February 2014 in the PNW

[luvssnow_spokane]

Of course. Ya all gotta start looking for the TRENDS not the outlier or drunk or high on crack single runs on a model!!!

A trend has to start from somewhere. Correct? 

[Jesse]

Of course. Ya all gotta start looking for the TRENDS not the outlier or drunk or high on crack single runs on a model!!!

The models were actually tending in a great direction up until this morning.

 

Try not to post unless you actually know what you're talking about. Although if that were the case we'd probably never see posts from you.

[MR.SNOWMIZER]

The models were actually tending in a great direction up until this morning.

 

Try not to post unless you actually know what you're talking about. Although if that were the case we'd probably never see posts from you.

One thing is almost a fact around here and that is most of the time a trend to a little warmer in this case might offer more snow. Pretty hard to pull of the perfection it takes to have both very cold outflow and tons of moisture. The real cold usually comes in right behind as you know.

[hailstop]

Temperature is one component, supersaturation w.r.t. ice is another. Temperature is a big factor mostly in the number of ice nuclei available as certain particles work as ice nuclei at certain temperatures. At -40 degrees any particle in the air becomes an ice nuclei meaning there's no supercooled water droplets at -40 Celsius or colder. When a cloud glaciates it's usually in response to cloud top temperatures getting fairly close to -40 or at least cold enough that most particles in the air are ice crystal nuclei. This then creates a feedback reaction via the Bergeron-Findeisen process by which some supercooled droplets turn into ice crystals at the expense of other supercooled droplets due to the supersaturation w.r.t. ice being lower than w.r.t. liquid water. Thus your pop-up cold pool Cb quickly glaciates from the top down to near the freezing level.

 

Actually had a great example of this late last week on the Coquihalla. They got something like 6 inches of snow that never showed up on radar. Models were just tracing out on QPF, but the temperatures were perfect...somewhere around -12 C to -15 C.

[MR.SNOWMIZER]

I still think it will work out to a snow event north of Olympia or even further south. But I think it will be 30 degree snow and might not stick much at first.

[Timmy Supercell]

Not much snow showing up on GFS lately for me, not even in long term. This is 2 winters in a row that I have done horribly on seasonal snowfall. I probably will struggle to add another 2-3 inches before Spring shows up.

[HighlandExperience]

I still think it will work out to a snow event north of Olympia or even further south. But I think it will be 30 degree snow and might not stick much at first.

 

EURO at least still shows a little snow.. Still plenty of time to trend better.

 

BTW if anyone has access to weatherbell, can you please post the snowfall maps for the 12z. Their maps are pretty to look at =)

[Phil]

Temperature is one component, supersaturation w.r.t. ice is another. Temperature is a big factor mostly in the number of ice nuclei available as certain particles work as ice nuclei at certain temperatures. At -40 degrees any particle in the air becomes an ice nuclei meaning there's no supercooled water droplets at -40 Celsius or colder. When a cloud glaciates it's usually in response to cloud top temperatures getting fairly close to -40 or at least cold enough that most particles in the air are ice crystal nuclei. This then creates a feedback reaction via the Bergeron-Findeisen process by which some supercooled droplets turn into ice crystals at the expense of other supercooled droplets due to the supersaturation w.r.t. ice being lower than w.r.t. liquid water. Thus your pop-up cold pool Cb quickly glaciates from the top down to near the freezing level.

Could you educate me a bit more on the micro-physical processes behind the Bergeron-Findeisen interaction? I vaguely remember the gist of it but have forgotten how to properly apply it via skew-T reading.

 

Thanks

[hailstop]

 

 

Yokoyama/Kuroda et al:

 

http://journals.aps.org/pra/abstract/10.1103/PhysRevA.41.2038

 

 

If you want to go above and beyond current limitations, there appears to be an electrodynamic component as well: http://www.its.caltech.edu/~atomic/snowcrystals/electric/electric.htm

 

Also, this was a big cause for the surprising snow totals on...Sunday night I think? When I got up the next morning, I found that at least three sites I monitor in the Lower Mainland had snow-to-liquid ratios of 30:1.

 

I hate it when that happens.

 

There was a sliver of 700mb temps at -12 to -17 C hanging out right above the Lower Mainland...and continuous lift into that layer.

[bainbridgekid]

18z NAM coming out now.

