AgWeatherNet Weekly Weather Outlook for December 3 to December 9, 2016

Changeable and Colder Weather on the Way

Nic Loyd, Meteorologist, 509-786-9357

The atmospheric circulation is set to experience a major pattern change this weekend that will have potentially significant consequences for Washington's weather. Given the active and dynamic nature of expected regime transition, highly variable conditions are possible in the coming days. Unfortunately, forecast models are struggling with the details, but this summary will endeavor to describe the potential impacts and associated uncertainty.

First, let us discuss the anticipated progression in broad terms, as I describe the parts of the outlook that carry a high confidence level. A mild storm system should cause rain to spread from northwest to southeast during the weekend, although south central areas may receive relatively little rainfall. By Sunday, windy conditions are likely, especially east of the Cascades, along with appreciable mountain snowfall. As the flow turns northerly early next week, colder and drier air is expected to infiltrate the region. In fact, it should be the coolest weather so far this season, which admittedly is not saying much. The chilliest areas east of the Cascades could fall to 10 degrees or slightly lower by Wednesday morning, while highs may not reach freezing. Briefly calmer conditions for early to mid next week could eventually yield to a moist and possibly high impact storm later in the period.

Several weather issues involve lower confidence levels, but are nonetheless important to mention. The behavior of a secondary low pressure area on Monday remains unclear, but some light lowland snowfall is possible, even in western areas. Also, the specifics of the late week storm are very unclear. Heavy western rainfall is possible at that time (which could start as snow in spots), along with a mixed bag of wintery precipitation east of the Cascades that could involve accumulating snow transitioning to a mix or rain before ending. This is a potentially noteworthy event that deserves careful attention going forward, although no clear statements can be made at this time, since the timing, precipitation amounts/types, and temperature profiles are still up in the air. Finally, warmer conditions are likely later next week.

The main points to consider are as follows:

  • Stormy and relatively mild this weekend, with some rain, wind, and mountain snow
  • Light lowland snow possible early next week
  • Colder, calmer, and drier around the Tuesday/Wednesday timeframe
  • Significant storm possible late in the week, but specifics remain unclear

Overall, it is too early to guarantee any specific major weather impacts next week, but these potential weather issues are still worthy of discussion. Although there is plenty of uncertainty in the forecast, we know that a changeable and meteorologically interesting December is in the works.

Temperatures
  • Above normal through Sunday, and then cooler.
  • Becoming warmer later next week.

Precipitation
  • Rain on Saturday night in western areas, and spreading eastward on Sunday morning. Snow in the mountains.
  • A chance of rain or snow early next week, and then drier.
  • A chance of rain or snow later in the week.

Wind
  • Breezy to windy at times, especially on Sunday, and again later next week.


8 to 14 Day Outlook - December 10, 2016 to December 16, 2016
  • Overall, near to above average temperatures and near to above average precipitation are expected during the 8 to 14 day time frame.

Important Points about Next Week's Weather

South Central Washington
  • Normal conditions for this time of the year would be highs in the upper 30s to mid 40s and lows in the mid 20s to low 30s.
Weekend
  • A chance of rain on Sunday morning. Windy on Sunday.
  • Highs in the mid 40s to mid 50s on Saturday, and mid 40s to low 50s on Sunday.
  • Lows in the upper 20s to 30s on Saturday morning, and 30s to low 40s on Sunday morning.
Next Week
  • A chance of snow or possibly rain on Monday, and again later in the week.
  • Highs in the mid 30s to mid 40s on Monday, and then cooler, and warmer later in the week.
  • Lows in the 20s on Monday morning, and then cooler, and warmer later in the week.

North Central Washington
  • Normal conditions for this time of the year would be highs in the mid to upper 30s and lows in the mid to upper 20s.
Weekend
  • A chance of rain, especially on Sunday morning.
  • Highs in the 40s on Saturday, and upper 30s to mid 40s on Sunday.
  • Lows in the upper 20s to mid 30s on Saturday morning, and upper 20s to 30s on Sunday morning.
Next Week
  • A chance of snow on Monday, and again later in the week.
  • Highs in the low to mid 30s on Monday, and then cooler, and warmer later in the week.
  • Lows in the 20s on Monday morning, and then cooler, and warmer later in the week.

Eastern Washington
  • Normal conditions for this time of the year would be highs in the mid 30s to low 40s and lows in the mid 20s to around 30.
Weekend
  • Rain likely on Saturday night and Sunday.
  • Highs in the 40s on Saturday, and upper 30s to mid 40s on Sunday.
  • Lows in the low to mid 30s on Saturday morning, and mid to upper 30s on Sunday morning.
Next Week
  • A chance of snow or possibly rain at times. Likely drier later Tuesday into Wednesday.
  • Highs in the low to mid 30s on Monday, and then cooler, and warmer later in the week.
  • Lows in the 20s on Monday morning, and then cooler, and 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 mid to upper 30s.
Weekend
  • Rain spreading southward on Saturday and into Sunday morning.
  • Highs in the mid 40s to mid 50s on Saturday, and 40s on Sunday.
  • Lows in the low to mid 40s on Saturday morning, and upper 30s to mid 40s on Sunday morning.
Next Week
  • Rain or snow likely on Monday.
  • Rain likely later in the week, possibly beginning as snow.
  • Highs in the upper 30s to mid 40s on Monday, and then cooler, and warmer later in the week.
  • Lows in the 30s on Monday morning, and then cooler, and warmer later in the week.
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