December 2016 Observations and Model Discussion for the Pacific Northwest

[HighlandExperience]

[MossMan]

BIG TIME!!!

Northern Snohomish Co! Kevin Martin says so.

[Heavy Snow]

Interesting setup with multiple models wanting to develop a coastal surface low as the southern steam low ejects. I can't think of previous examples of that.

 

February 19 1993

 

https://www.youtube.com/watch?v=TpV1qnlOhrg

[BLI snowman]

 

February 19 1993

 

https://www.youtube.com/watch?v=TpV1qnlOhrg

 

 

Yeah, some similarities for sure.

[SilverFallsAndrew]

PDX AFD going all in...

[snow_wizard]

The ECMWF ensemble is bullish on minus PNA continuing right through day 15. Pretty robust in fact.

[bainbridgekid]

PDX AFD going all in...

Portland NWS is a national treasure. 

 

LONG TERM...Wednesday night through Saturday...The quicker ECMWF

forecasts the warm front will spread precipitation, possibly heavy,

into Lane County Wednesday morning and into the north zones late

Wednesday afternoon. The GFS is around 12 hours slower. The east

winds through the gorge will likely delay the northern progression of

the warm front and think that the ECMWF is a bit too aggressive with

the warm front. However, think that a 12 hour delay by the GFS may be

too slow. It is very possible, that the front may move quickly into

the area then become stalled over Lane or Linn County before it

reaches the north.

 

For the current forecast, have went with a blend between the two

models, and have precipitation beginning to spread into Lane County

and the central Willamette Valley Wednesday afternoon, then into the

northern areas late Wednesday night into Thursday morning. Will the

cold air moderate before the precipitation arrives? Not likely. Will

the cold air moderate quickly when the warm front arrives? Very

possible for areas south of Salem, but unlikely for areas impacted by

the east winds. Therefore, low elevation snow will very likely return

to the region either Wednesday night or Thursday. And it may be a

swell time to go riding in a one horse open sleigh.

 

The details of how much snow will fall, how low the snow levels will

be, and what areas will see snow still need to be determined. Need

better model agreement and better knowledge of how deep the cold air

Tuesday and Wednesday will be. I am sure the models will change quite

a bit as we near this event so please check the updated forecast

regularly for the latest forecast and potential impacts.

 

The warm front should depart the area Thursday or Friday unless the

east winds slow the front even more, but a weak system approaching

from the north may continue a mix of rain and snow through Friday. A

series of lows will then approach from the north and continue active

weather for next weekend. TJ

[Perturbed Member]

If I recall, the 2014 setup originally had the models sending the lows a bit too far south for PDX to get anything but flurries. They did trend further north in the next few days but only just enough to get PDX some decent precip but it was still a central valley focused event. I hope the models keep the northward trending more modest like that time. 

[HighlandExperience]

If I recall, the 2014 setup originally had the models sending the lows a bit too far south for PDX to get anything but flurries. They did trend further north in the next few days but only just enough to get PDX some decent precip but it was still a central valley focused event. I hope the models keep the northward trending more modest like that time.

We need the low to trend right into the mouth of the Columbia.

[snow_wizard]

February 19 1993

 

https://www.youtube.com/watch?v=TpV1qnlOhrg

That one sucked up here. No telling how far north this will come in yet.

[Winterdog]

The low is a little further north yet on the 00z...By Thursday it'll be making landfall at Juneau.

The warmup is coming within a week no matter what that low does so I'm all for it going north just enough for solid precip covering all of western Washington.

[SilverFallsAndrew]

Thunderstorm in progress here!

[MossMan]

We need the low to trend right into the mouth of the Columbia.

Which could very well happen with the northward trend happening.

[Deweydog]

 

February 19 1993

 

Decent analog, especially with the surface low forming near Astoria early on the 20th. Nice catch.

[snow_wizard]

I would be happy if the low verified just a tad north of the 12z ECMWF. It already showed about 1.5 inches here. A little move north would kick that up nicely.

[MossMan]

That one sucked up here. No telling how far north this will come in yet.