 

Still holding out hope it hangs onto the much more fun Friday night - Saturday period but most likely it will trend toward the GFS, Euro and GEM and be drier/warmer than the last few runs.

[hailstop]

Snow formed between -15C and -20C is the "best"(driest) and produces the highest snow to water ratio(20~~25:1). Usually you want to look at 700mb temps for this.

 

Yup. The thing that suprised me about the 30:1 ratios on Sunday night was that I figured that the temps right at the surface would be enough to compact it, either through melting or aggregation. Didn't happen.

[IbrChris]

Could you educate me a bit more on the micro-physical processes behind the Bergeron-Findeisen interaction? I vaguely remember the gist of it but have forgotten how to properly apply it via skew-T reading.

 

Thanks

I'd have to review my notes to go into more detail, however the gist of it is on Wikipedia.

 

http://en.wikipedia.org/wiki/Bergeron_process

 

The example of hoarfrost on a window showing ice formation in one area while droplets persist in another, noting that droplets won't persist close in proximity to the hoarfrost formation is a good one. I've noticed it but it didn't click at the time that it was a manifestation of B-F on a surface (vs in the free air).

[Timmy Supercell]

What is the latest drought information for the PNW? Lately I noticed central and northern Cascades got some decent snow but the southern Cascades just about dodged last few events and I still stand at around 30% of my seasonal snow in Klamath Falls. Plus factoring in a record dry precip year from Jan-Dec 2013. 

[HighlandExperience]

What is the latest drought information for the PNW? Lately I noticed central and northern Cascades got some decent snow but the southern Cascades just about dodged last few events and I still stand at around 30% of my seasonal snow in Klamath Falls. Plus factoring in a record dry precip year from Jan-Dec 2013. 

 

Washington Cascades are doing just fine now. Most places are 100 to 105 % of normal. The last few weeks really helped.

[Phil]

You and phil are some real weather geeks. I love it. Awesome description from both of you guys!

Ibrchris is clearly above my level when it comes to synoptic scale forecasting.

[Timmy Supercell]

I guess I answered my own question concerning southern Oregon. According to this map I'm still in a severe drought. That figures. 

 

http://i58.tinypic.com/2v30bdi.jpg

[bainbridgekid]

18z NAM still showing a pretty widespread 2-4" snow event Friday night into Saturday morning from about Olympia North.

 

But it is definitely an outlier and . . . well . . . the NAM.

[catnip]

18z NAM still showing a pretty widespread 2-4" snow event Friday night into Saturday morning from about Olympia North.

 

But it is definitely an outlier and . . . well . . . the NAM.

 

It has shown this feature that last few runs I believe, but like you said, it seems to be an outlier for now.

[MR.SNOWMIZER]

18z NAM still showing a pretty widespread 2-4" snow event Friday night into Saturday morning from about Olympia North.

 

But it is definitely an outlier and . . . well . . . the NAM.

It is good for snow starting about hr 63. It looks like the gfs in the evolution just faster. This still looks good.

[HighlandExperience]

It is good for snow starting about hr 63. It looks like the gfs in the evolution just faster. This still looks good.

 

This thing still has good potential.

[Brennan]

18z NAM still showing a pretty widespread 2-4" snow event Friday night into Saturday morning from about Olympia North.

 

But it is definitely an outlier and . . . well . . . the NAM.

Which would probably end up being another 8-12 for Whatcom County.  <_>

[bainbridgekid]

It's amazing how much more pleasant watching snow melting slowly in the sunshine is than the depressing slushfest we usually go through (though we had that Monday.)

 

Still solid snowcover here except South facing slopes in the sun and there's still 4-6" of snow in the shade despite temperatures in the 40's yesterday and near 50 today.

 

And there's not even that many puddles because they are drying up in the sun since DP's have been in the mid 20's all day.

[Timmy Supercell]

The models were actually tending in a great direction up until this morning.

 

Try not to post unless you actually know what you're talking about. Although if that were the case we'd probably never see posts from you.

 

Considering many of my posts are just general weather updates from my town, sadly you'll still be seeing posts from me 

[catnip]

Well through HR42, looks like the arctic front is right at the border, some pretty good Frazer Outflow is going, and there appears to be some moisture along the front. No signs of a L spinning up offshore.... yet.

 

There it is....

