OHweather

Getting much more encouraged about the upcoming stretch…all ensembles have a ridge bridge across the Arctic in the 10-15 day with cross polar flow into a deepening trough into the central US. Get this into the 6-10 and that’s a pretty high confidence significant cold signal for someone. There is disagreement over how far east  the trough axis sets up, though I’d characterize this as an EPO cold shot and those often don’t make it into the eastern US as quickly as modeled so the GEFS may be a little more correct. Regardless of the exact evolution, the pattern will be turning much colder over most of the continent in late January and the gradient may setup somewhere across the sub. 
 

The GEFS could support a bigger cutter favoring the western sub, while the EPS and GEPS could support more of an Ohio Valley runner and clipper look. 
 

I feel confident we’ll have a legit period of wintry temperatures and increased snow potential the last week of January into the start of February, though still plenty of details (how cold, how much snow and where) to still sort out. From there, the question will be if we can maintain this favorable Pacific pattern with a ridge along the west coast into February or if we see things slide back west and allow the Southeast ridge to flex. We’ll also have to watch the stratospheric polar vortex for possible disruptions and the blocking on the above means near Scandinavia…both could lead to a more -NAO well down the road. So, lots of uncertainty the rest of the winter but we definitely have a window coming up…and we’ll go from there. 

I'm actually not extremely enamored with this setup...think we'll get a quick 1-3" of synoptic snow Thursday night in north-central and northeast OH. There's probably a lull of sorts early Friday between the synoptic snow and lake enhancement that will ramp up into the morning and continue through most of the day, with that activity ending Friday evening. The lake enhanced snow may be moderate for a time on Friday, especially in the hills and especially with some sort of Lake Huron connection coming into play with winds going NNW to nearly due N. Even during the lake enhancement, I think we're looking at persistent light to moderate snow, as the instability is marginal and the synoptic lift is modest...the hills/upslope will definitely help, but it'll be hard to get 1"+/hour rates out of this.

With the snow rather spread out, a struggle to get heavy rates, marginal ratios and warm ground, I don't feel this will be that exciting. That said, it will snow for a while and in the hills upslope/lake enhancement will add a good amount of QPF. I actually could see us needing to up amounts a bit farther west in the hills of the secondary snowbelt...someone in northern Geauga as well as Erie Co PA could squeeze out 8" with the upslope, but it'd be over a 24-30 hour period and I think most will probably be more in the 3-6" type range in the inland primary snowbelt. Guessing we'll need some advisories tonight or early tomorrow for it...kind of hoping we don't try pushing the warning button unless things look more impressive. 

The "negativity" aside, it will snow and accumulate and should look nice on the trees. More sustained cold may arrive towards the end of January...or at the least, a return of more frequent transient cold shots between the 50 degree days. 

11 hours ago, michsnowfreak said:

Thanks for analysis as always. You mention February will be a more traditional Nina look with a 1-2 week window of cold as it transitions.  Are you implying a mild rest of February? Or a gradient one?  February in Nina's used to be mild, however more recently that has not been the case. In fact the last 2 have been rocking with plenty of snow.

My guess is we go to a gradient pattern towards mid February with cold dumping into the Rockies and upper Midwest with a Southeast ridge. I think the Aleutian ridge will hold on for at least a few weeks which will keep dumping cold into North America, but usually that retrogrades after a while and ends up being a -PNA. I think we all have a crack end of January into early February…thereafter, odds probably tilt towards farther north and west being favored. 

52 minutes ago, NEOH said:

Nice to see the snow flying again. Temps are colder today so the grass is mostly covered. About an inch or so here. Take what we can get at this point I guess.

There were some nice bursts of borderline moderate snow last evening that quickly covered anything that wasn't paved, which was nice to see...even if the good snow lasted all of 20-30 minutes where I was! I'm getting a little more optimistic we get a crack at a better pattern for a couple of weeks around the end of Jan/beginning of Feb...but it's quite possible we don't get much of anything until then. Low odds we get a little wet snow with the low pressure going by this Friday if it tracks just right I guess, but I'm not optimistic. So, we'll see if that brief period around the end of this month can deliver. I'm sure we'll get some snow, but it's been scraps so far if you don't live up towards Erie or Buffalo (not that I'd want what Buffalo has had to go through this winter). 

