RU848789

and the IVT

Except for 12Z Saturday when it showed 0.5 QPF right along 95 (so 6"+ with ratios along 95 with ratios and 7-10" towards the coast), which is at least a significant hit (4-8"), so not sure on your definition of "hit." Certainly not "major" (8-14" is my definition of major).

My cutoff time has been 0Z tonight, so I'll wait a little a little longer before declaring the patient dead, plus I take seriously Walt's input here, as he's been rock solid on not going big early when many did, but also sticking with his few inches forecast, still, so while I'm pretty certain anything beyond 2-4" is dead for the 95 corridor I still think it's possible we could have a 1-2" event (and an outside shot at 2-4") instead of a complete whiff (which is also obviously possible given the models). So, I'm still following everything, but at a distance...

In hindsight, it looks like the Euro-AI model scored a significant modeling coup, as it never showed a major (8" or more - my definition) snowstorm for our area, unlike almost every other global model all of which showed at least a few runs with major snowfall. The Euro-AI had most runs in days 4-7 showing a minor to moderate hit with one run on Sat 12Z with significant (4-8", again, my definition) snowfall, but not major. Out of the rest of the models, the GFS was close to the Euro-AI, only showing one major snowfall run, also on 12Z Sat. The Euro, UK and CMC all had multiple major snowfall runs for our region in that timeframe (including some historic runs). So still a significant failure for the AIFS/GFS but an epic failure for the Euro/UK/CMC. IMO.

Here's the 2.5 day trend of the NBM since Saturday at 12Z (every 12 hours), showing how the NBM can be very misleading in trending situations, due to its time-lagged nature. I think everyone here knew this storm was mostly toast by yesterday at 12Z, but the NBM was still showing 6"+ for the 95 corridor with a bit less NW and up to 9" at the NJ coast. And it just showed <3" for the 95 corridor at 12z today. I think it's a useful tool when models aren't trending one way or another, significantly, but has been useless for this event.

We still have 1/2" to 1" on our lawn. That 0.6" of QPF that squeezed into 1.5" of snow/sleet/slush last Saturday and became a 1.5" dense concrete ice pack has had staying power, moreso than the 3.1" of snow that fell on top of it this past week.

2nd post...

Just wanted to memorialize the complete modeling failure for the Euro, GFS, CMC and UK models from 12Z Saturday to 0Z Monday, from major/historic snowstorm to essentially nada (need 2 posts for this due to size issues). I don't recall a faster implosion in the last 15-20 years, as the axis of heaviest snowfall shifted 150-250 miles over 36 hours in this case. Even Jan-2015 went from a forecast of 18-24" for most in NJ (and there was not model consensus on the high snowfall forecasts 12-24 hours before that event) to several inches for most of NJ, which is at least not a complete miss (and yes I know this one isn't 100% over yet, but it's close). March 2001 might be worse at least for me, as we had a forecast of 1-2 feet and got maybe 1" in CNJ. The only saving grace, kind of, is that it happened between 4 and 3 days out, which is a little less painful to me than having an actual forecast for a big storm and getting shut out.

I can only imagine what the weather boards would've looked like in the 70s and 80s, lol. NYC gets a 12" snowstorm about every 4.2 years (37 in 155 years at CPK), but had 13 such storms in the last 30 years, which is one every 2.3 years, so we've been spoiled in the age of the internet. Welcome to climo, as it's barely been 4 years since the last one in 2021. There were 4 in the 70s/80s or 1 every 5 years, which is probably why it seemed they were so rare when I was growing up.

If that's "noise" I'll take another dose of it at 0Z. That's a pretty big ~50 mile shift in the snow shield, not a minor tick NW. Doesn't mean it's right or that it's a great model, but at least acknowledge what actually occurred.

Walt et al - wondering what you think of the latest WPC map on likelihood of achieving warning level snowfall in the next 4 days (30-50% for CNJ/NYC/LI). I wouldn't think this would be so high, but iirc, WPC goes off the NBM and the NBM at 13Z is way more bullish than I would imagine, even considering it's time lagged (but I can't imagine it's still including very snowy outcomes from 12Z yesterday, can you?).

It ain't over til it's over, lol, with obviously more to come, although it is the end of its range NAM...

yes, significantly so with just minor snowfall from 95 east to the coast...

Interesting points. Wouldn't that be where hindcast analysis for some past storms comparing the "old" models to the "new and improved" ones would be helpful and possibly indicate that for major storms, where stability is pretty damn important, perhaps some work needs to be done to improve the models? Who gives a crap about predicting the heights at 500 mbar and SLP on sunny days (which is what most of the verification scores are based on, iirc; although I do know more detailed storm verification scores are kept on hurricanes)? I don't care if it's 73F vs. 80F for a high, but I do care about whether I'm going to get 1" or 6" of snow in 2-3 days. I do also wonder how much the AI models have been "trained" on datasets like what we've seen over the past few days (although there probably aren't too many of them).

Based on 12Z so far, you may end up being right.

The ensemble mean took a bit of a step back, but the Op didn't, at least at the surface with snow.

