Sunday, February 5, 2017

Increasing Threat of Lowland Snow Later Today and Monday

I don't want to send folks running to their supermarkets or distract from the big game today, but weather forecast models are suggesting increasing chances of lowland snow later today and tomorrow.  But there are nuances and uncertainties that are very important to communicate, and I will try to do so here.  Then I will run to the store to buy milk, bread and provisions. 😊

But before I talk about the general situation, let's note the significant wintry weather occurring in Whatcom County, north and east of Bellingham.  For most of the region, temperatures are now (7AM) too warm for snow, as shown by the vertical sounding at Sea-Tac, where the freezing level was around 1500 ft at 7 AM.   The snow level (the level where all the snow is melted) can be up to 1000 ft below that (500 ft).   Raining is falling on most of you in the west.
But up in Whatcom County, cold air is seeping into the area through the Fraser River Valley, with cool, northeasterly flow bringing temperatures in the 20s F north and east of Belllingham (see map).
As a result, there has been snow north of Lynden and freezing rain in regions northeast of Bellingham.  Power lines have been taken out by the ice (see the PSE outage map) and the some locations have been covered by ice (see picture by John Bosche)


Today, the air above the region will slowly cool as an upper level disturbance approaches (called an upper level short wave).  This will set the stage for the snowy fun later today and tomorrow.  I have studied Northwest snowstorms for years, and the situation is not optimal for a big snow event, but it is close enough and the models are now insistent enough that significant lowland snow from Seattle to Portland looks highly probable.

In this discussion I will show you the uncertainties, stressing the use of ensembles (many forecasts) to get at those uncertainties.   As noted many times in this blog, the European Center has the best large scale forecasts and their large ensemble is considered the best.   Below is a graphic showing their prediction for Seattle for the next several days. Each horizontal colored line indicates accumulated snow from one of their 51 ensemble forecasts (each is a little different in subtle ways).  Virtually all go for snow, with some showing as much as 10-12 inches.  The ensemble average (or mean) is for about 8 inches (see panel below), with their single high resolution run, a bit more.

Since their high resolution run seems to be on the same page as the ensemble, let's look at its solution, presented in two expanded panels. The heaviest snow is from south Seattle to Vancouver, WA and some of the amounts are impressive 6-15 inches. Not much in Portland.


 The high-resolution UW WRF model is driven by the best US guidance (the GFS).  Here are two forecasts for the 24h ending Monday and Tuesday at 4 AM.   Same general idea, but with less snow by a few inches.



What about the uncertainties?   Here are the ensemble forecasts for snow at Seattle Tacoma Airport from the US (NWS)  GFS (GEFS) ensemble.  A lot of variability (1.5-9 inches), with a mean (black line) of 5 inches,

Both the European Center and U.S. GFS ensemble are relatively course (20-30 km grid spacing), since they are global models.  The only real high-resolution ensemble is run by NCAR (National Center for Atmospheric Research), which runs a small (10 member) ensemble at 3 km grid spacing.  Here are the ensemble forecasts of snow at Sea-Tac from the NCAR system. The real snow starts tonight and there is a little over 4 inch accumulation.  Similar geographic distribution as noted above...and substantial uncertainty as shown by the brackets.  The National Weather Service needs a high resolution ensemble over the U.S. but has been dragging its heals about it...perhaps something to suggest to President Trump.

Finally, the National Weather Service has another, somewhat coarse and poorly designed, ensemble system called SREF.   It also show huge variation of snow accumulation at Sea-Ta, with ensemble mean of around 3 inches, with solutions from a trace to 9 inches.


Why the uncertainties?    A big issue is that temperatures are marginal, so whether snow falls really depends on the exact flow pattern and the precipitation rate (heavier precipitation brings down the snow level).

So what is the take away from all this?

Meteorologists can not give you a specific forecast with absolute certainty....we have to talk about probabilities.   Combining the best tools available to us (ensemble forecast systems at relatively modest resolution and a limited number of high-resolution forecasts),  it appears highly probable that there will be lowland snow from Portland to the Puget Sound lowlands.  In Seattle, there will be some rain and mixed rain/snow showers during the day, but the real action will start this evening and extend into Monday.  There could be some snow today on the higher hills of our region.   The most probable value around Seattle for the event is around 3-5 inches, with more to the south.  In Seattle, there is a perhaps 25% chance of getting only a dusting of snow, with mainly rain falling.  There is a similar chance of getting a major event with 6-12 inches.  These are similar probabilities as were given for the election of President Trump---so they are not negligible.

