December 2016 Observations and Model Discussion for the Pacific Northwest

[Phil]

Good or bad?

Tim would like it.

[Deweydog]

Definitely a little stronger with the Friday shortcake.  

[IbrChris]

I like the trends with the 00z and 12z model suites...not a lot of changes in the nearer term (over the next week or so) but it's increasingly likely we are looking at an even longer period of cool to cold temps...the 11-15 day 500 mb composites are looking very good for continued arctic air into the NW US courtesy of a high-latitude Rex block along 160 W...there's good model agreement between the GFS/Euro/CMC ensembles. Given the increasing likelihood of a period of moisture around Jan 6-8 it's plausible that we go into a second blast with snowcover. Ensemble means are hinting at this scenario, though there's the usual noise as well in the 11-15...both GFS and Euro ensemble mean suggests highs at or below 38 through the 11-15 day period. I find the pattern stability and longevity to be rather astounding from a meteorological perspective...not that a 2-3 week duration Rex block hasn't occurred in previous winters but that it appears we will have one in the "sweet" spot for 10-14 days (maybe longer). With snowcover there's real potential for records, especially if we can keep the jet suppressed into California and produce some clear/calm nights. I'm reasonably confident any significant period of near normal temps will be put on hold until closer to mid-month at the earliest. Current model output and vendor guidance suggests a mean temperature departure in the neighborhood of -10 to -11 F at PDX during the first two weeks of January.

Hold onto your butts...

[luvssnow_spokane]

18z  Friday looks to have a little more punch to it but looks to warm for snow.... 

[Gradient Keeper]

Dang.... cut-off better, but block a touch too close.... shortwave not digging as great. Block needs to tilt real soon. It might be better for us though after day 5

[MR.SNOWMIZER]

Not liking the 18 so far. Moving east.

[IbrChris]

Apples - Oranges

That's a thing of beauty

[Jesse]

18z Friday looks to have a little more punch to it but looks to warm for snow....

Friday never looked like a snow maker in the lowlands. Generally a sharper Friday trough has been boding well for more arctic penetration later in the run, though.

[snow drift]

Thanks for the update guys. Found wifi at this little place in chesaw!

My brother and his wife lived in Chesaw for a couple of years back in the mid 1990s. They couldn't earn a decent living over there. So, they moved back to Western Wa. I know they still miss it. I remember the stars on a moonless night over in Chesaw. It was like they were in 3d. It was absolutely mesmorizing!

[Jesse]

Not liking the 18 so far. Moving east.

The coldest stuff moves a little to the east toward midweek on even the best runs.

[Heavy Snow]

12z GFS-Parallel just came in and it looks good. I'll post about it in a bit unless somebody gets to it sooner. I know it's in beta version for December 2016. Anybody know how soon it will go live?

[BLI snowman]

18z looks a little colder for Sunday, better scenario for potential snow hanging around since it pretty much eliminates the southerly gradients that day.

[Timmy]

18z looks to be another step toward the euro through Sunday

[Heavy Snow]

I like the trends with the 00z and 12z model suites...not a lot of changes in the nearer term (over the next week or so) but it's increasingly likely we are looking at an even longer period of cool to cold temps...the 11-15 day 500 mb composites are looking very good for continued arctic air into the NW US courtesy of a high-latitude Rex block along 160 W...there's good model agreement between the GFS/Euro/CMC ensembles. Given the increasing likelihood of a period of moisture around Jan 6-8 it's plausible that we go into a second blast with snowcover. Ensemble means are hinting at this scenario, though there's the usual noise as well in the 11-15...both GFS and Euro ensemble mean suggests highs at or below 38 through the 11-15 day period. I find the pattern stability and longevity to be rather astounding from a meteorological perspective...not that a 2-3 week duration Rex block hasn't occurred in previous winters but that it appears we will have one in the "sweet" spot for 10-14 days (maybe longer). With snowcover there's real potential for records, especially if we can keep the jet suppressed into California and produce some clear/calm nights. I'm reasonably confident any significant period of near normal temps will be put on hold until closer to mid-month at the earliest. Current model output and vendor guidance suggests a mean temperature departure in the neighborhood of -10 to -11 F at PDX during the first two weeks of January.

 

Hold onto your butts...

Thanks for your detailed analysis.

[Phil]

So far, PV/U-wind integral weaker on 18z vs 12z, opposite relative to the 12z ECMWF in that regard. Good news.

[luvssnow_spokane]

Friday never looked like a snow maker in the lowlands. Generally a sharper Friday trough has been boding well for more arctic penetration later in the run, though.

I know....  just looked a bit juicier ... I never expected snow from it but the possibility "could" be there. Specially higher terrain.

[Perturbed Member]

I like the trends with the 00z and 12z model suites...not a lot of changes in the nearer term (over the next week or so) but it's increasingly likely we are looking at an even longer period of cool to cold temps...the 11-15 day 500 mb composites are looking very good for continued arctic air into the NW US courtesy of a high-latitude Rex block along 160 W...there's good model agreement between the GFS/Euro/CMC ensembles. Given the increasing likelihood of a period of moisture around Jan 6-8 it's plausible that we go into a second blast with snowcover. Ensemble means are hinting at this scenario, though there's the usual noise as well in the 11-15...both GFS and Euro ensemble mean suggests highs at or below 38 through the 11-15 day period. I find the pattern stability and longevity to be rather astounding from a meteorological perspective...not that a 2-3 week duration Rex block hasn't occurred in previous winters but that it appears we will have one in the "sweet" spot for 10-14 days (maybe longer). With snowcover there's real potential for records, especially if we can keep the jet suppressed into California and produce some clear/calm nights. I'm reasonably confident any significant period of near normal temps will be put on hold until closer to mid-month at the earliest. Current model output and vendor guidance suggests a mean temperature departure in the neighborhood of -10 to -11 F at PDX during the first two weeks of January.

