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November 2014
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Whiplash

Posted: November 20th, 2014

 

After two weeks meandering afar, the jet stream is about to whip back into place, aimed directly at us as, just as it’s supposed be at this time of year. The latest forecast shows six-straight days of rain, often steady, though never that intense. The mountains will also finally start to see accumulating snow. And as if there wasn’t enough going on, predicted tides next week will start to get notably high. The good news—though there’s plenty to appreciate in the above—is that after yesterday’s climatological precipitation maximum, we’ve already begun our long descent into next summer’s dry season.

 

Events will kick-off tomorrow when a strong frontal system knocks down the door left ajar by today’s quieter low pressure system. Coastal winds will approach 30mph at times and periods of rain will commence. A true cold front will pass tomorrow evening, and showers, including a convergence zone, will ensue into Saturday. Mountains snow levels will also plummet at the same time; the National Weather Service has therefore issued a Winter Weather Advisory

 

The next, stronger and wetter (and snowier) system is expected to arrive on Sunday. It has elements of an atmospheric river, and should thus be watched closely, but the flow is simply too progressive and wild for forecast models to agree. That uncertainty hopefully communicated, it does kind of look like Thanksgiving could be dry. Not that it’s supposed to be.

 


 

The latest National Weather Service forecast for Seattle indicates 0.64″ of rainfall tomorrow, followed by 0.33″ Saturday, 0.45″ Sunday, 0.53″ Monday, and 1.00″ Tuesday, and 0.38″ Wednesday. Southerly winds will be somewhat gusty, especially along the Sound tomorrow and again on Sunday; otherwise will remain light.

 

Over SPU’s mountain reservoirs, the latest NWS forecast shows up to 3″ of precipitation Friday through Saturday, plus another potential 2-3″ Monday through Wednesday. Not all of that will be in liquid form, however. Above 4000 feet, up to 4 feet of snow could fall through the middle of next week. Winds are also expected to remain near-steady 10-20mph se-sw through the weekend.

 

NWS Area Forecast Discussion
NWS Forecast Table Interface—Seattle
NWS Forecast Table Interface—Tolt Reservoir
NWS Forecast Table Interface—Chester Morse Lake

 

– JRH