The mountains are going to be hit hard with feet of snow...that is a near certainty.

I will let all of you decide whether to buy chicken wings for the Superbowl game or milk for tomorrow.  If I were you, I would purchase both.
____________________

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65 comments:

Unknown said...

Any chance you could add a few sentences about what the probabilities look like for Portland? I realize you're Seattle based, but lots of folks down here follow you too. Or maybe you could just link to some of the ensemble forecasts for PDX? Thanks!

Kenna Wickman said...

Thanks Cliff!

(Note the typo in the first paragraph - "break" should be "bread")

How does Friday look for Portland area and out Hwy 47 to Vernonia? Will there still be snow on the ground?

KW

Thecatguy93 said...

National Weather Service is only going for 1 to 3 inches in their winter weather advisory. Are they just being conservative?

-DC- said...

Snow already falling here in Federal Way with temp dropping from 35 to 32 over the past 1.5 hours.

Weatherfreak said...

Wow, not this is a very nice surprise!! Was thinking rain today then snow... Woke to moderate snow and 33 degrees in Lakeland Hills, just NW of Lake Tapps in SE Auburn. Grass is turning white and radar looks to be filling in nicely. I am at about 550'. Hoping colder continues to filter in and keep the snow level low throughout the day! ;)

Robert Wilson said...

Snow falling @830' in Newcastle, too warm to accumulate yet.

saxybrian said...

Snowing in maple valley now

lhsouthern said...

It's snowing here in Chehalis

Eric Blair said...

Thank you as always for the comprehensive update Cliff, an educated guesstimate is the best most of us can hope for at this time.

Glenn Kohler said...

I have about as much confidence that Trump wishes to improve science of forecasts as I do in the typical overblown forecast.

kermitzii said...

There is 8 or even 9 inches of snow on the ground outside. I live next to UBC in Vancouver BC. The entire city is coated as well but maybe 4 inches downtown.

Unknown said...

Same here in Kent's East Hill. Moderate to light snow, trace sticking to pretty much everything but the roads. PWS is hovering around 32/33 degrees. Reminds me of the Super Bowl snow storm we got in mid 1990'S. Can't remember the exact year but I remember it being one of the blowout losses for the Bill's.

Eric said...

Light to moderate snow started just west of Olympia around 7:30 this morning. We're at about 250 feet elevation. Starting to stick to the roads now as the air continues to cool.

BornInCaptivity said...

Been snowing all morning in north Tacoma, Stadium. No accumulation

cgt said...

Snowing hard in Bellingham 80' above sea level.
Maybe about an inch and building.
Thermometer by kitchen window showing 32ish.

larchitech said...

It's snowing in Olympia and starting to stick to the grassy areas. Let it snow, let it snow, let it snow.

Bre Snodgrass said...

Here in Bellingham, it's been snowing since about 8:30am. There's .5-1 in so far, and main roads are slushy.

Colleen said...

It's crazy to think Bellingham has less than an inch of snow. Reality could not be any more different up the road here in Lynden! There's currently nearly a foot & a half of snow and it's dumping again, with near white-out conditions. The forecast is starting to look pretty dire, and I'm not referring to an inability to go out for morning coffee. Many people can't get out of their homes. Driving is inadvisable. Between the weather & the Super Bowl, there's already been a run on gas & groceries. I realize many people yearn for a "fun" snow event, but right now, the situation here is anything but fun for people who need to engage in real life. Stay safe, all!

remnant1978 said...

Snowing like crazy in Lynden. Never got over the sidewalk packing accumilations from last 24 hours. Like 3' where it drifts. It's out of control, thinking of canceling clinic tomorrow.

Sandra said...

Snowing as hard as ever in Lynden. 1 inch of ice on everything.

Scott K. said...

I haven't seen a single snow predictions this winter actually happen, so I'm REALLY skeptical of this one.

Cliff, any comment on the HUGE destructive wind storm that Auburn had on Wednesday? So strong it broke my carport and several items in my backyard. We have never had a wind storm that strong before, and not a single blip anywhere in the news. I'm trying to repair my carport and garage before the 'potential'of any snow falls tonight.

