February 2017 Observations and Model Discussion for the Pacific Northwest

[Perturbed Member]

HIO just switched to south winds and spiked from 36 to 47 in less than an hour. PDX to the east is still in the mid 30s with a light east wind.

[ShawniganLake]

The cold air has been hanging tough up north here. Abbotsford has dropped to 28 with blowing snow and a 25mph NE wind.

 

Still seeing periods of snow here with snow sticking right down to sea level north of Victoria. Looks like about 2"+ since midnight. Storm total getting close to 10".

[SilverFallsAndrew]

From the PDX NWS. Right now I am thinking PDX - North for big accumulations. Though I should get at least a few inches in the post frontal airmass. 

 

So...we need to lay some cards down on the table, given that snow
could begin as early as Sunday. Despite low confidence in the
details, we feel it is prudent to issue a Winter Storm Watch CWA-wide
Sun-early Mon at this point. Many areas in the watch could very well
end up just rain, with the best chance for that being down toward
Lane County. However, SREF ensemble plumes show a mean of 2-3 inches
of snow in Eugene, with some members as high as 6-10 inches. The same
ensembles show a handful of members with 4+ inches for Newport. So we
can`t really leave anyone out of the watch at this point.

We will fine-tune the details as we get closer to the event. At this
point, based on the type of event and how dependent it is on precip
rates, my gut feeling is that there will be a wide variation in snow
amounts...even in the same general area. There could be a smattering
of 6+ inch snow reports in the lowlands while other areas see much
less. And...for the sake of snow removal budgets and kids` snow
days...there is still the chance that this could wind up being a
foothill event with snow levels staying 1000-1500 feet or so.
However, the hopes of that appear to be dwindling with each
successive model run.

Zones/Grids will be coming out shortly, followed by an updated WSW
with the Winter Storm Watch. 

[SilverFallsAndrew]

The great thing about this is there are so many models to cherry pick from. We can all pick our favorite and let it ride!

 

I would feel most confident right now if I were in the Kelso-Olympia zone. 

[SilverFallsAndrew]

Updated Forecast:

 

Seattle: 2-4"

 

Olympia: 3-6"

 

Kelso:   6-8"

 

PDX Metro: 3-6"

 

Salem: 1-2"

 

Eug: 0

 

Still a lot of uncertainty at this point, but there is a clear albeit slight northern trend in my opinion over the last few model runs.

 

NAM coming in I have updated these #'s to reflect that...

[SilverFallsAndrew]

The WSW reads like a generalized uncertainty warning...

[Jbolin]

Wow - amazing 00z EPS snowfall totals for Seattle metro. From Sunday-Tuesday:

 

Almost 100% show at least 2+ inches

43/51 (84%) show at least 6+ inches

32/51 (62%) show at least 10+ inches

Ensemble mean gets close to 10 inches

 

I'm officially starting to get excited.

D****T, there goes a good cup of coffee all over my laptop

[SilverFallsAndrew]

The 3K-NAM is something else...

[SilverFallsAndrew]

4KM NAM

 

[SilverFallsAndrew]

So the Para-NAM has 18" from SLE to Vancouver, WA. 21" at Wilsonville.

[TT-SEA]

NAM definitely trended north... but too far north could also be a problem.   This is at 1 a.m. on Monday morning at the height of the heaviest precipitation.

 

[FroYoBro]

I do not envy the NWS on this one. This is a situation where we probably won't know the big winners until it is happening in real time.

 

 

It does look like good the bullseye will probably be north of Portland at this point, but 25 miles shifts will make huge differences.

[HighlandExperience]

Nam definitely trending north. We can't let it run to far north.

[TT-SEA]

The 3KM NAM looks nothing like the MM5 NAM for tomorrow night.  What a modeling nightmare!

 

http://www.tropicaltidbits.com/analysis/models/nam3km/2017020412/nam3km_mslp_pcpn_frzn_nwus_40.png

[SilverFallsAndrew]

The High Res NAM actually trended south. I know a majority of the posters on here will ignore it, but I will wishcast on it!

[SilverFallsAndrew]

The 3KM NAM looks nothing like the MM5 NAM for tomorrow night.  What a modeling nightmare!

 

http://www.tropicaltidbits.com/analysis/models/nam3km/2017020412/nam3km_mslp_pcpn_frzn_nwus_40.png

 

Yeah, we have the MM-5 showing pretty much nothing south of PDX..... Then we have this...

 

[SilverFallsAndrew]

One thing to note. These snow maps are going off a 10:1 ratio. This will be very wet 32-34 degree snow, its likely the ratio will be no better than 7:1. So knock about 30% off these snow totals..

[SilverFallsAndrew]

http://www.cascadeaccess.com/~mnelsen/RPM_72_SNOW_12z.jpg

[Jesse]

Still seeing periods of snow here with snow sticking right down to sea level north of Victoria. Looks like about 2"+ since midnight. Storm total getting close to 10".

