February 27th-28th 2023 Winter Storm

12z Nam is slightly colder and more thumping for the metro.

The trend is definitely looking snowier for interior areas away from the coast. LOTS of moisture and higher snow rates will help lift snow amounts by a significant margin. Looks like I'll need to update my snow map later today.

Looks like snow may start as early as 6-7pm this evening. Heaviest snowfall between 10pm and 3am.

Frank_Wx wrote:The trend is definitely looking snowier for interior areas away from the coast. LOTS of moisture and higher snow rates will help lift snow amounts by a significant margin. Looks like I'll need to update my snow map later today.

If you’re going to update keep in mind there is a battle ground that pretty much follows the LIE. Do not be surprised to see a swath along the north shore of 4-6” with this one. Personally I think it happens in NW Suffolk and Nassau. A general 2-4” for LI is reasonable elsewhere with areas south of the southern state parkway in the c-2” range.

This is the battle ground IMO.

And also keep in mind a slight wobble of the 700/850 mb low and consolidation will have sig impacts on where it snows vs mixing.  No model is going to nail that and it's a nowcast type of thing.

We have dry air punch with weak H pressure yielding dew points in the low 20s west of the fall line.  I'm watching the ULL starting about 6 tonight to see where that goes.  That will tell the tale of this saga.

heehaw453 wrote:We have dry air punch with weak H pressure yielding dew points in the low 20s west of the fall line.  I'm watching the ULL starting about 6 tonight to see where that goes.  That will tell the tale of this saga.

DP is 18 here on the north shore of the island right now

NAM!!!!!!!
So much energy flying over LHV, NNJ, NYC METRO!

RGEM from 33 n Rain Superstorm

The -5 Omega red circle and just around this area is where it will thump snow on the scale of 1-1.5" per hour.

aiannone wrote:

heehaw453 wrote:We have dry air punch with weak H pressure yielding dew points in the low 20s west of the fall line.  I'm watching the ULL starting about 6 tonight to see where that goes.  That will tell the tale of this saga.

DP is 18 here on the north shore of the island right now

Good call out.  Here is the wet bulb surface freeze temps.

heehaw453 wrote:

aiannone wrote:

heehaw453 wrote:We have dry air punch with weak H pressure yielding dew points in the low 20s west of the fall line.  I'm watching the ULL starting about 6 tonight to see where that goes.  That will tell the tale of this saga.

DP is 18 here on the north shore of the island right now

Good call out.  Here is the wet bulb surface freeze temps.

That aligns well with the HRRR northern extent of the R/S line. Maybe this line pushes 20ish miles north but generally this looks to be the main r/s line.

HREF says hello

GFS coming in more amped!

nutleyblizzard wrote:

Kuch-Era map

With the 12z NAM coming around and the GFS and Euro largely holding serve, I'm feeling that my preliminary projection yesterday in the Obs Thread might just pan out. I'm not going to do a map, but here is what I posted yesterday and I think it still generally holds for now:

North of I-78 and all of LI: Mostly all snow with amounts in the 4-6" range.
North of I-195 (Trenton to Belmar) to I-78: Snow, mixing briefly in the middle with sleet/frz, before maybe ending as just snow with amounts in the 2-4" range.
South of I-195 (or the line from Trenton to just south of LI). A slushy inch or two of snow before mixing with sleet/frz, and then rain limiting any further accumulation.

I might alter that to say 2-4" along south shore of LI as opposed to 4-6" for all of LI and isolated 6-8" amounts for the more northern areas like the LHV.

The wild card here in that central (2-4) zone is the mixing factor. If you're in any area that doesn't mix, you'll almost certainly hit the high-end numbers, if you mix extensively you'll struggle to get to the low-ends.

sroc4 wrote:

Frank_Wx wrote:The trend is definitely looking snowier for interior areas away from the coast. LOTS of moisture and higher snow rates will help lift snow amounts by a significant margin. Looks like I'll need to update my snow map later today.

If you’re going to update keep in mind there is a battle ground that pretty much follows the LIE. Do not be surprised to see a swath along the north shore of 4-6” with this one. Personally I think it happens in NW Suffolk and Nassau. A general 2-4” for LI is reasonable elsewhere with areas south of the southern state parkway in the c-2” range.

This is the battle ground IMO.