However, what I did see this morning in the N. Auburn/S. Kent valley is a mix of snow/rain (more snow than rain) for a couple of hours. Rain radar show there's a nice vertical line with snow to the east and rain west which is right on top of my house.

Alexander Rohwedder said...

I've never been to a friends house around TGPNW that did not have at least one to two weeks of basic food and drinking water (taking into effect the water heater has 50 gallons on tap of drinking water.)
It feels like a decent snow event is coming up.

Otto Rogers said...

Been snowing all morning in Puyallup south hill, is this supposed to change over to rain and back to snow?

Robert Wilson said...

Newcastle: Still snowing steadily, still no accumulation.

snapdragon said...

A few wet flakes mixed with cold rain in Vancouver, WA. Melts on contact.

A good resource for Portland people is Mark Nelson of Channel 12. KPTV. His blog is very informative and he is more accurate than anyone else around here.

Unknown said...

It's 37 degrees and no snow in north Olympia.

Weatherfreak said...

Snow is picking up in the last 45min. in SE Auburn. Seeing more green on radar moving in from the SW. If the surface low moving up from the SW can pull down some more cold air from Bham, tonight could amazing! Football and snow, what could be better?!?! ;)

Sulla said...

Just plain old rain in Lynnwood. Same old, same old with snow to the north and snow to the south. Also call me cynical on this forecast, but perhaps I'll be surprised by morning.

lhsouthern said...

Yes.... Just let the sky open and let it snow!

larchitech said...

Still snowing in Olympia and the streets are getting slushy. And I see that the Weather Channel has named the storm Maya. https://weather.com/storms/winter/news/winter-storm-maya-northwest-midwest-northeast-snow-ice-early-february-2017

Jena Evans said...

Burn.

Anon the Great said...

Run. We're all gonna die!

Snowing well and truly in NE Olywa

Collin Young said...

Supposed to turn to snow on the evening

vida said...

"...the European Center has the best large scale forecasts and their large ensemble is considered the best. Below is a graphic showing their prediction for Seattle for the next several days."

Sad state of (funding?) affairs. If only we had similar competencies on this side of the pond/country !!

Mike P. said...

Between 1.5-2" in West Olympia just before 4pm. Tumwater about the same, but downtown Oly was trailing by about 0.5-0.75" vs. Westside. Been steady since noonish with no change to rain ever occurring like was forecast. If the expected storm that was supposed to begin around 6-7pm does hit with range of 2-8", we will probably already have 4+" on the ground when that starts. May be in for a REAL storm down here once all is said and done. 10-12" may not be out of the question...

-DC- said...

Heat of the day has passed and temps are starting to creep downward now. I suspect the snow will start sticking in the next hour or so.

Jena Evans said...

Wintery mix/ spitting snow for a couple hours near Haller lake in North Seattle. Hope it picks up.

Otto Rogers said...

About 3 inches here in South hill puyallup. Started to stick to roads around 2pm

Iris Rain said...

Giant flakes in Newcastle, turning to smaller, sticking to the roads and continuing to pelt down. Haven't seen it snow like this in years! :-)

Chronicles of a Sunrise said...

Finally saw the switch over @ 400 ft above Snohomish @ 8:00. Coating the grass nicely, but not the roads...yet.

jon bridgman said...

not a flake here in seattle, montlake

Michael DeMarco said...

Just started sticking on the Sequim Prairie at 200' - very very wet. 8:30PM

Jeff B said...

About 2" so far in Sammamish @ 400 ft. Wet (good snowman snow), but sticking on the roads.

Ryan Kelso said...

It has been snowing since dawn here in the great Napavine Triangle. I don't know what we'll wake up to tomorrow morning. If you don't hear from us in a few days, send in the military.

Jean Danek said...

5 Corners in Edmonds .... heavy wet snow since 8:00pm ...

Jean Danek said...

Edmonds 5 Corners .... heavy wet snow since 8:00pm ....... not sticking ...... slush ...

Donna Lohmann said...

That's strange. We've had wet snow for a few hours here in Fremont.

Scott K. said...

N. Auburn in the valley started snowing about 2 hours ago. We've got about an inch now, sticking to everything. Most snow we've had all winter (had none at all this whole winter prior to today).

It's still snowing hard

Skyhighdaddy said...