That is huge. You seem so calm about it. I'd be bouncing off the walls!

[Jbolin]

FWIW, Cliff Mass's thoughts:

 

http://cliffmass.blogspot.in/2017/02/significant-chance-of-lowland-snow-late.html?m=1

Used toilet paper

[SilverFallsAndrew]

I don't follow the RPM enough to know - how does it usually perform on snow totals?

Let's just say it has a mixed track record...does terrible in overrunning situations, a little better in these kinds of scenarios.

[FroYoBro]

http://www.cascadeaccess.com/~mnelsen/RPM_72_SNOW_12z.jpg

We'll get nothing and then I can finally ignore this model for all time.

[HighlandExperience]

12z NAM shows more snow for greater Puget Sound than any previous NAM run.

 

It's coming over to the dark side.

Things are lining up more close with the Euro. Even the silly Rpm has shifted snow north.

[SilverFallsAndrew]

Most lowland snow the GFS-OP has shown so far. 

[Perturbed Member]

Most lowland snow the GFS-OP has shown so far. 

 

Yeah, good to see it finally showing an isothermal profile. 

[Black Hole]

One thing to note. These snow maps are going off a 10:1 ratio. This will be very wet 32-34 degree snow, its likely the ratio will be no better than 7:1. So knock about 30% off these snow totals..

Add compression to the mix (if you actually are talking 12+ inches) and it may well compress even more. 

[Perturbed Member]

Some huge differences on the snow maps between 12km, 4km and 3km para NAM. Shows snow further south on the higher resolution ones.

http://www.tropicaltidbits.com/analysis/models/nam3km/2017020412/nam3km_asnow_nwus_61.png

[ShawniganLake]

That is huge. You seem so calm about it. I'd be bouncing off the walls!

I was up watching the snow several times overnight. I'm fairly excited. Just flurries here now. 3" so far today.

[SilverFallsAndrew]

Gem is a bit further south. But it was the furtherest north anyway. 

[Kayla]

Yep. Parts of Portland (mostly West Hills) got 12-16 inches with that big snowstorm, don't see why snow totals that large couldn't happen with this somewhere. 

 

 

I ended up with 20" of snowfall at the top of the West Hills. Was just an incredible thing to experience and up there in the top 3 weather events in my lifetime. 

 

What's truly remarkable is that tomorrows event has a chance to even top that, in the same year. Amazing.

[Perturbed Member]

GEM is further south, low is just a touch weaker. GFS looked about the same. 

[Perturbed Member]

I ended up with 20" of snowfall at the top of the West Hills. Was just an incredible thing to experience and up there in the top 3 weather events in my lifetime. 

 

What's truly remarkable is that tomorrows event has a chance to even top that, in the same year. Amazing.

 

Yeah, I remember thinking during that storm that it might be another decade or something before we get a storm like that in the area. It is crazy that we're actually seriously talking about another even more widespread event of a similar or stronger strength. 

 

Busting risk of this is higher than usual though, but the models have generally been pretty nice to PDX so far. 

[Kayla]

Yeah, I remember thinking during that storm that it might be another decade or something before we get a storm like that in the area. It is crazy that we're actually seriously talking about another even more widespread event of a similar or stronger strength. 

 

Busting risk of this is higher than usual though, but the models have generally been pretty nice to PDX so far. 

 

Yeah huge bust risk with this one no doubt. But when you are talking about historic type storms there is always going to be a very fine line.

 

NAM 3km and EPS have been my go to this winter season and they both look incredible.

[Perturbed Member]

Looks like the WRF is coming in pretty ugly...

 

 

EDIT:

 

The snow maps for some reason are showing it as not sticking but the soundings look ok for sticking wet snow. 

 

By 10 AM tomorrow:

 

http://www.atmos.washington.edu/mm5rt/data/current_gfs/images_d3/kpdx.30.0000.snd.gif

 

Column does eventually cool to freezing.

[Kayla]

12z GEM looks amazing for Seattle posters and has been very persistent about it.

[Kayla]

Looks like the WRF is coming in pretty ugly...

 

Definitely looks more like a Central Valley/elevation based event. Seattle area also misses out. But the WRF is like 0 for 20 this year.

[SilverFallsAndrew]

WRF is good south of PDX

[HighlandExperience]

Definitely looks more like a Central Valley/elevation based event. Seattle area also misses out. But the WRF is like 0 for 20 this year.

This is actually the best WRF run for Seattle. Yesterday it showed nothing on monday. Gem is consistently amazing up here.

[TT-SEA]

12Z WRF through Monday morning...

 

[luminen]

Light snow falling steadily over here. I'll have to get out and measure it at some point today.