RCNYILWX

It's not the big storm we all want, but the Euro showing a decent Pac hybrid clipper on the 22nd into the 23rd and then a follow up weaker wave into the morning of the 24th not far from here keeps some hope alive of getting snow cover down for Christmas. The ensembles also have a decent look toward the end of the run with a -EPO, -PNA, -NAO, -AO. May make for an active and not too mild stretch into January if that comes to fruition. Sent from my SM-G965U using Tapatalk

That's the one! I'll fix my original comment. Definitely a good cautionary system with respect to mid level warmth. I remember watching the mixing line surge northward on correlation coefficient on OKX and DIX during that event. You made a comment later that the models often underdo the warming aloft and that's absolutely right. It's tough to say yet that the NAM is handling it perfectly because even at this range it can be too amplified with key mass fields. That said, have seen it perform better than the globals several times out here re. warm nose aloft. Hopefully the Euro is capturing things well enough and a good chunk of the city and interior LI can manage to get several hours of heavy snow rates before mixing/dryslot.

Not gonna pretend that I'm optimistic for next week. It looks as usual too progressive on the operational modeling in that timeframe. The trend on the EPS last 2 runs to become much more northern stream dominant, which was the more likely outcome anyway, really diminishes the chances for anything to work out for us out here. All I can say is that it's far enough out for changes to occur from the current look. The cold looks like it'll be legit not very modified Arctic air, so all we can do at this point is hope that somehow we can get some snow down for what looks like it could be a very cold Christmas period. CAD for Christmas would certainly be a nice cherry on top of 2020 lol.

Only wraparound/CCB that I can remember really working out for a storm that didn't have a good track overall for the city and western and central LI was the Christmas 2002 noreaster. I guess you could kind of group in the late Feb 2010 Snowicane but that was an odd beast of a storm. Sent from my SM-G965U using Tapatalk

The NAM was actually supposed to be replaced this past summer as part of replacing the entire modeling infrastructure with the GFS's FV3 core. This is the setup the ECMWF and UKMET have, with all their modeling under the same core, from global to meso to ensemble and weekly/seasonal. Taking the NAM off line was pushed back because better verification needed to be seen of the GFS/FV3 doing the things the NAM does well as well as the NAM. The coming upgrade of the GFS, if it is a marked improvement, and that's obviously the goal of the effort, will eventually result in that timeline of the NAM being discontinued into focus. In addition, this newest upgrade of the HRRR may be the last significant one until the high res suite gets fully moved over to the FV3 as well. Sent from my SM-G965U using Tapatalk

Plot twist, Alek's backyard as the snow capital of the Chicago metro. Edit: In all seriousness though, the LES parameters aren't terrible tomorrow from a thermodynamics perspective and duration as well. When I looked yesterday, lake induced ELs were peaking on the forecast soundings at 6k-7k feet, which is a bit better than marginal. The problem is the possibility as partial ice loss as we lose saturation in a portion of the DGZ. Overall DGZ saturation won't be great and lift peaks below it, so flake size should be pixies. Hoping the FZDZ monster is avoided.

For winter weather headlines, the winds typically get grouped into the WSW. You wouldn't issue a HWW on top of a WSW, similarly wouldn't issue a Wind Advisory on top of a WWA. In our bulleted current text products, an extra bullet for additional details might be included that mentions the 45-60 mph wind gust potential. The one location it's probably tricky is out east on Long Island where changeover should occur quicker and amounts might not reach warning criteria but the winds do. My guess is because the snow/mix would be impactful enough plus the damaging winds, might do a WSW for simplicity. Not speaking for OKX though, just speculating based on how my office and surrounding offices typically handle multi faceted winter events.

The current ECMWF is 9 or 10km resolution. The parent NAM is 12km and NAM nest is 3km. The HRWs (ARW, NMM and NSSL) are 4km. Sent from my SM-G965U using Tapatalk