Occasional dustings of snow over the last 36 hours here that have struggled to stay on the ground for long during the daylight hours...running "event total" of 0.8" with less than 0.5" (so a T) on the ground at the moment. Racking it up this season. 

Kind of interesting to watch how the pattern has evolved from November 1 through early January. In general, for November and the first half of December, we had a north Pacific/Aleutian ridge that frequently resulted in a western US trough...a -PNA/fairly typical La Nina pattern, with what could be characterized as a relatively weak/retracted Pacific jet stream. Since then, we've switched to a strong north Pacific/Aleutian low, which is blasting the Pacific jet stream into the west coast and cutting off an Arctic influence into the CONUS. This can be characterized as a very strong and extended Pacific jet stream, more typical of an El Nino.

While the Pacific has been the issue preventing sustained cold for much of the late fall/early winter, it's been because we've gone from one extreme to another, with only a brief period in between in mid-late December where we managed a more favorable pattern for widespread cold in the CONUS. We have had blocking at times...the Aleutian ridge flexed to the point where it was a -EPO that facilitated cross-polar flow at times in November and December (which is the typical way to get Arctic shots in a La Nina), and we had a relatively robust -NAO for most of December...but we've seen a mix of Pacific patterns that are different but mild for the central/eastern CONUS in their own ways and have torched when blocking relaxes.

The Pacific jet stream will weaken considerably over the next week, finally, as much lower pressure over eastern Asia (a negative mountain torque, which requires a loss of westerly atmospheric momentum/a weakening of the jet stream to compensate) and a downturn in convection over the western Pacific warm pool (resulting in less latent heat release and a weakening of the gradient over the western Pacific, also weakening the Pacific jet) both suggest a quick loss of westerly momentum over the Pacific. This is why ensembles are hinting at the trough backing away from the west coast and allowing heights to rise at least somewhat after mid-January.

My guess is we transition back to a more typical Nina pattern into February when tropical forcing returns to the western Pacific and enhances the lingering La Nina circulation, but with perhaps another one of our "brief windows" in between where we can get a ridge along the West Coast in a spot that can increase polar/arctic influence into the central and eastern CONUS for 1-2 weeks around the end of January/early February as we make that transition. 

Merry Christmas! The LES warnings for Lake and Ashtabula today may not quite have been needed as it lifted back over the lake pretty quickly into this morning, but still a white Christmas with plenty of snow on the ground. In Mentor for dinner and probably a couple more inches on the ground here compared to Reminderville but nothing too crazy. 

Only about 4” or so of snow here, but many sites in northern Ohio and northwestern PA, including both Cleveland airports and Erie, met official blizzard criteria today. Here’s CLE 5 minute obs:

https://www.weather.gov/wrh/timeseries?site=KCLE

Note the <0.25 mile stuff, solid blizzard conditions from 8am-3pm and briefly 6-7am. 
 

Port Clinton OH is even more impressive, look at those gusts over 60 with temperatures below 0!

https://www.weather.gov/wrh/timeseries?site=KPCW
 

Areas east of I-75 over towards Lorain OH are more open and had extensive issues with blowing snow, including a fatal pileup on the turnpike. 

Several sites easily verified blizzard conditions today, with visibility frequently below 1/4 of a mile and gusts well over 35mph…along with sub zero temperatures. Cleveland Hopkins, Burke Lakefront, Lorain County, Port Clinton, Lost Nation (Willoughby), Akron Canton, and Erie all hit it for 3 hours straight or longer. Findlay, Akron Fulton and Youngstown have strong arguments but didn’t quite get into the sub 1/4 mile stuff for 3 straight hours, so it’s more debatable. Mansfield, Wooster and Ashtabula also met conditions briefly, but weren’t really close to doing it for 3 hours. 
 