Did we get nothing out of it?

[Timmy Supercell]

Thunderstorm in progress here!

 

Would you be kind to share some???

[Phil]

The ECMWF ensemble is bullish on minus PNA continuing right through day 15. Pretty robust in fact.

What you guys desperately need (going forward) is a +WPO episode. That'll promote effective poleward WAFz which will perturb the PV/NAM enough to allow a more effective NEPAC/EPO wavebreak when the tropics favor it again (which they eventually will). A flat -PNA ridge now will work against you in the long run because it inhibits the aforementioned wave driving, barring substantial help out of Eurasia. So, if you're stuck with the broad/flat ridge, the next round of waves refract/flatten and everything slides east.

[SilverFallsAndrew]

Thunderstorm in progress here!

 

Some small hail too...Kind of surprised!

[Heavy Snow]

Yeah, some similarities for sure.

Decent analog, especially with the surface low forming near Astoria early on the 20th. Nice catch.

 

Yeah interesting to note the high the day before was 41 at PDX and then 32/30 with lots of snow on the 19th.

[snow_wizard]

Did we get nothing out of it?

An inch or so. It was a bust overall.

[Heavy Snow]

That one sucked up here. No telling how far north this will come in yet.

 

It's tough because we all want Snow. I always hope for a region-wide event like December 2008.

[snow_wizard]

What you guys desperately need (going forward) is a +WPO episode. That'll promote effective poleward WAFz which will perturb the PV/NAM enough to allow a more effective NEPAC/EPO wavebreak when the tropics favor it again (which they eventually will). A flat -PNA ridge now will work against you in the long run because it inhibits the aforementioned wave driving, barring substantial help out of Eurasia. So, if you're stuck with the broad/flat ridge, the next round of waves refract/flatten and everything slides east.

In the current situation we just need some small details to go the right way. Obviously this isn't the most perfect setup, but it's good enough for some places to score.

[Parksvillewx]

URGENT - WINTER WEATHER MESSAGENATIONAL WEATHER SERVICE SEATTLE WA201 PM PST SUN DEC 11 2016WAZ503-120600-/O.NEW.KSEW.WW.Y.0036.161212T0200Z-161212T1800Z/WESTERN WHATCOM COUNTY-201 PM PST SUN DEC 11 2016...WINTER WEATHER ADVISORY IN EFFECT FROM 6 PM THIS EVENING TO 10 AMPST MONDAY...THE NATIONAL WEATHER SERVICE IN SEATTLE HAS ISSUED A WINTER WEATHERADVISORY FOR WESTERN WHATCOM COUNTY...WHICH IS IN EFFECT FROM 6PM THIS EVENING TO 10 AM PST MONDAY.* TIMING...SHOWERS WILL INCREASE TONIGHT AS TEMPERATURES FALL DUE  TO DEVELOPING FRASER OUTFLOW. RAIN SHOWERS OR SNOW SHOWERS THIS  EVENING WILL BECOME ALL SNOW SHOWERS LATE TONIGHT AND MONDAY  BEFORE ENDING.* AMOUNTS...1 TO 2 INCHES OF SNOW. ACCUMULATION NEAR THE WATER  WILL OCCUR LATER THAN AREAS FURTHER INLAND CLOSER TO FREEZING.* MAIN IMPACT...VERY SLIPPERY AND LOCALLY ICY ROADS WILL DEVELOP  OVERNIGHT CAUSING DIFFICULT TRAVEL.* OTHER IMPACTS...STRONG NORTHEAST WINDS DEVELOPING LATER TONIGHT  WILL CREATE BLOWING SNOW AND REDUCED VISIBILITY.PRECAUTIONARY/PREPAREDNESS ACTIONS...PEOPLE PLANNING ON TRAVEL THROUGH MIDDAY MONDAY SHOULD EXPECTWINTER DRIVING CONDITIONS.&&$$WEATHER.GOV/SEATTLEMERCER

[SilverFallsAndrew]

Seeing stuff like this show up consistently in the long range is nice...

