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Potential 12/8 Event Discussion Part I


earthlight

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The 18z NAM is more negatively tilted with the vort at 60h compared to the 12z run, and the heights along the east coast respond to that. It allows the pva to tuck the surface low more north before going northeast..which ticks things warmer for some areas but also brings impressive forcing into play.

You have to wonder if, at least away from the coast, this is the best run yet. Because the dynamics and heavy precip assure that you won't have light to moderate rain falling aka the GFS solution.

18z NAM is spitting out 9" of snow up this way. Ratios at 12: 1 look a bit high tho. 1.10 of liquid QPF

http://www.meteor.ia...=namm&site=kswf

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HAZARDOUS WEATHER OUTLOOK

NATIONAL WEATHER SERVICE NEW YORK NY

637 PM EST MON DEC 5 2011

NYZ078>081-177>179-062345-

NORTHWESTERN SUFFOLK-NORTHEASTERN SUFFOLK-SOUTHWESTERN SUFFOLK-

SOUTHEASTERN SUFFOLK-NORTHERN NASSAU-SOUTHERN QUEENS-SOUTHERN NASSAU-

637 PM EST MON DEC 5 2011

...DENSE FOG ADVISORY IN EFFECT UNTIL 7 AM EST TUESDAY...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST NEW YORK.

.DAY ONE...TONIGHT.

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE

INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

DENSE FOG ADVISORY.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE

INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

DENSE FOG ADVISORY.

THE PROBABILITY OF WIDESPREAD HAZARDOUS WEATHER IS LOW.

LOW PRESSURE PASSING OFF THE MID ATLANTIC COAST LATE WEDNESDAY

NIGHT AND THEN SOUTHEAST OF MONTAUK POINT THURSDAY MORNING COULD

PRODUCE SOME LIGHT SNOWFALL FOR THE NEW YORK CITY METROPOLITAN

AREA AND LONG ISLAND. THE ACTUAL TRACK...FORWARD MOTION AND

INTENSITY OF THE LOW ARE STILL SOMEWHAT UNCERTAIN...AND SMALL

CHANGES COULD HAVE IMPORTANT IMPACTS ON THE FORECAST...SO

STAY TUNED.

:snowing:

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The question is will NYC be able to drop below 32 or will it be another 33-34 degree snow event

It always tries to snow around december 5th lol i should have known that when i was seriously doubting this event a few days ago.

This event has a shot to produce. Dynamics could deliver us the goods yet again. It wants to snow!

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The question is will NYC be able to drop below 32 or will it be another 33-34 degree snow event

Doubt it drops to below 32. If we get snow, it'll probably be 32-34. And there can't be a let up or dry punch at all or temps will rise quickly. Just like the October storm. Those who stayed under heavier echoes got 5"-7"; while those who didn't, received only 1"-2".

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post-402-0-17216800-1323133081.gif

Changeover is almost instant with the onset of precip in northwest NJ/PA...And you have to wonder in the dynamic 18z nam scenario (with the right storm track) if further east would changeover much quicker than the models show as well (at the onset of heavy precip). Recall what happened with the October 29th event, it was hours ahead of schedule all the way to the city and down by me...Just something floating through my mind here.. We did that with a marginal October boundary layer, granted, that storm's surrounding weather pattern was much more vintage.

http://www.examiner.com/weather-in-newark/a-small-window-for-a-winter-storm-later-this-week-with-a-cold-shot-this-weekend

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But I think we also have to look at the 12/5/09 event. It changed to heavy wet snow but didn't last long enough or snow heavily enough to give coastal locations more than a slushy inch while well N&W got 4 to 6"

post-402-0-17216800-1323133081.gif

Changeover is almost instant with the onset of precip in northwest NJ/PA...And you have to wonder in the dynamic 18z nam scenario (with the right storm track) if further east would changeover much quicker than the models show as well (at the onset of heavy precip). Recall what happened with the October 29th event, it was hours ahead of schedule all the way to the city and down by me...Just something floating through my mind here.. We did that with a marginal October boundary layer, granted, that storm's surrounding weather pattern was much more vintage.

http://www.examiner....ot-this-weekend

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But I think we also have to look at the 12/5/09 event. It changed to heavy wet snow but didn't last long enough or snow heavily enough to give coastal locations more than a slushy inch while well N&W got 4 to 6"

was thinking about that storm today. A very marginal airmass ahead of that storm and it never cooled down at the surface and there was a nasty warm wedge at 925. A very FM as well.

Stupid RUC kept showing the changeover and it never happened for a lot of people.

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I turned over to snow by mid afternoon, it just didn't stick and the temp got stuck just above freezing. But the flakes were very wet and seemed mostly mixed with rain and melting. I know I was expecting a few inches out of it but barely got an inch. I was prepared for a similar event on 10/29 but ended up way wrong on that one.

was thinking about that storm today. A very marginal airmass ahead of that storm and it never cooled down at the surface and there was a nasty warm wedge at 925. A very FM as well.

Stupid RUC kept showing the changeover and it never happened for a lot of people.

