AgWeatherNet Weekly Weather Outlook for Jan 10 to Jan 16, 2020

A very cold and snowy week ahead, with potential implications for cold hardiness

Craig Oswald, Field Meteorologist, 509-786-9256
Joe Zagrodnik, Postdoctoral Research Associate

Discussion:

The outlook period looks to bring a stretch of very interesting and impactful weather to Washington State. With recent unseasonably warm temperatures that we have been enjoying, it seems the time has come for mother nature to even things out a bit. A region of strong high pressure situated in the middle of the North Pacific has helped to establish a strong northwest to southeast oriented jet stream stretching generally from southern Alaska to the northern California/Oregon coast. The implications of this are twofold. First, a series of disturbances are expected to travel along this boundary and impact the Pacific Northwest bringing unsettled weather and state wide precipitation for the weekend and into next week. Second, this places much of the northwest under a large trough, meaning an intrusion of cold air.

Light to moderate snow showers are expected through much of the state as temperatures gradually cool through the weekend with accumulations on the order of several inches. Areas of high terrain will see extended periods of snowfall into early next week with even larger snowfall totals. Travel through pass routes is anticipated to become quite difficult. However, while widespread snow is expected, lowland areas through the Basin and Palouse look to receive rain/mixed type precip through much of the weekend. The same goes for parts of south central Washington with rain/mixed precip expected through much of the weekend. Areas west of the Cascades look to maintain rain as their precip type through most of the weekend. Also, windy conditions are anticipated at times during the weekend with gusts approaching 40 mph, especially through the Basin/Palouse and in areas west of the Cascades. In, particular, the Fraser outflow will be very strong on Sunday over Whatcom county and the San Juans, potentially creating blowing snow conditions around Bellingham that can reduce visibility and produce drifting snow.

As mentioned, perhaps the most concerning aspect of next weeks weather are the plummeting temperatures expected for Sunday night and into Monday. The colder temps look to switch any rain/mixed type precip into snow statewide, even including those west of the Cascades, with modest accumulations through the lowlands. Temperatures are expected to drop hard statewide beginning Sunday evening and continue to do so through Monday. Temps look to bottom out by the Tuesday/Wednesday time frame with the absolute coldest temps to be located within north central/north eastern Washington. Here they look to dip to the -15°F range through the high terrain (low land areas look to drop slightly below zero at the coldest). Temps are expected to begin to recover after that but remain below average as we approach the following weekend. With this, winds are anticipated to subside, but remain breezy at times, by early next week, helping to mitigate any drastic wind chill effect.

There is still a bit of model uncertainty as to how far north or south the expected disturbance will pass through the Northwest at the beginning of next week (Monday into early Wednesday). This will affect how far north the snowfall will extend into the state. The main takeaway is to expect a snowfall event in the southern half of the state with an additional few inches of accumulation in most cases (more through high terrain). All lowland areas look to be impacted by snowfall as well thanks to the colder temps that will be present, including those west of the Cascades, but with only modest accumulations anticipated. Snow showers then look to taper off by mid week, offering a very brief reprieve from precipitation before a large surface cyclone is expected to begin impacting the Pacific Northwest by the end of the week. At the moment, the precipitation should start as snow everywhere, including west of the Cascades, although a changeover to rain appears possible at some point as temperatures will have recovered some. However, it is a little early to confidently know the precip type and changeover time as these areas will likely be very near the freezing line. More light to moderate snow showers are anticipated most everywhere else, including the entire state east of the Cascades.

With the sudden cold air intrusion looming for early next week, it becomes important to briefly discuss grape and cherry cold hardiness. In a sentence or two, temperatures through north central and north east Washington look to just reach the 10% bud kill threshold for grapes and flirt with this threshold for cherries but not reach it (with generally only a 2 to 3°F cushion). The coldest air is anticipated for Tuesday night into Wednesday morning, making this the time of highest risk. The remainder of the state looks to remain above any lethal temperatures with approx. a 5 to 10+°F cushion in most cases.

