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FXUS66 KSEW 170458 
  AFDSEW 
   
  Area Forecast Discussion 
  National Weather Service Seattle WA 
  858 PM PST Sat Dec 16 2017 
   
  .SYNOPSIS...A weakening warm front will pass mainly to our north  
  overnight. Expect a cold front to approach from the northwest  
  during the day Sunday, and then stall over the region Sunday 
  night. This will keep conditions wet and unsettled on Monday. A  
  stronger cold front will bring gusty winds to the area on  
  Tuesday, along with heavy snow in the mountains. 
   
  && 
   
  .SHORT TERM... 
  Precipitation was occurring over much of the CWA at this time. 
  Expect wet weather overnight through Sunday ahead of a frontal 
  system. The weakening warm front is expected to mainly pass to  
  our north overnight. The cold front will approach the area from  
  the northwest during the day Sunday. 
   
  The cold front will stall over the region Sunday night into  
  Monday with strong, moist, westerly flow over the area. The main  
  impact is possible heavy snow in the mountains, especially the  
  north and central Cascades between Mount Baker and Stevens Pass. A 
  Winter Weather Advisory is in effect from Sunday afternoon  
  through Monday morning. Snow levels are tricky and may waver  
  between 4,000 and 5,000 feet with generally 3 to 11" expected.  
  Snow levels will then lower to around 3,500 feet early Monday.  
  Snoqualmie Pass should see mainly rain or a rain/snow mix. 
   
  In the lowlands, cloudy and rain at times Sunday through Monday.  
  Total rainfall amounts will range from 1" along the coast to  
  0.50-1.00" in the interior. Temperatures will mainly stick in the  
  40s for both highs and lows, with a few low 50s possible both  
  Sunday and Monday afternoon.  
   
  A stronger and wetter Pacific frontal system will impact the area 
  on Tuesday. Heavy snow is possible in the mountains and snow 
  levels will be lower - dropping to around 2,000 to 3,000 feet 
  Tuesday night. It`ll be windy too, especially with the frontal 
  passage Tuesday afternoon. However, the models keep waffling on 
  the low strength and tracking. For now it just looks like a 
  blustery front and winds are below Wind Advisory criteria.  
  Showers will taper off Tuesday night as this system exits. 33 
   
  && 
   
  .LONG TERM... 
  Another pattern change will take place on Wednesday as a strong  
  upper level ridge builds over the NE Pacific. This gives Western  
  Washington dry, northerly flow which will help scour out the low  
  clouds and moisture. At this time, the ridge is dominant through  
  the extended forecast with dry weather through at least Christmas  
  Day. With a drier air mass in place, expect low temps in the 20s  
  to lower 30s with highs in the lower 40s. 33 
   
  && 
   
  .AVIATION...A warm front will move over the area tonight and 
  remain over the area Sunday with westerly flow aloft. The air mass 
  is moist and stable. 
   
  KSEA...Mostly mid level ceilings this evening will lower to MVFR 
  low clouds as a warm front moves onshore. MVFR low clouds are 
  expected to persist into Sunday. South wind 4-8 knots will 
  increase to 10-15 knots and become gusty Sunday. Schneider 
   
  && 
   
  .MARINE...A warm front will bring small craft advisory strength 
  winds to most waters tonight and Sunday. There will be relative 
  lull in between weather systems Monday. A stronger frontal system 
  will move through the area Monday night and Tuesday. Gales are 
  likely for the Coastal Waters with this system. Offshore flow will 
  develop Wednesday and continue into Thursday. Schneider 
   
  && 
   
  .HYDROLOGY...River flooding is not expected the next 7 days. 
   
  && 
   
  .SEW WATCHES/WARNINGS/ADVISORIES... 
  WA...Winter Weather Advisory from 10 AM Sunday to 10 AM PST Monday  
       for Cascades of Snohomish and King Counties-Cascades of  
       Whatcom and Skagit Counties above 3500 feet. 
   
  PZ...Small Craft Advisory until 10 PM PST Sunday for Coastal Waters  
       From Cape Flattery To James Island 10 To 60 Nm-Coastal  
       Waters From Cape Flattery To James Island Out 10 Nm-Coastal  
       Waters From James Island To Point Grenville 10 To 60 Nm- 
       Coastal Waters From James Island To Point Grenville Out 10  
       Nm-Coastal Waters From Point Grenville To Cape Shoalwater  
       10 To 60 Nm-Coastal Waters From Point Grenville To Cape  
       Shoalwater Out 10 Nm. 
   
       Small Craft Advisory until 4 PM PST Sunday for Admiralty Inlet- 
       East Entrance U.S. Waters Strait Of Juan De Fuca-Northern  
       Inland Waters Including The San Juan Islands. 
   
       Small Craft Advisory from midnight tonight to 4 AM PST Monday  
       for Puget Sound and Hood Canal. 
   
  && 
   
  
 
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