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Weekend Threat 12/14-12/15


IsentropicLift

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Thank you , Looks like the guys west of the CT river valley could wind up with a Foot  of snow if this is right . 

 

Sneaky WAA for HPN at 900 mb.

SFC 1001   106  -1.5  -1.9  98  0.3  -1.7  27  12 271.5 272.1 271.4 280.5  3.32  1 1000   117  -1.3  -1.6  97  0.3  -1.4  34  15 271.9 272.4 271.8 281.0  3.39  2  950   526  -0.9  -1.1  99  0.2  -1.0  76  20 276.3 276.9 274.8 286.5  3.72  3  900   960   1.5   1.3  99  0.1   1.4 134  21 283.0 283.8 279.6 296.1  4.68  4  850  1421   0.5   0.3  99  0.1   0.4 174  23 286.6 287.4 281.2 299.7  4.61
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Thank you , Looks like the guys west of the CT river valley could wind up with a Foot  of snow if this is right . 

Does LI get high end advisory criteria snow and ZR, and stay at 32 or slightly lower for warmest part of event on 6Z GFS ?  If we keep trending colder today, it is a locked warning event for NYC and LI.  Damming cold high is perfect to get ZR down to LI southshore, and keep ZR going right to the coast.  Early 1/1994 ice event again ?  If I had to guess a LI south shore forecast, it would be 2-4 inches of snow followed by .50 inch ice glaze... Warning event due to ZR.  It really looks like an ice storm for the immediate coast with WAA in the 900 to 850 mb levels.

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An overview the GFS soundings on the Bufkit show for NYC area start off very cold with good snow growth and ratios as high 15 to 1 on Saturday. Then Saturday evening snow growth and ratios worsen. And there is warm nose at 900-950mb with E/SE winds. that changes us to IP/ZR around 10pm Saturday. We see about 3-4" of snow before the changeover. The GFS keeps winds N/NE. So surface temps might be too warm. Otherwise it looks reasonable to me.

 

MMU, HPN also have warm nose Saturday night, around 900mb.

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An overview the GFS soundings on the Bufkit show for NYC area start off very cold with good snow growth and ratios as high 15 to 1 on Saturday. Then Sunday evening snow growth and ratios worsen. And there is warm nose at 900-950mb with E/SE winds. that changes us to IP/ZR around 10pm Saturday. We see about 3-4" of snow before the changeover. The GFS keeps winds N/NE. So surface temps might be too warm. Otherwise it looks reasonable to me.

MMU, HPN also have warm nose Saturday night, around 900mb.

Did you mean Saturday evening or Sunday?

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I'm more concerned about cold air drainage in the immediate suburbs than anything else. As long as the primary surface low drives as far north as most models indicate, there's going to be a mid level warm tongue moving northward by Sunday morning.

But in the suburbs, the cold air is deeper and more entrenched in the low levels than near the coast. So there could definitely be an extended period of IP or ZR and that could create significant travel concerns amongst other things, when on top of 4-6" of snow.

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I'm more concerned about cold air drainage in the immediate suburbs than anything else. As long as the primary surface low drives as far north as most models indicate, there's going to be a mid level warm tongue moving northward by Sunday morning.

But in the suburbs, the cold air is deeper and more entrenched in the low levels than near the coast. So there could definitely be an extended period of IP or ZR and that could create significant travel concerns amongst other things, when on top of 4-6" of snow.

The last few runs of the euro and gfs have not brought the surface line that far west of 95 and the 06z gfs being the coldest run yet. This airmass will not leave the suburbs very quickly!

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I'm more concerned about cold air drainage in the immediate suburbs than anything else. As long as the primary surface low drives as far north as most models indicate, there's going to be a mid level warm tongue moving northward by Sunday morning.

But in the suburbs, the cold air is deeper and more entrenched in the low levels than near the coast. So there could definitely be an extended period of IP or ZR and that could create significant travel concerns amongst other things, when on top of 4-6" of snow.