CLE verified a blizzard from 8am to 3pm! And briefly around 6-7am!

https://www.weather.gov/wrh/timeseries?site=KCLE

Not nearly as bad as what Buffalo is dealing with and not in the same league as 1978, but we can say we experienced a blizzard today which is uncommon around these parts. The cold and wind combination was unique. 
 

Estimating a bit over 4” of snow here, and we are still getting the occasional house shaking gust. 

It took a while for everyone agreeing on upgrading to the blizzard warning but it seems to have been worth it for the conditions. It was and still is pretty brutal out there. 

43 minutes ago, Frog Town said:

Nail in the coffin for the NW Ohio/SE Mich peeps...sorry.

.NEAR TERM /THROUGH FRIDAY NIGHT/...
Latest radar, 0z model guidance, and surface observations
suggest that we are perhaps entering a perceived "lull" in the
precipitation along the arctic front, especially across NW OH
this evening as the upper-jet energy begins to arrive across the
Lower OH Valley which will lead to explosive cyclogenesis late
tonight into Friday. This may lead to lower snowfall totals and
overall impacts across NW OH. However, we are currently watching
an area of precipitation across SW OH that continues to
strengthen, noted by multiple surface observations of moderate
to heavy snow at times. This area of precipitation will work its
way north and east into the region later tonight in conjunction
with the strong, arctic front. This will be the area to watch
for any significant impacts with regards to snowfall rates
and/or blowing snow overnight and into the morning hours.

The warnings for that area said 2-4” and you’re gonna get the 2” instead of the 4”…this was never going to produce big snow totals in OH, although the I-71 corridor is looking to be the ones who get luckier in those regards as opposed to NW OH. 

Definitely some noted trends for the post frontal snow to be a bit more robust tonight, even in central and southern Ohio. There isn’t a crazy ceiling here but even many of you folks getting a solid few inches down there seems more plausible now. 

Definitely some snowier trends with the post-frontal burst later tonight into tomorrow morning for a good portion of central and eastern OH. Thinking the Cleveland area has a good 4-6” down by midday with whatever light wraparound comes after. Curious to see how my drive back down 480 goes at 8 or 9am assuming I choose to try it. 

2 hours ago, RCNYILWX said:

How things might go tonight through tomorrow night when the winds max out. Remember this event well, January 26, 2014. Shows that not much snow is needed for truly gnarly conditions. We don't often get northern Plains weather (with notable exception of 2013-14 and 14-15 winters), but when it happens, the wide open areas outside of the heart of the Chicago metro are prime for blizzard conditions and significant drifting.

The morning AFD update from my office notes that consideration is still being given to upgrading a larger portion of the area to a Blizzard Warning. Think that there's likely to be large sections of north south roads, including some of the interstates, shut down due to blowing and drifting snow tonight through tomorrow night. Hope most people don't chance driving in those conditions.

Sent from my SM-G998U using Tapatalk
 

I'm pretty worried about something similar playing out in parts of NW Ohio tomorrow through at least early Saturday, where they're getting 2-4/3-6" of snow with 50-60mph wind gusts for a very prolonged period. Just for the sake of picking your brain a bit, do you know if there was blowable snow already on the ground that made that worse? And I guess my other question, was the strongest wind with the heaviest snow, or did it occur afterwards? Because to me, the new snow amounts, wind and duration of it in NW Ohio (which, like northern IL outside of the Chicago area, is actually quite flat and open) seems at least as bad as what resulted in the impacts described in that entry, though the strongest winds probably start ramping up after the heaviest snow. I could see parts of NW Ohio being absolutely crippled tomorrow into the weekend though. 

Euro trending a little more amped in recent runs 

I am really worried about the wind from parts of lower MI, IN, and OH into southern Ontario, northwestern PA and western/northern New York. You have a 5 standard deviation low followed by a 3.5 standard deviation high, very strong cold air advection, with flow funneling down the Great Lakes basin. 

Gusts could reach 60+ mph in a large portion of that corridor, with up to 75mph downwind of Lake Erie into the Buffalo and Rochester areas. Huge impacts in parts of that corridor, especially downwind of the lakes where lake enhancement will occur. 

