There has been plenty of snow already in the convergence zone.....here is a recent radar image, See the band with green in the middle...that is the convergence zone.
Some locations have gotten 1-2 inches already. Take a look at recent cam in Everett:
Getting pretty white!And here is a snow video taken in Lake Stevens this morning:
I have taken a look at the latest model runs this morning and they are amazingly consistent both in time and among the models. Although this give me confidence in their forecast, there is still uncertainty in exact positions of features and snow accumulations.
Here is the 24-h snowfall ending 4 AM on Thursday:
There are a lot of subtlies in play here. First, the snow will be very banded, which means there will be a lot of horizontal structure (spatial variations in snowfall between neighboring locations). Second, for the early part of the period there will be significant rainshadowing (snow shadowing) off the Olympics under northwesterly flow...which means Kitsap and south Sound will have snow reduced. Third, a LOT of the action will be at the boundary between NE flow moving out of the Fraser and vicinity and southerly flow moving up the Sound. The southerly flow will be forced to rise by the cold, dense northerlies--producing enhanced precipitation (snow). That is why you see the heavy band between Seattle and Bellingham. No guarantees EXACTLY where that interface will lie. Upslope flow on the Olympics should produce heavy snow on the northern Olympic slopes.And on Thursday, eastern Washington will get crushed by very strong northerly winds and extraordinarily cold temperatures (single digits and below zero).
So bottom line for snow. My prediction: South Seatttle--1-3 inches, North Seattle--2-5 inches, northern Snohomish (3-8 inches).
Good news for commuters and SDOT tomorrow: temperatures will remain above freezing, SO NO SOLID ICE LAYER like Nov 22, 2010.
I am planning to try another NOWCASTING experiment tomorrow (Wednesday). Frequent updates throughout the day on what is happening and will happen during the next few hours.
Finally, I would like to thank those that have contributed to the development of our local forecasting capability (upper right of this blog for more info)... I have already used some of the funds to replace some aging hardware.
PS: I am looking for video of Jim Forman if anyone has it or recording him tonight!
"So bottom line for snow. My prediction: South Seatttle--1-3 inches, North Seattle--2-5 inches, northern Snohomish (3-8 inches)."
ReplyDeleteWhen--Wednesday or Thursday? KUOW is saying afternoon/evening on Wednesday.
Sorry your talk was canceled!
Cliff said: Good news for commuters and SDOT tomorrow: temperatures will remain above freezing, SO NO SOLID ICE LAYER like Nov 22, 2010.
ReplyDeleteOn Wednesday.
But Thu is showing a high of 35F and a low of 24F (MOS for CapHill, Seattle). That doesn't sounds good for ice on roads and sidewalks on Thu through Friday morning (Friday high 35F).
what are your predictions for Skagit??
ReplyDeleteWhen Ivar's takes notice, you KNOW it's serious!
ReplyDeleteKeep Clam!
what is your snow prediction for Olympia?
ReplyDeleteThanks for the update, Cliff! Nothing happening in Seattle downtown at the moment, though I'm hearing folks talk about some snowfall on Capitol Hill...
ReplyDeleteLight snow bands on and off all moring in Bellingham, and lots of cars driving around with quite a bit on them.
ReplyDeleteTop of Orcas islan is frosty white.
Is the snow expected to accumulate today or tomorrow?
ReplyDeleteI have this strange feeling that the south sound will be hit harder than you think sir. Time will tell though, right?
ReplyDeleteUpdate: very light snow in downtown Seattle now...
ReplyDeleteReally pouring big snowflakes right now in SEA! Here we go!
ReplyDeleteWill be interesting to watch where that boundary sets up and where it triggers major convergence. Model trends have been shifting that band further south, so maybe Seattle/Bellevue and evirons get the brunt of this. Will be fun to watch play out.
ReplyDeleteAppreciate the update and any NOWCASTS that you may provide :)
It's Forman time people! Keep clam indeed.
