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NYC/PHL January 7-9 Potential Part Deux


NickD2011

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Wow, there sure will be some amazing gradients in snow totals over a short distance. It sure looks like northern Jersey and the lower Hudson Valley continue to be targeted by the NAM for the biggest snowfall, along with Long Island if some of that QPF isn't wasted by initial temps. in the mid to upper 30s.

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This is going to be one heck of a 'surprise' large event for some folks. Yes, probably a farily small area, but a highly populated one. I wouls guess at this point from C NJ through S NE a general 1"-3" will fall, but whoever gets lucky and that band stalls over them might be looking at VERY impressive snow rates, and up to 10-12" of snow.

Sounds about right, the evening rush hour commute up and down the turnpike from about exit 8a should be interesting. Guidance has been very consistent with focusing the heavier precip just north and east of NYC. A line from i80 north is about the cut off.The 12z nam had the same idea just a wider area of the extent of the heavier snow bands from the inverted trough.

I still liks 2 - 5 from i-195 to i-80 more north and east of there.

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doubt it will occur as modeled by the NAM but I'm literally in the 1.25+ bullseye...if something like this verifies someone in a really small area could pick up 15'+

Well no one can be sure it will occur exactly like that both in geographic alignment and qpf output. That being said It seems we can start to gain some confidence on the general area that may be the final target along with it's potential snowfall amounts. If it does target an area reaching up into the higher terrian of extreme NE PA, NW NJ and SE NY (especially Catskills) I strongly suspect a few areas in the best of the band could reach or exceed 12"

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ok, so with the NAM a significant hit for the NYC/nearby hudson valley area, are there any other "short term" models of value in this crazy setup that might serve us well, or is it all about the GFS/Canadians' depictions at this point that are important? Good analysis in here tonight...Thanks all!

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I don't know why he said I was wrong. Mods deleted it.

Srefs certainly only show .10" for NYC.

NAM is awesome, obviously.

I dont know if the SREFS are telling us that the NAM is overdone and an outlier but its something to consider. Actually, looking at the 21 SREF spread plots on NCEP, there is not as much spread as I thought. Most are pointing to a much weaker event than the NAM is showing.

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I think it's great that the NAM continues putting NYC and northern surrounding in the highest QPF zone for the reason that it shows the potential with this event--a narrow area will likely see 6"+ with the potential for a few isolated totals to a foot. As has been stated, the problem is that the band is narrow--while tonight's run is encouraging, I wouldn't feel comfortable until the band is actually forming. Still, I think the NAM and the other higher resolution models will deal with this setup better than the GFS and other globals at this point. If I was at Upton I'd probably go with a general WWA for the area, with explicit language stating the potential for someone to see 6"+ from this setup.

I think it's likely NYC sees at least an inch at this point, but I'd be uncomfortable for going more than that still.

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Doesn't the 0z NAM carry more weight as it's the 0z run as opposed to the srefs which were 21z?

Not necessarily, when you have many members that are run within the SREF all pointing to a similar outcome, I think probabilistically that weighs more regardless of when the model is initialized.

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I dont understand how Christmas weekend everyone was hopping on the SREF train since it was trending west west west, now because it does not show this NAM solution, its wrong? I think probablistically the SREF may be telling us the NAM may be overdoing things. We shall see.

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one good way to find out is to see what the rgem does in about 30 mins....

Personally, if I was in NYC right now, I'd be most looking forward to the WRF and NMM late tonight. Those should be very telling as to whether the NAM is correct in forecasting isolated 12"+ amounts (not as to location yet, but the potential).

I dont understand how Christmas weekend everyone was hopping on the SREF train since it was trending west west west, now because it does not show this NAM solution, its wrong? I think probablistically the SREF may be telling us the NAM may be overdoing things. We shall see.

The SREFs busted terribly for DC during the Christmas storm. The NAM was actually the most accurate when we were close, as it never backtracked like the GFS and EURO did, as it always left DC high and dry.

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I dont think hes wrong. The SREFS have shown large spread with many members much weaker and less than the NAM.

I'd trust the actual NAM over the Srefs for mesoscale features. There was a major bust in State College on 1/7/2002 using that logic. Only a few SREF members supported the ETA, and it turned out to be correct. Of course this happened much closer to the event.

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I think it's great that the NAM continues putting NYC and northern surrounding in the highest QPF zone for the reason that it shows the potential with this event--a narrow area will likely see 6"+ with the potential for a few isolated totals to a foot. As has been stated, the problem is that the band is narrow--while tonight's run is encouraging, I wouldn't feel comfortable until the band is actually forming. Still, I think the NAM and the other higher resolution models will deal with this setup better than the GFS and other globals at this point. If I was at Upton I'd probably go with a general WWA for the area, with explicit language stating the potential for someone to see 6"+ from this setup.

I think it's likely NYC sees at least an inch at this point, but I'd be uncomfortable for going more than that still.

I'm leary with the NAM and I have 1.25 of QPF up this way. That would be around the foot mark.I would be happy with .50 of QPF

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Most models tend to underestimate precip in norlun events (although the NAM would presumably do much better than the globals) but on the other hand the NAM tends to overdo QPF. There are reasons to believe this could be a stronger norlun type event than is typical outside Maine - both in terms of duration and intensity. But I don't trust the NAM QPF output. I would take half the NAM QPF as a representation of the snowfall potential wherever the core bands setup (something like 5"-7") but the full QPF as the very localized maximum (~14"). General 1-4" outside the lucky spots.

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I think it's great that the NAM continues putting NYC and northern surrounding in the highest QPF zone for the reason that it shows the potential with this event--a narrow area will likely see 6"+ with the potential for a few isolated totals to a foot. As has been stated, the problem is that the band is narrow--while tonight's run is encouraging, I wouldn't feel comfortable until the band is actually forming. Still, I think the NAM and the other higher resolution models will deal with this setup better than the GFS and other globals at this point. If I was at Upton I'd probably go with a general WWA for the area, with explicit language stating the potential for someone to see 6"+ from this setup.

I think it's likely NYC sees at least an inch at this point, but I'd be uncomfortable for going more than that still.

To be honest with how well SPC hit the banding with the blizzard I will feel comfortable when they issue there MD for heavy snow sometime Friday! ;)

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Personally, if I was in NYC right now, I'd be most looking forward to the WRF and NMM late tonight. Those should be very telling as to whether the NAM is correct in forecasting isolated 12"+ amounts (not as to location yet, but the potential).

Just a note to that,: the NMM is the NAM. The NMM hi-res window is just a 4-km version of the 12-km NAM.

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I dont understand how Christmas weekend everyone was hopping on the SREF train since it was trending west west west, now because it does not show this NAM solution, its wrong? I think probablistically the SREF may be telling us the NAM may be overdoing things. We shall see.

isnt the sref's a more reliable model when getting within the 48 hour window of an event? the nam is typically known for overdoing qpf numbers frequently as well correct?

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