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NYC Jan 20/21 Obs and Discussion Thread


am19psu

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12z GFS looks like less QPF than 06z. Especially from PHI on southward. Of course we couldn't get all the models to agree even at less than 24hrs out. I think the main reason for the less QPF is that its such a fast mover, and likely too fast in my opinion.

Only less for like you said areas south, like Philly. This is believable because there is nothing to prevent the northward development of this storm. The trough at h5 isn't overly deep and with the initial energy heading to our west, it likely the coastal would develop just off the NJ coast. If the storms started to gets its act together quicker down by Maryland, then the solution would be different. Regardless if you live near the Oakland area, you look safe for a 3-6+ snowfall.

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judging by how well the GFS had done with the past few systems :thumbsdown: and what most of the rest of the 12z guidance has been showing, I think the 12z GFS is an outlier at this point. Even the 12z UKIE gives more than the GFS which is known for being a progressive model.

We should all be looking at the short term hi-res models now anyway, imo.

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LI needs to watch out for the coastal front... mixing issues would not surprise me

That's what I was thinking too when I first glanced at the latest surface charts. But really most of the warming is in the boundary layer. Actually right near the surface is the only level with an easterly component to the flow. Aloft is pretty cold. So I would hazard a guess that this stays a wet snow mostly everywhere except maybe along the south shore or east end of Suffolk.

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Is their really that little snowpack down in the Brunswick area? Up here in Bergen and Passaic counties most areas still have 6-12" with a layer of ice ontop. Still massive piles everywhere where the snow was plowed. To be honest, if we get another 6-12" with this event I'm not quite sure where they are going to put it :popcorn:

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I got one of those prop planes and seeded the clouds with rock salt last night so that I can lower the freezing temps in the upper levels. It is certain to rain now.... brooo haha!!! :lol:

I thought I heard a ruckus. Looking good for 4 - 6 (more north and east for C-NJ/N-NJ. What a winter

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With this coming in overnight, I doubt temperatures near those levels are reached.

But with the surface low tracking from inland Va through SNJ, there's a few hours of good southerly flow right into our area before the moisture arrives. It's plenty cold aloft, but I can see places near the ocean creeping up close to freezing. Elevation and distance NW will mitigate warming obviously.

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But with the surface low tracking from inland Va through SNJ, there's a few hours of good southerly flow right into our area before the moisture arrives. It's plenty cold aloft, but I can see places near the ocean creeping up close to freezing. Elevation and distance NW will mitigate warming obviously.

You do realize that with cold 850 temps it will still snow right? Their is a reason why its possible for it to be 35 at the surface and still snowing. Of course, the dew points matter as well. If anything, the coast probably gets in on a little rain snow mix but then again thats the norm for them. Snow all the way to the beeches is not the norm around here and people need to realize the reality after being spoiled the last two winters.

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You do realize that with cold 850 temps it will still snow right? Their is a reason why its possible for it to be 35 at the surface and still snowing. Of course, the dew points matter as well.

Ok what about in late Feb or March when we have cold 850 temps but a warmer surface and get rain instead of snow. Why don't we receive snow then if the 850 temps dictate if it will snow or not? Would all of that be related to dew points as well?

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judging by how well the GFS had done with the past few systems :thumbsdown: and what most of the rest of the 12z guidance has been showing, I think the 12z GFS is an outlier at this point. Even the 12z UKIE gives more than the GFS which is known for being a progressive model.

I think the NAM is too wet. Otherwise all the models are in basic agreement with the progression. QPF is not a particularly reliable parameter... certainly not one to assess outlier status based on.

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Ok what about in late Feb or March when we have cold 850 temps but a warmer surface and get rain instead of snow. Why don't we receive snow then if the 850 temps dictate if it will snow or not? Would all of that be related to dew points as well?

but its not late feb or march

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NYC is very cold in the upper levels based off NAM soundings. Only the surface is a little warm, 30-32.5

What I'm talking about is the immediate coast, i.e. coastal NJ and maybe Suffolk. The good part is that even the more amped NAM doesn't really intensify the precip until the low is headed east and the winds back around, so any problems with a mix could only be at the start when it's light. I do agree that the developments so far look very positive today. Someone could get 8" or more if the low really starts to bomb out.

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You do realize that with cold 850 temps it will still snow right? Their is a reason why its possible for it to be 35 at the surface and still snowing. Of course, the dew points matter as well. If anything, the coast probably gets in on a little rain snow mix but then again thats the norm for them. Snow all the way to the beeches is not the norm around here and people need to realize the reality after being spoiled the last two winters.

Not just cold 850s but cold 925s too! Yes I think it will snow most everywhere. I was just referring to the possibility of a distinct coastal temp gradient or front and the likelihood of surface temps approaching freezing.

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I think there is fairly good agreement overall, .3-.5 in and around NYC so a good 3 to 6" bet with the possiblity for a few inches more if everything works out well. Its not like the GFS came in with a tenth of an inch.

12z GFS looks like less QPF than 06z. Especially from PHI on southward. Of course we couldn't get all the models to agree even at less than 24hrs out. I think the main reason for the less QPF is that its such a fast mover, and likely too fast in my opinion.

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but its not late feb or march

yea... I think what he is trying to figure out is that we often times get snow during the heart of winter with marginal surface temps, but it doesn't seem to work out for us as we head towards spring....

I'll just say that sun angle can do a whole lot of harm as we start getting into march.. it can really warm the boundary layer fairly significantly, even if it's very cloudy.

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yea... I think what he is trying to figure out is that we often times get snow during the heart of winter with marginal surface temps, but it doesn't seem to work out for us as we head towards spring....

I'll just say that sun angle can do a whole lot of harm as we start getting into march.. it can really warm the boundary layer fairly significantly, even if it's very cloudy.

Yeah a storm like this starting at 9am on march 1st would prob not do much of anything for us in the metro area

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Ok what about in late Feb or March when we have cold 850 temps but a warmer surface and get rain instead of snow. Why don't we receive snow then if the 850 temps dictate if it will snow or not? Would all of that be related to dew points as well?

Depends on the degree, height, and thickness of the boundary layer warmth. This time around it looks cold right down to the surface, where it should be at worst around 33F (except maybe far east end). I would expect the freezing level to be below 500ft or so even in SE areas.

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More amplified trof? Deeper surface low? Wetter?

I don't trust the hi-res models for moderate events. I think they're almost always too wet. But I would expect them to basicly fall in line with the NAM.

Trough. They are out to hour 12, so cant tell precip yet.

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More amplified trof? Deeper surface low? Wetter?

I don't trust the hi-res models for moderate events. I think they're almost always too wet. But I would expect them to basicly fall in line with the NAM.

All three. The trough is stronger, the surface low stronger and they are wetter as result. they are only out to 12 hrs.

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