Sunday, January 15, 2012

Interesting Differences in Local Snow

Today there were dramatic differences of snow--even within the City of Seattle--that illustrate some of the challenges of forecasting around here.

Some of you in Ballard and northwest Seattle complained that you hardly saw much snow , while luck denizens of Capitol Hill, perhaps 5-6 miles away, got 3-4 inches in places.  Here are a few pictures from Capitol Hill, courtesy of Joseph Chan, a UW undergrad (taken around 2:20 PM).



You notice the Seattle DOT plow on the job!   A lot of snow.

It turns out there was a band of heavy precipitation--oriented southwest to northeast- that remained quasi-stationary and crossed the southern part of the City.   Here is a radar image at  2:32 PM...see the band?

And here is the estimated 6-h snowfall ending 4: 37 PM from our new SnowWatch application:
As I mentioned earlier, a low pressure area moved down the coast.  Then this low moved eastward south of us.  During a period in the early afternoon we had a situation with southerlies moving up the southern Sound from this low and other air moving southward towards towards the low from the north.  These airflows converged together---like an alternative convergence zone--and caused air to rise...giving us the enhanced snow.  Don't believe me?  Check out the winds at noon.  Notice the winds from the ferry runs in the north and south Sound are in opposite directions.   And there was a reversal of the winds aloft.
 Enough fun.  Some serious weather ahead.  Snow will pick up substantially tomorrow afternoon as another upper trough approaches---many will get several more inches on Monday and Tuesday.  Here is the 24-h snowfall forecast ending 4 PM on Monday and Tuesday, to illustrate.  There will be more Olympic Mt. snowshadowing in the central Sound for this event since the flow is forecast to be more westerely.  Of course, this is not cast in concrete and the exact distribution of snow has considerable uncertainty.


Big snow dump in the mountains during the second period!   But the bigger story is what happens on Wednesday as a strong warm front approaches.  

Dare I show it to you?

Here is the 24-h snowfall ending 4 PM on Wednesday.   More inches...and most of that falls in the lowlands in the morning...before temperature surges and it starts to rain.
SLUSHMAGEDDON A vision that should scare any mayor.  And one I am sure will put a smile on the face of KING-TV's Jim Forman.  If the warm/low goes farther south than forecast there could be much more snow.   Wednesday has the potential to be a very major snow event, but the uncertainty is still large....more tomorrow.




32 comments:

Thepull said...

This setup looks really bad for flooding on the coast if the heavy rains later in the week pan out.

ninaf said...

We got no snow in Magnolia. :(

Buddy said...

In the NWS discussion said they were going to drop extra sondes. I dunno if it solved anything.

The GFS is still considerably further north with Wed. warm front compared to the NAM, Can. and SREF.

I dunno which to root for. Warmer/ more precip or colder/drier side. Pick your poison.

LMeyers said...

Cliff do you see less snowy exit for this pattern..

CA said...

Scott Sistek just tweeted that the models are "still a mess,"-meaning that there's still no agreement among them.

snapdragon said...

Lots of NOTHING in Hazel Dell (SW WA).
I should not have gotten my hopes up.
Poo.

Hey Cliff, which do you trust more- accuweather.com, or weather.com? (or, neither?)

JewelyaZ said...

I hope the model disagreement means less snow... I'd be glad to be cold and dry here in Bellevue and across the bridge to the U district.

mary bailey said...

Love your comment about Jim Forman. Snowstorms (and any other disasters) just wouldn't be the same without him.

Olga said...

Well, it looks like there is a good chance for my first grader to once again whoop with joy: "we're so LUCKY to be living in the convergence zone!!!" (decent snow in Mountlake Terrace; and we have our eyes out for Leah...)

Brian Lutz said...

I thought that snow seemed awfully localized. Yesterday around Noon I was at church about a mile north of Downtown Bellevue when we got about an inch of snow within an hour that began sticking to the roads, which led to a partial cancellation of the meetings. Just a mile away in Downtown, there was basically nothing (although the snow caught up a couple of hours later and put some pretty intense snowfall in the area for an hour or so.)

Big Wave said...

Re: Dropsondes, yes, totally cool little instruments. Over the oceans, you chuck these out of high flying aircraft to gather info for the data hungry monster models. For hurricanes, it really helps to do this upstream to assist divining where the darn things will go. In the Pacific, the aircraft have been flying routinely for winter storms prediction for some years now. Dr Mass would know how much. Come to think of it, those little sondes were originally invented to aid atmospheric researchers (I think, correct me if I'm wrong) - and they have! Huge credit has to go to all the folks who developed them...

ChrisChristensen87 said...

Winter Storm Watch issued! East wind event maybe as well?!

Scott K. said...

All of you might also be interested in reading NOAA's information regarding Tuesday night/Wednesday's storm track:

http://www.wrh.noaa.gov/total_forecast/getprod.php?prod=XXXAFDSEW&wfo=SEW

Each model run shows a large potential for 6+ inches, even at worst case (best case?). There is a potential that the snow on Wednesday will not turn to rain until Thursday, which could lead to some really REALLY impressive snow totals for pretty much all of western washington, save maybe the south border area.

Mindy and Paul said...

"You notice the Seattle DOT plow on the job! A lot of snow."

And is that Hizzhonor's home in the background? ;^)

ILoveWinter! said...

