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12/29 - New Years Storm Threat Discussion

Dsnowx53

By Dsnowx53,
in New York City Metro

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PB GFI

PB GFI

Posted
Posted

The 12z ECMWF is a bit wetter for the NYC area. It's 00z run had 0.26" of precipitation, whereas the 12z run has a QPF of 0.33"

So the .50 models arent worlds apart , I will take colder prog of Euro , i trust its positioning this far out , maybe higher res see a little more QPF . so solid 4 looks doable most places prob 6 suff county mid island and north into eastern CT

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KEITH L.I

KEITH L.I

Posted
Posted

Even EWR is borderline but would probably be able to stay all snow with decent enough rates... temperatures there hover just above 0C. My LGA bufkit file wouldn't load for some odd reason. Even New Brunswick briefly goes over to rain with a 1.3/0.9C surface.... it goes above freezing at 920 hPa....

I'm not saying that this will verify but I simply wanted to clear up any idea that the GFS was favorable for NYC east or central Jersey.

well if this setup doesn't mean snow for the coast i am baffled..Come on..it's late December lol with a storm going 150 se!.lol..could be just one of those winters..lets hope for the best

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psv88

psv88

Posted
Posted

Upton

HIGH CONFIDENCE THAT THE PCPN WILL BEGIN TO MOVE IN SAT MORNING.

ALL PCPN INITIALLY SHOULD BE IN THE FORM OF LIGHT SNOW WITH

GUIDANCE EASILY BRINGING LOWS TONIGHT DOWN WELL BELOW

FREEZING...INTO THE TEENS INLAND...AND THE 20S NEAR THE COAST. THE

TEMP GUIDANCE ACTUALLY WARMS TEMPS TO ABOVE FREEZING ACROSS MANY

PARTS OF THE CWA BY THE AFTERNOON...BUT USING WET BULB TEMPS ONCE

THE PCPN HAS STARTED...THIS WOULD BRING TEMPS DOWN 4-5

DEGREES...AND THUS RESULT IN MOST AREAS SEEING SNOW THROUGH THE

DAY. THE MAIN AREA OF UNCERTAINTY WOULD BE THE EASTERN PART OF

LI...WHERE THOUGH THE EASTERLY FLOW SHOULD PRODUCE A MAINLY

ISOTHERMAL PROFILE...AND KEEP TEMPS NEAR FREEZING...THERE IS THE

POSSIBILITY OF RAIN MIXING IN BY THE AFTERNOON...WHICH WOULD LEAD

TO LOWER SNOW AMTS. THE MODELS ARE AGAIN IN DECENT AGREEMENT WITH

THE HEAVIEST QPF MOVING THROUGH BETWEEN 15Z AND

00Z...CORRESPONDING WITH THE TIMING OF THE UPPER LEVEL ENERGY

MERGING WITH THE INTENSIFYING SURFACE LOW AS IS PUSHES OFF THE

COAST. THE HIGHEST AMTS ARE EXPECTED OVER THE EASTERN AND SOUTHERN

HALF...SO IF THE EASTERN HALF OF LI DOES REMAIN ALL SNOW...IT

COULD SEE THE HIGHEST SNOW AMTS...ALONG WITH EASTERN CT.

HOWEVER...IF THERE IS A TRANSITION TO RAIN...AMTS WILL BE LOWER.

THE HIGHER CONFIDENCE RIGHT NOW IS IN IT REMAINING SNOW FOR THE

MAJORITY OF THE TIME.

THE OTHER ISSUE WOULD BE IF THE QPF AXIS SHIFTS TO THE NORTH AND

WEST...WHICH WOULD THEN RESULT IN THE NYC METRO AREA AND HUDSON

RIVER VALLEY SEEING HIGHER AMTS...POSSIBLY BETWEEN 1 TO 2 INCHES

MORE. THE CONFIDENCE RIGHT NOW IS THAT THE HIGHER AMTS WILL BE

EASTERN CT...AND LI...BUT THIS SHIFT POSSIBILITY SHOULD BE NOTED.

WITH ALL THIS IN MIND...TOTAL SNOW FALL AMTS RANGE BETWEEN 2 AND 4

INCHES...WITH THE LOWER AMTS TO THE NORTH AND WEST OF THE NYC

METRO AREA...AND THE HIGHEST EASTERN LI AND CT. NCEP SREF PLUMES

GENERALLY CONCUR OF BETWEEN 1 AND 3 INCHES OF SNOW ACROSS THE

CWA...WHILE HPC GUIDANCE HAS AROUND 2 INCHES AROUND NYC

METRO...AND 3 TO 4 INCHES OVER THE EASTERN HALF OF THE CWA...SO

OVERALL TOTALS BETWEEN 2 AND 4 INCHES SEEM REASONABLE AT THIS

POINT. THIS WOULD LEAD TO A MARGINAL ADVISORY EVENT...BUT THE

UNCERTAINTY STILL OF AREAS REACHING AT LEAST 3 INCHES...HAVE

WITHHELD THE ADVISORY AT THIS TIME.

AS PREVIOUSLY MENTIONED...GUIDANCE OVERDOING THE TEMPS DURING THE

DAY SAT...SO WENT WITH HIGH TEMPS GENERALLY 4-5 DEGREES LOWER THAN

THE COOLER MET GUIDANCE. USED A BLEND OF THE MET/MAV FOR OVERNIGHT

LOWS TONIGHT AND AGAIN SAT NIGHT. ALL AREAS BOTH NIGHTS WILL SEE

TEMPS DROPPING BELOW FREEZING...INTO THE TEENS WELL INLAND...AND

IN THE 20S ALONG THE COAST. FORTUNATELY WINDS ARE NOT EXPECTED TO

BEGIN GREATLY INCREASING AGAIN UNTIL SUNDAY...SO WIND CHILL VALUES

WILL ONLY BE A FEW DEGREES COOLER THAN THE TEMPS.