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post-402-0-17216800-1323133081.gif

Changeover is almost instant with the onset of precip in northwest NJ/PA...And you have to wonder in the dynamic 18z nam scenario (with the right storm track) if further east would changeover much quicker than the models show as well (at the onset of heavy precip). Recall what happened with the October 29th event, it was hours ahead of schedule all the way to the city and down by me...Just something floating through my mind here.. We did that with a marginal October boundary layer, granted, that storm's surrounding weather pattern was much more vintage.

http://www.examiner....ot-this-weekend

The 10/29 storm had much more impressive dynamics and a good conveyor circulation than this storm is likely to have...we can still get a half decent CCB in this with a more potent vortmax like the 18z NAM...but it will not match 10/29's dynamics....another poster made a comp to 12/5/09...maybe between the two is the upside of this one. I think moderate precip should be good enough for snow at least in the northern and western suburbs of NYC and probably NYC itself, but its a question of just how much the lower 50mb can be overcome.

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I turned over to snow by mid afternoon, it just didn't stick and the temp got stuck just above freezing. But the flakes were very wet and seemed mostly mixed with rain and melting. I know I was expecting a few inches out of it but barely got an inch. I was prepared for a similar event on 10/29 but ended up way wrong on that one.

i was never able to get rid of the 925 warm wedge, only saw some wet snow for an hour Huge dissapointment.

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Haha amazing we are talking a potential moderate snow event with a crappy pattern. Although not common, it's certainly possible. Whatever we get, take it and run with it......

I've heard this line, though with slightly different phrasing, at least two dozen times since 1998. I always cringe a little.

I attribute the myth largely to DT. I think he was the first to describe the pattern ingredients for coastal snowstorms in a generalized way that "weenies" could identify and understand. At least for the online weather enthusiast community. "50/50", "southeast ridge", blocking etc...

Of course the reality is that snowstorms, in particular light and moderate storms, come in an infinite variety of shapes and sizes. All you need is cold air from cloud to surface, a crystallization/condensation nuclei, -10C or lower in the snow origination zone, and rising air. A favorable "pattern" makes it a little easier, but there is a lot of randomness in snowstorm correlations and distributions.

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Haha amazing we are talking a potential moderate snow event with a crappy pattern. Although not common, it's certainly possible. Whatever we get, take it and run with it......

But I agree it does seem kind of amazing to be tracking a threat amidst a lousy weather period when it looked and kind of still looks like a continuation of a lousy pattern, Thursday notwithstanding. But at our latitude, it's usually hard to get any kind of snowstorm, even with all the favorable indices and pattern characteristics. I always feel fortunate when it snows IMB.

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But I think we also have to look at the 12/5/09 event. It changed to heavy wet snow but didn't last long enough or snow heavily enough to give coastal locations more than a slushy inch while well N&W got 4 to 6"

Absolutely...That storm is a great case to go off of for this... And we did go back to mainly lighter rain after the slushy inch largely because we got stuck in a subsidence region if I remember correctly.

post-402-0-26116700-1323134769.gif

I do remember It took a pretty long time to switch from cold rain to snow in New Brunswick though.

The 10/29 storm had much more impressive dynamics and a good conveyor circulation than this storm is likely to have...we can still get a half decent CCB in this with a more potent vortmax like the 18z NAM...but it will not match 10/29's dynamics....another poster made a comp to 12/5/09...maybe between the two is the upside of this one. I think moderate precip should be good enough for snow at least in the northern and western suburbs of NYC and probably NYC itself, but its a question of just how much the lower 50mb can be overcome.

I 100% agree with you Will, if for no other reason except that I'm not seeing any -70 omegas showing up on the bufkits LOL. that was ridiculous leading up to the October event... Though i will say that the CCB was actually pretty lame with that October storm down this way. Radar looked much much more dramatic than what was actually falling/accumulating on the back side (unless you were in the higher elevations of Morris/Sussex counties as they just kept ripping all day). The most severe part of that storm by far and what also brought down the coldest surface temps during the entire storm was the initial burst that shot northward by late morning/early aftn on the 29th. The comma head wasnt great for whatever reason, and I think that had to to do with the H7 low looking like a disheveled mess, not closing off ideally as it passed through us.

Sorry if that was too much of a digression lol

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Well it's harder than at 28F. But it will stick if the intensity is great enough. I got 10" in Oct and never dropped blow 34.0F.

the intensities on 10/29 were fantastic. No evidence there will be such a large area anywhere as intense as that.

Arent you around 800 feet?

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Absolutely...That storm is a great case to go off of for this... And we did go back to mainly lighter rain after the slushy inch largely because we got stuck in a subsidence region if I remember correctly.

post-402-0-26116700-1323134769.gif

I do remember It took a pretty long time to switch from cold rain to snow in New Brunswick though.

I 100% agree with you Will, though i will say that the CCB was actually pretty lame with that October storm down this way. Radar looked much much more dramatic than what was actually falling/accumulating on the back side (unless you were in the higher elevations of Morris/Sussex counties as they just kept ripping all day). The most severe part of that storm by far and what also brought down the coldest surface temps during the entire storm was the initial burst that shot northward by late morning/early aftn on the 29th. The comma head wasnt great for whatever reason, and I think that had to to do with the H7 low looking like a disheveled mess, not closing off ideally as it passed through us.

Sorry if that was too much of a digression lol

nasty dry wedge that stopped ice cystal formation, part of the H7 problem. NAM showed it and it didn't look like it lasted long enough to matter but it was about double the amount of time the NAM showed.

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