This is not the most exciting storm if you're simply going for big snow amounts/rates (though, rates will briefly rip pre-dawn Friday behind the front). I'm guessing public perception will be super mixed...people who have been hearing about a huge storm for days but stay inside on Friday will be underwhelmed when/if we only get a few inches of snow. But, those who hear we're only getting a few inches of snow and venture out on Friday will probably be caught off guard by how brutal the conditions are. Roads really will not be fun Friday through early Saturday with the flash freeze/quick snow accum early Friday followed by intermittent snow and extensive blowing/drifting snow.

As for my expectations, I still think a 3-6" type snow (more up the eastern lakeshore from LES, but I'm also not optimistic in much of a lake boost into NE Ohio...maybe north of I-90 from Lake County points east gets some more help) with 50-60 MPH wind gusts and brutal wind chills (-20 to -30F seems quite likely Friday through early Saturday) is a lock. I think we all get a quick 1-3"/2-4" burst behind the Arctic front...it won't last long, but the upper dynamics are briefly very supportive early Friday before we dry slot.

The GFS continually deepens the low a bit quicker and slows it down, giving us more wrap-around later Friday into Friday night, and would support probably a 6-10" type snow (the front, plus several more inches of wrap-around). My impression is it's overdone, but it's insistent and given how closed off/deep the trough aloft is, perhaps there's room for the system to intensify and slow down slightly quicker. The Euro is not THAT different than the GFS but deepens the low a bit slower and lifts it northeast slightly quicker, so we get less QPF with the wrap-around. However, the Euro still suggests deep saturation through the low and mid-levels through early Saturday and has mid-level warm air advection/isentropic lift late Friday into Friday night, as the low occludes and warm air aloft starts wrapping back in from the north, so I think the Euro would still bring some wrap-around snow...but, it's much less dramatic than the GFS. 

The GFS solution still casts doubt on the winds. All models suggest we have no problem mixing to about 850mb Friday afternoon into Friday night, and all models suggest at least 50 knots of flow at that level. So, I think 50-60 MPH gusts (lakeshore and NW Ohio more 60, interior NE Ohio more 50) are still likely across the board. The GFS (and the FV3 WRF) have 850mb winds of 60-70 knots in that window, and soundings from the GFS and FV3 suggest widespread 60mph gusts, even inland, with potential for 70+ right against the lake is possible. That's probably the difference between a typical amount of power outages and something more widespread. With how cold it is until early next week, more than isolated power outages could quickly become an issue with homes getting cold and potential damage to infrastructure. A general rule of thumb given the setup being quite favorable for strong winds is that the wind speed in knots at 850mb Friday afternoon through Saturday roughly correlates to surface gust potential in MPH (i.e. 60 knots at 850mb probably supports 60 mph gusts...the lakeshore may do even better). 

Still another day to watch trends. I've largely punted LES potential for most of us but do think there's room for trends with the wrap-around snow and what the peak wind gusts end up being, which still is the difference between an impressive/impactful storm and something more life-threatening. Will the GFS trend weaker/faster, or will other models trend stronger/slower? That's the question... 

1 hour ago, vpbob21 said:

I have to laugh a bit when I read the main storm thread and watch posters going apoplectic over every 20 mile shift in the models.  The important thing is that this system is going to be, unless things change dramatically, an absolute monster producing an enormous footprint over the Lakes and northern Ohio Valley.  This is a setup where the oft used sentence from the NHC applies - "do not focus on the actual path of the storm, as effects will be felt far away from the center".  It will probably not matter much whether we get 3 inches or 15 as the winds (which may well be underforecast) will be lifting a tremendous amount of snow.

This afternoon's LOT discussion said it best.  It is for the Chicago CWA but could apply anywhere in the Lakes:

It is also worth stressing that the amount of snow that falls is
a secondary or tertiary concern among the hazards. The expected
temperatures will leave this snow extremely susceptible to blowing
around and even if only a couple inches of snow falls, a blizzard
would still be likely given the nature of the snow and magnitude
of the strong winds.

I would expect a blizzard warning to be needed at least over the northern couple rows of counties (where the combination of wind and snow looks to be most severe) and possibly for the entire CWA.  I hope you guys at CLE continue to hit it hard.  This is looking like a truly life threatening storm.

