Monday, February 9, 2009

Surprise Convergence Zone snow





Last night a convergence zone formed in the wake of the passing front and was sufficiently intense to drive the snow level down to the surface (see radar image at 2 AM and now). There are reports of a trace to 1-2 inches. It is over now. The Seattle profiler shows the event clearly..with the low-level windshift and the cooling of the air due to evaporation and melting. "Surprise" convergence zone snow showers are a traditional here in Puget Sound country....rarely a year passes without one. To get a handle on such events a coastal radar would be very useful...allowing us to secure much better forecasts 3-9 hr ahead.

The next snow threat includes snowshowers today...which will be brief... and then this evening when the convergence zone should reestablish itself according to the latest high resolution model runs. The air is cold enough that heavy showers can bring wet snow down to the surface.

Tuesday looks as before....incoming weather system that will bring snow to the Kitsap and SE Olympics slopes...as well as the Chehalis River Valley. Near the Olympics the snow could be heavy...6-12 inches are possible. Tonight I will analyze this threat in some detail.

16 comments:

Brian said...

Hey Cliff, some weather stations are talking about another PSCZ setting up later this afternoon or evening. What do you think about this?

Also, I live ontop of a hill in Redmond at about 600', and I was wondering if you think that this next system on Tuesday that they are saying is going to hit the Hood Canal area good, is going to hit us good too?

We normally have the cold air stay around longer then places around us.

Thank you! :)

andycottle said...

I`m here in wooodinville atop Hollywood hill, elevation 300ft, and I got a trace of snow with temo falling down to 32 and dp 30 when the snow was falling. So I`m sure it`s gona be bit ice out there for a little bit..

Anonymous said...

Woke up to 2" of snow in Duvall! I'm hoping for round 2 tonight... what do you think, Cliff?

Big Sven said...

Seems like everybody missed the snow last night. (We got 2" at 800' on Squak Mt., and it was very slow going getting off the mountain)

I'm reading your book and I know you say PacNW weather isn't particularly hard to predict given the dearth of data in the N. Pacific, but I've yet to be convinced. Seems pretty hard to predict.

Anonymous said...

Does this snow have any impact on the snow that is supposed to come tonight?

(Teresa in Sammamish where it ISNT MELTING MUCH, too lazy to log in)

Anonymous said...

From a post on February 1:

"Anonymous, actually the GFS is fairly decent in forecasting long-range patterns IF it is consistent as it has been. Contrary to what the last anonymous poster said, the chance of models being correct a week out is pretty good if that consistency is there - I've seen it many times.

I bet we see cooler weather with maybe even some snow chances next week. The ECMWF is not as aggressive but still suggest something similar."

Leave it up to the meteorologists who know what they are talking about to call that a week in advance!!

Anonymous said...

To the previous Anon: If we had believed the GFS forecast from a week ago, we'd be solidly in arctic air right now.

So it cooled down a little, but we're still just talking about fringe snow chances here.

Anonymous said...

Actually no, the GFS a week ago wasn't showing solid arctic air here now.

But that's not the point of the long-term model forecasts anyway. The point of the long-term forecasts is to get a general pattern, not make specifics.

Anonymous said...

Some runs did show arctic air, and there was in fact very little consistency. The only consistency was a cooling trend, which no one really disputed at the the time, as I recall.

Anyway, I highly doubt you're a real meteoroligist, but that's beside the point.

What's really wrong here is your implication that Cliff doesn't know what's he talking about.

Josh-B said...

Looks like the storm doors have opened up down south into Oregon and California.

Anonymous said...

How much snow could Olympia get tomorrow morning? We usually get pretty cold here.

Anonymous said...

From the snow loop

http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?mm5d2_ww_snow1+//72/1

it looks like the Olympia area should be snow-free.

- Pete [from Olalla]

Dan said...

Anonymous,

Actually I am in fact a meteorologist. I never said Cliff was wrong either, and never implied that. But I don't really care if people know whether I am or not. I'm just trying to help on here and provide some information. Thanks.

Brian said...

OH MY WORD! I live on Union Hill in Redmond, and we just had a HUGE ice pellet/hail storm. The ice pellets & hail are bigger then pea size and put down an inch of hail in about three minutes. My family were all sitting talking in a room, and we couldn't even hear each other it was so loud.

Wow. I have never seen anything like this. Very, very unique!

Anonymous said...

We will have to see how much snow Olympia ends up getting. The Chehalis valley area is under a Winter Storm Watch and that loop doesn't show them getting hardly any snow.

Zach said...

Hailing moderately inbetween Woodinville and Redmond. Road is covered with it.