AgWeatherNet Weekly Outlook for January 22 to January 28, 2021

A couple opportunities for low elevation snow during the upcoming week

Mark Ingalls, AgWeatherNet Intern
Joe Zagrodnik, AgWeatherNet Postdoctoral Research Associate
Craig Oswald, AgWeatherNet Field Meteorologist

Synopsis:

Dry conditions under northerly flow are expected to bring mostly clear skies to the Pacific Northwest to start the weekend. Saturday afternoon, increasing clouds are likely ahead of an incoming weather system bringing lowland rain and snow levels below 1,000 ft Sunday into Monday. Upper level troughing will hold over the region through the remainder of the period allowing for continual shower activity in the Cascades and on the Olympic Peninsula. More widespread precipitation is expected with an upper level low Tuesday afternoon into Wednesday. Again, lowland snow is possible but the lowest elevations (Seattle, Tacoma, and the Tri-Cities) may just see rain or a rain/snow mix. Snow and near sea-level rain shower activity remains in place through Thursday, especially in and west of the Cascades.

Discussion:

Decreasing clouds on Friday will lead to a mostly clear, cool night across much of Washington. Some areas of fog may develop overnight, particularly around Walla Walla, Chehalis, and the Hood Canal, but cold air streaming in from the north will keep dew points low enough in most areas to limit fog development. Mostly sunny conditions are expected Saturday, with an increase in clouds moving from west to east.

Rain and snow showers are expected to impact Washington Sunday into Monday. West of the Cascades, snow levels for this event look to be around 500 to 1000 feet except around Bellingham where light snow accumulations may make it to sea level. East of the Cascades, all areas stand a chance at seeing snow, but afternoon temperatures and lower precipitation values in the Lower Columbia Basin are likely to limit snow accumulations. A few inches of snow are possible around Spokane, on the Palouse, and in northern parts of the basin. Significant travel impacts are expected along the Cascade passes.

Shower activity in and west of the Cascades is expected in the postfrontal environment Monday afternoon and evening. Locally lower snow levels can be anticipated in some of the stronger convective cells, allowing for a chance of rain, snow, and graupel at sea level. With the nature of these convective showers, it's impossible to determine who will get what more than perhaps a few hours in advance, but those in Western Washington should be prepared for impacts to their commute Monday afternoon.

A drying period with only limited shower activity in the Cascades, Northwest Interior, and near Vancouver should occur from the cessation of precipitation Monday until the next system starts moving in Tuesday afternoon. Snow, mixing with rain below 1000 feet, will move from southwest to northeast across Washington Tuesday night into Wednesday morning. Similarly, snow will taper off from southwest to northeast, ending for most by Wednesday morning but lasting into the nighttime hours around Spokane.

Low elevation snow is particularly hard to forecast for the Puget Sound region where both topography and large water bodies like the Puget Sound and Lake Washington combine to create a unique temperature profile. Significant travel impacts are again expected for the mountain passes, with delays also possible elsewhere throughout the state.

It is certainly possible that snowflakes will make it to Seattle's waterfront, but current indications are that snow accumulations will be limited below 500 feet in elevation. Snowfall predictions for specific neighborhoods and towns around the Puget Sound region lies outside the scope of this product, so those who stand to be impacted by a lowland snow event in the Greater Seattle area should pay attention to National Weather Service forecasts and local media.

Some snow showers remain possible statewide Thursday. For Western Washington, an incoming system will bring more widespread activity than east of the Cascades. It looks as though this round will have a bit less moisture embedded in it than what's expected for Sunday-Monday and Tuesday-Wednesday. An active weather pattern should continue into the following weekend, but current indications are that warming temperatures statewide will bring an end to lowland snow chances for now. More details in future outlooks.

Recent precipitation has brought improvements to the drought situation in Central Washington. In this week's update, the National Drought Mitigation Center removed the area of extreme drought from around Mattawa in their Drought Monitor product. Severe drought remains in place for places like Yakima, Prosser, Goldendale, and Mattawa, with moderate drought conditions noted for Wenatchee, Othello, and the Tri-Cities. Water year-to-date precipitation values in the Tri-Cities and Yakima remain around 60%-70% of normal. Hopefully precipitation values over the next week and beyond will continue to improve the situation.