 

 

 

Yeah, I agree with your overall sentiments and concerns...though, still time for trends which can impact the overall severity of the storm in our area (and everyone else's). The overall evolution is pretty locked in, wholesale changes are not coming and this will be a significant event for a very large area. The very cold temperatures and strong, possibly damaging winds are locked in and any amount of snow will be a problem given those two factors. Now, I do think snow amount matters...I think there's still ceiling for a 4-8/6-10" type snow event in northern Ohio. It's probably less than likely, I feel like 3-6" is more likely, but there will be a lot of forcing and some embedded heavier bands of snow on the west/southwest side of this low pressure as it dramatically deepens Thursday night through Friday night and many models continue to flirt with that impacting northern Ohio which is how those higher amounts could come into play. Amounts will gradually drop off to the south, but it seems like the whole state gets at least a couple inches. However, while I agree that 2" of snow will be made much worse by the cold and wind, 6"+ is just that much more to blow around and makes it substantially worse. 

My "baseline expectations" remain similar to above...by baseline, I have relatively high confidence that things will be AT LEAST this bad:

-A couple to a few inches of snow seems like a likely low end. Perhaps a brief burst of accumulation right behind the Arctic front early in the day Friday. Likely a dry slot behind the front, then wrap-around snow returning later Friday into Friday night, transitioning to SW flow lake effect on Saturday. 

-50 to 60 mph wind gusts seem quite likely, and they may be stronger. Strongest winds generally Friday afternoon and Friday night as the pressure gradient really cranks, but probably a brief surge to 50+ mph gusts immediately behind the front early Friday given the extreme pressure rise and dramatic temperature drop. 

-Temperatures drop from the upper 30s/lower 40s to the single digits in about 6 hours Friday morning behind the front. Temperatures stay in the single digits or teens all weekend, and may dip below 0 Friday evening, especially in western Ohio. Wind chills of -15 to -25 seem likely Friday afternoon through Saturday night, and there's some potential for -30 or colder Friday afternoon into Friday night if winds are on the higher side and temperatures are at least as cold as expected

This is a notable storm with very difficult to impossible travel Friday through Saturday morning due to a flash freeze, accumulating snow, and substantial blowing and drifting snow to go along with scattered tree/power-line damage and some power-outages from the wind. Northwestern Ohio, due to its openness, and the lakeshore, due to higher gusts, will probably see the most significant issues from the blowing and drifting, though everyone will see significant blowing and drifting of whatever snow falls. In addition, it'll be dangerously cold outside. This is kind of like a "realistic floor", unless wholesale changes occur (unlikely) we can expect it to be at least that bad.

Now, it could be even more significant too. I already mentioned the snow. The subtle trend east on the 0z guidance showed all models depicting 4-8" or so type snow amounts in most of northern Ohio. That's not a slam dunk yet, but is possible. Temperatures may be a bit colder than modeled given the origins of the airmass, though that could be somewhat dependent on getting a good, deep snowpack so is not a given. Winds could also be stronger than the 50-60 MPH I mentioned, especially in western Ohio and then in the northern couple tiers of counties points east. This system checks a lot of boxes for high wind potential...very strong cold air advection, a very tight pressure gradient, an unusually deep low that's still intensifying when we see our strong winds, and also a large tropopause fold accompanying this system. When winds overperform, some or all of these factors are in place. Given the 850mb winds progged to reach at least 65-75 knots somewhere on the backside of the low pressure Friday into Friday night, with some models showing 80+ knots, the other very favorable factors suggest that gusts could be into the 60-70 MPH range, locally stronger where the strongest 850mb winds occur. Will that occur over northern Ohio? Not sure yet, but again many models show gusts of that magnitude here or nearby so it's within the realm of possibility. If some or all of these factors trend more significant, it ups the potential for more widespread power outages along with true, significant blizzard conditions for parts of western and northern Ohio. 

