12/29 Winter Storm OBS/Disco Part II

[SnoSki14]

My high was originally supposed to be in the low 30's. Now it is going to be near 40 tomorrow.

Wow really, my forecast. high is around 33-34 tomorrow.

[TWCCraig]

Haarp?

Oh god, I can't believe we actually have people on this forum that believe that $#!*.

(Sorry mods if this was a little off topic)

[Guest Pamela]

Those splits are more common in Nassau county. In February 1999 there was a storm where the south shore of Nassau saw all rain from about 5am -10am while the entire north shore saw a crippling ice storm with power outages all over the place. 12/19/95 and 2/11//94 also had some notable differences between north and south shore in Nassau but those were mainly sleet/snow differences not rain/snow.

It is rare that major differences show up between north and south in the big storms...if they are big, they are usually cold enough for everyone. It is in the minor and low end moderate events that differences are most common. Between the north and south shores of Nassau County, there is probably a 6" difference in snowfall in an average year.

[SnowGoose69]

Upton has me at 40 now too and im just South of the lie in western nassau.. Going to be interesting watching how this unfolds.. Right now my temp is only down to 30 was hoping it would be colder....

I think we'll see highs generally 34-38 before the snow starts, the dewpoints though will be 20-25 which makes the difference. It depends what sort of deck we have at sunrise, if we're only BKN at 120 or 250 we may be able to get closer to that 38, if we're already overcast under 10,000 feet it will be tough for some areas to even make 35.

[XtremeWx]

0z RGEM shows rain for NYC east.

http://collaboration.cmc.ec.gc.ca/cmc/cmdn/pcpn_type/pcpn_type_gem_reg.html

[MJO812]

Not a good trend on the Nam and now the RGEM.

[earthlight]

RGEM looks a good bit worse than the last several runs...lost the heavy precip and also seems a bit warmer.

[Isotherm]

We need the rest of 00z guidance to depict a more rapid deepening of the coastal and especially H85 low. The NAM maintains the primary at similar intensity to the coastal through early afternoon, which probably means rain for NYC southeast if correct, changing to snow by late afternoon.

This is for 18z tomorrow:

• 
  

[IntenseBlizzard2014]

Can you guys post the progression of the storm from the RGEM?

[jm1220]

Snowfall maps by most models, especially like the GFS treat LI likes it's part of the ocean, so that's why you see basically nothing for LI. I'm very sure we'll get over an inch. I don't think this will be a rain event, maybe some mix and a change over to rain for a very brief period of time at worst.

It's going to be very marginal and close for us. We have to hope that big vertical velocities can overcome the shallow warm layer at 900-925mb. If the CCB can develop over us, we should be able to. If not, it will likely stay a sloppy mess for much of the event while it's cold enough elsewhere. It goes with our territory.

[Chris L]

RGEM is, well, like John said, not quite good as it was before.

[Fantom]

Rgem ticked a bit SE. Bout .35 QPF NYC metro (extrapolated). Take the 2"-4" fake option left and RUN with it.

[earthlight]

Can you guys post the progression of the storm from the RGEM?

Here's the height of the storm. The rest of the frames show light to moderate rain from NYC east and light to moderate snow from NYC west.

[WintersGrasp]

Ouch...RGEM is like an inch of snow even in NNJ

[IntenseBlizzard2014]

Here's the height of the storm. The rest of the frames show light to moderate rain from NYC east and light to moderate snow from NYC west.

Westchester County is still safe, but tooooo close for comfort.

[PB GFI]

If the euro craps out then i will tap. Not now

[jm1220]

RGEM is, well, like John said, not quite good as it was before.

I'm starting to think a lot of coastal locations are cooked if we can't get some of the developing CCB. We need the dynamics to overcome the stale airmass and initial easterly winds that the primary low brings in. Without that, I think much of Long Island, coastal NJ and possibly even NYC (probably not the North Shore) gets some slop and that's it. For late December, this airmass isn't impressive at all when we can't even generally get below 30 at night.

[Isotherm]

Better hope the rest of 00z guidance/globals depict the more rapid closing off of low/mid level centers, otherwise, we're torched from NYC southeast. I think there's a chance the mesoscale modelling might be onto something, but this is a very difficult forecast as is always the case w/ thse energy transfers. Rain/snow p-type is a headache.

[IntenseBlizzard2014]

Meh. I'll take whatever I can get.

[KEITH L.I]

at least the nam is showing a little light snow for New years eve..the 850 line is way south..but again that means nothing this year lol

[TWCCraig]

Good disco from Upton:

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...

