eduggs

I am also largely discounting the 12z GFS solution locally. I think there could be snow somewhere in the northeast next weekend, but I think it's a longshot for NYC and the immediate suburbs. That said, there is some decent in situ cold on the GFS run specifically. I also want to try to dispel the myth that the GFS produces snowfall maps. A model output can be perfectly accurate and seem completely wrong in terms of forecasted snowfall if 3rd party vendors are used. So we should usually just ignore them and use model output and forecast soundings.

I don't agree with this summation. 8" is unlikely just based on typical snowfall frequencies in NYC and the low model skill at this range. But the GFS depiction - as is - shows a very wintry scenario. We would absolutely not need dramatic changes from what the 12z GFS shows to get significant snowfall near our region. As shown it's actually quite close to a long duration, region-wide snowstorm. But a snowy outcome is still very unlikely for the other reasons that you've mentioned.

Agreed on all your points. However, I was under the impression that NCEP doesn't disseminate forecasted snowfall amounts. I could be wrong, maybe it's an experimental parameter...? But obviously 3rd party snowfall accumulation algorithms should be ignored at this range, particularly with a marginal wintry setup. The only point that I partially disagree with is the temperatures. The low level temps are actually pretty cold - and with a continued LL cold drain - particularly just outside NYC. I think the scenario as modeled (12z GFS), with a thick cloud cover or nighttime precipitation, could support accumulating snow outside of high-impervious %, urban areas. I consider a snow threat a very low likelyhood outcome right now for the immediate NYC metro area.

Agree with the bolded part - I think that's the primary cause of disappointment when "patterns" don't deliver. I've been arguing for years that long range pattern recognition/correlation is far more effective in hindsight than foresight. The problem is that the numerical indices used to characterize patterns are too simplistic and not strongly correlated enough with local weather to be much utility for long range snowstorm hunting. The historical sample size of patterns is also too small for robust analysis, even if the base state weren't evolving. Models can't resolve future long range "patterns" much better than they can see individual trofs and ridges. So considering that nuances of synoptic pattern evolution largely determine distribution of snow in non-mountainous, mid-latitude regions, it's almost impossible to identify favorable wintry periods more than 10 days in advance. I know I'm mostly alone on this point, but I will continue to try to chip away. The increased attention to long range forecast over the past few years has seemingly come at the expense of good mid-range forecasting and discussion. I would hope that people would start to see the futility of the long range stuff after a few seasons of terrible performance... particularly those with a science background or some knowledge of statistics.

That's impressive. I know the City was straddling the rain-snow like throughout the event. What bugs me is seeing the map showing less than 10" in areas that got more snow that I've seen in any other event in 30 years.

That snow map is too low in the Hudson Highlands, particularly western Putnam County and northern Westchester. Whenever I see that map I remark at how the sparse reporting stations and spotter reports in the area lead to unrepresentative precipitation maps. I do remember a very sharp west to east gradient from Orange County to the CT border. But the highlands near the river were clobbered. 20-30 inches on both sides of the river above 600 ft.

If the Canadian ULL is further southeast, yes you would get more in situ cold air locally and probably a weaker storm or no storm. Alternatively, model runs from a day or two ago that showed a stronger SLP, particularly incorporating wintry precipitation, showed partial phasing of the ULL with the other wave. In this modeled scenario, the ULL was much further southwest, all the way down into the Midwest in some cases. The SLP being downstream of the longwave trof in an area of PVA would allow for rapid surface deepening. In this scenario, cold air would bleed in slowly from the northwest as opposed to being in place beforehand. But this would also result in a much bigger storm. I personally prefer this latter scenario for a shot at a stronger storm. But right now there is virtually no model support for this scenario.

IMO it would be better if the northern stream wave and associated surface low diving through southern Canada were further southwest (and diving southward into the US), allowing a phase with the system moving towards the eastern US coast. If there is a surface low northeast of us, it will be very difficult to form a meaningful SLP along the east coast. Unfortunately I think the big storm idea is becoming very unlikely.

The past 2 runs of the ICON have trended slightly more favorably for this period if looking for a bigger storm. It's still not close, but a positive trend helps to keep hope alive. We need that n/s wave to lose as much latitude as possible to our west. I guess the vorticity lobe is actually an offshoot of the PV since it dives directly from the arctic. Historically it's tricky to get these features into the right position for phasing and east coast cyclogenesis.

Confidence intervals are missing from your stats. Considering the sample size and complexity of the underlying weather/climate systems in question, it seems highly likely any "warm" and "cold" periods in the historical record on specific dates represent random chance/noise.

It's playing out very much like the model consensus from 36 hours ago. The south trend yesterday was just a weird blip.

Bit of a hole NENJ through southern Westchester the past hour or two. Best banding just to the NW through EPA, NWNJ, Orange, Putnam.

To me based on the current radar it looks like parts of the LHV and WCT could exceed a foot.

Orange County went from 12-15" on the 12z 3km NAM to a dusting to an inch. That's brutal. The south trend might not be over.

3-5 hour period of moderate to heavy snow and out. Still starts as rain for most.