 

http://www.tropicaltidbits.com/analysis/models/gfs/2016121118/gfs_mslp_pcpn_frzn_nwus_39.png

[snow_wizard]

The NE winds have begun to migrate southward now. Almost to Bellingham.

[BLI snowman]

Yeah interesting to note the high the day before was 41 at PDX and then 32/30 with lots of snow on the 19th.

 

That was a much better initial airmass to work with (-15c 850mb temps over PDX on 2/16) but it had moderated rather substantially by the 18th. Pretty similar conditions to Wednesday.

[Deweydog]

Yeah interesting to note the high the day before was 41 at PDX and then 32/30 with lots of snow on the 19th.

Much drier air mass ahead of that system, plus that 41 was symptomatic of the steadily deteriorating sun angle at the time.

[MossMan]

An inch or so. It was a bust overall.

I'm getting tired of Oregon getting everything over the last 4yrs...we need a Dec. 1990 redux. Why can't we just simply get a massive Arctic blast plowing down the sound...seems like that is an impossible task these days.

[SilverFallsAndrew]

2/19/93 was one of my most vivid early childhood memories. 13" of snow that day in Silverton, 12" in Salem, 8" or so at PDX. One of the biggest one day snow storms in the Willamette Valley in the past 50 years. 

[bainbridgekid]

Yeah interesting to note the high the day before was 41 at PDX and then 32/30 with lots of snow on the 19th.

True, but the air was very dry with DP's in the upper teens the day before.

 

It's hard to stay in the 30's that late in the year with any sunshine at all and PDX pulled off 2 highs in the mid 30's with clear skies on the 16th and 17th. Pretty legit airmass.

[SilverFallsAndrew]

I'm getting tired of Oregon getting everything over the last 4yrs...we need a Dec. 1990 redux. Why can't we just simply get a massive Arctic blast plowing down the sound...seems like that is an impossible task these days.

 

You guys did WAY better in January 2012, January 2007, November 2006, oh yeah AND Nov 2010 and Feb 2011. 

[Deweydog]

2/19/93 was one of my most vivid early childhood memories. 13" of snow that day in Silverton, 12" in Salem, 8" or so at PDX. One of the biggest one day snow storms in the Willamette Valley in the past 50 years.

The NAM nailed that one.

[MossMan]

You guys did WAY better in January 2012, January 2007, November 2006, oh yeah AND Nov 2010 and Feb 2011.

And you guys have been far and away the winners since 2012...too many years now.

[Parksvillewx]

The NE winds have begun to migrate southward now. Almost to Bellingham.

 

Hoping the outflow ramps up this way too. I miss the days of heavy strait effect snow.

[Perturbed Member]

It's tough because we all want Snow. I always hope for a region-wide event like December 2008.

 

I'd always prefer a region wide event too, but PDX hasn't had anything interesting this entire decade except Feb 2014. We need a proper widespread heavy snowfall. I'm tired of all these garbage 0 to trace snow events. 

[Perturbed Member]

And you guys have been far and away the winners since 2012...too many years now.

 

We had just Feb 2014. I remember a marginal 3-5 inch snowfall in December 2009 as well. Other than those, nothing has been going on here. 

[Phil]

In the current situation we just need some small details to go the right way. Obviously this isn't the most perfect setup, but it's good enough for some places to score.

I believe we discussed this last winter. I'm telling you, that NPAC ridge simply won't re-amplify poleward unless that powerful PV can be contained. Those U-winds are just ripping from the troposphere up to the mesosphere now. The reason we saw such prolific wave amplification take place there was because the PV was so exceptionally weak..now it's recovered and it's taking over.

 

A broad -PNA ridge actually assists in the +U-wind/+EPO system. On the other hand, the +WPO system is the loading pattern for the -EPO/-NAM and destructively interferes with the +U-wind regime in the western Arctic.

[BLI snowman]

FWIW, the forecast in February 1993 called for flurries in Portland with the low staying well to their south. That was a big bust.

[Deweydog]

Sounds like the legislature debating the state budget. Everyone wants the biggest piece of the pie!