Lurker on this thread, originally from College Point Queens, been working at NWS Chicago since 2010. Jealous of this storm, as it's been exceptionally boring out here and big snowstorms like Superstorm 93, Blizzard of 96 etc drove my passion for the weather. Anyway, certainly can't discount the depictions of the NAM and the RGEM in this timeframe. It was comforting to see the Euro with an all/mostly snow solution for the city. That said, think big picture old school meteorology before we had access to this firehose of data. The parent mid-level low has trended stronger and farther run over run (looks like we'll even get fringed by light snow out here which was very low probability just a few days ago). With the pretty far north and west mid-level low center tracks, this seems to be a setup that favors a very intense front end thump with very strong large scale and mesoscale ascent (low level f-gen and steep lapse rates) in the warm conveyor belt. Hopefully not like the [Edit: March 4 2017] storm that got flooded with warm air and caused a mix much quicker. Recall the 93 Superstorm had a terrible track for the coast but we still got 10-14" on the front end because the warm advection thump was that intense. For the city and a good chunk of Long Island, you could see most of your liquid equivalent QPF as snow but then dry slot and mix with the 700 mb deformation zone displaced well to the north and northwest. Good luck to everyone that's been tracking this storm! Wish I was heading up to the Catskills to ski on Thursday lol.

Thanks for posting those, never got around to it yesterday. 12z run today looks better than yesterday anyway. Sent from my SM-G965U using Tapatalk

Yep it's thread the needle but since literally the only threat in the extended, gonna stay interested. Also, a white Christmas would be a bonus with how depressing it is around here otherwise in December, especially this year. 12z EPS looks a bit better than previous 12z and 00z runs and starting to see an uptick in 24 probs of accumulating snow, owing to increased member support. The GEM and GFS in that timeframe show how we can easily get hosed if northern stream is dominant and too progressive. It's safer to bet that the pieces won't come together. On a positive closing note for the possible setup, the antecedent air mass will probably be bad like this weekend, but the incoming air mass looks to be legitimately cold. Sent from my SM-G965U using Tapatalk

Having experienced some of the greats in the east (1993 Superstorm, Blizzard of 1996, late February 2010 Snowicane to name a few) and GHD I, hands down GHD I was the most intense non mountain winter storm I've witnessed. Since living out here, I've missed the more recent east coast big dogs, but don't think any have surpassed GHD I for a widespread area in terms of wind and snow combo. The most comparable widespread intense wind/snow combo on the east coast to GHD I in recent history was in the same winter as that one, the December 26, 2010 "Boxing Day Snowstorm". Was legit paralyzing for the NYC area. Sent from my SM-G965U using Tapatalk

Euro ensemble still with a reasonably solid look around that time and even some individual member support. Risk there is the ridging out ahead, and any system favoring far north/northwest sub. However, the smoothed out ensemble mean isn't going to do a good job picking up the influence of the -NAO and its tendency to limit how far north/west systems can track. This is despite the ensemble mean showing a strong signal of a -NAO and the teleconnection chart from the 12z run backing that up. @Hoosier are we allowed to post images from WeatherBell on here? I could post some visuals to illustrate better if I can. Sent from my SM-G965U using Tapatalk

In grasping at straws mode, but just looked at the 12z EPS, and heading into Christmas Eve and Day it does have a pretty interesting look, with a frigid cold trough dumping into the Plains and ridging out ahead into the east though still with a -NAO signal. Surface pressure anomaly even hints at a surface trough over the southern Plains lifting into the lakes and an expansive high over the northern and central Plains. A few of the individual members as expected from the above hint at some potential in the region during that timeframe. 00z run wasn't too different so we'll see if any continuity develops in that timeframe. Also GEFS not crazy far off but not as potentially interesting as the EPS. While we could do a lot worse than that modeled pattern, need to get it within 10 days. The hope is that *if* a system does develop in that timeframe, the -NAO could help prevent warm cutter. Sent from my SM-G965U using Tapatalk

Even though modelers will tell you the RAOB data doesn't affect performance much, it's not what we're seeing anecdotally with a lot of these systems. It seems like with every system in recent winters, drastic changes and or variability occur prior to main wave or one of the primary waves coming ashore from the Pacific, followed by a relative stabilizing once there's full RAOB sampling. Sent from my SM-G965U using Tapatalk

If you're in northern DVN to northwest 1/3 or so of LOT to MKX, have to like where you sit at this point. For points south, if weaker and southeast trend from last winter resumes, not sure that really helps because the strong dynamics are an important factor in getting the potential 6"+ accums.

