Tuesday, February 24, 2009

More SNOW?!&%$





There has been some hyping of wind in some media outlets...it will get breezy as low pressure moves north of us this afternoon...perhaps 15-20 mph sustained for a few hours in well-exposed locations, but no windstorm. The showers we have been getting has produced significant snow in the mountains (see image), and this will continue the remainder of the week. FINALLY, we are starting to rebuild the snowpack...and I expected 1-2 feet snowfall at pass level and above by Friday. So grease your skis now.
But I did want to note the threat of snow showers in the lowlands on Thursday...something the National Weather Service hasn't mentioned yet. I cold front will move trough around dinner time on Wednesday, bringing in much colder air (see image, sea-level pressure--solid lines, colors are temperature, blue and purple are coldest). A upper trough will move through behind the cold front providing upward motion. A surface low associated with it, is heading towards the snow "sweet spot" off of SW Washington, and a Puget Sound convergence zone may for Thursday morning (graphic). There should be some cold air moving SW through the Fraser River Valley. Finally, this mornings high resolution run is showing snow reaching the surface Thursday morning (graphic--which shows 24-h snow ending 4 PM Thursday) . There is substantial uncertainty...and considering the time of the year and marginal temperatures, we are on the edge of this, but there is a significant chance (perhaps as high as 50-60%) that some snow showers with some accumulation could occur on Thursday AM. So I hope our friends in Metro and various DOTs are keeping a sharp eye on this!


Finally, let me note I will be at Town Hall tomorrow night (Wed) at 7:30 PM talking about the science of local weather prediction. And at the same time Knute Berger will be talking in another room at the same venue about his book "Pugetopolis"--which includes "weather wimps" in the title.

PS: There have been several snow events during the last few days of Feb, first week of March. But if we don't get it then, the probably drops precipitously the second week of the month.

26 comments:

Joan Neslund said...

Holden Village
11 Miles S Stehekin WA
48.2°N 120.75°W (Elev. 3224 ft)

10 am
4 inches of fresh wet snow (finally) and 32 degrees and getting warmer.

Anonymous said...

Yay, bring on the snow!! I think you added an extra 'h'... snow would be a treat, not a threat. :)

Anonymous said...

For the mayor, it is a threat...for us a treat.

Craigf said...

Yeah baby let is snow... I would love a good dumping and some serious cold.. This does not look to be a long lasting event but I can always dream of getting surprised! It has been known to happen...

Thanks for the heads up Cliff... I know that many have been alluding to this for about a week now so glad to see that it may actually come true. :)

Joseph Ratliff said...

KOMO4 is predicting Thursday being a possible rain-snow mix or possible snow for a little bit...but the next day the warmth will take it away.

I think it's a little too late in the season for a REALLY big dumping of the white stuff.

Anonymous said...

IMO Komo is downplaying the snow chance for Thursday, the airmass at this point appears to be cold enough for all snow, the only question will be precipitation amounts. This will be a fun system to track because the slightest shift one way or the other will dictate more or less snow, or no snow and cold rain, we shall see. Right now at face value many areas will see some snow starting as early as tomorrow night.

Julie Anderson said...

I happen to remember Andy talking about snow chances for this Thursday last week - and Cliff blew it off because it was "too far away" to forecast. Maybe I'll switch to reading Andy's blog instead of this one.

Way to go Andy.

Anonymous said...

All Andy did was explain what the model showed when he brought up snow, it had nothing to do with forecasting, Cliff was correct blowing it off, and the models have not been consistent with the potential for snow since then up until yesterday and today. Andy does not forecast the weather, he just explains what the models are showing that could potentially but not guarenteed will happen for a particular timeframe. He does do a good job of explaining the models but he also realizes the likeliehood of certain things showing up more than 3-5 days away may not happen. This system could also turn out to be just a cold rain on Thursday as much as it could be widespread snow event.

Josh-B said...

Andy, Andy, Andy
Where is your candy

inkprincess said...

I remember last year, sometime in March I think, we got a surprise storm out here in Gig Harbor. Ended up with 3in of glorious snow (in about 2 hours time!). I'm hoping for a repeat at some point this year! :)

Julie Anderson said...

I love how forecasting involves saying "oh, that's too far in the future, we can't forecast it yet." Real forecasters saw the consistency in such features from model run to model run, as well as between the GFS, ECMWF and GEM models, and make a forecast instead of ignoring it. What a joke.

Anonymous said...

What matters a little to me is whether snows Wednesday night and whether it sticks and disrupts the school buses Thursday morning. If it snows in the Wed or Thu afternoon and sticks only to the grass, so what. Hard to imagine the roads getting bad when it hasn't been below freezing--everything was frozen back in Dec/Jan.

As far as newbies following the models, why not? They're online for everybody to see and guess at what may happen. Does not seem unlike open source programming, you can probably get some stuff for free that is good, but maybe not. And you can always fall back on XP if Linux isn't your thing. Dunno if that analogy is good, but it didn't cost you anything.

Kevin Purcell said...

Though I note the NWS have a "rain/snow mix" forecast too with the qualifier: "Rain showers likely before 10am, then rain and snow showers likely. Snow level 1200 feet lowering to 300 feet. [...]. High of 42. Chance of precipitation is 70%."

