AgWeatherNet Weekly Weather Outlook for December 2 to December 8, 2017

Unsettled This Weekend; Strong High Pressure Builds Next Week

Nic Loyd, Meteorologist, 509-786-9357

One final frontal passage will cause the recent unsettled weather pattern to persist into this weekend. Therefore, widespread light rain (and isolated wet snow), mountain snow, and breezes can be expected. However, the main meteorological storyline should be the major pattern change that is set to occur early next week. For the first time in a long while, a strong ridge of high pressure looks to develop across the region. As a result, rather calm, stable, and precipitation-free conditions are likely to develop, and may linger for the foreseeable future.

As you may recall, such a pattern in the summer would lead to a sunny heat wave. However, as we enter December, this upper level dome of warm air is expected to initiate the development of temperature inversions, stagnant atmospheric conditions, and potentially poor air quality. Thus, despite the rapidly warming air mass next week, somewhat chilly weather is forecast for the lowlands, at least for a while.

Temperatures could be a tough call, and will likely be highly dependent upon the details surrounding the ultimate coverage and persistence of the fog/freezing fog and low clouds. Areas that remain clear are anticipated to observe larger diurnal temperature fluctuations, while locations that become mired in low clouds may see small day to night changes. Generally, the progression of these types of high pressure events is such that regions of night/morning fog eventually give way to a more widespread low cloud deck east of the Cascades, and another for interior western Washington.

It will be important to watch for slick morning roads later next week due to the potential for freezing fog and freezing drizzle in the lowlands. For the higher elevations, and especially the exposed slopes in the coast range, Olympics, and Cascade west slopes, very mild and pleasant weather is possible by the end of the period.

Here are the key upcoming weather intervals:

  • Unsettled this weekend
  • Clearer, drier, and calmer early next week
  • Increasing stagnation and low clouds later next week

Temperatures
  • Generally slightly above normal.
  • Cooling in the lowlands early next week, and then warming in the mountains and at the coast later in the period.

Precipitation
  • Rain likely on Saturday in the west, with a chance of rain (or possibly isolated wet snowfall) in the east.
  • A chance of lingering showers on Sunday.
  • Mostly dry next week.

Wind
  • Breezy at times this weekend, and generally light thereafter.

8 to 14 Day Outlook - December 9, 2017 to December 15, 2017
  • Overall, above average temperatures and below average precipitation are expected during the 8 to 14 day time frame.

Frost Risk Summary
  • This Weekend: Moderate risk.
  • Next Week: Moderate to high risk.

Important Points about Next Week's Weather

South Central Washington
  • Normal conditions for this time of the year would be highs in the 40s and lows in the mid 20s to low 30s.
Weekend
  • A chance of rain, especially later on Saturday.
  • Highs in the 40s on Saturday, and mid to upper 40s on Sunday.
  • Lows in the upper 20s to mid 30s on Saturday morning, and upper 20s to 30s on Sunday morning.
Next Week
  • Mostly dry, with possible fog and low clouds, especially later in the week.
  • Highs in the upper 30s to mid 40s on Monday, and cooler later in the week.
  • Lows in the 20s to low 30s.

North Central Washington
  • Normal conditions for this time of the year would be highs in the mid 30s to around 40 and lows in the mid to upper 20s.
Weekend
  • A chance of rain or possibly snow, especially later on Saturday.
  • Highs in the upper 30s to low 40s on Saturday, and low to mid 40s on Sunday.
  • Lows in the low to mid 30s on Saturday morning, and upper 20s to mid 30s on Sunday morning.
Next Week
  • Mostly dry, with possible fog and low clouds, especially later in the week.
  • Highs in the mid 30s to low 40s on Monday, and possibly cooler later in the week.
  • Lows in the 20s.

Eastern Washington
  • Normal conditions for this time of the year would be highs in the mid 30s to mid 40s and lows in the mid 20s to around 30.
Weekend
  • A chance of rain or possibly snow, especially on Saturday night.
  • Highs in the upper 30s to 40s on Saturday, and mid 30s to mid 40s on Sunday.
  • Lows in the upper 20s to 30s.
Next Week
  • Mostly dry, with possible fog and low clouds, especially later in the week.
  • Highs in the mid 30s to low 40s.
  • Lows in the 20s, and possibly warmer later in the week.

Western Washington
  • Normal conditions for this time of the year would be highs in the mid 40s to around 50 and lows in the 30s to around 40.
Weekend
  • Rain or showers likely on Saturday.
  • A chance of showers on Sunday.
  • Highs in the mid 40s to low 50s on Saturday, and mid to upper 40s on Sunday.
  • Lows in the upper 30s to mid 40s on Saturday morning, and mid 30s to low 40s on Sunday morning.
Next Week
  • Mostly dry, with possible fog and low clouds for interior areas by mid week.
  • Highs in the 40s on Monday, and then warmer, especially at the coast, later in the week.
  • Lows in the 30s on Monday morning, and possibly cooler by mid week.

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