Winter Storm Watch for Seattle and all of western WA

[TT-SEA]

Thats fine... but the GFS has never showed the strong and cold system that the ETA has shown.

Now that the preferred model in the short term (the ETA) is trending towards the warmer and weaker GFS I would be shocked to see the GFS change.

We will see in about 2 hours.

[TT-SEA]

Interesting to note... the ETA now shows the precipitation lingering in a PSCZ from downtown Seattle to Snoqualmie Pass during the entire day on Wednesday.

This lingering effect is indicative of a weaker system. That means that PSCZ will probably be in the form of rain or rain/snow mix with 500mb heights up to 5460 by Wednesday evening.

[AnthonyC]

If 500 mb thicknesses are at 540, everything will be in the form of rain. But if the last model run had thicknesses at 510, I find it hard to believe it could change that drastically in one model run. We shall see in the next two or three runs. In the extended, although the snow/cold pattern is over for awhile, there's no BIG ridge over the west coast. Actually, by January 20-25 another smaller trough could encompass the PNW...500 mb thicknesses are down to 528. The only MAJOR arctic air found is in the Eastern US. The rest of the country is in a zonal flow.

Anthony

[W13]

Thats fine... but the GFS has never showed the strong and cold system that the ETA has shown.

Now that the preferred model in the short term (the ETA) is trending towards the warmer and weaker GFS I would be shocked to see the GFS change.

We will see in about 2 hours.

Actually, we are only about an hour away from seeing the latest GFS for Day 1 and Day 2.

Hopefully, it is looking better than it has in past runs for the colder and stronger system.

[W13]

Yes Anthony, we should expect flip flops to occur and then switch back to what they once were after a few runs. It has happened many times during the last few snow events.

[R-Dub]

Going to be a cold one!
As for the next system, like everyone else is saying 50/50! Don't know how much I trust the models, system shifts a little one way or the other, or gets stronger or weaker makes a big difference, lots of variables! I may just sit back, quit looking at the models, and let mother nature do her thing.

1/10/05
7:17:12 PM CURRENT
Clear
Temperature (ºF) 25.9
Humidity (%) 81.2
Wind (mph) NNW 3.9
Daily Rain (") 0.00
Pressure ("Hg) 29.95
Dew Point: 23.4 ºF
Snow Depth 1"

[W13]

30 F at 7:31 PM

[AnthonyC]

Wow, down to 24 F at 7:45pm. This could be the coldest night of the year. I'll update my forecast low to 19 F tonight...with no wind and tremendous radiational cooling, nothing to stop the temperature from dropping and dropping...add the snowpack, and you have temperatures in the teens. I like your "nonchalant" attitude towards the forecast models R-Dub. I think I may do the same thing. These forecast models almost stress me out sometimes...esp. when arctic air is being advertised. I guess next week should be more relaxing.

Anthony

[W13]

29 F at 7:49 PM

[AnthonyC]

Anyone read the latest NWS discussion? Very interesting...

[R-Dub]

Yeah at least Albright gave some indepth explaination! I didn't fully understand the retrogression thing he was talking about. Very cold air? I thought the models have been saying that all along. He is the expert though. Sounds like there will be more precip and longer duration. Also I am hoping the convergance zone forms a little more north. Typically it forms right over my head and moves south, we shall see.

[AnthonyC]

R-Dub,

Current models indicate a less progressive/amplified pattern. The current ridge at 150W...which is VERY amplified...is beginning to shift eastward and weaken. Without this amplification and retrogression, you lose the northerly flow and thus arctic air is eliminated from the forecast. As has been advertised the past week, a Siberian airmass is plowing through Western Canada as we speak. This kind of airmass is very unusual...esp. for Western Canada. Originally, models pointed to this airmass moving through the Pacific Northwest, but as the week progressed they backed off the idea and shunted most of the arctic air east of the cascades. BUT...latest GFS models show the current weakening ridge amplifying once again and retrograding back to 150W. If that were the case, and with a 1060mb surface high in Western Canada, brutal arctic air would filter through Western Washington...compared to 1990 and 1950. This solution seems EXTREMELY UNLIKELY but the past two model runs have hinted at the idea. I saw this a few hours ago, but didn't want to bring it up. Now that the NWS is talking about it, I feel a little better. BUT STILL HIGHLY UNLIKELY!! At least tomorrow night/Wed. morning is looking better. I just want another three inches. I'll be happy!!

Current temp. is 21 F...coldest night of the year.

Anthony

[TT-SEA]

I think I am getting the hang of reading models.

That last discussion is pretty much what I said earlier. Mostly rain... longer lingering convergence zone with maybe some snow.

I truly think when the convergence zone forms... places north of Everett and south of Sea-Tac will be dry.

I doubt there will much snow accumulation.

[R-Dub]

Anthony, when could this big arctic air hit if it were? If it doesn't, is it still supposed to get cool to cold this week? I am pretty lost right now, though you cleared a lot up thank Anthony!

[TT-SEA]

Anthony - when do you see this happening? I did not see any arctic air in the latest 00Z run of the GFS.

Very interesting insight though.

I like this site... even the other threads. Very intelligent people on here with the same passion for the weather that I have.

[andycottle]

Weather Outlook:

Viewing tonights 00z GFS...it appears that the best time for precip on Wednesday will be from 00z through about 12z with .25" or more..in terms of liquid precip. And ETA...shows precip from about 06z through about the early-mid hours of thursday. It also shows the famous PSCZ right in my area of N.King(Woodinville, Bothell..ect)/S.Snomish county. Now looking at the MM5 modle from UW...it`s not really showing any snow on the 1hr and 3hr snow rate map. But 1 and 3hr precip rate map...looks like a good deal of precip comes in around the 4 to 5am hour. Temps should be pretty cool at the surface as 925MB temps are -6C(21F), with 850MB temp of about -10C and height of around 1410M. 500MB heights not seeming all that low. However up at the 700MB level...heights are showing well below the 1300M mark....2885 to 2880M. Though airmass seem a bit dry up there to.

So my thoughs are that we`ll at least get a little bit of snow. But with the famous PSCZ...it`s very possible to see a dumping of snow as they are known to drop heavy amounts of precip in a short time span.

-- Andy

[skipnfamily]

Snow_Wizzard is over on the new message board I made up...Just letting you know..

http://groups.yahoo.com/group/pacnorthwestgroup/

[W13]

20 F at 6:20 AM

Hopefully it doesn't warm up too much today, that would be the perfect scenario.

[W13]

Snow_Wizzard is over on the new message board I made up...Just letting you know..

http://groups.yahoo.com/group/pacnorthwestgroup/

Thanks for letting us know!

[andycottle]

I dont think it supposed to warm up too much today, and infact, Seattle NWS is saying precip could start as snow. Hopefully when the PSCZ comes into my area, the precip will STAY snow. -- Andy