Not huge amounts and just on the top of the big hills in Seattle and it won't stick around.

Anonymous said...

Going to be weird if it snows to monitor it. The KATX radar station on Whidbey Island is down until further notice.

Let it snow :)

andycottle said...

Josh and all... I would like to go into some detail about my thoughts for snow on Thursday for the GFS/WRF is showing, but Cliff may get after me for doing so.. :o(

Maybe Cliff will have different thoughts? Sure I know there`s uncertainty, but that it what you deal with in weather. Not to mention that the models could do a full 360 degrees and be rainy/sunny, ect.

Julie...feel free to come on over to my blog, and thanks for the comments to. :o)

What I will say about the snow is that it looks like a reasonable chance with maybe a few quick inches, but at same time, this is the first run in 12z WRF that has come up in such a short time frame. We`ll see how it plays out.

andycottle said...

Why is the weather radar down anyways? Guess we`ll have to look at other sites to watch the snow when and if it comes.

Anonymous said...

Julie..you have it completely wrong. The issue was that there WAS NO consistency of the model runs that far out. That is why making the forecast for snow that far out made little sense...

climo man said...

Probably another(yawn) non-event for us folks within the Seattle City Limits--although some snow may be likely in the usual CZ Target Zero areas.
I think the real snow action may be in the north part of Eastern Washington, especially in the east slopes of the Cascades and Okanogan Highlands.It appears that the Van. Island trough, the low of Oregon, and the Arctic air boundary are going to phase together in the next 24 to 48 hours somewhere over Washington, perhaps just east of here.
It will also be interesting to see if the Arctic boundary is strong enough, and moves SW enough, to affect the temperature and winds at Bellingham by Thursday.(Bellingham, incidentally, has had modified Arctic air outbreaks as late as the first week in April.)

Anonymous said...

'Anon@8:19pm' and 'Anon@5:41pm' are spot on with their comments. There has been very little model consistency at the synoptic (global GFS and NAM) and mesoscale (WRF) during the entire week or so of split flow ~NW of WA. 'Julie Anderson' please inform yourself or don't try to rebutt something when you have no idea what you are talking about, it makes you look pretty silly.

There is a big difference between describing maps of model output and forecasting the weather.

Anonymous said...

Actually there was consistency. I was watching. :)

Andy I might check out your blog. What's the address?

Anonymous said...

Re: 'Anon@9:50pm',

OK, then please describe the evolution of each of the models you "watched" and how they were "consistent". I would like to know which models you "watched" and the pattern that you saw.

You couldn't have been looking at the GFS, NAM, or UK since they all had major uncertainity.

Anonymous said...

To show one example of how the GFS has NOT been consistent over the past week look at the following loop.

The linked loop compares different GFS model runs starting from Thursday Feb. 19 through Wednesday Feb. 25. Therefore what you see are 36hr-180hr forecasts valid for the same time, Thursday 4am.

GFS model output over last week

As you can see the GFS model was/is very uncertain for the PacNW and only gathers some essemblence of pinning down the forecast in the last 12-24 hours. There are still decent differences in timing/position of the trough/low during these last runs.

Again, my point is there has been high uncertainty as of late. A few who say otherwise are either making things up, have memory problems, or don't understand what the pretty lines mean.

Anonymous said...

Seems the National Weather Sevice agrees that there had been little consistency earlier in the week for the Thursday forecast.

NWS-Seattle 3am Weather Discussion:

AS THE UPPER LOW MOVES INLAND LATE TONIGHT AND THURSDAY...A COOLER
AIR MASS WILL SWING INTO WESTERN WASHINGTON. CONFIDENCE IN THE
POSITION OF THE LOW IS NOT GREAT...AS THE MODELS ARE BRINGING IT
INLAND FURTHER NORTH WITH SUCCESSIVE RUNS.

...

LONG TERM...THE LONGER RANGE MODELS ARE HAVING LOTS OF DIFFICULTY
PINNING DOWN HOW THINGS WILL PLAY OUT FOR SATURDAY AND BEYOND.

Anonymous said...

Anonymous at 8:01...

that doesn't say anything about the past weeks' inconsistency.. just the past day or so.

Anonymous said...

Anonymous at 7:40pm, thanks for the link! Looks pretty consistent to me!

Anonymous said...

Re: Anon@12:30pm,

Assuming you can keep your AM's and PM's straight... I'll reply as if you referred to the Anon@7:40am comment.

lol, well if you think a 1020hPa high with no-precip is consistent with a 1008hPa surface minimum with precip I'd like to know what you are smoking cause it must be potent stuff.

I have an answer now to my earlier musings... you like the pretty lines and colors.

Re: Anon@12:28pm:

Assuming you aren't the 12:30pm Anon... which I doubt... see the GFS link and my comments above as they apply to you (again). Your comment also implies skill increases with forecast time (oops, wrong again)... if the forecast, as confirmed by the NWS above, is highly uncertain 24-48 hours out, 9.5/10 times it sure won't be stable 72+ hours out. Again see the GFS loop for proof of that.

Waiting for your evidence. ;)