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December 2014

Warmer and Wetter

Posted: December 4th, 2014

Some like it hot.



Perhaps you’ve seen reports that 2014 will go down as the planet’s hottest year on record. Check out the 8-14 day outlook from NOAA’s Climate Prediction Center (above) and you can see that North America will be doing its part this month to ensure the dubious distinction. We’ll be helping locally, too, as we approach 60°F thanks to some pineapples next week.


The low pressure system to which today’s weak, warm front-like disturbance was attached will weakly spin into southeast Alaska this weekend. Pesky light showers are expected to diminish tomorrow morning and some clearing may take place by the afternoon. The system’s dying cold front is forecast to pass through Saturday morning and provide another round of light, nuisance-level conditions, but late Saturday and most of Sunday look to be pleasant at the moment.


The atmosphere gets interesting on Monday, though. A giant area of low pressure is expected to develop well out over the Pacific and steer the jet stream closer toward us. A rapid succession of rainy systems looks likely on Monday, Tuesday, and Wednesday. None look too problematic at the moment, but part of Wednesday’s is a thin atmospheric river. Again, its orientation and speed currently look somewhat favorable to both urban drainage and mountain watershed environments, but it’s worth watching closely.


Also worth watching is Thyphoon Hagiput, which is bearing down on the Philippines right now. When West Pacific tropical cyclones eventually join forces with the jet stream they can wreak havoc on the overall flow. Any such changes wouldn’t likely happen for almost two weeks, however.



The latest National Weather Service forecast for Seattle has 0.26″ tomorrow, 0.16″ Saturday, 0.03″ Sunday, 0.69″ Monday, 0.89″ Tuesday, and 0.97″ Wednesday. The UW WRF-GFS and ECMWF are in general agreement, though the latter provides about a 1.50″/12-hour punch on Wednesday, which is more or less what happened last Friday.


Over SPU’s mountain reservoirs, the NWS forecast shows up to 1.00″ tomorrow and Saturday, followed by over 3.00″ Mon-Wed. Snow levels will remain high, between about 4500′ on Saturday and as high as 8000′ toward Tuesday.




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