November 2017 PNW Discussion Thread

[HighlandExperience]

I got back on Weatherbell earlier today. Just too much going on to not have those maps!

Post wxbell maps. I love those

[Jesse]

PDX only had 1 big event. All the other events brought minimal snowfall. We totaled about 7 inches for the entire winter down in the central valley. Was mostly just consistent cold with the occasional inch or so. Going to be really bummed if we are in the warm sector of these every time. At least you guys got the cold temps last winter. We are stuck in the 40s.

Last winter was pretty dang solid in the valley and Portland area. This isn’t Spokane.

[wxmet]

RGEM 00z 1-3" around Seattle with higher amounts to the south and east. Rain transitioning to moderate snow.

 

[Gradient Keeper]

Wow. 00z CMC after day 6 goes nuts with a significant arctic blast for the Columbia Basin and Gorge! If verified HUGE east winds for PDX metro.

 

 

 

[Timmy]

Last winter was pretty dang solid in the valley and Portland area. This isn’t Spokane.

We had snow on the ground for over a month consecutively here as well. Seemed like a pretty solid winter for pdx metro.

[TigerWoodsLibido]

Wow. 00z CMC after day 6 goes nuts with a significant arctic blast for the Columbia Basin and Gorge! If verified HUGE east winds for PDX metro.

 

 

 

 

 

Winds look southerly.  Bend will be in the icebox though.  Wow that will be epic over there.

[luvssnow_spokane]

Wow. 00z CMC after day 6 goes nuts with a significant arctic blast for the Columbia Basin and Gorge! If verified HUGE east winds for PDX metro.

 

 

 

Exciting... if it shifted west

[Gradient Keeper]

Looking at the 500mb loop shows a lobe of the PV over Hudson's Bay swings southwestward shoving the deep arctic air into AB/BC, eastern Washington. Not a lot of confidence the 00z CMC Op solution plays out. We'll see....

[Timmy]

Looking at the 500mb loop shows a lobe of the PV over Hudson's Bay swings southwestward shoving the deep arctic air into AB/BC, eastern Washington. Not a lot of confidence the 00z CMC Op solution plays out. We'll see....

Seems funky without much of a ridge in the pacific.

[Gradient Keeper]

Winds look southerly.  Bend will be in the icebox though.  Wow that will be epic over there.

 Surface map shows a PDX-DLS of -12mb, OTH-GEG -20mb+. Raging east winds with that deep cold air piling up against the east slopes of the Washington Cascades.

[TigerWoodsLibido]

 Surface map shows a PDX-DLS of -12mb, OTH-GEG -20mb+. Raging east winds with that deep cold air piling up against the east slopes of the Washington Cascades.

 

Ah so a mountain wave event...love those where it's so strong it blows over rather than through the gaps.  It gave us the Feb 2014 set of deformation bands that saw 10" in Pacific City

[Gradient Keeper]

 Surface map shows a PDX-DLS of -12mb, OTH-GEG -20mb+. Raging east winds with that deep cold air piling up against the east slopes of the Washington Cascades.

If we can't get a legit arctic blast I'll take this....... for now. I'm sure it'll be gone on the next run. lol

[ShawniganLake]

Down to 27 here. I think my expectations were maybe a little too high (low). I thought we would have been colder with clear skies and very little wind.

[wxmet]

GFS 00z Downtown Seattle Skew-T Sounding looks for pretty optimistic Sunday morning. Saturated dendritic growth zone combined with some decent mid-level lifting.

 

[snow_wizard]

PDX only had 1 big event.  All the other events brought minimal snowfall.  We totaled about 7 inches for the entire winter down in the central valley.  Was mostly just consistent cold with the occasional inch or so.  Going to be really bummed if we are in the warm sector of these every time. At least you guys got the cold temps last winter.  We are stuck in the 40s.

 

I distinctly remember Portland getting hit solidly at least twice with other lesser events.

[TT-SEA]

A little less snow on the 00Z ECMWF but its pretty clear that most of King County will see snow falling tomorrow night and Sunday morning...

 

[snow_wizard]

Down to 27 here. I think my expectations were maybe a little too high (low). I thought we would have been colder with clear skies and very little wind.

 

 

Good grief...the night is still young and it's very early November

[snow_wizard]

A little less snow on the 00Z ECMWF but its pretty clear that most of King County will see snow falling tomorrow night and Sunday morning...

 

 

I think that's an improvement over previous runs though.  Looks promising.

[ShawniganLake]

Good grief...the night is still young and it's very early November

Jeeze. I wasn’t really complaining, just making an observation. I thought we might have a shot at the low 20’s (maybe 23). We tend to decouple very quickly here, 25 or 26 tomorrow morning seems pretty likely. Probably not a daily record.

[snow_wizard]

Jeeze. I wasn’t really complaining, just making an observation. I thought we might have a shot at the low 20’s (maybe 23). We tend to decouple very quickly here, 25 or 26 tomorrow morning seems pretty likely. Probably not a daily record.