CHALLENGING FORECAST THIS TIME FRAME. LOOKING AT

OPERATIONAL/ENSEMBLE FORECASTS OF SFC LOW TRACK...LOOKS PERFECT

FOR SNOWFALL ACROSS THE CWA RIGHT AROUND THE 40/70 BENCHMARK.

OF COURSE...IT IS NEVER THAT SIMPLE WHEN FORECASTING WINTER

WEATHER FOR THESE COASTAL LOCATIONS.

12Z NAM RUN WETTER...WITH CLOSE TO 1/2 INCH OR HIGHER QPF WITH

THIS EVENT. GFS LESS. HOWEVER...ALL MODELS INDICATE ENOUGH LOW

LEVEL WARMING FOR A MIX OR CHANGEOVER FOR A GOOD PORTION OF LONG

ISLAND SATURDAY AFTERNOON.

THE REASON IS THE EXPECTED PATTERN ALOFT. LOOKING AT 12Z-18Z TIME

FRAME...H8 LOW STILL TO THE WEST...AND A H950 TO H850 WARM UP OCCURS

AS THE MORNING PROGRESSES SATURDAY DUE TO SE/SOUTH FLOW. TIME OF

DAY NOT IDEAL FOR COLDER SFC TEMPS...AND ONSET OF LIGHT PRECIP.

ONCE THE SFC LOW AND CLOSED LOW ALOFT (H9 AND H8) DEVELOP AND

DEEPEN TO OUR SOUTHEAST...ENOUGH COLD AIR WILL GET DRAWN IN FROM

THE NORTH TO BEGIN A CHANGEOVER AT THE COAST. ALSO...ONCE

PRECIPITATION INTENSITY INCREASES DURING THE MID TO LATE AFTERNOON

HOURS...ENOUGH EVAP COOLING OCCURS FOR A CHANGEOVER AS BOUNDARY

LAYER COOLS...SOMETHING THE MOS DOES NOT HANDLE WELL.

I WILL UNDERCUT MOS SOMEWHAT FOR THESE CSTL LOCATIONS...BUT UPPER

30S POSSIBLE FOR A TIME SATURDAY.

AS FOR THE REMAINDER OF THE AREA...NYC METRO/NE NJ/LOWER HUDSON

VALLEY AND MOST OF SRN CT...THIS SHOULD BE AN ALL SNOW EVENT. SOME

MIXING POSSIBLE RIGHT ALONG THE SOUTH COAST OF NYC AND SERN CT

DURING THE AFTN.

OVERALL...STILL EXPECT 2 TO 5 INCHES...WITH BANDED PRECIP LIKELY

PRODUCING TOTAL OVER 6 INCHES IN SPOTS FROM NRN NYC THROUGH THE

LOWER HUDSON VALLEY AND INTO PARTS OF CT.

[nzucker]

Better hope the rest of 00z guidance/globals depict the more rapid closing off of low/mid level centers, otherwise, we're torched from NYC southeast. I think there's a chance the mesoscale modelling might be onto something, but this is a very difficult forecast as is always the case w/ thse energy transfers. Rain/snow p-type is a headache.

I think this is mostly snow for everyone in the NYC metro area (unless you're way out towards the South Fork of LI, in which case you might mix). Dewpoints are running in the low to mid 20s, we've got a weak surface low tracking south of the area, and there's a development of a CCB later in the storm. This seems like a classic cold storm for me with places near the coast actually getting slightly more snow. I think a lot of these meso-models are overdoing the BL warming.

[IntenseBlizzard2014]

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...

CHALLENGING FORECAST THIS TIME FRAME. LOOKING AT

OPERATIONAL/ENSEMBLE FORECASTS OF SFC LOW TRACK...LOOKS PERFECT

FOR SNOWFALL ACROSS THE CWA RIGHT AROUND THE 40/70 BENCHMARK.

OF COURSE...IT IS NEVER THAT SIMPLE WHEN FORECASTING WINTER

WEATHER FOR THESE COASTAL LOCATIONS.

12Z NAM RUN WETTER...WITH CLOSE TO 1/2 INCH OR HIGHER QPF WITH

THIS EVENT. GFS LESS. HOWEVER...ALL MODELS INDICATE ENOUGH LOW

LEVEL WARMING FOR A MIX OR CHANGEOVER FOR A GOOD PORTION OF LONG

ISLAND SATURDAY AFTERNOON.