Here's the snow depth output, which might be more realistic in this setup with ratios likely to be sub 10:1 for much of the event. Sent from my SM-G965U using Tapatalk

Not too surprised to see how things have trended for the Chicago area. Going to have to see significant changes tonight and tomorrow to have hope of getting decent snows into the heart of the metro and south metro. At this point, far north and northwest metro clearly has best shot. Sent from my SM-G965U using Tapatalk

Also shows marginal temps overall. Surface 0 line is way up in northwest IL valid 12z Saturday. Gonna need heavy rates to consistently overcome the boundary layer issues. Sent from my SM-G965U using Tapatalk

In that setup, your backyard would be screwed until winds flip northwesterly Saturday evening. Lake is still quite mild. Sent from my SM-G965U using Tapatalk

Some initial thoughts on weekend system... When I posted a few days ago, wasn't too optimistic because of the bad antecedent air mass and rain prior to any snow. What happened in the past obviously doesn't determine what happens in a different event in the future. But, the fact that good rain to snow scenarios are rare suggests that lots of things need to work out at this latitude, so to be skeptical in this range. Give a nod to Euro for decent run to run consistency past couple days. But since it's the only model that's been showing this on the operational, want to see some multi-model support before getting more excited. While the EPS members trended better up until 06z run this morning, what I've noticed in the ensembles overall (including 12z GEFS) is that a majority the members with a solid hit favor areas north and northwest of here. The 12z UKMET looks like many of these ensemble members. It's gonna be a big time thread the needle to get a strong enough system to get good totals without it being biased farther northwest in the key synoptic features. Also wanted to note to use caution in getting too excited by the 10:1 and Kuchera maps from the Euro. As modeled on recent runs, temps don't fall solidly below freezing until the end of the event, along with good cold advection aloft (850 mb) not arriving til Sunday morning. These are all reasons to lean lower than 10:1 for ratios. I'd suggest looking at the snow depth output from WxBell or weathermodels.com as a good first guess and then can assess reasons why you'd get ratios to 10:1 or higher in spots.

First post a long time. Have nothing really optimistic to add to what's been written recently for the next few weeks. Barring no major changes for the weekend system (I'm not currently liking that period to work out), going to have to hope there's something snow wise in the cooler interlude behind that. Interestingly enough, both the GEFS and EPS have a -NAO look for most of their recent runs. Problem is they both develop a ++EPO toward the end of the run, which would torch the CONUS even in the presence of a -NAO. Would in all likelihood mean another warm Christmas period if that look pans out. Concur that January is probably best chance for a decent snow pattern for a time. For what they're worth, weeklies kind of point that way as well. In our local winter outlook (NWS LOT), we leaned warmer (actually got a nastygram from CPC for going against their temperature outlook 2 winters ago so we didn't explicitly say warmer than normal), and AN precip, which has strongest signal in Ninas. Since December is leaning dry, we should get most of our winter precip in J-F. Snow wise, think somehow we'll end up within range of normal. Last year was crappy as we all know and it eeked out just slightly below normal, though did have a head start from late Oct-Nov events. We're overdue for an area wide higher end warning event, so hoping we get 1 or 2 systems to track favorably. Figure if we do get into a more classic Niña pattern, we can manage to get one to work out ala 1999. Sent from my SM-G965U using Tapatalk

I think you might be right on that, someone can correct me if I'm wrong though. Sent from my SM-G965U using Tapatalk

Lurker on this thread from the Chicago NWS office. I'm originally from NYC, so interest in weather started with noreasters, especially Blizzard of 96. Anyway, have noticed a lot of discussion on WxBell snow map algorithms. Last winter out here we found that for the Euro the modeled snow depth algorithm often did a better job than the clown maps. Curious if any of the other mets on here have noticed similar. For all those getting a pasting from this storm, enjoy! Sent from my SM-G965U using Tapatalk

Liking the ARW tomorrow night and Euro continues to be locked in. If we had northwest flow aloft, would've been better for faster propagation and maintaining severe farther south. That said, temps well above 80 deep into evening with 70s Td, and breezy southerly winds should yield at most a shallow stable layer. Expecting the outflow and 850-300 mb thicknesses pointing southeast ahead of the MCS to do the trick in keeping it decently strong farther south than you'd normally expect given less than ideal 500 mb flow and time of night. As Alek has been mentioning, in support of this idea is strong low level jet pulling from a very steep lapse rate plume, and large (>2k j/kg) MUCAPE reservoir. Best chance for severe winds in LOT CWA looking like northern tier but could see severe threat extending south toward I-80. The faster movement the better to maintain intensity farther south. Edit: spoke to SPC day 2 update forecaster and it sounds like he's gonna pull the risk areas farther south, with slight possibly down near or slightly across WI/IL state line.