 

Oh...if it was 27 here at this time it would probably drop to 20 by morning.

[snow_wizard]

The ECMWF is showing some pretty insane precip totals tomorrow night / Sunday morning.  WAY more the GFS.  If true that would help our snow chances.  It shows a pretty good slug of cold air advecting into King County once the low center moves to the east of us.  We often do well in backwash situations

[stuffradio]

It's 26 here right now.

[TT-SEA]

The ECMWF is showing some pretty insane precip totals tomorrow night / Sunday morning.  WAY more the GFS.  If true that would help our snow chances.  It shows a pretty good slug of cold air advecting into King County once the low center moves to the east of us.  We often do well in backwash situations

 

Ohhhhh... it will be right.     Glad you are connected to the ECMWF surface maps on the WB.    Its so far superior to the WRF.   

[Jesse]

Jeeze. I wasn’t really complaining, just making an observation. I thought we might have a shot at the low 20’s (maybe 23). We tend to decouple very quickly here, 25 or 26 tomorrow morning seems pretty likely. Probably not a daily record.

Is it really normal for you to only drop another degree or two over the next eight hours?

 

In my experience the coldest temperatures usually occur right around dawn on clear, calm nights.

[wxmet]

The ECMWF is showing some pretty insane precip totals tomorrow night / Sunday morning.  WAY more the GFS.  If true that would help our snow chances.  It shows a pretty good slug of cold air advecting into King County once the low center moves to the east of us.  We often do well in backwash situations

Agree. The snow maps aren't really reflecting the potential. Strong CAA down the Pugent Sound Sunday morning. 

 

http://wx.graphics/models/ecmwf/2017110400/washington/ecmwf_uv10m_washington_42.png

 

 

[ShawniganLake]

Is it really normal for you to only drop another degree or two over the next eight hours?

 

In my experience the coldest temperatures usually occur right around dawn on clear, calm nights.

Yep. It’s pretty common. I would guess we might have an outside shot at 24F tonight if it stays clear and calm.

 

I’m really not sure why that is. A 6 or 7 degree drop between midnight and sunrise would be huge for this location.

[SilverFallsAndrew]

Down to 32 under cloudy skies here.

[TT-SEA]

ECMWF shows a high of 39 in Seattle on Sunday with snow (or rain/snow) hanging around most of the day.

 

Sounds like such a dark, damp, gloomy day.

 

Indeed it will be with those conditions.  

 

The common refrain on this forum all winter is that 34-38 degrees with chunky rainy is hideous.  God awful is a frequently used description. 

[BLI snowman]

No, we really don't. We need legitimate CAA from Fraser outflow (I'm thinking 12-28-1990) to develop strong northerlies here during the winter. At least outside of any mircoscale stuff, passing showers, etc. 

 

Makes you appreciate January 1950, which somehow managed several really impressive days with brisk northerlies and little gorge assistance around Portland (1/2, 1/14, 1/24).

[TT-SEA]

850mb temp over Seattle was -5C this afternoon and the 00Z ECMWF shows -6C on Sunday afternoon.

 

The 925mb temp was -3C this afternoon and it shows -2C on Sunday afternoon.

 

Is that a wash?   Seems like -6C and -2C should be snow-worthy in the lowlands with no onshore flow?

[bainbridgekid]

Just posted this on Facebook. Bring on the public snow forecast curse?

 

***MORE SNOW POSSIBLE THIS WEEKEND?***

Looking like another very interesting and potentially somewhat snowy setup late Saturday night through early Sunday afternoon. The situation is remarkably complex, but here are the main factors coming together to possibly give us snow:

1. As the snowflakes around today demonstrated, we currently have a very chilly airmass in place. Tomorrow won't be quite as cold, but should still see high temperatures around Seattle remain largely in the low 40's before dropping toward freezing again tomorrow night. This airmass is very impressive for this time of year.

2. Over the next 36 hours, a weak area of low pressure will be forming offshore and moving in from the West, reaching the coast late Saturday night and moving inland Sunday morning. As of right now, forecast models show the center of low pressure staying well South of Seattle, coming ashore near the OR/WA border. This is key because it should allow cold Northerly winds to continue to spill Southward through Western Washington, moving from the higher pressure in British Columbia toward the area of low pressure to our South.

3. As this system moves inland, most models show what is called a deformation zone on the Northern edge of the area of low pressure around the Seattle area Sunday morning. The solid precipitation rates in this zone, combined with the continued North wind being pulled in from the North, should create some very low snow levels Sunday morning.

 

There are several huge question marks that remain in the forecast:

1. Exactly where will this area of low pressure track? If it comes in too far South, Seattle will be drier and will likely lack the precipitation rates required to get the snow level down below about 500 feet. Too far North and we run the risk of seeing a warming South wind wrap around the low. The perfect track? We may end up getting several inches of snow.

2. How far North of the low will this band of moisture extend? Currently, most models show Seattle near the Northern edge of the bulk of the precipitation. However, computer models have a bias in these situations of cutting off the North end of deformation zones slightly too far South. This bias would work in our favor as of now. More moisture = higher chance of snow.