So to sum up, very high confidence in a widespread significant impact from bitter cold, strong winds, and some snow accumulation. Some potential for more extreme, life-threatening impacts if snow or wind trend higher, which some guidance suggests is possible. With the amount of people planning to travel ahead of the holiday, this is a big deal. We have had internal discussions on potential headlines, timing of them, and messaging. Headlines will be done with extensive collaboration with all surrounding offices and WPC...there's already been a concerted effort to help steer the message and headlines. Given the scope of the system and overall confidence in impacts, expect headlines to be issued on the early side of normal. We still have a couple of days to watch trends and see if it's just a widespread high-impact event, or if locally more extreme impacts end up playing out closer to our area. 

My forecast duty for this storm may be minimal...I've been on evening shifts over the weekend and to start this week. The ill-fated LES Warning for Erie County was mine. I start midnight shifts Thursday night...it is possible I stay at the office on Friday, as I may not be able to get back Friday night if I drive all the way home as it looks now. However, I will be on the long term forecast desk so may not get to touch the grids for this storm. That said, it's a team effort with messaging to our partners and social media so I will still be dealing with the storm. 

Overall, an interesting next several days around these parts, first with some more tracking and forecasting and then we see what the storm manages to bring to our area. We look to trend milder towards the New Year, and I think we'll be ready for that to come. 

I'm setting my local expectations to rain changing to a couple-few inches of wrap-around snow, with 50-60mph wind gusts and a dramatic temperature drop. I feel like that's a safe floor and is still quite a storm, though with fairly modest snow amounts. There's some potential it trends a bit less wrapped-up and east which could up the snowfall some, but given current depictions I would keep snowfall expectations somewhat in check unless we start seeing a solid east trend. My guess is the lake effect quickly becomes a southwest NY thing, as with a very deep low just to our NNE I feel winds would quickly go rather southwesterly as it pulls away. 

Just looking at the last several Canadian and GFS runs, seems like the general waveguide over the US isn't changing much, but changes upstream/downstream of our trough over Canada are influencing how quickly the system goes negatively tilted and can really wrap up...

GFS:

Canadian:

The two areas I'm focused on are the lobe of the PV near Hudson Bay, which on the GFS and Canadian has gradually trended west/weaker in recent runs. This could allow heights to rise more aggressively in front of our storm, supporting a quicker wrap-up and stronger "cut". However, the other area is the lobe of the PV over northwestern Canada and how it interacts with the +PNA ridge trying to pop on the west coast. In today's 12z runs, that has trended farther west, leading to a flatter ridge. This nudges the base of the trough causing the storm a bit farther east/northeast, supporting a slightly slower wrap-up.

I feel like the trend for the Hudson Bay lobe of the PV to be weaker/farther west has been more consistent (a nod in the "amped" direction) but the trends over western Canada have not, so that could continue to go either way and lead to subsequent adjustments.

I doubt we see wholesale changes to the setup, but the exact max snow amounts and where that swath occurs can trend both west/heavier and east-northeast/lighter. A very high floor set-up as with such a strong trough closing off aloft, with Arctic air involved, a lot of areas will get strong winds and some amount of snow/blowing snow (even if it isn't a lot of snow farther east of the low track). 

2 minutes ago, AppsRunner said:

This run did not show exactly what I wanted, so it is clearly wrong.

Good analysis. 

Most models had light QPF last night and soundings suggested some convective snow showers with the trough passage, but for some reason it wasn't forecast particularly well. Close to an inch here, and the snow showers last evening were decent. It seems like a rain to wrap around snow/wind/cold situation and the end of the week...just something to get a good plowable snow in the whole area would be nice. 

While it's been cold with good lake effect at times, this has quickly turned into a frustrating start to winter if you're not up the I-90 corridor east of Lake County, with another decent lake effect event this weekend largely aimed up the eastern lakeshore. BUF already has warnings out and we'll need something for Erie and perhaps Ashtabula Counties. That said, big cold is coming next week and I think it'll be hard to avoid a light synoptic snow/snow showers along the arctic front, followed by lake effect, later next week. Hopefully the wrapped up solutions come to fruition and we get a larger synoptic snow out of it...potential is there but I do worry it struggles to wrap up quickly enough. Plenty of time to watch trends. 

