered rain showers through Thursday however) before the next disturbance moves in from the west Friday/Friday night. This looks to again be a frontal type rain band as part of a weaker surface cyclone that is expected to move into northern British Columbia from the west. Widespread rain is likely for western Washington with eastern Washington likely to see mostly scattered type rain showers.

Low temperatures for the period look to generally remain in the low to mid 40s through fruit growing areas of the state. Mid 30s have the potential of being realized particularly Sunday and Monday nights in the usual cold spots as skies look to trend clear and winds light to calm after Saturday's disturbance works its way southeast through the state. Dew points also look to continue to rise through Saturday, helping to keep overnight minimums from plummeting below freezing. With the return to an unsettled weather pattern mid week, overnight lows in the colder locations look to remain in the low 40s at this time due to the increase in cloud cover and wind.

For interest, drought conditions continue to worsen in Central Washington, with the US 97 corridor now being listed under severe drought by the National Drought Mitigation Center. Much of the state has experienced a dry spring so far (with Sea-Tac only recording 0.01 of precipitation between April 1 and April 16), but for Central Washington dry conditions have been in place since the beginning of the year.

The trajectory of the weather systems in January and February largely left places like Yakima and Wenatchee dry while at the same time causing significant flooding west of the Cascades and around the Blue Mountains. So far this year, Omak has recorded just 1.79 inches of rain compared to its normal value of 5.02.

While January and February brought copious rainfall amounts to parts of the state, most of the area has been dry since then. This is thanks to a persistent ridge of high pressure centered over the north Pacific. This has funneled rain and snow into the Southwestern United States.

For the same time period that Omak received 1.79 inches of precipitation, Yuma, Arizona has recorded 3.96 inches. Their average year-to-date value is 1.20, showing that this anomalous pattern is impacting the entire west. For the last two months, most of the Pacific Northwest has recorded rainfall values that are 25% to 75% of normal whereas Southern California, Southern Nevada, and significant portions of Arizona are above 150% of normal. One bit of good news is that snowpack in Washington state remains near normal for mid-April.


8 to 14 Day Outlook - Apr 24, 2020 to Apr 30, 2020
  • Near average temperatures and slightly above average precipitation are expected during the 8 to 14 day time frame.

Important Points about Next Week's Weather

South Central Washington
Weekend
  • Wind: Mostly light and variable through the weekend.
  • Precipitation: Mostly dry conditions expected with the low chance for a passing rain shower Saturday before trending dry through Saturday night.
  • High Temps: Mid 70s Friday, near 70 Saturday, low 70s Sunday.
  • Low Temps: Near 40 Friday night, low 40s Saturday night, low 40s Sunday night.
  • Sky Cover: Sunny Friday, mostly cloudy Friday night, partly sunny Saturday, partly cloudy Saturday night, sunny Sunday, mostly clear Sunday night.
Next Week
  • Wind: Becoming W/SW and blustery through the day Tuesday and remaining elevated through mid-week. Gusts around 40mph possible. Conditions expected to trend lighter Thursday night and remain light for Friday.
  • Precipitation: Dry early in the week with scattered rain showers Wednesday and trending dry Wednesday night. Another round of scattered rain showers expected for Friday.
  • High Temps: Upper 70s Monday, mid 70s Tuesday, near 70 Wednesday, near 70 Thursday.
  • Low Temps: Mid 40s Monday night, mid 40s Tuesday night, mid 40s Wednesday night, mid 40s Thursday night.
  • Sky Cover: Sunny to mostly cloudy.