ReplyDeleteModels were originally saying NW interior would be hit with 4-6 inches. Latest runs have the mid and south sound getting much more, and us folks in B'ham maybe missing out altogether.
ReplyDeleteShame - would have been nice to get one more blast of winter.
Got 2 inches last night 5 miles ESE of North Bend. Really coming down now, and just starting to stick. Very pretty, but I'm sick of winter. I hope it goes out with this blast.
ReplyDeleteNothing here at Eastgate (south Bellevue) so far, but I'm taking the laptop home tonight since it sounds like driving tomorrow should be avoided if there's not a need for it.
ReplyDeleteIs Bainbridge Island seriously going to get 2.5 - 3" like that map appears to suggest? Wow.
Keep clam, like everyone says. :-)
The time lapse video for today at Dale Ireland's webcam is pretty incredible. I have never seen so many changes in the clouds direction and it shows clearly different cloud layers moving in opposite directions.
ReplyDeletehttp://www.drdale.com/cam/index.htm
We need Jim Foreman over here STAT! Snowing in Seward Park!
ReplyDeleteIs this stuff expected to last very long? Do I need to make my traditional "snow is coming emergency run to Costco"?
Thanks a ton Cliff, it's so cool to get the scoop.
Tiny snow flakes started here in W.Seattle at about 2:30 even though I still could see patches of blue sky. They're starting to get bigger now, but no sign as to whether they'll last, yet.
ReplyDeleteUpdate to previous note: in the moments that it took to post my comment, it has definitely turned to steady snow here. That was fast.
ReplyDelete"That doesn't sounds good for ice on roads and sidewalks on Thu through Friday morning"
ReplyDeleteActually, though it's no guarantee we WON'T see ice, we typically get VERY dry weather from the Fraser River Valley, so once we get past any snow events, sublimation (solid/ice straight to gas, bypassing liquid phase)tends to occur pretty rapidly.
Always good to be prepared just in case, but keep a watch for how it actually plays out.
Nothing yet in Western Skagit County, although Concrete, Rockport and Marblemount reported 2-3 inches overnight, according to Cocorahs. Here in Anacortes it's been mostly sunny with broken cumulus clouds.
ReplyDeleteYou will appreciate the PEMCO radio spot for the First Snowflake Freakout Lady!
ReplyDeletehttp://www.youtube.com/watch?v=r7zptjhuVe4
Snow earlier, now the sun is shining down at Boeing Field.
ReplyDeleteInteresting to compare this morning's NWS Storm Warning to this afternoon's. They are much more confident of snow and more rather than less. I am now rather confident the kids will have some snow days here - the clincher was when the NWS mentioned wet roadways freezing tomorrow afternoon. The school district won't like that at all.
ReplyDeleteThanks for the update as always! I'll be bringing the laptop home and wearing sturdy boots and a ski coat to the office tomorrow. (That way it won't snow right?)
ReplyDeleteOn a web-functionality note, what kind of site are you hosting the snow video at? For some reason it's being auto-blocked as a TV stream in my office. FWIW, YouTube usually works fine, it's a picky keyword filter I think. Figured I'd bring this up in anticipation of any decisions to live-blog the commutes tomorrow.
Thanks again for your valuable work and keeping the community informed!
Based on today's skiing in the Methow the snow must be low in water content. It was slow sledding. Send more snow over here Cliff.
ReplyDeleteNWS Winter Warning (sounds like another weather cocktail or a 9% dark beer) is now saying:
ReplyDeleteSNOWFALL WEDNESDAY MORNING WILL BE RATHER WET AND SLUSHY IN NATURE. TEMPERATURES WILL FALL INTO THE 20S FROM NORTH TO SOUTH LATER WEDNESDAY AFTERNOON AND WEDNESDAY EVENING. THEREFORE...A FLASH FREEZE WILL LIKELY AFFECT THE AFTERNOON OR EVENING COMMUTE OVER MUCH OF WESTERN WASHINGTON.
They've also revised the forecast overnight lows downwards with this afternoons update.
