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NYC/PHL Jan 25-27 Potential Bomb Part 5


earthlight

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Biggest problem with that sounding is that 700 mb temps are above -10C. Even if flake production is above that level, there can be a lot of riming lower down to ruin the ratios.

Yep, it's noticeable. But I'm sure people won't be complaining about ratios with the heavy dumping that's ongoing at that time.

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per ens first part starts hrs 36-48 as lgt precip with prob a 4-6 hr break or just scattered showers....2nd part comes in after hr 48 to 60

I'm not sold on two distinctly separate periods of precipitation. I think there will be a light mix in the area by late morning with intermittent intensity until the steadier, heavier stuff movies in later in the afternoon. The idea of a true break in the action is still pretty fuzzy.

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I'm not sold on two distinctly separate periods of precipitation. I think there will be a light mix in the area by late morning with intermittent intensity until the steadier, heavier stuff movies in later in the afternoon. The idea of a true break in the action is still pretty fuzzy.

as long as the second piece with the actual surface low, 700, 850 and 500 come up as progged, it can do whatever it wants to before it gets here.

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yes, that first piece would be hard to be anything more than slop that didn't stick, so its pretty inconsequential what it does.

Sounding for MBY looked like rain mixed with a little sleet for part 1. Hard to tell exactly for in between 54 and 60hrs, but looks like GFS shows the same wet snow bomb here...and it did for us on the 12z also.

If it panned out exactly as on the GFS, I can only imagine the wailing and nashing of teeth in the rain areas waiting for that flip to heavy wet snow just past 54. Come to think of it, I watched the def band to my west for hours on 12/25/2002 while it was just spitting here...but it did eventually make it.

Clarification: what I am calling part one might be different...I'm referring to the time prior to hour 54 before the CCB gets cranking.

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as long as the second piece with the actual surface low, 700, 850 and 500 come up as progged, it can do whatever it wants to before it gets here.

I'm a bit more greedy I guess. GFS shows a short duration thump, with an annoying cutoff on the NW side. With a bit more overrunning ahead of the low, this could be a longer duration event.

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18z GFS

http://wxweb.meteostar.com/sample/sample.shtml?text=knyc

Most epic depiction of LR cold in a while... from days 7-14 NYC does not get above 22 degrees with multiple lows below 0. In la-la land, but continues the depiction of a continuation of the current MUCH below normal temperature regime through at least early February.

More notably, NYC is likely snow by hour 54 and sees 10-12" of concrete this run. :snowman:

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18z GFS

http://wxweb.meteost...shtml?text=knyc

Most epic depiction of LR cold in a while... from days 7-14 NYC does not get above 22 degrees with multiple lows below 0. In la-la land, but continues the depiction of a continuation of the current MUCH below normal temperature regime through at least early February.

More notably, NYC is likely snow by hour 54 and sees 10-12" of concrete this run. :snowman:

we'll probably get above freezing at least tomorrow and likely wednesday as well, but besides that I don't see above freezing temperatures for a while with at least -10 850's entrenched in the region for the foreseeable future, at least according to the GFS and EURO. Also the 18z GFS shows the pattern's potential with a massive +PNA and southern stream disturbance with a northern stream s/w riding down the eastern side of the PNA ridge looking to phase with out southern energy, just as the GFS truncates. Still produces a storm but it seems like its overrunning + a coastal graze. Either way this winter is shaping up to be amazing

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18z GFS

http://wxweb.meteost...shtml?text=knyc

Most epic depiction of LR cold in a while... from days 7-14 NYC does not get above 22 degrees with multiple lows below 0. In la-la land, but continues the depiction of a continuation of the current MUCH below normal temperature regime through at least early February.

More notably, NYC is likely snow by hour 54 and sees 10-12" of concrete this run. :snowman:

Within a few hours of 54 I think there could be some sleet mixed in across the area. Small temp errors in either direction are common, and with a deep layer near freezing, it's reasonable to expect a little mixing. But the surface looks pretty cold from that point on. This might not be concrete at all. It's not going to be powdery with poor snowgrowth and temps near or just below freezing, but this shouldn't resemble a heavy spring snow pasting.

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strong signal from the 18z GEFS for a large and powerful deform.

I don't see that signal. Most members are a bit too far east. And none are as wet as the operational. Though they probably wouldn't be, considering the lower resolution. But then I don't see how you could use them to pinpoint a signal for powerful deformation snows.

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One meteorological point in reference to questions about saturating the column: in general, precipitation is driven by supersaturation, i.e., when saturated parcels of air at the surface and lower levels of the atmosphere are subjected to momentum transport into the middle and even upper levels of the atmosphere ("vertical velocities" produced, typically from temperature/pressure gradients resulting from "colliding" low and high pressure systems), which are much colder and and when the saturated parcels cool, those parcels become "supersaturated" i.e., they temporarily hold more moisture (water vapor in air) than is thermodynamically favored (much like sweet tea can hold far more sugar in solution than thermodynamics would indicate - the sugar is supersaturated, but eevntually will come out of solution as sugar crystals, given the right impetus) and once supersaturation relief is initiated (often by seed nucleates in the atmosphere), these parcels can almost instantaneously convert the supersaturated portion of the water vapor into snow crystals via vapor deposition. Therefore, if all of the column becomes saturated, that means the column is moisture laden to the extent that it won't take much transport of saturated parcels of air upwards at almost any level to lead to snow growth - it's a measure of the "potential energy" available for snow growth. I'll admit my meteorology might be a little shaky, but my understanding of supersaturation-driven nucleation and crystallization phenomena is pretty advanced, as I do a lot of that work for a living in Pharma and the same processes we use for crystallizing organic molecules from solvents via supersaturation should apply to crystallizing snowflakes from air via supersaturation. Hope this helps a little.

On another note, if Wednesday starts out relatively tranquil and rainy in the I-95 corridor and then we see a 6-hour period of hellacious snows as depicted and that period is anywhere around the afternoon rush hour, it's going to be an absolute disaster, like Jan 1987 was, when all the snow hit after everyone was safely ensconced at work. That's a case where either you get out early or stay late and let the idiots all get stuck.

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I don't see that signal. Most members are a bit too far east. And none are as wet as the operational. Though they probably wouldn't be, considering the lower resolution. But then I don't see how you could use them to pinpoint a signal for powerful deformation snows.

large and powerful deform. band does not mean that every ensemble member shows as much as the OP. IMO 0.5+ that falls as snow on the backside could be considered large and strong given the situation. Almost every member shows this

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