*HOWEVER*, in order to better gauge the anticipated minimum temperature for your area, please pay close attention to local weather reports and forecasts as the beginning of next week approaches. To monitor the latest and most accurate kill temperature for your grape cultivar, please follow this link:

http://wine.wsu.edu/extension/weather/cold-hardiness/


Key Points:

  • Statewide precip with low land snow expected next week.
  • Cold temps next week, especially mid week.

Temperatures
  • Near to slightly above seasonal temps for the weekend.
  • Drastic cool down beginning Sunday evening with temps well below normal for the upcoming week.

Precipitation
  • Statewide rain/mixed/snow showers through the weekend and much of next week.
  • Low land snow next week.
  • Large snow totals for many parts of Washington State, especially high terrain.

Wind
  • Windy conditions primarily for the weekend/beginning of the week with gusts approaching 40 mph. Particularly through the Basin/Palouse and areas west of the Cascades. Winds to ease early in the week but are expected to become breezy again by the end of the week.

8 to 14 Day Outlook - Jan 17, 2020 to Jan 23, 2020
  • Below average temperatures and near to 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
  • Occasional light rain showers expected. Mixed precip in upland areas likely. Mostly cloudy to overcast.
  • Highs in the mid 40s through the weekend.
  • Lows near 40 Saturday morning, and upper 30s Sunday morning.
Next Week
  • Moderate chance for light snow showers early in the week before trending dry. Light snow to move back in at the end of the week. Partly sunny to overcast.
  • Highs in the mid 30s Monday and quickly cooling to the low 20s by mid week. Temps to begin rebounding by weeks end.
  • Lows near 30 Monday morning and quickly cooling to mid teens by mid week. Temps to begin rebounding by weeks end.

North Central Washington
Weekend
  • Periods of light to moderate snow showers expected. Mostly cloudy to overcast.
  • Highs in the mid 30s Friday and Saturday, and low 30s Sunday. Cooler throughout higher terrain.
  • Lows in the upper 20s Saturday morning, and mid 20s Sunday morning. Cooler throughout higher terrain.
Next Week
  • Moderate chance for light snow showers early in the week before trending dry. Light snow to move back in at the end of the week. Partly sunny to overcast.
  • Highs in the mid teens Monday and cooling to upper single digits by mid week. Temps to begin rebounding by weeks end. Colder throughout higher terrain.
  • Lows near 10 Monday morning and cooling to just below zero by mid week. Temps to begin rebounding by weeks end. Colder throughout higher terrain.

Eastern Washington
Weekend
  • Light to moderate snow showers expected. Mixed precip in lowland areas likely, switching to snow Sunday evening. Mostly cloudy to overcast.
  • Highs in the mid 30s through the weekend.
  • Lows in the low 30s Saturday morning, and upper 20s Sunday morning.
Next Week
  • Light snow showers expected to linger early in the week before briefly trending dry by mid week. Light snow to move back in at the end of the week. Partly sunny to overcast.
  • Highs in the mid 20s Monday and cooling to mid teens by mid week. Temps to begin rebounding by weeks end.
  • Lows in the upper teens Monday morning and cooling to lower single digits by mid week. Temps to begin rebounding by weeks end.

Western Washington
Weekend
  • Extended periods of light to moderate rain switching to mixed/snow Sunday evening. Fairly consistent light to moderate high terrain snow. Mostly cloudy to overcast.
  • Highs in the mid 40s through the weekend. Much cooler throughout the Cascades.
  • Lows in the upper 30s Saturday morning, and mid 30s Sunday morning. Much cooler throughout the Cascades.
Next Week
  • Scattered light snow showers expected to linger in the region early in the week before briefly trending dry by mid week. Light to moderate rain/mixed/snow to move back in at the end of the week. Snow showers over the Cascades to remain more consistent. Mostly cloudy to overcast.
  • Highs in the mid 30s Monday and cooling to upper 20s by mid week. Temps to begin rebounding by weeks end. Much cooler throughout the Cascades.
  • Lows in the upper 20s Monday morning and cooling to lower 20s by mid week. Temps to begin rebounding by weeks end. Much cooler throughout the Cascades

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