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NYC/PHL Jan 18-19 Potential Threat Thread


am19psu

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0z and 6z gfs runs output look very wet at this point. rain soak snow then a arctic freeze?

The 06Z GFS picks up on the overrunning snow a bit better from 108-114 but probably only a tad of what would actually occur with the setup it shows....my analogs for this event in order of most similar to least are 1/8/99, 1/17/94, 2/18/00, 12/14/03, 1/11/91....all of those but one produced significant snows for the coastal areas of NY/CT/NJ before a changeover to sleet and rain, 1/17/94 is the only one which did not and the high was positioned a bit more south in that event which caused a south flow when it moved ashore as opposed to ESE....1/17/94 and 1/8/99 were the only two which had a ridge on or off the west coast as this event would, the others all exhibited a progressive pattern.

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Lots of different options out there for this storm, but none seem to bring snow to the coast. Given the MJO is moving into Phase 7, I suspect we'll all be tracking this into next week, but we're going to need a cold air source somewhere.

The way the modeling looks on this one as of today, I'd agree Every GEFS member is going over to rain after not much snow (wouldn't rule out more freezing rain) at ABE, PHL & HPN. Need a 50/50 low to develop, everything to unfold faster or for the pattern to be much more progressive, i.e. an overall lighter precipitation event.

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Yeah that would be one of a couple of ways or if everything transpired faster and you'd spend more time in snow and less in something else. At this point every GEFS ensemble member is turning PHL, ABE & HPN over to rain with really not that much snow on the front end.

Tony,

To respond to your post at the end of the medium range thread, I'd venture to guess that the gfs/gefs is perhaps underestimating the amount of overrunning qpf at this point in time, but it goes over to rain on every member regardless like you said. We shall see how everything evolves though. I'm hoping to see trends of a weaker wave on the gfs and I believe further southeast placement of the PV would help too.. then we could possibly squeeze out an all frozen event in these parts withe the +NAO

As far as the MJO goes, with the emergence into phase 6 and heading into phase 7 over the next couple of days and assuming we believe the mjo wave will be strong enough to influence our pattern, then I would think an inland track is favored for early next week. Would love your opinion on that. You know better than I how poor the phase 6 and even phase 7 composites are in screaming warm east/se ridge.. though phase 7 is the beginning of a change to good things of course.

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Tony,

To respond to your post at the end of the medium range thread, I'd venture to guess that the gfs/gefs is perhaps underestimating the amount of overrunning qpf at this point in time, but it goes over to rain on every member regardless like you said. We shall see how everything evolves though. I'm hoping to see trends of a weaker wave on the gfs and I believe further southeast placement of the PV would help too.. then we could possibly squeeze out an all frozen event in these parts withe the +NAO

As far as the MJO goes, with the emergence into phase 6 and heading into phase 7 over the next couple of days and assuming we believe the mjo wave will be strong enough to influence our pattern, then I would think an inland track is favored for early next week. Would love your opinion on that. You know better than I how poor the phase 6 and even phase 7 composites are in screaming warm east/se ridge.. though phase 7 is the beginning of a change to good things of course.

Chris,

There have been snowy events with a +NAO, but it gets shakier for every degree of latitude one goes south. Yeah I suppose its possible, I'm just seeing more ice and sleet than snow at this juncture "north and west". If we flashed back to the model runs of Jan 6-8 for the last event, we'd find the op models too east (except for some reason the NOGAPs), just applying a westward correction that would seem more likely because of the NAO. I haven't honestly looked at MJO and storm track, more just with temps. The track could only go so west with everything snow covered so would assume that a coastal hugger would be as far west as it gets. But you are right about the primary, just way too much southerly flow and the modeling does not do that well with warm air abvoe 850mb, shoot we nearly got sleet into PHL Tuesday night.