[bainbridgekid]

Well through HR42, looks like the arctic front is right at the border, some pretty good Frazer Outflow is going, and there appears to be some moisture along the front. No signs of a L spinning up offshore.... yet.

That's a little premature.

 

The arctic front is still solidly in BC at hour 42 and doesn't reach the border until around hour 66-72 or so.

 

This will be a case where Fraser outflow starts well ahead of the arctic front itself so that could be misleading you. In fact, Fraser outflow is already happening despite very warm upper level temps.

 

A weak low does pop up off the Washington Coast Saturday which would make things fairly interesting over the weekend. Continues to be drier than the NAM though.

[Jesse]

18Z is meh for down here. Bulk of the cold digs into SW Canada. The westerlies bursting through the minute the PV approaches just keeps it from digging as far south as previously shown. Climo probably also plays a factor. Most events at this point in the season have a fairly stark North/South gradient. This one looks like it will be no exception.

 

Could be another great event for Whatcom County. Hopefully the Seattle area can get in on the action as well this time.

[Weather101]

18Z is meh for down here. Bulk of the cold digs into SW Canada. The westerlies bursting through the minute the PV approaches just keeps it from digging as far south as previously shown. Climo probably also plays a factor. Most events at this point in the season have a fairly stark North/South gradient. This one looks like it will be no exception.

 

Could be another great event for Whatcom County. Hopefully the Seattle area can get in on the action as well this time.

NWS pretty much called it a repeat of last weekend in there statement that areas further north have a better chance.

 

Special Weather Statement

SPECIAL WEATHER STATEMENT

NATIONAL WEATHER SERVICE SEATTLE WA

232 PM PST WED FEB 26 2014

 

WAZ001-503>512-514>517-271200-

SAN JUAN COUNTY-WESTERN WHATCOM COUNTY-SOUTHWEST INTERIOR-

EAST PUGET SOUND LOWLANDS-WESTERN SKAGIT COUNTY-

EVERETT AND VICINITY-SEATTLE/BREMERTON AREA-TACOMA AREA-

ADMIRALTY INLET AREA-HOOD CANAL AREA-LOWER CHEHALIS VALLEY AREA-

EASTERN STRAIT OF JUAN DE FUCA-WESTERN STRAIT OF JUAN DE FUCA-

NORTH COAST-CENTRAL COAST-

232 PM PST WED FEB 26 2014

 

LOWLAND SNOW IS POSSIBLE IN WESTERN WASHINGTON THIS WEEKEND.

ONCE AGAIN HIGH PRESSURE OVER SOUTHWEST CANADA WILL PUSH COLD AIR

INTO WESTERN WASHINGTON THROUGH THE FRASER RIVER VALLEY. THE BEST

CHANCE OF SNOW ACCUMULATION WILL ONCE AGAIN BE IN THE NORTH PART

OF WESTERN WASHINGTON AND NEAR THE MOUNTAINS. THE FORECAST HAS A

GREAT DEAL OF UNCERTAINTY SO STAY TUNED AS THE WEEKEND NEARS.

[Jesse]

NWS pretty much called it a repeat of last weekend in there statement that areas further north have a better chance.

 

Their.

 

Please. It's not that hard.

[Weather101]

Their.

 

Please. It's not that hard.

Lol is that your pet peve?

[Deweydog]

Their.

 

Please. It's not that hard.

 

Your going to be a great teacher!

[hailstop]

Your going to be a great teacher!

 

<twitch>

[Jesse]

Your going to be a great teacher!

I am.

[Deweydog]

I am.

 

Kevin Martin style?

[Weather101]

Kevin Martin style?

LOL

[TT-SEA]

Not sure why the WRF is so out to lunch for this weekend.

 

It shows basically sunny skies and dry weather while the GFS operational run shows precip.   

 

The ECMWF shows precip all weekend as well... so its going to happen.

[Deweydog]

Not sure why the WRF is so out to lunch for this weekend.

 

It shows basically sunny skies and dry weather while the GFS operational run shows precip.   

 

The ECMWF shows precip all weekend as well... so its going to happen.

 

It's!!!

[Jesse]

Kevin Martin style?

 

If only you really knew me.

[Weather101]

It's!!!

!!!!!!!!!

[Deweydog]

 

If only you really knew me.

 

I was just curious... You don't have your master's in teaching do you?  

[Guest Monty67]

Your going to be a great teacher!

You're