December 2015 in the Pacific Northwest

[TT-SEA]

I was referring to the way the ECMWF has trended toward the GFS on handling the all important Bering Sea low.

 

 

So?   Still does not show anything interesting.   Let me know when you are shoveling your driveway later next week that the GFS was right.  

[Gradient Keeper]

HR 114 Bering Low is just a bit further east not holding back as far towards Siberian Coast. We'll see what that means further in the run.

http://www.tropicaltidbits.com/analysis/models/gfs/2015120912/gfs_z500_mslp_namer_20.png

[MossMan]

Drove down to North Bend to check out the flooding... nothing too serious. About the same as what happened in November. I was able to drive my car through everything.

 

http://s30.postimg.org/xxn2t8g4h/2015_12_09_07_58_37.jpg

 

 

http://s27.postimg.org/uoizkj8pv/2015_12_09_07_57_59.jpg

 

http://s1.postimg.org/7hswrdmdb/2015_12_09_07_57_34.jpg

The flooding up here in northern Snohomish Co hasn't been as bad so far as the Nov. event. It was sure a fun drive back over on I-90 yesterday from Yakima. Heavy rain from Cle Elum to Bellevue. The center lane stretch of road from the summit to Bellevue is getting down right dangerous with the grooves creating rivers when it's raining heavily. Saw a few people hydroplane and almost loose it.

[TT-SEA]

Basic problem next week is going to be the lack of real cold air anywhere close.   Much like November.   The 500mb may look great at a couple points in time but the results will be underwhelming I believe.

[westcoastexpat]

The week leading up to Christmas looks more like a typical La Nina pattern than El Nino. The first half of December, however, has been classic strong El Nino.

[TT-SEA]

The flooding up here in northern Snohomish Co hasn't been as bad so far as the Nov. event. It was sure a fun drive back over on I-90 yesterday from Yakima. Heavy rain from Cle Elum to Bellevue. The center lane stretch of road from the summit to Bellevue is getting down right dangerous with the grooves creating rivers when it's raining heavily. Saw a few people hydroplane and almost loose it.

 

 

Its really bad going up the hill on I-90 from North Bend to the Snoqualmie Ridge exit in heavy rain.   Like driving upstream through a river moving fast in the other direction.  

[IbrChris]

We all knew yesterday's 18z GFS was a bunch of bull...in all likelihood (high of 20 on day 16 anyone? Bueller?). However the overnight ensembles have cooled significantly (2-3 deg for highs and lows in the late 6-10 and 11-15) which is quite a change for the ensemble mean. Looking more like a several day period of highs in the 30s to 40 and lows in the mid-upper 20s with the coldest period looking like the 19th-22nd. Very gradual cooling trend from now up to that point. A few outside members suggest a modified arctic blast with a P10 forecast (10th percentile) of 30/20 at PDX around the 21st-22nd.

At this point I'd say quite a bit better agreement around the cooler solutions we have seen the past few days but any risk of arctic air is still very slight. Low snow levels perhaps getting close to the valley floor but probably more like 1000-2000'.

The morning consensus forecast for PDX shows the following departures by period (deg F):

1-5 day: +3.7
6-10 day: -2.5
11-15 day: -4.4

[MossMan]

Not sure if I have ever seen as many warnings and advisories as the current NWS Seattle map is showing.

[TT-SEA]

The week leading up to Christmas looks more like a typical La Nina pattern than El Nino. The first half of December, however, has been classic strong El Nino.

 

 

Ninos don't always look like a typical Nino pattern... and Ninas don't always look like a typical Nina pattern.   Variability is normal is all types of years.

 

Strong Ninos tend to be more active and Nina-like in November and December.   Look at 1972 for a good example.   1982 and 1997 also had some very active weather in November and December.

[Gradient Keeper]

Through HR 144 500mb pattern looks similar to previous 00z runs. Now we really find out how well this run ends up next few frames as the Aleutian ridge reorganizes and we'll see how amplified/strong it is, or isn't.