My thoughts will all change with the 12z run. ;)

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Chris,

There have been snowy events with a +NAO, but it gets shakier for every degree of latitude one goes south. Yeah I suppose its possible, I'm just seeing more ice and sleet than snow at this juncture "north and west". If we flashed back to the model runs of Jan 6-8 for the last event, we'd find the op models too east (except for some reason the NOGAPs), just applying a westward correction that would seem more likely because of the NAO. I haven't honestly looked at MJO and storm track, more just with temps. The track could only go so west with everything snow covered so would assume that a coastal hugger would be as far west as it gets. But you are right about the primary, just way too much southerly flow and the modeling does not do that well with warm air abvoe 850mb, shoot we nearly got sleet into PHL Tuesday night.

My thoughts will all change with the 12z run. ;)

Tell me about it. My dad said it started in Holmdel with the half dollar wet flakes the other night, while 5 miles to my east in Red Bank they had 2 hours of sleet at the onset. Models crapped the bed on that part, but a good call by HPC (and I think you guys mentioned it too? I read the HPC part on the boards) in bringing that sleet threat in despite no model support. They were taking a bit of heat on that reading through some comments the other night, and looky what happened.

Anyhow, I agree with your thoughts about this next event. As long as we dont torch and wash away the snowpack, then I'll be okay with the rain event. All the great winters have a few warm storms involved at some points.

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Tell me about it. My dad said it started in Holmdel with the half dollar wet flakes the other night, while 5 miles to my east in Red Bank they had 2 hours of sleet at the onset. Models crapped the bed on that part, but a good call by HPC (and I think you guys mentioned it too? I read the HPC part on the boards) in bringing that sleet threat in despite no model support. They were taking a bit of heat on that reading through some comments the other night, and looky what happened.

Anyhow, I agree with your thoughts about this next event. As long as we dont torch and wash away the snowpack, then I'll be okay with the rain event. All the great winters have a few warm storms involved at some points.

Prior to New Years Day it was warmer leading into the rain, not the case this time even if it is rain.

Judging from a response comment I read sounded like we (PHI & HPC) were both thrown under the bus.

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Depending on where the high pressure sets up and whether this dams or not, I could see FZRA being an issue. Right now, it's modeled too far east for anybody, but a small delay could be a huge headache.

I'm worried about ZR here in the NYC northern suburbs at 350' elevation...it's going to be hard to scour out the cold air with an antecedent arctic airmass following the clipper, the high pressure to our northeast, and the deep snowpack. This could be a very nasty storm if the GFS verifies with a prolonged period of overrunning snows changing to ice in the elevated NW suburbs. Westchester schools may have to burn their third snowday in three weeks. The ECM/GGEM suggest a coastal storm, but the temperature profile is much in doubt; the 0z GGEM was cold enough for mostly snow, whereas the 0z ECM was warmer than expected given the Benchmark track.

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Realizing the NAM only goes out to 84, the setup doesn't seem so bad. There is a +PNA, the PV is centered in Canada with a lobe under the diminishing -NAO blocking signature near Greenland, and a CPF coming straight South into central and western Canada. The Northern Jet however is bottled up in Canada for the most part save for the trof in the NE which is lifting out.

Setup could be worse at this range anyway, but as several posters mentioned, by 108-132 hours the Northern Jet is progged to be virtually non-existent in the GL/NE.

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Looks like freezing rain/sleet then quickly over to widespread mod/heavy rain. I was up in Northern Passaic County NJ last night where everything eventually runs off into the Passaic River basin and I can tell you the snowpack is quite massive with piles in some places ten feet high along with about 1.5-2' on the ground. The snowpack further down river is more like 1'-1.5'. Slightly warmer temps + widespread heavy QPF + modest snowmelt = FLOODING. That's probably our main concern at this point. BTW, any chance the low closes off as it moves through the Ohio River Valley?

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12Z GFS still advertising a fairly decent front end thump of snow across interior NY and PA, with a CAD signature with a strong high to the north and potential icy situation across central PA and south central NY.

It looks as if about .25" QPF falls as snow Monday night here in the suburbs, then changes over to ice and eventually rain. Starting to look like another threat as the high pressure is in a perfect position for a CAD signature with the powerful PV vortex supplying the cold from Central Canada.

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It looks as if about .25" QPF falls as snow Monday night here in the suburbs, then changes over to ice and eventually rain. Starting to look like another threat as the high pressure is in a perfect position for a CAD signature with the powerful PV vortex supplying the cold from Central Canada.

yep... system very slow to progress with the cold front, with the upper flow pretty much trying to parallel the surface flow.