So being north of that line but about 50 miles or so (maybe more like 30) Am I in for the possible higher amount in your new map frank? When you say coastal areas I am never sure what exactly you mean, but this image is very helpful thanks scott. Still a margin that is near razor thin, hoping it can stay south of me and stay mainly snow.

sroc4 wrote:

nutleyblizzard wrote:

Kuch-Era map

10.1 inches I would take that in a heartbeat, even half, do I buy that much I honestly do not know.

Anybody who finds themself in the "middle zones" on some of the accumulation maps (i.e. 2-4") is going to have to seriously nowcast because the real range there is probably more like 2-6" because if there is a lot of mixing, you're gonna struggle to get more than 2", but if you stay mainly snow, you could definitely "overperform" in that zone with some of the snowfall rates we are expecting.

Not a big fan of the surface temps.  I'm at 41.  Yes it's dry air, but nonetheless surface temps are pretty warm.  Indicative of not having a 1035 H parked over Quebec.

heehaw453 wrote:Not a big fan of the surface temps.  I'm at 41.  Yes it's dry air, but nonetheless surface temps are pretty warm.  Indicative of not having a 1035 H parked over Quebec.

Agree on this. I'm up to 42* (albeit with a dewpoint of 23* which is the saving grace). I'm actually wondering if even some areas that go over to snow maybe even briefly start as rain because of these temps before the precipitation picks up. Or if we deal with virga for awhile due to the dry air.

Here is a hypothesis that will need some digging into and maybe SROC can attest and aid with this:
Theer is a pretty long duration Geomagnetic Storm Event happening since last night

GFS 12Z says hi

billg315 wrote:

heehaw453 wrote:Not a big fan of the surface temps.  I'm at 41.  Yes it's dry air, but nonetheless surface temps are pretty warm.  Indicative of not having a 1035 H parked over Quebec.

Agree on this. I'm up to 42* (albeit with a dewpoint of 23* which is the saving grace). I'm actually wondering if even some areas that go over to snow maybe even briefly start as rain because of these temps before the precipitation picks up. Or if we deal with virga for awhile due to the dry air.

That's very possible. I was at 27.2 this morning here so ground was frozen, but certainly doesn't help my cause going into low 40s.

Some things I like to remind myself of as we get closer:

1) latent heat release. This storm is producing quite a bit of convection out in Illinois. This can pump things out ahead a little bit. We look for this factor when storms are modeled to far out to sea to try to nudge the system more N and W. No idea if this will come into play but could be a wildcard for fringe spots.

2) speed and duration. This likely comes in ahead of schedule and lasts more quickly than we think it might and ends quicker. Think of how many times one model or another made it look like it would precipitate hours longer than it ended up. I think any appreciable accumulating snows are done by daybreak.

3) what falls from the sky may not be what accumulates. 6 inches could fall. But how much melts initially. How much gets compacted with snow that is more wet than powdery and does qpf get wasted on sleet? All of that can result in 2.5 inches of slush and yet a 3-6 call would have still been accurate

There’s probably more but regardless many their first real snow tonight!  I do think from 80ish on north is going to end up doing quite well.

MattyICE wrote:Some things I like to remind myself of as we get closer:

1) latent heat release. This storm is producing quite a bit of convection out in Illinois. This can pump things out ahead a little bit. We look for this factor when storms are modeled to far out to sea to try to nudge the system more N and W. No idea if this will come into play but could be a wildcard for fringe spots.

2) speed and duration. This likely comes in ahead of schedule and lasts more quickly than we think it might and ends quicker. Think of how many times one model or another made it look like it would precipitate hours longer than it ended up. I think any appreciable accumulating snows are done by daybreak.

3) what falls from the sky may not be what accumulates. 6 inches could fall. But how much melts initially. How much gets compacted with snow that is more wet than powdery and does qpf get wasted on sleet? All of that can result in 2.5 inches of slush and yet a 3-6 call would have still been accurate

There’s probably more but regardless many their first real snow tonight!  I do think from 80ish on north is going to end up doing quite well.

#2 is a persistent pet peeve of mine. Models love to indicate long, drawn out events that in reality end much more abruptly once the storms begin to accelerate northeast.

amugs wrote:GFS 12Z says hi

Not a fan of the GFSin the short term, or even the long term the last couple of years.

As shown there NYC straddles the change line and seems to snow heavy snow, at least from Central Park north, almost throughout. That could surprise many total wise if it happened as depicted. I would tend to think it won’t happen quite as intensely as depicted there.