And you can make the argument that .3 ICE on top of 4 inches of snow with temps in the 20`s are far worse than 6 inches of snow .

Secondly one thing I would continue to watch , this system has gotten wetter and colder .

Something to watch over the next 24 hours , the Canadian is the furthest south . So curious to see if this trend continues

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And you can make the argument that .3 ICE on top of 4 inches of snow with temps in the 20`s are far worse than 6 inches of snow .

Secondly one thing I would continue to watch , this system has gotten wetter and colder .

Something to watch over the next 24 hours , the Canadian is the furthest south . So curious to see if this trend continues

That has been the theme with this storm so far. Getting colder and wetter todays model runs are going to maybe solidify that trend in my opinion. Being im on the coast though i still dont thing we'll get anything noteworthy but if trends continue it may

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I'm more concerned about cold air drainage in the immediate suburbs than anything else. As long as the primary surface low drives as far north as most models indicate, there's going to be a mid level warm tongue moving northward by Sunday morning.

But in the suburbs, the cold air is deeper and more entrenched in the low levels than near the coast. So there could definitely be an extended period of IP or ZR and that could create significant travel concerns amongst other things, when on top of 4-6" of snow.

 

I agree about the mid-level warm tounge. The 850mb and 925mb lows especially are hanging out too long to our west. What interesting on the GFS Bufkit is that LGA gets colder at surface during Sunday AM changes back to some freezing rain,before ending.

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At this point, I just don't see much in the way of accumulating snow for areas south of Rt. 287/78 juncture. Yes, there will be precipitation that falls during a time that the column is supportive of snowfall; however, most of NWP show significantly disorganized areas of precipitation, which normally spells trouble for snowfall. I think we're looking at a mix at best during the first 1/3 or 1/4 of this event for the NYC metro and C NJ. Almost all of the recent NWP looks quite wet for this area. I would be interested to see Don's take on the climatology/statistics of occurrences of snowfall on days when there is a snow depth >1 inch for various reporting stations. I suspect that the occurrence is quite low.

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Guest Patrick

Compared to Mt Holly's idea...they are in decent agreement, but they can't both be right.  Although there is only a one inch difference between the low range from okx office and the high range from phi office.

 

AS OF NOW, WE HAVE 2-5 INCHES OF SNOW
BASICALLY FROM INTERSTATE 95 NORTH AND WEST WITH THE GREATEST
AMOUNTS TOWARD THE POCONOS. ICE ACCUMULATIONS ARE A TENTH OF AN
INCH OR LESS ATTM. THE PRECIPITATION SHOULD TAPER OFF FAIRLY
QUICKLY EARLY SUNDAY MORNING AS THE SYSTEM MOVES AWAY.

 

 

Upton going with 6-8" for interior NJ into NW areas. WSW criteria verbatim.

 

StormTotalSnowFcst.png

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It's amazing that we are even having all these events along with the cold when the NAO/AO are positive, the AO is forecast to be raging positive greater than +4 in a few days.

Clearly the EPO is in charge compared to all the other indices and the AO, NAO, and PNA all play second fiddle to it.

Hopefully we could get more of a +PNA though because it could really help us get a bigger event over here, it's trying to go more positive on the latest indices forecast.

As for this event, 4-6" with some ice on top is probably a good call, and can be adjusted with more model runs today and tomorrow.

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I'm thinking 2-4 here in Brooklyn...we'll almost certainly get above freezing with the strong WAA and high drifiting east, but the antecedent airmass is very cold. Looking at high temperatures below freezing here today and tomorrow with lows in the teens.

I think if the initial WAA snows affect us, we could see the high end of that, maybe 4-6". If the initial overrunning overshoots us and goes mostly through SNE, we will likely have only 2-3". But I'm liking the colder model trends, maybe we can salvage this with very little plain rain.

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