THERE IS A CHANCE THAT SNOW OVER CENTRAL PUGET SOUND LOWLANDS COULD BE ACCOMPANIED BY A CLAP OF THUNDER.
Thundersnow! Woot!
We have a flight leaving at 6 PM tomorrow night...what are the chances of actually getting to go on our vacation to southern california?
ReplyDeleteI am from the midwest so I don't know how SeaTac handles these storms bu I imagine they aren't very good at handling a few inches of snow.
Survived my first snow storm last year in November and now it looks like we're in for another big blow! This native Low Country South Carolinian is enjoying herself immensely! :) Looks like it'll be an interesting commute tomorrow... that is if I can make it off this steep hill. HA!
ReplyDeleteSnowed big fat flakes most of the afternoon at Eastgate near where I work but both there and in Issaquah there has been little to now accumulation, just lots of heavy snow flakes and granules falling from the sky. The ground isn't quite frozen enough. I sure hope that changes and I get enough to build me a snow-cat :)
What about the Portland Metro area? I know we will get something, but any ideas as to when and how much?
ReplyDeleteThanks!
He's lovingly known as "Danger Jim" in our house.
ReplyDeleteNothing on the ground in Issaquah. Just an enthusiastic 4yo boy snow-dancing at the window.
Did Jim Cantore just say Professor Cliff Mass will be on later in the program?
ReplyDeleteEveryone -- Watch TWC - Comcast 78 to see Cliff :)
We had graupel and sun off and on all day in Port Townsend. Addressing a previous comment- SEATAC handles the snow pretty good. I flew out on Christmas Eve in 2008 and it was snowing hard. We were in the air a little late but not bad. We got deiced, taxied out, took off really steep to get above the storm before the wings iced up. Fun!
ReplyDeletehttp://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?mm5d3_ww_snow1+///1
ReplyDeleteLooks like the central sound gets hammered!!!
We ended up with a good 6.5" here, 5 miles ESE of North Bend. Still just barely snowing. Waiting to see what happens over night. NWS is calling for an additional 2-4" tonight, 5-9" Wednesday, and another 1-3" during the day Thursday. I've got two kids moaning and groaning that this happened during Winter Break!
ReplyDeleteDr. Mass-
ReplyDeleteWhat do you think of Walter Kelley from Q 13 Fox?
Is his forecast accurate?
Bert
I hope to be there at your rescheduled talk at Ivars.
But what about Bellingham? Are we out? I could really use some snow!
ReplyDelete(Claire, ask b to snow dance for us k ;) !?!)
snowed all day today until about 1:30 p.m. 3 miles NNE of Monroe. All told had about 2 1/2" of snow. It warmed up and the sun came out for a bit in the afternoon, but there's still a good inch and a half of slushy snow on the ground. Perhaps a nice base layer for the next round tomorrow!
ReplyDeleteWe're are in the shadow of the Olympics here on the Key Peninsula/Vaughn Bay.
ReplyDeleteWe've had nothing but severe clear and sun all day (stars out now). Been steady south/southwest wind of 10 kts all day, too.
From the AFD Seattle:
ReplyDeleteIN FACT...CLOUD TOPS WERE COOLING
OVER THE SW PORTION OF MAINLAND BRITISH COLUMBIA. THERE ALSO
APPEARED TO BE HINT OF A WEAK CIRCULATION ASSOCIATED WITH THE
COOLING CLOUD TOPS. NOT SURE THE MODELS HAVE A GOOD HANDLE ON PRECIP
TRENDS ACROSS THE FAR N...THUS WILL UPDATE THE WARNING TO MAKE IT
EFFECTIVE IMMEDIATELY FOR SKAGIT COUNTY NWD.
Is another Low?
I wonder how this affects the Frasier river outflow and snow across the north.
We were looking for Jim Foreman sighting last night at Snoqualmie Pass...was he there? Did we miss him?
ReplyDeleteJim Foreman was last seen caught in a snow drift (boot bottoms showing only).
ReplyDeleteDiane :)