Quick Storm Saturday, Well Above Average Warmth Next Week

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Will this be another post on this extraordinary dry, ridge dominated pattern? Yes… errr, well, somewhat. There is actually a storm to talk about! Now, it’s nothing strong, but this should bring us the first rain since early December, which for California’s wet season is an exceptionally long period without precipitation, on top of the already historically driest year on record: 2013.

January 8th Graphic

Over the last several days, a train of Pacific storms (probably in accordance with the trend into a negative PNA) has slammed into British Columbia, Washington, and Oregon, giving them up there some pretty hefty rain and mountain/inland snow.

The tail ends of these systems and weakening moisture plumes have streamed across northern California the last few days, bringing us increases in clouds, the closest to any action we’ve seen in a while. Up in the northwest corner of the state and into southwest Oregon, they’ve picked up a bit of rain, but nothing significant for their standards.

Latest system bringing Oregon, Washington, and extreme northwest California some precipitation.

Latest system bringing Oregon, Washington, and extreme northwest California some precipitation.

The last system in the parade will impact Washington and southern BC as a fairly strong cyclone, deepening to around 974mb by the time it impacts southern British Columbia. The system is supported by a 120 – 135kt jet, which will extend down southwest far enough to tap into a .9 – 1.2″ precipitable water plume.

00z NAM's 300mb winds and surface pressure valid for early Saturday morning, indicating a moderate to strong jet streak blasting under a 980 - 970mb low off the WA/S. BC coast.

00z NAM’s 300mb winds and surface pressure valid for early Saturday morning, indicating a moderate to strong jet streak blasting under a 980 – 970mb low off the WA/S. BC coast.

That lift, combined with a narrow but rather strong band of vertical motion (lift) along and just ahead of the cold front as it slides through Saturday morning, into the afternoon and locally into the early evening further south. This will support a narrow band of moderate precipitation, especially over the western slope of the sierra, where precipitation could be heavy at times, falling as snow above about 4500 – 5000ft.

00z NAM's 700mb vertical velocities (fill) and 500mb heights. Warm colors are positive (upward) lift, with purple colors indicating rather strong lift along the cold front.

00z NAM’s 700mb vertical velocities (fill) and 500mb heights. Warm colors are positive (upward) lift, with purple colors indicating rather strong lift along the cold front.

QPF wise, most of the valley should see at least a couple hundredths of an inch, with .1 – .3″ along the east side of the valley and up in the northern valley, where lift is maximized against the western slope of the sierra and northern mountains in the north end of the valley. In the mountains, .5 – .75″ of liquid is indicated by most operational models, which translates to 3 – 6″ of snow above around 5000 – 6000ft. Locally 6 – 10″ is possible above 7000ft, generally near the crest.

00z NAM's 6 hour snow valid from Saturday afternoon into the early evening. Blues indicate amounts over 4", see the table on the left side of the image for further reference.

00z NAM’s 6 hour snow valid from Saturday afternoon into the early evening. Blues indicate amounts over 4″, see the table on the left side of the image for further reference.

After this system passes, it will dig out another trough into the eastern U.S., and in combination with a fierce westerly jet blasting across the western Pacific, our ridge will come right back and get quite amplified over the western U.S., which will bring with it some very warm, potentially record-setting temperatures for this time of year, including mid to upper 60s in the valley… locally low 70s.

Jan 8th 2_1

Looking at long range indications, the GFS indicates a larger scale pattern change around the 20th, but most of the GFS’s ensembles contain most of this action in the Pacific Northwest. The ECMWF doesn’t go out this far, but it keeps us trapped under the ridge through the 18th. We’ll just have to wait another week to see what evolves from this ridge.

I may post an update late this weekend or early next week to cover the potential record temperatures, and to look ahead a bit more for any sign of hope precipitation wise.

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