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earthlight

earthlight

Posted
Posted

My best guess at this point is 1-3" near the coast and 2-4" from about 20-30 miles inland in NJ north of Trenton to NYC including SE NY & SW CT. There could be a stripe of 3-6" totals but it's hard to say where that might be. If the storm develops closer to the coast and faster..maybe from NE NJ into CT and southeast SNE?

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psv88

psv88

Posted
Posted

My best guess at this point is 1-3" near the coast and 2-4" from about 20-30 miles inland in NJ north of Trenton to NYC including SE NY & SW CT. There could be a stripe of 3-6" totals but it's hard to say where that might be. If the storm develops closer to the coast and faster..maybe from NE NJ into CT and southeast SNE?

You see Upton's disco?

They think model guidance is 5 degrees too high. Looking at the RGEM, in its kill zone, it also has only the normal areas as rain.

Therefore, i think coastal NJ and LI see the most no? 3-6? I dont see why the areas with the most QPF would see only an inch of snow, ratios shouldnt make that big a difference, imho

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earthlight

earthlight

Posted
Posted

You see Upton's disco?

They think model guidance is 5 degrees too high. Looking at the RGEM, in its kill zone, it also has only the normal areas as rain.

Therefore, i think coastal NJ and LI see the most no? 3-6? I dont see why the areas with the most QPF would see only an inch of snow, ratios shouldnt make that big a difference, imho

4-5 degrees might be a little much. It could end up that the coast sees about the same as everyone else, but I'm taking a bit of a sref/euro ens blend track right now which leaves the 0.50" line just offshore and running through Central LI.

2-5" is the best call area wide but I think 1-3" will be more common nearer to the shores and on Eastern LI and the south/southeast shore.

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PB GFI

PB GFI

Posted
Posted

NYC

NAM .50 - .75 ,SREF .50 - GFS .35-,EURO .35 ,MM5 .40 ..

even if i took nam away

4 inch looks really a good bet for most areas .

Like the Euro track with the colder surface temps as 850`s are fine and anticipate precip shield is bigger than progged .

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PB GFI

PB GFI

Posted
Posted

Blows my mind how we could have a 983mb low at 72W and STILL not have significant precipitation being thrown back west.

4KM NAM still has about 1"-1.25" of QPF

If the system comes off hatteras at 1008 and goes to 983 then its

intensity and qpf would match . so 1 has to b off

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earthlight

earthlight

Posted
Posted

I wouldn't anticipate a bigger precip shield. It makes sense that it's tucked in because the dynamics are compact and tucked in just to the northwest of the surface low where the small but robust cold conveyor belt develops.

The best lift transfers to the coastal low pretty rapidly once the best positive vorticity advection starts aloft and that's why you're seeing the lift to our west almost jump overhead to the coast. The surface low is strong but it is also a compact structure and the CCB will follow suit. There is the potential for a screw job somewhere.

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Isotherm

Isotherm

Posted
Posted

My best guess at this point is 1-3" near the coast and 2-4" from about 20-30 miles inland in NJ north of Trenton to NYC including SE NY & SW CT. There could be a stripe of 3-6" totals but it's hard to say where that might be. If the storm develops closer to the coast and faster..maybe from NE NJ into CT and southeast SNE?

Pretty much agree with your totals but I think your 1-3/2-4 gradient is too far inland. I'm not buying much mixing beyond a couple miles of the beaches. Once the coastal low takes over, which will be by 18z tomorrow, any mixing concerns should be very limited as the storm intensifies. Most of us should wetbulb to freezing fairly easily with the stronger vv's overhead. I think any mixing might happen at the onset of pcpn if the northern stream primary low is still dominant. The key is to get the energy transfer quickly to the coastal and deepen the low to remove sticking issues.

As it stands now, I like a general 2-4" with lollipops to 6" across most of the region, with 1-3" along the immediate shoreline.

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eduggs

eduggs

Posted
Posted

You see Upton's disco?

They think model guidance is 5 degrees too high. Looking at the RGEM, in its kill zone, it also has only the normal areas as rain.

Therefore, i think coastal NJ and LI see the most no? 3-6? I dont see why the areas with the most QPF would see only an inch of snow, ratios shouldnt make that big a difference, imho

It looks like a relatively short period of possible moderate to heavy snow for eastern section... probably less than 6 hours. That means things have to come together quickly for it to work out. If some QPF is lost to non-accumulating snow and/or the more substantial banding does not organize itself or remains offshore, then eastern sections won't see the most snow.

I would lean cold for now, despite steady model trends towards a stronger, closer SLP. For right now I think elevated interior sections of LI have the best chance of significant accumulations. But confidence is also lowest out there. NW of the City has the highest chance of at least 2" IMO, but lesser chances for more significant snow. Some of the stronger ensemble members of several models definitely change much of LI to rain, even if you correct for a BL warm bias. Some areas well N and W could see ratios in the 12:1 - 15:1 range considering cold 850mb - 700mb temps. And the QPF gradient out there isn't too great, so there could be a secondary snow maximum well inland.

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