eduggs

No noteworthy changes between the 18z and 12z HRRR through 41 hours outside typical noise. 850mb heights look a tiny bit flatter.

No concerns on the 18z HRRR through 29hrs. It's a touch flatter, colder, and slower down south... exactly what I was hoping to see. But it's obviously not impacting us yet. Sure the HRRR is less reliable at range, but its 6-hr trends are sometimes useful.

Yup. ECM-AI was maybe a hair better.

Locally I've seen 1 storm of this forecast magnitude locally since 2019. Interior NNJ missed out on a few coastals in recent years. There have been very very few 6" storms around these parts over the past half decade outside of higher elevations... really hoping we can bring this one home. Weekend daylight snows are the best!

Models have been showing steadily less precipitation into Michigan and southern Ontario reflecting the lessening trof angle. That makes the synoptics more workable for us and makes it much less likely the NAM will signal a shift to a sleet bomb ending as ZR. As I've mentioned, when Saranac Lake, NY and Burlington, VT get big snows, we usually do not.

The GFS has been holding out on bringing sleet to NENJ, Westchester, and the south shore of CT. This run it finally did briefly - even viewed on the 6hr panels. But its run-to-run shifts fortunately haven't been huge. And it looked like the GFS actually made bigger moves south of us around 48hr with an initially sharper trof before shifting east later in the run... like it was playing catch up initially on the phasing but still picking up on the trend towards a more positively tilted trof angle.

Sleet to LI by 0z but still a great run CNJ north.

The GFS is joining the other guidance but not quite to the RGEM it looks like. Pretty good model agreement.

Looks like the GFS is going to be more amped/warmer than 6z at least.

Agreed about the primary - that's key. A weaker, further south primary won't push the dryslot as far north. That could lead to a continuation of light precipitation after the thump into the overnight as opposed to a quick end. The RGEM has been steadily flatting the longwave trof, which would be associated with a weaker primary... but models historically weaken this feature too quickly.

Add the RRFS to the models that have improved at 12z. It shifted the thermals and surface features south. Looks like a great run for most of our forum. And it's not quite over here with some light wraparound stuff still to move through.

RGEM and ICON look like holds to me in terms of the thermals. The ICON might actually be a tiny hair warmer but 6z was a weenie run. The NAM was better. I guess the positive takeaway is we have pretty good run to run consistency and even inter-model consistency now that the GFS is getting closer to consensus.

Synoptically very similar to 6z on the RGEM but less thump. Big snowfall gradient right across the urban corridor - but not much room for comfort. The overall longwave trof has steadily been shifting less sharply tilted over the past 5 or 6 runs on the RGEM if anybody wants to cycle through them on TT. This has been gradually delaying the onset and shifting the northern limit of the primary surface reflection south. I was hoping for an improvement but we got a hold with less lucky banding.

NAM! Great to see the primary shift south. Sweet run! The sleet is usually north of where 3rd party graphics show it, so the 3km is probably closer to reality with that run. But it's huge to reverse the north/warming trend that it was showing for several runs! And this run introduces more lingering snows into Monday! Also saw last night's ICON - wow. RRFS also shifted south but yikes on the Euro. Could be a big gradient across CNJ or SENY. LFG

Ptype isn't accurately depicted for the Euro on Pivotal. It's a 3rd party vendor issue not a model issue. Most of what is shown as ZR is actually IP.

RGEM and NAM are 10-12 hours of snow before a flip to sleet. There could be a few hours of heavy snow. RGEM begins transitioning in NYC by around 3pm with the NAM a few hours later.

It has actually adjusted steadily north with both primary and secondary lows for several cycles in a row. I see no reason why it won't continue to do so.

That was an unusual event fairly well forecasted at very long lead times. I remember seeing a graphic on CBS or NBC 6 days before the event with the entire east coast highlighted with 1-3 feet written on the screen. I've never seen anything like that since.

I'm not disappointed yet. I'm looking forward to a major event and also holding out hope for even better trends. I don't think the current state of model output is as favorable as the clown maps would indicate. If you blend the synoptics of the Euro, UK, and CMC with the NAM thermals it starts to look uncomfortable. I also think people have short memories when it comes to the many many events where the NAM surged the warm tongue inside 48 hours and dramatically changed the forecast landscape. Heck even December 26th played out like that even though some refused to admit it. People overgeneralize and anthropomorphize things like arctic air and high pressure and think it makes us immune to synoptics. We fail to see and acknowledge obvious things like the trof axis being very far west... which historically favors the interior and New England for the best snows. Fingers crossed for everyone to get buried, but I plan to acknowledge the bad with the good.

It's interesting how being objective and balanced about a snow threat can upset some people so much. Everything has to be positive and rosy and amazing or the sensitive types freak out. Yes I will enjoy whatever snow falls probably more than most people. And the edge I was referring to is the threshold of something historical that gets remembered and mentioned in future years. Yes I do think 6"+ is likely in and around NYC, but 4" is plausible on the low low end if several things trend negatively. Just as 18" is plausible on the high end. Anyone who's followed weather for a while knows nothing is ever guaranteed. 12 hours of snow to sleet to dryslot should be a lot of fun. It's a high impact event. But if we can somehow get north of the dryslot, it could morph into the 24 hour plus event that some models were showing 2 days ago... and that a lot of the online/media hype is based on.

I had looked at the maps that were available at the same. And now that I've looked closely, I can confirm my suspicion that the 18z ECM looks nothing like the GFS and did not meaningfully trend towards it. If anything the shortwave near the MS valley that tracks to Detroit looks a little sharper... but overall it's very similar to 12z in all respects.

I like the AI models a lot for QPF distribution, but they don't resolve vertical temperature well at all so they are likely to significantly underestimate sleet. Just look at the NAM forecast soundings... there is a very pronounced warm layer between 700mb and 850mb. The AI models will not resolve that well. So it's not really correct to say that the models bring a foot to the City when they really only forecast QPF and temperature at a few layers. They don't forecast snow. 3rd party vendors do. And I am discounting the GFS since it has no support and has already shit the bed on several major events this year when it was a notable outlier. A slight shift north from the 18z position on the AI models could move the 4-6" range awfully close to Staten Island/Brooklyn etc.

I think that's a bit of wishful thinking. The GFS is still on its own with jackpot snows from DCA to NYC. If the 18z was better than 12z, it was a minor shift. I haven't seen good images yet of 500mb/700mb/850mb.

Most of us are still right on the edge IMO. I disagree with the sentiment that today has seen positive trends. I'm encouraged by the stability of the AI models, but the UK, CMC/RGEM, ECM, and NAM have persistent mid-level lows that are right at the cusp of eating into snow totals with sleet. That really hasn't changed much since last night. I expect that future NAM runs will lead the way in terms of signalling how far advanced the warm nose gets. This could still be 4" or 18" at NYC.

Except for those no longer under development, every single model is better than it used to be. And compared to 10 years ago they are significantly better than they used to be. Personal feelings otherwise stem from various cognitive biases and being hyper focused on a localized area.