Wednesday, February 1, 2017

Precipitation Returns to the Northwest

Potential Snow Even On Monday over the Lowlands:  More Later in a New Blog
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The last week has been relatively dry and cool, but the circulation pattern over the West Coast is about to change as high pressure aloft is replaced by moderate, moist southwesterly flow.

Thursday will be the last dry day for Washington, with a line up of increasingly wet storms invading the State starting Friday.  The forecast for the 72h precipitation ending 4 PM Sunday (see below) says it all: WET, with some of the mountain areas getting 2-5 inches, with more over northern CA.

The big concern right now is about freezing rain and snow in the Columbia Gorge and Portland.   In many ways, the situation is FAR less threatening than in early/mid January and less ominous than feared earlier this week.  The temperatures are much warmer around Portland this time and it is clear that substantially warmer air will invade on Friday, making an extended wintry period unlikely in the Rose City.  Eastern WA will have snow for sure.

The situation at 10 PM Wednesday is shown by a sea level pressure forecast, with low-level air temperature shown as well.  Blue is cold air.     Frigid air is now over eastern Washington, with just moderately below normal temperatures over western WA.  A large pressure difference across the Cascades is producing strong winds in the Columbia Gorge and parts of Portland.

The observations at 8 PM (temp is black, gusts in red), show mid-30s in Portland and teens in eastern WA.  Cold enough to snow.


Tomorrow, a very weak warm front will move northward over Oregon (see forecast precipitation for the 3-h ending 4 PM Thursday).  There could be some very light snow to start, and as warm air surges in aloft, some light freezing drizzle.
 The next pulse of precipitation will come in Friday morning (see forecast at 4 AM) and by that time the temperatures will be above freezing aloft.  Thus, the threat of snow will be over.  There will be a chance of freezing rain over the western side of Gorge into Friday afternoon, after which it will warm sufficiently to be rain even there.
After than, one wet/warm system after another will hit our region.   The precipitation totals forecast by the NWS GFS system for the next 180 h (7.5 days) is amazing (see below), with the West Coast for central CA northward flooded by heavy precipitation.  Temperatures will be cool enough for massive snows in the mountains.  


To illustrate, here is the prediction 72h snowfall ending 4 AM Sunday.  Nearly three feet at higher elevations in the Cascades and more snow over eastern WA.  Lots in the Rockies as well.


As I have said in an earlier blog, the West Coast drought is effectively over.  

18 comments:

Ansel said...

I'm starting to lose hope for a decent lowland snow this year. For all the cold weather...

Eric Blair said...

I heard some folks in my hood complaining this morning about the forecast being another "bust," and I had to ask them why they weren't happy about that reality, instead of disgruntled. Same deal when this blog's proprietor was heavily slammed over the huge storm that barely missed the NW coast last Fall. I was overjoyed about that forecast being off the mark, and an ounce of prevention is usually better than a pound of cure, as the expression goes.

Joel Kawahara said...

I'm really, really looking forwards to Trinity reservoir getting to 80% full. It is 60% right now and if the precip actually falls as predicted in Northern California there is hope to see Trinity Lake statistically full at 80%.

Some good things have happened for salmon in California this year. The Sacramento Winter Chinook spawning and rearing areas were given water cooler than the RPA and cooler than the agreed to temps between CDWR, BOR and NOAA. There is hope that this brood of Winter Chinook has not experienced the very high mortality seen in fall 2014 and 2015.

The lower Klamath dams are on their way to being removed. JC Boyle and others are going through FERC delicensing and decommissioning and removal will begin in 2021. The states of Oregon and California have agreements in place to keep irrigators and fish in balance. The Upper basin has SWE of 116% (today) and again, if the forecast is accurate, due for more.

The only area of the West that hasn't received exceptional snow is the Idaho panhandle. As a region they are generally 60-75% of official median SWE. With luck, the "including the Rockies" snowfall forecast by the UW models will add to their totals. It is critical that Dvorak Reservoir on the Clearwater has lots of cold water going into the summer. Cold water releases from Dvorak is the only way to control water temperature in the Snake River above Lower Granite dam. Water temps throughout the Columbia , all the way to Astoria, can get lethally hot for salmon. The cool water in Lower Granite pool and up into the Clearwater are necessary for salmon survival through summer months.

Frank Blau said...

I really wish you would caveat your "California Drought is over" comments with maybe the NORTHERN California drought is over. Central and Southern California (and the Inland Empire areas) are still considerably below historical water capacity. A few months of rain isn't undoing years of drought. All you have to do is look at long term reservoir data anywhere south of San Luis Obispo and you can see that clearly.

Frank Blau said...

I have a question about RH%.

The values on the UW Rooftop are currently reading as between 16% and 18%. Out here in Sammamish I am getting readings of about 40%-45%. And all the visual products that I look at also indicate around 40%. Is there something about those sensors that make them read lower on the roof there?

Colleen said...

No mention made of this, but Whatcom County is looking at potentially several days of snow, unfortunately. Ansel needs to move up here. We had lowland snow in December & January, and in the north part of the county, the icy road conditions lasted for weeks. Really hoping our forecast proves to be wrong!

jeff said...

The NOAA forcasts for Moses Lake predicting low overnight temps are wrong a lot. Almost always colder than the forcast.

Bryan Black said...

I think you guys up in the sound will get your snow this next week. We have had it 5 times in the Willamette Valley near Salem. Never happened that many times in my life. In the years to come, I wonder if we will see more extreme blocking high pressures pushing up into Alaska and sending the polar jet down over the PNW more often in these ENSO neutral years?

mel said...

Snow is falling in the lowlands now!

John said...

Good to hear, thanks.

Unknown said...

Snowing in Kenmore this morning, after a little snow last night.

Kevin said...

Hi Cliff,

All the NWS forecasts discussions yesterday were insisting there would either be light freezing rain on nothing at all in Western Whatcom County this morning (Friday). Only the 3 am update started talking 1-3 inches up here. Meanwhile, the Canadian forecasters issued a snowfall warning for Vancouver and southern BC (to the US border), as early as mid afternoon yesterday.

Clearly, the Canadian's were much more accurate for this part of the region.

I'd love your insight as to why the Canadian forecasting group was so much better with this situation that the NWS.

Thanks!

Lori said...

Snowing in Clearview, near Woodonville!

David B. said...

There's a dusting of sleet (about 1/4") this morning here on Bainbridge Island. Roads aren't any worse than slushy in spots.

Personally, I doubt we'll see any more lowland snow this year. At least I got to see 3" (briefly; it turned to rain and melted within a day) of snow in early December out this way. One of these years the pattern of Portland getting all the goods while Seattle gets mostly shut out will end.

Unknown said...

Snowing west of Hood Canal all morning, accumulations light.

Sean Mooney said...

I would love to hear a breakdown on what caused the drought. Seemed like El Niño and La Niña weren't as much of factors as was expected, but I'm not sure.

tracksdc89 said...

It's a relief to hear that, at last, we are in for a stretch of some "normal" winter weather (i.e., rain) for the time being at least. Not that anyone likes to get rained on, it's that we need our rainy season if we are to have another hot and dry April as we did last year.

Colleen said...

There's a notable freezing rain & northeaster event here in north Whatcom County. As is so often the case, even Bellingham is altogether different. Rain there early evening; nothing unusual. Ten miles up the road was/is another matter altogether, but it stands to reason that this little microclimate is off the radar ~ though significant economically as far as agriculture goes.