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March 22-23 OBS/Disco


nzucker

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6z NAM is about perfect if you like snow. I just checked the soundings and if you like snow the only time the upper levels above 850 get above freezing to change things over to sleet is between both main pushes of precipitation this afternoon. When that next push of moisture comes in tonight, the column cools completely below freezing again. This storm will be at least 90% snow for everyone in Northern New Jersey and both main pushes of precipitation will happen after or near dark.

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NAM finally got a clue - for several runs prior to this one, it's been showing a rather amplified shortwave entering the base of the trough tonight, and a nice consolidated 850 mb low, but lackluster QPF.

One caveat, however, convection to our south over the mid-Atlantic may rob some of the precip. up here. SPC WRF shows this possibility, although it's still wetter than the 0Z NAM.

Here's the SPC WRF 1-hour precip valid 0z tonight:

post-88-0-59719000-1300869452.gif

Why, hello there, 6z NAM.

http://www.nco.ncep....am_pcp_024l.gif

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Unfortunately, the ongoing snow right now makes for a rough commute in northern NJ and extreme western LI, even if the snow doesn't stick much after dawn. Most people in those areas went to bed expecting light snow or a mix beginning around dawn with no snow on the roads during the morning commute aside from the most elevated areas, and what's going on now is quite different.

In fairness, I think OKX is factoring the sunup forecast. What we are seeing now is not what they are forecasting for. they are forecasting for the daylight hours. And once the sun comes up, most areas will see marginal snow sticking save the higher terrain.

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NAM finally got a clue - for several runs prior to this one, it's been showing a rather amplified shortwave entering the base of the trough tonight, and a nice consolidated 850 mb low, but lackluster QPF.

One caveat, however, convection to our south over the mid-Atlantic may rob some of the precip. up here. SPC WRF shows this possibility, although it's still wetter than the 0Z NAM.

Here's the SPC WRF 1-hour precip valid 0z tonight:

post-88-0-59719000-1300869452.gif

Yeah, often times, models don't handle convective feedback very well, but in a lot of cases, convective feedback is a real process that needs to be considered. Do you think convective feedback could also have an effect on the surface low's track, as well as the precip shield? I would think it would want to place the surface low closest to the convection? If that's true, it could be a reason why the GFS had been so insistent in being so far north, since it might not have been picking up on the convection so well. I mean, we have mod risks in the Ohio Valley!

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On the whole, yes, but I think precip. will be more banded/convective than suggested by the NAM (meaning some areas will get shafted a bit), and with the caveat that convection over southern PA/NJ/MD/DE may rob us of some of the precip. shown by the NAM.

So you agree with its solution?

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The main period of accumulating snow tonight will be from around 8PM to 3AM, but due to the convective nature of precip. there will likely be periods of moderate/heavy snow interspersed with lighter snow from around 8PM to 3AM. Total accumulations on grassy surfaces ranging from:

3-5" in NE Queens and far northern Bronx

1-3" in Manhattan, southern Bronx, the rest of Queens away from immediate coast, and northern Brooklyn

Trace to 2" in southern Brooklyn, the Rockaway peninsula, and JFK airport.

What do you think happens tonight for the general NYC area?

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The main period of accumulating snow tonight will be from around 8PM to 3AM, but due to the convective nature of precip. there will likely be periods of moderate/heavy snow interspersed with lighter snow from around 8PM to 3AM. Total accumulations on grassy surfaces ranging from 3-5" in NE Queens and N Bronx to 1-3" in Manhattan as well as Queens and Brooklyn away from immediate coast, to a trace to 2" in southern Brooklyn, the Rockaway peninsula, and JFK airport.

That doesnt include what's happening right now, does it JC? The roads are already covered here and this morning's commute will be tough lol. Might end up with 1-2" just with what's falling right now.

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Yes, it does include what's falling now. My forecast for JFK reflects the fact that it's a mini heat island surrounded by jet exhaust where snow has a lot of trouble sticking. Your area, though only about 5 miles from JFK, is suburban and thus will likely see more than JFK - probably about 2-5". Out of curiosity, how much did you get in the April Fools 1997 storm? JFK had only 1.7" and LGA only 0.4".

That doesnt include what's happening right now, does it JC? The roads are already covered here and this morning's commute will be tough lol. Might end up with 1-2" just with what's falling right now.

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