Ton of uncertainty here, as others have mentioned the shortwave that will cause all this is still entangled in a larger trough. That said, some trends to watch...the reason we're seeing many suppressed solutions in the op runs (with many ensemble members also suppressed) is they have too broad of a ridge out west extending into the southern Plains, which doesn't allow the shortwave to dig as much and "round the corner" as quickly. While the NAO block has trended stronger and is pinning a large trough over southeastern Canada, it still is located far enough north that the shortwave does have room to dig, if it's amplified enough and if the ridge out west isn't too broad. Those are certainly trends that we've seen before, so it's possible this trends in a more amplified direction.

Have lost some of the huge cutter solutions and there's definitely a trend for more members to jump to the coast quicker. However, still many deep solutions over the Ohio Valley and Great Lakes, so while trends over the last day or two may have been somewhat unfavorable for a big storm in this sub-forum, I wouldn't rule out some trend back in the other direction yet.

Even if we don't see a big storm, have to feel that such a large upper-level trough and Arctic front would bring some light snow from all the jet support and squalls along the front to a large portion of the region. 

Pretty strong/consistent signal for 9-10 days out...

The incredible block amplifying over AK pushes a large chunk of cold air south, with cross-polar from from Siberia to the northern Plains. As ridging pops near the west coast, the trough is pushed southeast and amplifies over the central US. All the pieces are there for a large storm. Where the ridge near the west coast sets up, and how much downstream troughing there is over eastern Canada will determine how amped or suppressed any eventual storm ends up being. 

Pretty incredible agreement on an extreme 5-day mean pattern on all 3 ensembles 5-10 days out (December 16-21)...and this point, that's unlikely to significantly change:

Euro ensemble:

GFS ensemble:

Canadian ensemble:

All three have a huge ridge over the northeast Pacific and Alaska extending to the north pole, facilitating prolonged and robust cross-polar flow. Plus, a west-based -NAO persists. 

Sub-tropical jet looks fairly active, thanks to a ton of momentum getting added to the Pacific jet stream over the next week or so (this also contributes to the huge ridge into Alaska). Suppression is a concern, but this is definitely a robust clipper pattern too with such amplified flow out of Canada. And, if we can get sufficient wave spacing and a shortwave can amplify, the blocking does support amplified, slow-moving systems across the central and eastern CONUS...but again, would need proper wave spacing or else we'll get more numerous but more suppressed systems in the sub-tropical jet. Because this is a La Nina there will be a gradient with frequent systems somewhere, likely south of the entire region at times, but when blocking relaxes or if a stronger shortwave in the subtropical jet comes along it could shift north at times. 

Regardless of how much it does or doesn't snow, much of the CONUS will be cold to very cold in the lead-up to and then through the holidays. Severe cold will pour into the northern Rockies and Plains at times, with large pieces of that coming east. Really is hard to draw up a better pattern for Arctic air outbreaks, and at least some snow potential appears to exist. 

A couple important things happening teleconnection wise in the near future...first, a huge Siberian high descends into eastern Asia later this week. A strong "positive" east Asian mountain torque, which will add significantly to the Pacific jet stream:

Note how shortly after the huge high descends out of Siberia, the Rossby wave train amplifies significantly over the Pacific, allowing the huge ridge to pop into Alaska. It does not hurt that the MJO is becoming more coherent and moving into the western Pacific after mid-December:

This also adds to the Pacific jet...looking at the op Euro, note how early on in the loop there's some enhancement to the Pacific jet from the first little high descending over East Asia. This begins amping ridging towards Alaska. Then, the larger high descends and convection increases over the western Pacific, adding a ton of momentum to the jet and causing the ridge to amplify in a huge way over the eastern Pacific:

Long story short, the north Pacific ridge has had a propensity to amplify this fall and is about to do so in its most significant fashion yet over the next 5-10 days...this will lead to a pattern very supportive of extreme cold into the northern Rockies and Plains, with cold anomalies dominating most of the CONUS before and during the holidays. Snow potential will inevitably come and it's possible the sub-tropical jet has some activity, but some uncertainty lingers regarding more significant snowstorm potential.