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Looks cold enough for snow for NYC north.

yes, it certainly seems cold enough at all levels to support snow, even in the city, for at least part of the time... Lower hudson valley, northwestern NJ and points north and west look to be good with several inches of snow per GFS... now I'm waiting to see how much of that bitter airmass the GFS is gonna try to pull down a bit later on.

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yes, it certainly seems cold enough at all levels to support snow, even in the city, for at least part of the time... Lower hudson valley, northwestern NJ and points north and west look to be good with several inches of snow per GFS... now I'm waiting to see how much of that bitter airmass the GFS is gonna try to pull down a bit later on.

Incredibly cold over NW Canada with -40C 850s showing up under the polar vortex that migrates through Alaska. We might get a modified version of that airmass, which will end up being bitterly cold with tons of snowpack remaining and the weather forecasted to turn clear.

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Incredibly cold over NW Canada with -40C 850s showing up under the polar vortex that migrates through Alaska. We might get a modified version of that airmass, which will end up being bitterly cold with tons of snowpack remaining and the weather forecasted to turn clear.

yea, I was just pulling up the 850 mb temps myself.. The storm vista graphic doesn't have any intervals past -40C... this might give them reason to maybe make one or two more.. :lol:

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Doesn't anyone else think this next storm looks more like a heavy rain/flooding threat than anything else? Seems like these situations always end with the warmer air aloft arriving sooner than later and keeping the ice snow threat minimal. Their is quite the snow pack on the ground in most spots and a widespread 2" event probably means moderate flooding.

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Doesn't anyone else think this next storm looks more like a heavy rain/flooding threat than anything else? Seems like these situations always end with the warmer air aloft arriving sooner than later and keeping the ice snow threat minimal. Their is quite the snow pack on the ground in most spots and a widespread 2" event probably means moderate flooding.

is the QPF really that high? I see what you are saying, but the snowpack would absord alot of the rain, 2 inches of rain is one thing, but if we're an inch or less, it's probably not that big of a deal (although the streets will flood given that most sewers are blocked by 2-3 foot snowbanks)

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The one part that seems suspicious of an all Rain event is Mondays High is supposed to be in the low 30's before a storm comes tracking up coast where alot of Models have it taking a track up or near the benchmark..Let me say this if it was an all rain event on top of a snowpack followed by an Arctic freeze there would be some real problems with everything turning into a sheet of ice...

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is the QPF really that high? I see what you are saying, but the snowpack would absord alot of the rain, 2 inches of rain is one thing, but if we're an inch or less, it's probably not that big of a deal (although the streets will flood given that most sewers are blocked by 2-3 foot snowbanks)

On some of the runs yes, on others not quite as much...

12Z GFS

gfs_p60_174l.gif

06Z GFS

gfs_p60_144l.gif

00Z GFS

gfs_p60_162l.gif

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Doesn't anyone else think this next storm looks more like a heavy rain/flooding threat than anything else? Seems like these situations always end with the warmer air aloft arriving sooner than later and keeping the ice snow threat minimal. Their is quite the snow pack on the ground in most spots and a widespread 2" event probably means moderate flooding.

Well.... if the strength and the placement of the high pressure over Canada is anything like the GFS is advertising, there could be quite a bit of icing, but it's definitely more of an interior threat. The snowpack would aid in keeping surface temps a bit colder than what might be advertised too.

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Doesn't anyone else think this next storm looks more like a heavy rain/flooding threat than anything else? Seems like these situations always end with the warmer air aloft arriving sooner than later and keeping the ice snow threat minimal. Their is quite the snow pack on the ground in most spots and a widespread 2" event probably means moderate flooding.

I think it is to early to say either way if this will be more wintry or more rainy. Flood threat does exist but that would depend on several factors included the current water content of the snow pack and its ability to absorb additional moisture, what surface temps would be if it was rain, ie rain and 35-40 vs 45-55 and what current river flow levels are. Regardless of all that a flood threat is one scenario to watch for just as an ice threat also is one to watch for especially north and west of NYC and PHI in the favored areas to CAD best.

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