AgWeatherNet Weekly Outlook for January 29 to February 4, 2021

Return to Southwesterly Flow to Promote Wet Conditions

Mark Ingalls, AgWeatherNet Intern
Craig Oswald, AgWeatherNet Field Meteorologist

Synopsis:

The main influence of weather conditions in Washington for the weekend and into next week will be the presence of an upper level trough off shore. General shower activity can be expected in and west of the mountains through Tuesday, with shortwave disturbances enhancing precipitation values Saturday, Sunday, and Tuesday. Snow levels are expected to be around 3500 feet through the weekend, dropping to around 2500 feet Monday night. Wednesday we shift from a troughing pattern to a strong ridge building offshore allowing for drying in more arid parts of the state. This isn't expected to last long, however, as models indicate an upper level disturbance approaching Thursday night or Friday.

Discussion:

Over the past week, the Pacific Northwest has seen a prolonged stretch of lower-than-normal snow levels. Periodic precipitation is still expected for most locations, but an upper level trough located offshore is switching the flow regime to southwesterly. And similar to the southwesterly flow regime last week, Washington can generally expect off/on rain and snow showers through Tuesday, with enhancement of such thanks to weak upper disturbances embedded in the flow. The southwesterly flow will result in somewhat warmer conditions and higher snow levels for the region through the weekend.

However, the first system for the weekend comes Friday evening into Saturday with rain and mountain snow showers expected for most of the state. This is thanks to a decaying band of frontal type precipitation moving into the Pacific Northwest from the west. As usual with these westerly systems, the lowest chance of showers lies in the Columbia Basin, with only a low chance of light rain in that area. More widespread rain and mountain snow comes Sunday, accompanied with breezy conditions as the upper level trough sets up offshore. The strongest winds are expected along the coast south of Aberdeen and downslope along the west side of the Blue Mountains. With snow levels right around pass level, significant travel impacts are possible.

The larger trough starts to work eastward across the region Monday and Tuesday, lowering snow levels to around 2500 feet. This lies below pass level and several inches of snow are expected in the cross-state mountain corridors. The common theme for the outlook period with regard to lowland precipitation type will generally be as such. Northern Washington and the Eastern Washington region will generally see rain/snow mix during the overnights with minor accumulations possible by morning. During the day, precipitation will trend toward rain. However, it is certainly possible that a few snowflakes may mix in with any daytime rain, especially throughout northern Washington. Do not expect much, if any, accumulation during the day. The Columbia Basin looks to generally remain as rain for the period and western Washington remaining as rain as well.

Rain and mountain snow showers are expected Wednesday and Thursday, but these will be more scattered in nature and aren't likely to drop much in arid portions of the state if anything at all. Models are fairly united in showing an upper level disturbance exiting the Russian Far East, crossing Alaska, and dropping into the Pacific Northwest but diverge on the timing of this incoming system. It could come in as early as Thursday evening, but may end up being more of a Friday-Saturday event. It is also worth noting that with forecasts that far out, there is an inherent level of uncertainty with the position of the upper level ridge. If it ends up east of current model guidance, inversions and low level fog may be the dominant pattern to end the forecast period. If it is further west, however, the storm system may end up targeting Northern California.


8 to 14 Day Outlook, February 5 to February 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: S Sat & Sun, breezy in areas with gusts to 25 mph.
  • Precipitation: Rain showers possible Sat night & Sun.
  • High Temps: Low 50s Sat & Sun.
  • Low Temps: Low 30s Fri night, upper 30s Sat night, near 40 Sun night.
  • Sky Cover: Mostly cloudy to overcast with areas of fog.
Next Week
  • Wind: S and light Mon, S and breezy Tue, W and light Wed, S and breezy Thu.
  • Precipitation: Chance of rain Mon and Tue.
  • High Temps: Near 50 Mon, upper 40s Tue, mid 40s Wed & Thu.
  • Low Temps: Mid 30s Mon night, low 30s Tue-Thu night.
  • Sky Cover: Mostly cloudy Mon-Tue. Partly cloudy Wed-Thu.

North Central Washington
Weekend
  • Wind: SE and generally light.
  • Precipitation: Chance of rain and mountain snow Sat & Sun.
  • High Temps: Upper 30s Sat & Sun. Cooler in higher terrain.
  • Low Temps: Near 30 Fri night, low 30s Sat & Sun night. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast. Patchy lowland fog.
Next Week
  • Wind: S and light Mon, S and breezy Tue, W and light Wed, S and breezy Thu.
  • Precipitation: Chance of rain and mountain snow Mon, Mon night, and Thu.
  • High Temps: Low 40s Mon-Tue, low 40s Wed-Thu. Cooler in higher terrain.
  • Low Temps: Near 30 Mon & Tue night, upper 20s Wed & Thu night. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy Mon-Tue, partly cloudy Wed, increasing clouds Thu.

Eastern Washington
Weekend
  • Wind: Generally S and light.
  • Precipitation: Chance of rain and overnight rain/snow mix Fri-Sun.
  • High Temps: Low 40s Sat, mid 40s Sun. Warmer in the Lewis & Clark Valley.
  • Low Temps: Near 30 Fri night, low 30s Sat night, mid 30s Sun night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly cloudy to overcast.
Next Week
  • Wind: S and light Mon, S and breezy Tue, W and light Wed, S and breezy Thu.
  • Precipitation: Chance of rain Mon, chance of rain/snow Thu.
  • High Temps: Mid 40s Mon, low 40s Tue, upper 30s Wed & Thu. Warmer in the Lewis & Clark Valley.
  • Low Temps: Mid 30s Mon night, upper 20s Tue night, mid 20s Wed & Thu night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly cloudy to overcast Mon, partly cloudy Tue-Wed, mostly cloudy Thu.

Western Washington
Weekend
  • Wind: S/SW and light except on the coast and in the strait where it will be breezy at times.
  • Precipitation: Rain and mountain snow Fri night-Sun.
  • High Temps: Upper 40s Sat-Sun. Cooler in higher terrain.
  • Low Temps: Near 40 Fri night, low 40s Sat & Sun night. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast.
Next Week
  • Wind: S/SW Mon-Tue. W Wed, W and windy in areas Thu.
  • Precipitation: Rain and mountain snow Mon-Tue & Thu.
  • High Temps: Near 50 Mon, upper 40s Tue-Thu. Cooler in higher terrain.
  • Low Temps: Near 40 Mon night, upper 30s Tue-Thu nights. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast.

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