 

Hold onto your butts...

 

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[Phil]

Tropical forcing does look different this run. Might explain the poleward shift in the STJ.

[Heavy Snow]

12z GFS-Para shows some moisture as the colder air sets in for PDX Metro Sunday night. Then colder air settles in with moisture chances throughout the run. Here are days 10, 12, 14 and 16. Good pattern with nice block and developing SE ridge. Still a long ways out though but fun to look at.

 

http://www.tropicaltidbits.com/analysis/models/gfsp/2016122812/gfsp_mslp_pcpn_frzn_us_19.png

http://www.tropicaltidbits.com/analysis/models/gfsp/2016122812/gfsp_mslp_pcpn_frzn_us_42.png

http://www.tropicaltidbits.com/analysis/models/gfsp/2016122812/gfsp_mslp_pcpn_frzn_us_45.png

http://www.tropicaltidbits.com/analysis/models/gfsp/2016122812/gfsp_z500a_nhem_41.pnghttp://www.tropicaltidbits.com/analysis/models/gfsp/2016122812/gfsp_z500a_nhem_45.pnghttp://www.tropicaltidbits.com/analysis/models/gfsp/2016122812/gfsp_z500a_nhem_47.pnghttp://www.tropicaltidbits.com/analysis/models/gfsp/2016122812/gfsp_z500a_nhem_53.png

[MossMan]

18z GFS shows considerable more snow for King County by hr 90 than 12z. 3-4 inches vs. trace-2 inches.

How about Snohomish Co?

[Perturbed Member]

Impressive agreement between the 12z GEM and 18z GFS for Jan 6th.

 

GFS

http://www.tropicaltidbits.com/analysis/models/gfs/2016122818/gfs_mslp_pcpn_frzn_nwus_33.png

 

GEM

http://www.tropicaltidbits.com/analysis/models/gem/2016122812/gem_mslp_pcpn_frzn_nwus_32.png

[MikeInEverett]

The block on the 18Z is absolutely insane.

[BLI snowman]

18z is officially a cold little run.

[Deweydog]

The GFS is officially leading the way again!

 

Clearly has the best handle on the pattern.

[EA_TTD]

The block on the 18Z is absolutely insane.

It's BJ Raji and Vince Wilfork all rolled into one!

[Heavy Snow]

Impressive agreement between the 12z GEM and 18z GFS for Jan 6th.

 

GFS

http://www.tropicaltidbits.com/analysis/models/gfs/2016122818/gfs_mslp_pcpn_frzn_nwus_33.png

 

GEM

http://www.tropicaltidbits.com/analysis/models/gem/2016122812/gem_mslp_pcpn_frzn_nwus_32.png

 

Looks similar to the L that dropped a nice snowstorm to the lower half of the Willamette Valley Dec. 2013.

[Jesse]

The GFS is officially leading the way again!

 

Clearly has the best handle on the pattern.

Nah, it just moved toward the Euro.

[FroYoBro]

D**n. That would be so amazing if it actually verified. 

[Front Ranger]

Pretty similar. Should put Flatiron's theory that timing is everything to the test.

You're referencing me a frightening amount lately. I'll take it as a sign of deep respect, bordering on man crush.

[Deweydog]

You're referencing me a frightening amount lately. I'll take it as a sign of deep respect, bordering on man crush.

 

No one is immune from my crushing banter.  

[Front Ranger]

Friday never looked like a snow maker in the lowlands. Generally a sharper Friday trough has been boding well for more arctic penetration later in the run, though.

Jaya had mentioned it as potentially bringing snow to the Puget Sound region.

[Deweydog]

PDX has turned into quite the little fog hog lately.  Still in the 30's there, sunny and 45 here.  

[Gradient Keeper]

18z was interesting

[Farmboy]

The GFS is officially leading the way again!

 

Clearly has the best handle on the pattern.

Clearly....

[MossMan]

Jaya had mentioned it as potentially bringing snow to the Puget Sound region.

Especially in the PSCZ areas and of elevation! 

[Gradient Keeper]

That block was the size of 65-70% of the United States! I've never see anything even close to that on any model run in my life. This is how you get a 1950, 1862, or 1899......... wow

[MossMan]

 

http://www.tropicaltidbits.com/analysis/models/gfs/2016122818/gfs_T850_nwus_42.png

Oh my!

[Front Ranger]

No one is immune from my crushing banter.

It's OK to admit you have favorites. Especially with your kids.

[Heavy Snow]

That block was the size of 65-70% of the United States! I've never see anything even close to that on any model run in my life. This is how you get a 1950, 1862, or 1899......... wow

 

Your best post ever.

[MossMan]

That block was the size of 65-70% of the United States! I've never see anything even close to that on any model run in my life. This is how you get a 1950, 1862, or 1899......... wow

Could this be it...what we have been waiting for our entire lives??? i'm feeling all tingly inside! 

And thanks for adding me to your facebook group!