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Snow Friday 1/19/24: is it a period of light snow (less than 2"), or is there a chance of a 5" swath in part of the NYC subforum? Event OBS.


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Posted by a met on another board named rb924119:

All this talk about H5 and the latest NAM run, but nothing is being mentioned about the rest of the atmosphere??? Come on, my fellow snow-starved weather nut family, we’re better than this!! lol to me, the changes at H5 seem to be relatively minor compared to previous runs, but it’s what’s happening everywhere else that made the difference. Let’s work from the lower levels, upward, starting at the 850 hPa level.

850 hPa (and even further below): Notably stronger f-gen/isentropic forcing likely induced by enhanced low-level vortex tube stretching and associated cyclonic vorticity/curvature thanks to an anomalous westerly wind component coming across the Appalachians. We aren’t dealing with a regular trough here; it’s actually a lobe of the Tropospheric PV, which is highly anomalous at this latitude, and therefore, modeling has been under-representative of the effects that this will have on the atmosphere.This also goes for all levels above this as well.

700 hPa: similar to the changes seen at the 850 hPa level.

250 hPa: Notably stronger jet streak with our area located in the left exit region, which allows enhanced forcing for ascent. This is directly a result of the enhanced f-gen in the lower levels. All of these enhanced forcing mechanisms align, which resulted in the higher output.

In my opinion, having only looked at this tonight, the enhanced solution would seem to fit the anomalousness of having a lobe of the tropospheric PV rotating overhead, and modeling being slow to pick up on that, and I would therefore not be surprised to see these trends continue across guidance over the next couple of runs.

Carry on.

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1 hour ago, NorthShoreWx said:

Most of the winters in the first half of the 80s had at least 1 good month, mostly in January and the Januarys were cold so the snow stuck around for a bit.  Here are snowfall stats from Syosset that include the early 80's.  Note that even then March was running snowier than December:

https://www.northshorewx.com/ClimateData/SyossetSnowfall1974-1985.pdf

 

 

Thanks, this is great.  And that's absolutely right about the snow sticking around.  We've had storms during the great run since 2000 in which 15" fell in the dead of winter that were totally gone so quickly that it was almost not to be believed.  Yet back then a 5 inch snowfall would mess up my Newsday delivery work for weeks.

It's not surprising but still noteworthy how Syosset's numbers look as compared to say at the other end of 135.  Those numbers, especially from 80/81 - 84/85,  average about 5" higher than what I usually see for LI.  And you definitely know better than me that good as those numbers are, the sweet spot for LI a good 25 miles east of there are even better, right?  The gradient between, say, Amityville and Stony Brook is significant. 

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Wow, Lee Goldberg, who's usually fairly conservative, just called for 3-6" for much of CNJ, all of SNJ (except the SE coast) and a big chunk of EPA/northern DE, with the 3" line running very close to 78 from about Allentown to Elizabeth and then to the Southern Parkway on LI, with 3-6" south of that line and 1-3" north of that line. South of that line is where he and many other pros are thinking the Norlun Trough sets up and focuses the most lift and snow. Hopefully I can get a screen grab of his map once they put the forecast up.

I have to say, I'm still concerned that all of the current global models (and their ensembles) are showing basically 1-3" but yet many forecasters are going with 3-5" in much of CNJ/SNJ/EPA.  Is that mostly based on the NAMs?  As an aside, I'm also surprised (but comforted) the NBM is showing so much snow - figured the blend would be heavier on the globals and not show much over 3"

snowfall_acc-imp.us_state_ne_s.png

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The NAM is an obvious, clear outlier as always. Total trash model. Anyway, this is a 1-2 inch snow event for the area iMO. I don’t think the 3 inch amounts happen until you get into central NJ on south. On the bright side, at least it’s going to snow

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1 hour ago, coastalplainsnowman said:

Thanks, this is great.  And that's absolutely right about the snow sticking around.  We've had storms during the great run since 2000 in which 15" fell in the dead of winter that were totally gone so quickly that it was almost not to be believed.  Yet back then a 5 inch snowfall would mess up my Newsday delivery work for weeks.

It's not surprising but still noteworthy how Syosset's numbers look as compared to say at the other end of 135.  Those numbers, especially from 80/81 - 84/85,  average about 5" higher than what I usually see for LI.  And you definitely know better than me that good as those numbers are, the sweet spot for LI a good 25 miles east of there are even better, right?  The gradient between, say, Amityville and Stony Brook is significant. 

I dated a girl from Massapequa (now my wife) and the commute up and down 135 was very interesting during borderline events. 

I think those Syosset stats are pretty accurate but they are a product of my misspent youth.  If you compare them to BNL there are some obvious differences, but I also find that to be true with Smithtown and BNL certain years.  We're about 18 miles from OKX and Syosset is twice that.

I've long tried to put my finger on a sweet spot, but it's difficult. Part of the difficulty is the data just isn't there to make an objective conclusion.  Best guess is along the north shore between Huntington, or maybe even NE Nassau and Rocky Point.  In most years, the bullseye is somewhere in that area, but in exceptions it can be anywhere; south shore, east end, even Queens.

OKX/BNL is the snowiest spot with a long term reliable record on the island, but it's the only such record anywhere near the north shore and I suspect the elusive sweet spot averages 2 or 3 inches more snowfall than BNL.  In fact that may be the case in much of the north shore region to the west of there.  I took a stab at this almost 20 years ago, but life has interfered with that project:

 https://www.northshorewx.com/lisnowfallpatterns.html

PS one of these years I'll redo the website and make it more phone friendly (and easier for me to update)

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1 hour ago, SnowGoose69 said:
QPF wise Euro looked like it was gonna go boom but then flat lined


The inverted trough is going to set up south of the area. It’s going to be hard to get enough strong forcing north of that to get more than 1-2 inches here. The best dynamics from the upper low and jet streak look to be south of the metro area, also, the 1005mb surface low way off shore isn’t exactly awe inspiring. And we’re also going to have dry air and subsidence issues to overcome the further north you get from the inverted trough. If the upper trough wasn’t so positively tilted, this probably would have been a major coastal snowstorm

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5 hours ago, Stormlover74 said:

Wow href

 

Screenshot_20240117_233423_Discord.jpg

This SPC HREF was errant on the 16th west of I95.  I did not buy into it today though I wish cast it.  I think conservative is a more likely scenario 24 hours in advance. I appended the NWS 4AM/18 ensemble chance of 2" and 4" snow. Color bar has the probs. 

Screen Shot 2024-01-18 at 4.39.10 AM.png

Screen Shot 2024-01-18 at 4.40.12 AM.png

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18 minutes ago, MJO812 said:

Right now the heaviest snow looks to be in SNJ southward with the norlun. Time is running out for a north shift.

 

The way things are shaping up,we might actually be better off with it showing it south. Everything has been trending north as soon as it arrives here. 

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7 minutes ago, nycsnow said:

This isn’t even advisory level for NYC. Upton said they’d only issue one for travel purposes 

I think they are being generous even saying 3 inches for this. 3 inches is the absolute ceiling for this in our area and if it does happen, I think it’s closer to central NJ. Definitely not widespread here. All of the good lifting and surface convergence is south of us with the inverted trough and the good upper dynamics/diffluence with the jet streak and upper low is also south of here. I believe we are going to have bigger dry air and subsidence issues than people are thinking right now, especially given we are north of the IVT, that is going to probably eat up a decent amount of QPF and it may be a virga fest for awhile at the start

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