A Storm, and then Cold

Monday, January 7, 2013
10:13 A.M.

It’s refreshing to finally have another decent storm roll through the area. As I have stated many times on this blog, I vehemently dislike boring winter weather. Today’s the first day of winter quarter at the UW, and weather-wise, it’s off to a stellar start. We’ll see about otherwise… it looks like I’ll be working like a dog on my science and math classes again.

Currently, not too much is going on. There is a bit of precipitation in the mountains, with a 31 degree rain-snow mix at Snoqualmie Pass (the fact that it is below freezing and there is still some rain mixed in shows that there is significant warming aloft), and the lowlands are mild, mostly dry, and a tad breezy.

But this will change. One thing I wish the UW website would add is isobars to their 3-hour 12km precip charts, so if any of you readers can convince some of the people in the atmospheric sciences department to add these, that’d be super awesome. Anyway, here’s the surface wind speed forecast over the area for Tuesday afternoon. There is a pretty good swath of gale-force winds to the south of a rapidly developing low off our coast.

Valid 01:00 pm PST Tue, 08 Jan 2013 – 33hr Fcst – UW 12z WRF-GFS: 12km 10m wind speed
Here is the 3-hour precipitation forecast at the same time. A warm front is in the process of moving through our area. Snow levels will be above 5,500 feet at this time, so there will be rain or a wintry mix at all the passes.
Valid 01:00 pm PST Tue, 08 Jan 2013 – 33hr Fcst – UW 12z WRF-GFS: 12km 3 hour precip
You can clearly see the bent-back occlusion on this low, which is the mark of a rapidly developing cyclone. There isn’t much of a cold front at this time, but it will develop rapidly and start delivering heavy rain over our area Tuesday night.
Valid 10:00 pm PST Tue, 08 Jan 2013 – 42hr Fcst – UW 12z WRF-GFS: 12km 3 hour precip
Seattle could see around an inch of rain from this storm, while some parts of the Olympics could see nearly five inches. As far as river flooding is concerned, the exceptionally flood-prone Skokomish River might flood, but the flooding will only be minor. All the rivers are running rather low because of the dry streak and chilly temperatures that have accompanied it, so it will take a lot of precipitation to bring even the Skokomish to bankfull. 
After the cold front passes, the snow levels will fall below pass level, and stay there for the rest of the week. However, there is plenty of mountain terrain above 5,500 feet, and those places will continue to pick up snow until it tapers off Wednesday night. The picture below shows the 72-hour snowfall forecast over Washington, and you can see that there are some very heavy amounts in the Northern Cascades. Those whites indicate over 5 feet of snow in the next 72 hours. Snoqualmie will get considerably less, but a foot of snow is nothing to laugh at.
Valid 04:00 am PST Thu, 10 Jan 2013 – 72hr Fcst – UW 12z WRF-GFS: 12km 72 hour snowfall
Starting Thursday, snow levels will fall to sea level, and some places could see some snow showers, especially if a convergence zone develops. I’ll post more about this today on my long range blog at weatheron.net. There are no major snow events on the horizon.
Have a nice day. 🙂
Charlie
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