Really nice progression of QPF steadily increasing (likely snow at >10:1 ratios with temps around 20F) on the ECMWF-AIFS since yesterday. it now shows 0.5" QPF along 95 (that would be ~7" at 14:1 ratios) and up to 0.7" QPF for the coast (10" at 14:1), whereas it was only showing 0.1-0.2" QPF yesterday along 95. Considering that the AIFS has been the one model always showing a coastal scraper to even a complete miss for days, this is a big shift NW with the precip shield.

In 12 hours we went from every model showing a significant to major (or more) storm at 12Z to all but one of them showing nothing more than a coastal scraper (several inches towards the coast with little to no snow along/NW of 95). Not sure what's more unprecedented, most of the models showing a major to historic storm over the last 48 hours (which is extremely rare 4.5-6 days out) or that near consensus going into the shitter 4 days before the event for almost every model. Almost. Until the Euro saved Christmas, lol. Seriously, though, if the pros/experts are dumbfounded how are us hobbyists supposed to feel? One thing I will say, though, is that If a much less snowy outcome isn't a blip and is somewhat close to where we end up, it would prove to be perhaps the biggest modeling coup ever - for the Euro AIFS, which for days has been showing a coastal scraper or complete miss (apart from 12Z today, where it did show 3-5/4-8" snow for most) and has never shown a major storm unlike every other model (multiple runs). Let's hope it's not a coup. Debating not tracking at all tomorrow and being surprised on Monday, lol.

Somehow I missed this yesterday - fantastic post, thanks! And thanks for posting it here, also. Loved your inclusion of the historical anomalies associated with NYC snowfalls over 18" over 30 years and your excellent discussion of how the current projected pattern matches these features, as well as the easy-to-understand graphics showing what you discussed. I'm guessing that's how you guys see the 500 mbar pattern 24 to maybe 48 hours before the event in a model run and say "we're loaded for a big snowstorm" (or not if you don't see it) - would that be correct? I've never studied synoptics, so don't have much feel for how the pros infer this. I do have a couple of questions, though, if you can indulge me: i) I see that you showed the Euro pattern about a day prior to our potential event start on Thursday to match the NCEP graphic which says the anomaly is seen 1 day in advance ("preloading"), but I was wondering if one sees this anomalous pattern for a few days before such an event and not just at 1 day before the event (and could that give one more lead time on confidence in a big snowstorm); and ii) I get that this is the composite anomaly for 18" snowstorms, but is there data on how often such anomalies occur and what percentage of them lead to 18" snowstorms for NYC (or even any snow)? I would imagine there's some percentage of time when these patterns don't lead to big snow, although maybe less frequently when they're as close to the event as 1 day before the event, but that's just a gut instinct. TIA.

Strange winter part of the storm. Started out like gangbusters, putting down 1.1" in about 2.5 hours and then poof, precip just turned off since about 5:00 pm and it's now up to 33F with some light rain falling - possibly missed another 1-2 hours of snow. Seems like this one is over south of 78 for wintry precip and even north all the way towards 84 has changed over to sleet and freezing rain already. That's 1.1" vs. my prediction yesterday of 1.4" and the NWS prediction of 2.0", so a bit of an underperformer south of 78 and given similar reported ~1" or so amounts for most N of 78, that's a more significant underperformer there, where 1-3/2-4" were forecast, although reports of icing are common N of 78 with temps still below 32F, so could still be a significant impact event for that. These snow to mix to rain systems are just very difficult to predict accurately, especially aloft. Brings me to 15.9" on the season, which isn't too far behind normal for this date.

High wind warnings up for tomorrow afternoon for the entire region through Monday afternoon for west winds 25 to 35 mph with gusts up to 60 mph expected. https://forecast.weather.gov/wwamap/wwatxtget.php?cwa=PHI&wwa=high%20wind%20warning

Been wondering the same thing...

Have had moderate snowfall for most of the last hour and we're up to 1.0" on the colder surfaces (it's still 32F), much faster than I expected; have about 1/4-1/2" on most untreated paved surfaces now, as you can kind of see in the pic below. Precip has lightened up a bit and looks like there might be a lull for the next ~20 minutes or so.

Surprisingly, we've had consistent light to moderate snow for 90 minutes and as of 3:45 pm we have 1/2" on the ground on colder surfaces and we also have a light coating on our driveway and sidewalks (untreated), whereas any street in town is just wet (we just ran errands and ate downtown). It's 32F, which is a touch colder than forecast and could mean this will overperform (vs. the updated NWS 1.5" forecast for my house; was 2.0" last night and my prediction last night was for an underperformer with 1.4" for my house) unless the warm air moves in more quickly. Sleet/mix line looks to be from about Philly to LBI, so could have several or just a few more hours of snow. It also helps that 75% of our property still had 1/2" or so of snow/sleet/ice cover, which is 32F, enabling an easier start of accumulation.

Always interested in snow, but just not optimistic, south of 78, especially with 33-34F temps, light to moderate intensity and snow falling during the day (yes there is more indirect sunlight impact on 2/15 vs. 12/20). Earlier today when the NWS had 2.0" for my house, I predicted 1.4" for my house and that will mostly be on the grass. Unless one of the snowier, higher intensity models is right. One can hope.