THE REASON IS THE EXPECTED PATTERN ALOFT. LOOKING AT 12Z-18Z TIME

FRAME...H8 LOW STILL TO THE WEST...AND A H950 TO H850 WARM UP OCCURS

AS THE MORNING PROGRESSES SATURDAY DUE TO SE/SOUTH FLOW. TIME OF

DAY NOT IDEAL FOR COLDER SFC TEMPS...AND ONSET OF LIGHT PRECIP.

ONCE THE SFC LOW AND CLOSED LOW ALOFT (H9 AND H8) DEVELOP AND

DEEPEN TO OUR SOUTHEAST...ENOUGH COLD AIR WILL GET DRAWN IN FROM

THE NORTH TO BEGIN A CHANGEOVER AT THE COAST. ALSO...ONCE

PRECIPITATION INTENSITY INCREASES DURING THE MID TO LATE AFTERNOON

HOURS...ENOUGH EVAP COOLING OCCURS FOR A CHANGEOVER AS BOUNDARY

LAYER COOLS...SOMETHING THE MOS DOES NOT HANDLE WELL.

I WILL UNDERCUT MOS SOMEWHAT FOR THESE CSTL LOCATIONS...BUT UPPER

30S POSSIBLE FOR A TIME SATURDAY.

AS FOR THE REMAINDER OF THE AREA...NYC METRO/NE NJ/LOWER HUDSON

VALLEY AND MOST OF SRN CT...THIS SHOULD BE AN ALL SNOW EVENT. SOME

MIXING POSSIBLE RIGHT ALONG THE SOUTH COAST OF NYC AND SERN CT

DURING THE AFTN.

OVERALL...STILL EXPECT 2 TO 5 INCHES...WITH BANDED PRECIP LIKELY

PRODUCING TOTAL OVER 6 INCHES IN SPOTS FROM NRN NYC THROUGH THE

LOWER HUDSON VALLEY AND INTO PARTS OF CT.

[PB GFI]

Finally sanity

[jm1220]

at least the nam is showing a little light snow for New years eve..the 850 line is way south..but again that means nothing this year lol

Means nothing when the water's in the 40s, easterly winds bring that warmth in, and there's no high to lock in a cold airmass. 850s are almost irrelevant here until the water cools. The warmth is underneath.

[LocoAko]

NAM is mighty warm in the low levels...there seems to be a sneaky warm layer near 925mb and the p-type maps are catching on and showing a transition to rain for a period making it all the way up to Newark.

Boy howdy, remember when everyone was hating on the GFS this morning when it showed something similar and blindly trusting the NAM?

[Nikolai]

Means nothing when the water's in the 40s, easterly winds bring that warmth in, and there's no high to lock in a cold airmass. 850s are almost irrelevant here until the water cools. The warmth is underneath.

plz explain how warm 925mb temps are a result of the ocean if the BL temps are actually below freezing thnx

[snywx]

I think this is mostly snow for everyone in the NYC metro area (unless you're way out towards the South Fork of LI, in which case you might mix). Dewpoints are running in the low to mid 20s, we've got a weak surface low tracking south of the area, and there's a development of a CCB later in the storm. This seems like a classic cold storm for me with places near the coast actually getting slightly more snow. I think a lot of these meso-models are overdoing the BL warming.

NAM & RGEM seem to show 2 precip maxes.. One here in the far interior and another right along the coast.. Should be interesting to watch unfold tomorrow

[Isotherm]

I think this is mostly snow for everyone in the NYC metro area (unless you're way out towards the South Fork of LI, in which case you might mix). Dewpoints are running in the low to mid 20s, we've got a weak surface low tracking south of the area, and there's a development of a CCB later in the storm. This seems like a classic cold storm for me with places near the coast actually getting slightly more snow. I think a lot of these meso-models are overdoing the BL warming.

I've generally had your opinion as well over the past 12 hours, but it is legitimately concerning that both the RGEM and NAM have warmed the boundary layer to a point where rain is possible well inland.

It's entirely possible that the mesoscale models are too bullish on this feature and inaccurately portraying the development of the coastal low. Often times these lows tend to intensify a bit quicker than progged, especially with warmer SST's, so we'll see what we can do. I'll wait for the rest of 00z guidance before abandoning the snow idea.

[sferic]

NAM & RGEM seem to show 2 precip maxes.. One here in the far interior and another right along the coast.. Should be interesting to watch unfold tomorrow

Hope you in Middletown and me in Liberty have a suprise with 6 inches. Was actually going to go to the Galleria in Middletown tomorrow, but not now.