eduggs

Just now, HVSnowLover said:

This has been the trend for a while. Always was concerned overrunning would not make it to us 

I suppose it could come back a little bit in short term modeling. But it looks like we'll mostly have to wait for the main deal up here.

Slightly positive signs I see are the 06z GEFS ticking up with QPF on the northern edge and the NAVGEM bumping north again with a pretty good run. Usually it's good to be on the NW edge of a mature 700mb circulation. It could even come down to nowcasting. We'll see.

Hopefully we are the Binghamton of this event.

Most guidance is now struggling to get precipitation into the area on Sunday.  Delays it into Monday and possibly late Monday for northeast suburbs.  That shortens the potential duration of snow by several hours.

The GEFS continue to be a little concerning. Pretty similar QPF to 18z for the metro, but slightly drier again along the northern edge of precip. They are much less robust than yesterday.

2+ liquid most of the area on the Canadian. That's about 24 hours of light to moderate snow and 12 hours of moderate to heavy snow. We should assume that it won't play out that perfectly. 

The ensembles show a reasonably wide range of solutions. This is far to one side of average likelihood... but still not quite the best case scenario. 

CMC is a bit hit for the area.  Not suppressed.  Brief mixing from the City east.  Still major snows everywhere.

The ICON has about 1.5 - 2.6" liquid across the area. I think that's overdone, but it's not far fetched if the event plays out as depicted. Could be at least 12:1 ratios for part of the event. Of course there could be a lot of compaction over 2 days.

The GFS looks really good as is. But it might not be picking up some mesoscale banding on the NW side of the stalled low. And it might be a little warm at the surface. But regardless it still shows a major long duration event. There's clearly concern that the initial WAA precipitation might not make it very far northeast and then how far NW does the most intense precip. from the developing coastal low make it... and where is the pivot?  700mb and 850mb lows move very little for 12-24 hours! Someone should really cash in.

The NAM still looks like it would have a sharp cutoff near the NY - NJ border as the initial overrunning dissipates and activity switches towards the Delmarva. 

Yes the end of the NAM run is clearly further north with all features than last run.  But the 18z was discouragingly suppressed. This run is a slight relief, but we need to see other guidance stop slipping southeast.

GEFS QPF bumped up this run. Over 1" for the entire area and 1.5+ for coastal NJ, NYC, and part of LI.  That's pretty big for ensembles at this stage, although it will probably tick down next time the OP does. For now it's nice to see bigger QPF numbers. But the big ticket is the long duration. None of the 6-hr panels have huge QPF, but it steadily adds up over 1.5 days. Of course with a stacking and stalling system there are always concerns with banding far NW, dryslots, mixing and a possible SLP slide east.

7 minutes ago, TriPol said:

2 days and all NYC gets is 9 inches?!

Ignore the specific snow map numbers. The Canadian shows between 1 and 1.5" liquid for most of the area - mostly snow around and north of the City. There is a random QPF minimum right near the metro. But that's not representative of the wider area. It could easily end up as a maximum instead. That's a pretty good look for 6 days out.

If I'm being nitpicky it's not a particularly dynamic storm as modeled.  The vorticity isn't huge, so the PVA and upper level divergence is only modest. As a result, surface low deepening is not explosive, and correspondingly, precipitation doesn't explode either. But the upside is a possible long duration event and banding on the backside. 

That GFS run is pretty close to perfect for most of the metro area. Ignore QPF for now. Just loop 700mb. Entrenched cold air. Long duration. Intense frontside and backside. Multiple mechanisms for generating heavy snow during different phases of the storm. It probably won't play out nearly that well, but as modeled it has lots of elements to make for a fun storm.

Just now, HVSnowLover said:

I still don’t know why people post 10:1 snow maps for systems that clearly won’t produce 10:1 ratios. 

Well they sure are nice to look at. It's really hard to force myself to ignore them and instead consider ptype, thicknesses, ratios etc...

This seems to have played out as modeled for the most part so far: 0.1 - 0.2 inches of liquid. A dusting to an inch of snow (slightly more near and north of 84) with a glaze on top. Rain and snow showers - mostly light - should continue intermittently through the overnight. Hopefully not too many people were fooled by the numerous inaccurate snow maps. In most cases the model is not wrong. The 3rd party algorithm to calculate snowfall is wrong.

10 hours ago, HeadInTheClouds said:

The early consensus from the models from those systems 6 days out was suppression also only to come farther north with time. The 16-17th storm was a developing secondary that models had coming north to southern Jersey and then shunted east. It came further north and hugged the coast and we know what the result was. I'm not saying that will happen this time, just that there is a long way to go for this one. 

By my recollection, the northward shift and dryslot associated with the Dec. 16/17th event was related to the primary tracking pretty far north and being slow to dissipate.  And the secondary was slow to deepen and never developed a mature circulation to pull in cold air or develop a classic commahead. I don't recall a hugging track being the problem. But it doesn't really matter and has no bearing on what is likely to happen next week.

3 minutes ago, HeadInTheClouds said:

Actually the trends this year have been for the lows to track further north in time. It happened in Dec 16-17th storm and with the minor event today. 

Yes, but they've mostly been weak primary lows trending north, typically with dampening upper levels. Not so much strengthening coastal lows or 2ndary lows hugging the coast.  Take today - primary low into Lake Ontario with a weak 2ndary 100s of miles offshore. Something very similar could play out with the next threat.

The GFS is still not very enthused about snow. 1-2" positive depth change N&W with little or nothing for the City or coast. As depicted, rain washes away what little does accumulate initially.

I think we can beat the GFS estimates, but it's a good starting point. We'll see how the radar looks tomorrow morning...

3 minutes ago, HVSnowLover said:

Agree although I think the light blue zone may get the best rates with the initial burst, ecm has a similar zone. 

The Stormvista maps count everything except plain rain as accumulated snow at 10:1. The EC map I saw earlier was similarly overdone. But today's guidance has increased expected snowfall for the immediate metro area for sure.

The 0z RGEM is pretty snowy tomorrow, esp. I-78 north. Solid advisory snowfall.  Subtle but significant trends today!

15 minutes ago, MJO812 said:

Icon

Take 40% of that for a better estimate of model forecast snow accumulations locally.

1 minute ago, HVSnowLover said:

The mid level warming I think is a real problem for most of the sub forum. The only savior could be if the initial push has any juice to it. 

We have all sorts of problems for this one. To my eye there's not a lot that looks good... except I guess an airmass that is marginally supportive of snow. We have to hope for modeling errors... a little more lift producing mechanisms, a little further south, and a little colder.

It snows for 36+ hrs in parts of eastern SNE on the NAM and GFS. The EC and CMC are less. Even 12 hours of light to moderate snow would make a pretty significant event. Kind of funny after most of the SNE forum was throwing in the towel over the weekend.

I think there could be some sneakily big totals in parts of SNE. The inverted trof feature has shifted to that area and moisture appears to linger between the two systems. Eastern areas also have the advantage of ocean enhancement. It looks like a potentially long duration event over there with a fluff factor. Exactly what we were looking at locally 2 days ago. Those mesoscale features are fickle. But for now eastern SNE went from zilch to WSW and we went from plowable snow to freezing drizzle advisory. Bad luck I suppose.