Started sticking after 7:30pm in Renton Highlands ~500'. Looks to be 3/4"-1" on the ground now 9:30pm.

windlover said...

Woke up to heavy rain at 5:30 a.m. It turned to snow around 6:00. Been snowing all day. We have 10 inches so far and it's still coming down hard. In Eatonville. Roads are a mess. Cars in ditches and accidents everywhere. Power outages due to transformers blowing and trees coming down because of the heavy, wet snow.

David Diaz said...

Snowing since 8pm in Kirkland highlands and about an inch on everything. Dumping hard.

LSC-L said...

Snowing lightly in south Bellevue where it's currently 32.5-degrees (at 10:52pm). So far, we have about 2" accumulation. (We're located in the 4500-block of 119th Ave SE, at about 200-ft elevation.)

Mark Allyn said...

Columbia Neighborhood in Bellingham at about 11 PM Sunday. About 1 inch of new powder on about 1 inch of crust on my front lawn. Very lightly snowing. Nothing at all similar to what earlier comment mentioned about Lynden.

Talked to someone else in church this morning. They told me about 6 inches in Sudden Valley (southeast of Bellingham) as of this morning when we here in Bellingham had about 1 inch.

I think that what we have here in Whatcom are extremely localized micro-climates. You can have 1 inch in location A yet 1 mile away in location B you have 8 inches.

They tell me that Whatcom is so micro-climate that you really cannot forecast anything here at all.

Example, last summer, NWS Seattle gave a heat advisory for Bellingham on August day. Well, that evening, I had to turn on my heat!!!!

Question for Cliff: Do you know if NWS Seattle has any facilities here in Bellingham? Or are they guessing everything from down at Seatac?

julie said...

Scheduled to drive 300 miles from rural Ferry County back to QA Hill home in Seattle on usual monthly trek. Lots of (usual for here) snow in NE WA (but it gets plowed and sanded regularly) and will need to decide Snoqualmie or Stevens. Happy to have any useful info by 10 AM when I need to decide. I check wsdot and NWS hourly regularly but nice to have local reports. Passes always a challenge but challenge of lots of traffic plus snow in metropolitan area is not something I look forward to after that. Any very local observations on those cross state or in city will be appreciated.

Westside guy said...

At 12:20am Monday, just outside of Sumner (still in the valley) we've got 7 inches with more coming down.

Gary said...

Oly, East Bay Ridge just above Swantown:

It's been snowing all afternoon and evening Sunday and just now (Mon AM) let up. Very wet stuff, air temp has been just a smidge above freezing for many hours. Accumulation ~6"; hills are very slippery. When I went out to pick up our pizza around 9pm (surprise! They weren't delivering), I saw one snowplow that wasn't plowing, no hills sanded or blocked off, and VERY few drivers out on the roads.

When not eating pizza, I was outdoors knocking the snow off of my evergreen leafy and plumey exotic shrubs and trees, which are very fragile under conditions of wet snow/ice and no wind. Those whose branches have not broken but have been significantly bent downward may never recover.

Megan Baldwin said...

Issaquah Highlands up on a 500' steep hill with 5.5 - 6" so far and it's still coming down. I've been sick with a nasty flu, but it seems that Mother Nature decided to have a little mercy on me because hands down, this is the highlight of my year. I'm so incredibly happy!

Unknown said...

Woke up to 13 inches on car just south of Bonney Lake at 550 feet...

windlover said...

Woke up to 14 inches.

carl costenbader said...

4.75 inches of snow 4 miles east of Lacey at 234' in elevation.

Unknown said...

Newcastle got at least six inches- maybe eight overnight. It looks like a winter wonderland outside. Thanks for the great forecast Cliff. You deserve kudos for calling it. Did you call the Patriots 4th quarter comeback as well?

Lavendel M said...

Yep, Sumner/Orting has easily 8 inches! Love it!

Mikki Townshend said...

Bainbridge definitely has snow! 3-4 inches on the deck.

Scott K. said...

Little over 4" in N. Auburn in valley. Have friends and family reporting 4" in port orchard, over 11" in issaquah (500ft), and 5" in des moines.

Mitch said...

Buried in 12 inches down here in Buckley. Interesting observation, Weather Underground (not sure if they are completely owned by The Weather Channel) was the only site really calling for significant snow fall (12-20 cm) for Buckley with their "Best Forecast" model.