[Gradient Keeper]

HR 162 500mb ridge/anomaly center a tad less amplified than previous 6z/00z/18z.. Next few frames reveal if we see a mediocre run, or a real good one. 2nd key player deep low in Bering is a bit weaker/further east.

[TT-SEA]

HR 162 500mb ridge/anomaly center a tad less amplified than previous 6z/00z/18z.. Next few frames reveal if we see a mediocre run, or a real good one.

 

 

Look boring.   Moving towards ECMWF.

 

At least it will be drier.  

[SilverFallsAndrew]

The suspense!

[Gradient Keeper]

I don't think this run ends up very good

[TT-SEA]

I don't think this run ends up very good

 

 

Nope... its a huge move towards the ECMWF solution.

 

No surprise.  

[Gradient Keeper]

That 2nd Bering Low is key.. We need it to deepen rapidly as 18z/00z showed... that pumps up the ridge... 6z/12z today did not and thus the low was further east ridge doesn't amplify.

[TT-SEA]

That 2nd Bering Low is key.. We need it to deepen rapidly as 18z/00z showed... that pumps up the ridge... 6z/12z today did not and thus the low was further east ridge doesn't amplify.

 

 

Not likely to happen... at least the pattern next week will deliver winter weather to the Intermountain West and Midwest where its been so warm.

[IbrChris]

12z GFS would still bring highs in the mid-upper 30s to the westside lowlands by the 18th. Slightly milder than 6z in the days prior. Cold enough for snow assuming moisture is around.

[luvssnow_spokane]

Not likely to happen... at least the pattern next week will deliver winter weather to the Intermountain West and Midwest where its been so warm.

 

looking pretty good to meeeee.  Not sure how this is not a decent run... The is up to hour 210.

 

 

[Gradient Keeper]

Maybe we jumped the gun after HR 180 it improves, looks better than 6z a tad...

[Timmy]

Not likely to happen... at least the pattern next week will deliver winter weather to the Intermountain West and Midwest where its been so warm.

yeah they really need the cold and snow i feel so bad for them.  Especially all the mid-west ski resorts that don't really exist. 

[IbrChris]

NW flow suggests at least a little moisture...but also snow levels above the lowlands, closer to 1000-2000'

 

Pretty darn chilly with mid 30s for highs 19th/20th SEA-PDX...lows dependent on moisture/cloud cover but potentially well into the 20s.

[Gradient Keeper]

HR 72-120 Bering Sea Low #1 needs to be 925-935mb and track through the western Bering towards the Siberian Coast. This holds the energy back and pumps up the initial ridge setting the stage for everything. The next key player Bering Sea Low #2 at HR 156-180 moving towards the Bering/western Aleutians. If it's around 945-960 it tends to track further west as the 18z/00z showed, the ridge will amplify/anomaly shoved north and block develops over Gulf of Alaska. If not, and it's around 970mb it tracks a bit further east as the 6z/12z shows the north Pacific ridge doesn't amplify as robustly less probable to see a real cold solution/arctic blast, more likely to see modest cold/glancing blow focused over eastern WA/OR perhaps. These are what we want to watch for. It seems models are trending towards Low #1 tracking westward as all models look very similar at 500mb through HR 120-144, but how Low #2 is handled is uncertain right now.

[TT-SEA]

Maybe we jumped the gun after HR 180 it improves, looks better than 6z a tad...

Eastward shift in the mid range will eventually reach that period on the next few runs. There is no real cold air anyways... dry and chilly is the best outcome.

[IbrChris]

There's no arctic blast, but potentially a colder version of our late Nov cool spell. Pretty clear any arctic air will be across Rockies/northern Plains.

[Gradient Keeper]

Eastward shift in the mid range will eventually reach that period on the next few runs. There is no real cold air anyways... dry and chilly is the best outcome.

If the 2nd Bering Low behaves we'll end up with a block and the northeast flow will eventually grab a big chunk of cold air down into BC/AB. Looks pretty cold east side and perhaps deeper cold air than what we saw in November.

[TT-SEA]

If the 2nd Bering Low behaves we'll end up with a block and the northeast flow will eventually grab a big chunk of cold air down into BC/AB. Looks pretty cold east side and perhaps deeper cold air than what we saw in November.

