Thursday, March 7, 2019

Snow Showers Move Into Western Washington

A band of snow showers has moved into western Washington this morning, but most roads  should be ok.

The 6 AM composite radar image shows the shower activity, which is associated with the approach of an upper level low.  The main band is moving through now and should be out of the way by 8 AM.  But more random snow showers are behind it.


You can also see it in the infrared satellite picture.  Most of the shower activity should be over by 10 AM.


The key issue is temperature, which is marginal since there is onshore flow--coming off the relatively mild Pacific Ocean.   The latest temperature profile from Seattle SnowWatch indicates a freezing level (elevation at which temperatures decline to freezing) at around 1200 ft (see plot), which means the snow level is roughly 200 ft.  So snow is falling nearly to sea level, and even there, wet flakes could mix in during heavier showers.  More snow on top of local hills and away from the water.


Last night's high-resolution UW WRF model run suggested a total snowfall amount through 1 PM of roughly 1-2 inches away from the water....but that is not snow accumulation on the ground....which would be much less (since the snow will be wet, there is melting on the ground, compaction).


A key datum is the road temperature.   Again using the Seattle SnowWatch site one sees the road temperatures (boxes) are above freezing.  Surface air temperatures are are also shown.


So there will be a few hours of snow showers, which may accumulate a bit on grass and bushes above a few hundred feet.  Roads may get a light accumulation during heavy showers that will melt quickly.  During the day, temperatures should warm and the showers should decline. 

There is further snow potential this evening, particularly in any convergence zone forming over  the north Sound.  Last night's WRF run shows snow total through 4 AM Friday shows as much as 3-4 inches of snowfall, which might end up being half that much as accumulation over vegetated surfaces.


Want to see the difference a few hundred feet make?   Here is the latest WSDOT cams at the Mukilteo ferry terminal and at Paine Field (around 450 ft).  No snow at one, a dusting at the other.



23 comments:

Ben Green said...

Solid 2.5 inches on the grass in Seabeck at 450 feet this morning and 1.5 inches on the roadway. Very slippery. Not bad Cliff !

Unknown said...

My plane has been delayed for over an hour slralre at SeaTac...

MAC in Bellingham said...

Perhaps up to an inch accumulated on the grass at our house in Bellingham near the airport where our elevation is around 150', but not much on the roads. Last night we were out where the elevation is 100 feet lower and there was much less snow. Night time temperatures hit a low of 32.5F at 4 am but most of the time it has been 2 to 3 degrees above freezing. It is currently 35F. Not cold enough to freeze the rain gauge with about .03 accumulated precipitation. Wind direction shifted from the north to southerly last night at 6 pm, which is why we are a bit warmer.

SR said...

Snowing hard at 600 feet in South Bellevue at 7AM. Close to 2 inches on th ground.

Unknown said...

1.5" on the ground in Kingsgate (Kirkland) at about 400 ft. 32 degrees and still snowing

Kirsty said...

Kenmore Simons Rd inch so far still bucketing down. Steep hills here already slippery.

J said...

So, Mar 7...interesting....

Unknown said...

2 1/2 on ground and road at sea level, more on the hill in Union (plow just came by).

Just AboveNOAA said...

Snow!?! panic panic panic it's accumulating! panic panic appointments to keep!! panic... oh wait, it's melting. nevermind. Thankee Professor!

TVN said...

THe roads are definitely not OK on Education Hill in Redmond. It's a total mess. Our high schoolers returned home after attempting the drive. They saw a school bus going sideways...cars littered everywhere. There's an inch and a half. School district still says school officially on but apparently very few people have managed to make it to Redmond High....including teachers.

Tina said...

In a rural area between Lake Stevens and Marysville, we have 2+ inches on the ground and accumulating on the road as well. It's been snowing hard for a few hours.

SkyKeke98294 said...

There were 1-2 inches of snow on the ground and the maltby area around highway 522 at 7:45 a.m. this morning. Large, wet flakes falling, compacted snow was making back roads very slippery. Even some hazardous road conditions along highway 522 between Paradise lake road and the highway 2 interchange in Monroe. Especially on Bridges. Current conditions in sultan at 8:15 a.m. we have steady snow falling. 1-2 inches of fresh accumulation. Roadways are mostly wet and slushy with patchy ice, especially on Bridges and overpasses. Current temperature is 30°f.

SkyKeke98294 said...

There were 1-2 inches of snow on the ground and the maltby area around highway 522 at 7:45 a.m. this morning. Large, wet flakes falling, compacted snow was making back roads very slippery. Even some hazardous road conditions along highway 522 between Paradise lake road and the highway 2 interchange in Monroe. Especially on Bridges. Current conditions in sultan at 8:15 a.m. we have steady snow falling. 1-2 inches of fresh accumulation. Roadways are mostly wet and slushy with patchy ice, especially on Bridges and overpasses. Current temperature is 30°f.

JS Clark said...

Scottish on the roads in snohomish at 140 feet. Historically, when is the last time the region saw snow down to this level on March 7th?

JS Clark said...

Half inch on rooftops and stylish on the street in Snohomish at 140 feet elevation. When is the last time the region got this low of snow on March 7th?

Unknown said...

Snohomish proper has it coming down hard. Accumulation on the road at least a half inch plus in the last hour.

Stan Axe said...

As of 8:30 this morning, our yesterday->today's accumulation, at ~500ft on the hill above Lyman, is about 3".
And still snowing...

Carl Gray said...

It dumped really hard for 3.5 hours from 3am to 6:30am in Hoodsport on Hood Canal. We ended up with almost 4 inches at sea level and quite a bit more in the surrounding foothills.

TW B said...

3" at 1000ft on the Eastside. Slippery stuff, school bus sideways on the hill. And we still have snow from the last storm. When is it going to warm up?

Dave Myron said...

We received about 4" of new (to go on top of the 8-10" of compacted snow still on the ground from a month ago…) on South Tiger Mountain at 1600'

Unknown said...

Just be glad it’ll take off eventually. Call me loser townie guy

Elston Hill said...

The 509 from Burien to the 1st Avenue Bridge had abnormally slow traffic this morning which suggests snow impacted the driving conditions there. Ironically, Going north from there on the 99 to downtown was abnormally clear, probably reflecting that traffic was jammed up further south.

clive boulton said...

4:30 am today in the North Sound. Google Home device said the temperature outside was 34F, yet the side roads at slight elevation were in covered in crisp frozen snow. Police were assisting 2 spin outs and our vehicle lost road grip on bridges and moderate hills (and I was gingerly touching gas pedal). Kiro7 5:00am weather/traffic report also seemed to under state just how slippery road conditions were due to black ice. Overall I am now subtracting 2F from reported temperatures because reports are wrong. i.e. based on icy road conditions it was 32F not 34F.