Really hoping the low tracks farther to the south... a lot farther! Here in Eatonville that warm air seems to pour into our area right away, starting us out as rain way before everyone else.
The models are still so far apart on Wednesdays snow. Sounds like we may get some good snow tonight though, so I guess I'll take that. Sure wish it would stay longer than a day though!

Zathras said...

The track of the low on the UW WRFGFS can be tracked with each run using the dprog/dt feature

http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?mm5d3_slp+v2012011821///

I don't watch the ECMWF or look at the NAM (wrfwrf?) that closely from home, but I do watch that wrfgfs. I want to see the low track south of Seattle, and it wouldn't hurt if it were deeper, that would help to pull the cold air down in northerlies, tapping on the Fraser. Fun to watch each run!

I helped the kids start mounding up snow for an igloo. Good think I had the blue tarp out to help scoop it up.
We have 2" on the ground at my spot
in MLT, froze up good last night so the kids aren't all muddy for a change.

The kids and I and my wife have all kept an eye out for the Dog Cliff, sorry no sightings from us--we live across the park from the Rec paviliion, and I think if the dog were
near our block we ought to have seen
it, walking to and from school etc.

Hermes said...

I should've taken a photo as proof, but we had 5 inches at my house on the south end of the Central District.

glassfloat said...

Does anyone know where to find the ferry wx graphics online?

Isaac Molitch said...

In Madison Park we had 8.255 cm (3.25") on Sunday.
Lovely on all the trees.
It was the most sticky snow I've ever seen (and I've seen alot having grown up in Pennsylvania). Massive snowballs in just a second.
I had to go out and knock the very heavy snow off of the evergreen broadleaf shrubs- for example we have several rhodies that were weighed down almost flat!

Ben said...

New forecasts from the NWS show lower than expected temperatures for Wednesday morning and afternoon. Any new information about how much snow and when it will turn to rain on Wednesday?

Charlie Phillips said...

Around how much snow does it take to cancel UW classes? It takes about a half an inch to close Seattle Public Schools...

Ken said...

3-4 inches in downtown Kirkland:

https://picasaweb.google.com/lh/photo/0TRk2KGssbn2oPfPdbS1PIFxVila5CddA-QwWNi-RSI?feat=directlink

At Central Way and 6th. Going up I-405 (left of picture) was quite a sight to see yesterday. Looking forward to more (yes, I am crazy).

Dan said...

NWS is officially predicting snowmageddon now:

".SHORT TERM...VERY HIGH IMPACT WINTER WEATHER IS EXPECTED THROUGH WEDNESDAY NIGHT OR THURSDAY. SNOWFALL AMOUNTS AT SEATAC COULD EXCEED ANYTHING SEEN SINCE NOVEMBER 1985...A TOP 5 RECORD 24 HOUR SNOWFALL AMOUNT. "

http://www.wrh.noaa.gov/total_forecast/getprod.php?prod=XXXAFDSEW&wfo=SEW

Thompsonized said...

I notice the winter storm warning is getting closer and closer and around Ellensburg.

Angus Nordlund said...

Hi Cliff - can we get another NOWCast tonight with your take on the upcoming storm for Mon PM - Tues PM/Wed AM - Im reading all the info I can find but cant make sense of it all! I need you to show the way.

Megan Baldwin said...

My thoughts exactly, Angus.

Seeingred said...

Perfect example of differences in local snow. We live on top of the hill on Rose Hill in Kirkland and we easily had 7 inches.
I think the snow looks great, but I seem to be the only one in the area that doesn't want a foot of snow. I am always laughing about why people live here if they want a ton of snow.

convergence zone said...

When it rains, North Everett and South Marysville get hit with the miserable convergence zone - almost like the Snohomish River acts like a 'wick' drawing the rain clouds up. How come when it snows it misses us? Maybe an inch of snow in N. Everett/S. Marysville. My kids are pretty disappointed (and it makes for a needless snow day - they might as well be at school.)

Hermes said...

Seeingred:

"I am always laughing about why people live here if they want a ton of snow."

Exactly because it rarely happens. If we had that much snow every year then people would either not care or not like it.

Derek Pai said...

Cliff, would it help to publish your confidence levels alongside each forecast, as well as your historical performance on similar predictions?

For example, say today is Tuesday:
- Wednesday, 70% chance of moderate snow (80% confidence, 65% accuracy).
- Thursday, 40% chance of light snow (60% confidence, 52% accuracy).
- Friday, 50% chance of snow/rain mix (40% confidence, 35% accuracy).

I think the problem is that people don't see the inherent uncertainty listed in the forecasts they're shown in the news.

Or maybe news outlets wouldn't publish that information because people would rather be indignant at uncertainty than adapt their lives to it.

Derek Pai said...

Cliff,

I think part of the problem is that people don't see the inherent uncertainty listed in the forecasts they're shown in the news.

Would it help to publish your confidence levels alongside each forecast, as well as your historical performance on similar predictions?

For example, say today is Tuesday:
- Wednesday, 70% chance of moderate snow (80% confidence, 65% accuracy).
- Thursday, 40% chance of light snow (60% confidence, 52% accuracy).
- Friday, 50% chance of snow/rain mix (40% confidence, 35% accuracy).

Or maybe news outlets wouldn't publish that information because people would rather be indignant at uncertainty than adapt to it.

Desi said...

About 12 inches since 12am near downtown Olympia! Still coming down like crazy!