Could happen.

[Gradient Keeper]

There's no arctic blast, but potentially a colder version of our late Nov cool spell. Pretty clear any arctic air will be across Rockies/northern Plains.

Arctic blast unlikely, but wouldn't rule out anything right now. If the next few runs handle the 2nd Bering low further east with a less amplified ridge, then I'd rule it out entirely.

[luvssnow_spokane]

Arctic blast unlikely, but wouldn't rule out anything right now. If the next few runs handle the 2nd Bering low further east with a less amplified ridge, then I'd rule it out entirely.

We do not need a full arctic blast here to have meaningful snow event. Just saying that it sometime helps as it is less dry and leads to more potential. YEs our highs may be in the mid to upper 30s but our lows at night will be well below freezing. I see plenty of potential but it may be sloppy at times. Interesting setup needless to say.

[Gradient Keeper]

We do not need a full arctic blast here to have meaningful snow event. Just saying that it sometime helps as it is less dry and leads to more potential. YEs our highs may be in the mid to upper 30s but our lows at night will be well below freezing. I see plenty of potential but it may be sloppy at times. Interesting setup needless to say.

True. I'd be perfectly happy with 29-32 and heavy snow. I don't need 15-25 degrees.

[TT-SEA]

Some blue sky here... and windy. And colder. Much better.

[HighlandExperience]

We do not need a full arctic blast here to have meaningful snow event. Just saying that it sometime helps as it is less dry and leads to more potential. YEs our highs may be in the mid to upper 30s but our lows at night will be well below freezing. I see plenty of potential but it may be sloppy at times. Interesting setup needless to say.

 

I prefer marginally cold temps near sea level with heavy snow/cold rain, than Dry Cold.

 

We haven't received squat in recent years.

[MossMan]

Suddenly has gotten very dark here at work, looking at the radar it appears my location is about to get hammered by a pretty good squall!

[MossMan]

I prefer marginally cold temps near sea level with heavy snow/cold rain, than Dry Cold.

 

We haven't received squat in recent years.

I agree! I believe Nov. 26th 2006 was a non Arctic event for my area...that received 16" of 32 degree heavy wet snow that was amazing (but quite destructive)

[ShawniganLake]

I agree! I believe Nov. 26th 2006 was a non Arctic event for my area...that received 16" of 32 degree heavy wet snow that was amazing (but quite destructive)

There was a well defined arctic boundary with that event.  You just happened to be on the warmer side of it, but still cold enough for snow.  It was in the mid 20's up near the border that afternoon with blowing and drifting snow. 

[ShawniganLake]

Putting the long range GFS freak out stuff aside, seems like there is reasonable agreement on the increased likelihood for some pretty low level snow chances Tuesday-Thursday of next week.  500ft snow levels for northern Washington and southern BC seem like a pretty good bet. 

[MossMan]

There was a well defined arctic boundary with that event. You just happened to be on the warmer side of it, but still cold enough for snow. It was in the mid 20's up near the border that afternoon with blowing and drifting snow.

Ok gotcha, that's right. And the boundary didn't sag south through my area until the evening of the 27th. That was quite the event for Marysville northward. What are some past examples of good snowfalls with a pattern currently depicted?

[Gradient Keeper]

12z CMC after HR 156-168 definitely improved/colder than any of its previous runs.

[stuffradio]

Wow, it's actually starting to get sunny here...

[ShawniganLake]

Ok gotcha, that's right. And the boundary didn't sag south through my area until the evening of the 27th. That was quite the event for Marysville northward. What are some past examples of good snowfalls with a pattern currently depicted?

Not sure that the pattern depicted is ever going to lead to big results.  Those type of systems don't usually carry a ton of moisture, unless they get invigorated by some arctic air and intensify, which seems unlikely for now.

 

Third wrf run in a row with snow for northern regions.  First one to spread the snow down the sound.

 

http://www.atmos.washington.edu/mm5rt/data/current_extended/images_d2/wa_snow24.180.0000.gif