North Central Washington
Weekend
  • Wind: Mostly light and variable through the weekend.
  • Precipitation: Mostly dry conditions expected at lower elevations. Scattered rain showers likely through upland and mountain areas beginning Friday night and through Saturday. Trending dry Saturday night.
  • High Temps: Mid 60s Friday, mid 60s Saturday, upper 60s Sunday. Cooler through higher terrain.
  • Low Temps: Mid 40s Friday night, low 40s Saturday night, low 40s Sunday night. Cooler through higher terrain.
  • Sky Cover: Partly sunny Friday, mostly cloudy Friday night, partly sunny Saturday, partly cloudy Saturday night, mostly sunny Sunday, partly cloudy Sunday night.
Next Week
  • Wind: Becoming westerly and blustery through the day Tuesday and remaining elevated through mid-week. Gusts around 40mph possible through the Basin. Conditions expected to trend lighter Thursday night and remain light for Friday.
  • Precipitation: Dry early in the week with scattered rain showers late Wednesday, trending dry Thursday. Extended periods of rain fall in upland/mountain areas likely with some snowflakes mixed in during the overnight. Another round of scattered showers expected for Friday.
  • High Temps: Low 70s Monday, low 70s Tuesday, mid 60s Wednesday, mid 60s Thursday. Cooler through higher terrain.
  • Low Temps: Low 40s Monday night, mid 40s Tuesday night, low 40s Wednesday night, low 40s Thursday night. Cooler through higher terrain.
  • Sky Cover: Mostly sunny to mostly cloudy.

Eastern Washington
Weekend
  • Wind: Mostly light and variable through the weekend.
  • Precipitation: Mostly dry conditions expected with the low chance for a passing rain shower Saturday before trending dry through Saturday night. Greater chance for scattered shower activity along the Idaho border.
  • High Temps: Mid 60s Friday, near 60 Saturday, low 60s Sunday.
  • Low Temps: Upper 30s Friday night, upper 30s Saturday night, upper 30s Sunday night.
  • Sky Cover: Sunny Friday, partly cloudy Friday night, partly sunny Saturday, mostly cloudy Saturday night, mostly sunny Sunday, mostly clear Sunday night.
Next Week
  • Wind: Becoming W/SW and blustery through the day Tuesday and remaining elevated through mid-week. Gusts around 40mph possible. Conditions expected to trend lighter Thursday night and remain light for Friday.
  • Precipitation: Dry early in the week with scattered rain showers Wednesday and trending dry Wednesday night/Thursday morning. Another round of scattered rain showers expected for Friday.
  • High Temps: Mid 60s Monday, mid 60s Tuesday, near 60 Wednesday, upper 50s Thursday.
  • Low Temps: Low 40s Monday night, low 40s Tuesday night, low 40s Wednesday night, near 40 Thursday night.
  • Sky Cover: Mostly sunny to mostly cloudy.

Western Washington
Weekend
  • Wind: Mostly light and variable through the weekend.
  • Precipitation: Scattered rain showers likely to begin moving in from the north Friday night and continue through Saturday. Greater shower activity through the Cascades and Olympics. Trending dry Saturday night.
  • High Temps: Near 70 Friday, near 60 Saturday, mid 60s Sunday. Much cooler through the Cascades and Olympics.
  • Low Temps: Low 40s Friday night, near 40 Saturday night, near 40 Sunday night. Much cooler through the Cascades and Olympics.
  • Sky Cover: Partly sunny Friday, mostly cloudy Friday night, mostly cloudy Saturday, mostly cloudy Saturday night, mostly sunny Sunday, partly cloudy Sunday night. Areas of fog Friday and Saturday nights.
Next Week
  • Wind: Becoming W/SW and breezy through the day Tuesday and remaining elevated through mid-week. Gusts around 30mph possible. Conditions expected to trend lighter Thursday night and remain light for Friday.
  • Precipitation: Dry early in the week with rain showers Wednesday, trending to mostly scattered rain showers Thursday. Extended periods of rain fall in upland/mountain areas likely with some snowflakes mixed in during the overnight. Another round of widespread rain showers to move in Friday.
  • High Temps: Mid 60s Monday, low 60s Tuesday, low 60s Wednesday, near 60 Thursday. Much cooler through the Cascades and Olympics.
  • Low Temps: Low 40s Monday night, mid 40s Tuesday night, low 40s Wednesday night, low 40s Thursday night. Much cooler through the Cascades and Olympics.
  • Sky Cover: Partly sunny to mostly cloudy.

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