AgWeatherNet Weekly Weather Outlook for December 16 to December 22, 2017

Unsettled and Variable Weather on the Way

Nic Loyd, Meteorologist, 509-786-9357

The large high pressure ridge is finally weakening, which means that fresher and milder air will return to the lowlands this weekend. Although conditions should generally become more unsettled, the weather will be changeable and only briefly stormy. On Saturday, as an anemic system exits the region, a slight chance of rain may linger in the west, but mainly dry weather is expected elsewhere. The west is likely to see some rain on Sunday, which could eventually spread eastward toward Pullman and Spokane while mainly skipping over central Washington.

Moisture streaming over the top of a dirty ridge is anticipated to cause lingering rain in the west on Monday, before a stronger storm approaches the state on Monday night. The result is forecast to be rain for many regions on Tuesday and into early Wednesday, and even a chance of rain in central Washington. Wind looks to be an issue as well in the Tuesday/Wednesday time frame.

However, another benign high pressure ridge is possible later next week, which means that lowland temperature inversions and stable conditions should become increasingly likely by next weekend. Initially, clearer skies can be expected starting on Wednesday. Still, fog/low clouds and stagnant weather may eventually arise. Warmer air and stronger mixing suggest rather mild conditions for early in the week, but a pulse of cooler air is likely later in the period. Overall, in spite of this short term pattern change, the stable high pressure ridge may return once again later in December.

Key Points:

  • Strong inversion ends this weekend, with increasingly unsettled conditions
  • Mild early next week
  • Stronger storm likely for Tuesday, with widespread rain and wind
  • Cooler, calmer, and drier later in the period

Temperatures
  • Generally above normal, especially early next week.
  • Possibly cooler later next week.

Precipitation
  • A slight chance of rain on Saturday in western Washington, and a slight chance of rain or snow in far eastern Washington.
  • Rain likely in the west on Sunday, with a chance of rain in the east.
  • A chance of rain on Monday, and then rain likely (and mountain snow) for Tuesday and into early Wednesday.
  • Drier later next week.

Wind
  • Breezy on Sunday, and breezy to windy on Tuesday and Wednesday.

8 to 14 Day Outlook - December 23, 2017 to December 29, 2017
  • Overall, near to below average temperatures and below 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 mid 30s to mid 40s and lows in the 20s to around 30.
Weekend
  • Mostly dry. A slight chance of rain on Sunday.
  • Highs in the mid 30s to mid 40s.
  • Lows in the 20s on Saturday morning, and mid 20s to mid 30s on Sunday morning.
Next Week
  • Mostly dry. A slight chance of rain on Tuesday and into Wednesday morning.
  • Highs in the upper 30s to 40s on Monday, and then warmer, and cooler later in the week.
  • Lows in the mid 20s to 30s on Monday morning, and then warmer, and cooler later in the week.

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

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

Western Washington
  • Normal conditions for this time of the year would be highs in the mid to upper 40s and lows in the 30s.
Weekend
  • A slight chance of rain on Saturday, and rain likely on Sunday, especially in northwestern areas.
  • Highs in the mid to upper 40s on Saturday, and upper 40s to low 50s on Sunday.
  • Lows in the mid 30s to low 40s on Saturday morning, and 40s on Sunday morning.
Next Week
  • A chance of rain on Monday, and then rain likely for Monday night and Tuesday. Showers possible on Wednesday morning.
  • Highs in the mid 40s to mid 50s on Monday, and then warmer, and cooler later in the week.
  • Lows in the 40s on Monday morning, and then warmer, and cooler later in the week.

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