3. Exactly how cold will it be? As with many of our possible snow situations, temperatures will be extremely borderline. The difference between a 1,000 foot snow level and sticking snow at sea level is usually only about 3 degrees. It's very difficult for forecast models to nail down temperatures that precisely, and current projections range from a sea level snow level to one around 800 feet.

4. What time of day will the bulk of the precipitation fall? The sweet spot for accumulating snow is about Midnight to 8 AM to avoid daytime heating. Right now, most models show the bulk of the precipitation around Seattle falling between 4 AM and 10 AM. This would be close to ideal, but if it hits a few hours later, accumulations would be difficult to come by.

 

Bottom line: This is an extraordinarily complex situation, but midnight Saturday night to about Noon Sunday bears close watching for more wet snow around Seattle. The most likely situation as of right now is for Trace-1" amounts for most places, with 1-2" on the higher hills, but there is absolutely potential for things to end up better than that. Right now, the most likely spots to see meaningful accumulations are SW of Seattle near Hood Canal and any higher hills, but anybody has a shot. It looks mainly dry North of Everett as of now, but that has the potential to change as well.

[BLI snowman]

I distinctly remember Portland getting hit solidly at least twice with other lesser events.

 

We really only had two sweet tracking storms last winter here, 12/14 which was fairly nice outside of the downslope areas, and 1/10. There weren't any other occasions where NW OR and SW WA was in the best spot.

[bainbridgekid]

We really only had two sweet tracking storms last winter here, 12/14 which was fairly nice outside of the downslope areas, and 1/10. There weren't any other occasions where NW OR and SW WA was in the best spot.

I don't remember the specific tracks, but I know there were at least a handful of times my buddy in Camas sent me pictures of his neighborhood snowed/iced in while it was either dry or rainy here.

[Brennan]

What happened in January 2012... the snow event... what was the pattern like?

[bainbridgekid]

FWIW, the 6z NAM has a TON of moisture around Seattle in the deformation band. Actually gives Seattle about 1.25" of QPF between 7 PM Saturday and 10 AM Sunday.

 

Face value shows a lot of it falling as cold rain, but this goes to show the potential this thing has.

 

[wxmet]

Pretty clean setup for 1-3 inches in the PSL, although surface temperatures will likely keep things on the lower end on that range. High pressure to the north flowing down NNE winds and low pressure tracking to the south.

 

[Brennan]

FWIW, the 6z NAM has a TON of moisture around Seattle in the deformation band. Actually gives Seattle about 1.25" of QPF between 7 PM Saturday and 10 AM Sunday.

 

Face value shows a lot of it falling as cold rain, but this goes to show the potential this thing has.

 

namconus_apcpn_nwus_12.png

Holy shiiiiit. North please... north... please

[Geos]

FWIW, the 6z NAM has a TON of moisture around Seattle in the deformation band. Actually gives Seattle about 1.25" of QPF between 7 PM Saturday and 10 AM Sunday.

 

Face value shows a lot of it falling as cold rain, but this goes to show the potential this thing has.

 

namconus_apcpn_nwus_12.png

Got a feeling we're going to do well with this. Cold out there with 27°

[Geos]

URGENT - WINTER WEATHER MESSAGE

National Weather Service Seattle WA

421 AM PDT Sat Nov 4 2017

 

WAZ504-507-509-511-555-556-558-559-042300-

/O.NEW.KSEW.WW.Y.0036.171105T0700Z-171105T1600Z/

Southwest Interior-Everett and Vicinity-Tacoma Area-

Hood Canal Area-East Puget Sound Lowlands-Bellevue and Vicinity-

Seattle and Vicinity-Bremerton and Vicinity-

421 AM PDT Sat Nov 4 2017

 

...WINTER WEATHER ADVISORY IN EFFECT FROM MIDNIGHT PDT TONIGHT TO

8 AM PST SUNDAY ABOVE 500 FEET...

 

* WHAT...A trace to as much as 3 inches of snow above 500 feet

Saturday night into early Sunday morning. Highest snow amounts

expected in the Hood Canal area.

 

* WHERE...Portions of the Western Washington interior from Everett

southward including the Hood Canal area.

 

* WHEN...Midnight to 8 AM Sunday.

[ShawniganLake]

It’s interesting that the GFS is showing a decent amount of precip up this way today but the WRF-GFS has been consistently totally dry. The 6z operational has 0.4” of liquid falling at YYJ today. One of them is going to be really wrong.

 

Edit.

 

Environment Canada thinks the WRF is way wrong. Forecasting 2-4” here today in a SWS

 

“Arctic air is in place over the South Coast of BC and an area of low pressure is set to arrive this afternoon, producing another round of snow.

 

The highest snowfall amounts are expected over higher elevations of southern Vancouver Island where there is the potential for 5 to 10 cm through this evening. Elsewhere on Vancouver Island amounts of 2 to 4 cm are likely while the Lower Mainland and Sunshine Coast will only have a chance of 2 cm.”