8 to 14 Day Outlook, January 29 to February 04, 2021
  • Near average temperatures and above average precipitation are favored for the period.

Important Points About Next Week's Weather

South Central Washington
Weekend
  • Wind: Generally S and light.
  • Precipitation: A low chance of snow Sun, possibly mixing with rain around the Tri-Cities.
  • High Temps: Near 40 Sat, mid 30s Sun.
  • Low Temps: Low 20s Fri night, mid 20s Sat night, upper 20s Sun night.
  • Sky Cover: Decreasing clouds Fri PM, mostly clear Sat, overcast Sun. Patchy freezing fog Sat AM.
Next Week
  • Wind: E and breezy Tue, otherwise light and variable.
  • Precipitation: Low chance of snow, possibly mixing with rain around the Tri-Cities, Wed & Thu.
  • High Temps: Upper 30s Mon-Tue, near 40 Wed & Thu.
  • Low Temps: Upper 20s Mon night-Thu night.
  • Sky Cover: Partly to mostly cloudy Mon-Thu. Patchy freezing fog Tue AM.

North Central Washington
Weekend
  • Wind: Light and variable.
  • Precipitation: Chance of snow Sun.
  • High Temps: Mid 30s Sat, low30s Sun. Cooler in higher terrain.
  • Low Temps: Mid teens Fri night, low 20s Sat night, mid 20s Sun night. Cooler in higher terrain and deep valleys.
  • Sky Cover: Mostly clear Sat, mostly cloudy to overcast Sun.
Next Week
  • Wind: E and breezy Tue, otherwise light and variable.
  • Precipitation: Chance of snow Tue-Thu with better chances in the mountains.
  • High Temps: Mid 30s Mon-Thu. Cooler in higher terrain.
  • Low Temps: Mid 20s Mon night-Thu night. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast.

Eastern Washington
Weekend
  • Wind: Light and variable.
  • Precipitation: Chance of snow Sun PM and night.
  • High Temps: Low 30s Sat, mid 30s Sun. Warmer in the Lewis & Clark Valley.
  • Low Temps: Upper teenss Fri night, low 20s Sat night, mid 20s Sun night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly clear through Sat, increasing clouds Sun AM, mostly cloudy to overcast Sun PM.
Next Week
  • Wind: E and breezy Tue, otherwise light and variable.
  • Precipitation: Lingering isolated snow Mon. Chance of snow Wed-Thu. Possibly mixing with rain in the Lewis & Clark Valley.
  • High Temps: Low 30s Mon-Tue, mid 30s Wed-Thu. Warmer in the Lewis & Clark Valley.
  • Low Temps: Mid 20s Mon night, low 20s Tue night, mid 20s Wed-Thu night. Warmer in the Lewis & Clark Valley.
  • Sky Cover: Mostly cloudy to overcast. Patchy freezing fog Tue AM.

Western Washington
Weekend
  • Wind: Generally S/SW and light for most.
  • Precipitation: Rain and snow expected Sat night & Sun. Snow level 500-1000 feet.
  • High Temps: Mid 40s Sat & Sun. Cooler in higher terrain.
  • Low Temps: Near 30 Fri night, upper 30s Sat night, mid 30s Sun night. Cooler in higher terrain.
  • Sky Cover: Mostly clear through Sat, increasing clouds Sat night, cloudy Sun. Patchy fog.
Next Week
  • Wind: S Mon, E and breezy Tue, SE/E Wed-Thu.
  • Precipitation: Rain and snow showers Tue night-Thu. Snow level possibly below 1000 feet.
  • High Temps: Low 40s Mon-Thu. Cooler in higher terrain.
  • Low Temps: Low 30s Mon night, mid 30s Tue night, low 30s Wed-Thu night. Cooler in higher terrain.
  • Sky Cover: Mostly cloudy to overcast.

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