Major Nor'easter snow storm (possible top 20) Noon Wednesday-Noon Thursday Dec 16-17, 2020

[Rittenhouse]

14 minutes ago, jm1220 said:

Might mean no rain but it doesn’t say much if anything about sleet. That’s determined by mid level temps and conditions not surface.

The low dew points this morning indicate the strength of the cold air mass in place. Stronger high = less chance for mixing.

[SnowGoose69]

The 3km NAM has sleet to JFK and EWR at 23-00 but then miraculously holds it off and even pushes it south until 05Z.  Not sure I believe a push like that gets held off

[bluewave]

Yeah the NAM has a sneaky warm layer right near where the sleet -snow mix line occurs tonight. Pretty good SE LLJ around 800-850 mb.

LEV PRES  HGHT  TEMP  DEWP  RH  DD   WETB DIR SPD THETA THE-V THE-W THE-E   W
     mb     m     C     C    %   C     C  deg knt   K     K     K     K    g/kg
-------------------------------------------------------------------------------
SFC 1012    22  -2.6  -3.9  91  1.3  -3.1  29  21 269.6 270.1 269.4 277.2  2.82
  1 1000   119  -3.8  -4.6  94  0.8  -4.1  31  29 269.3 269.8 269.1 276.6  2.70
  2  950   522  -5.8  -6.1  98  0.3  -5.9  47  49 271.3 271.7 270.1 278.2  2.54
  3  900   947  -4.2  -4.5  98  0.3  -4.3  75  59 277.2 277.7 274.3 285.6  3.04
  4  850  1402  -0.8  -1.2  97  0.5  -1.0 104  53 285.3 286.1 280.0 297.0  4.11
  5  800  1888   0.4  -0.2  96  0.6   0.1 130  54 291.5 292.4 283.5 305.2  4.70
  6  750  2404  -1.9  -2.1  98  0.2  -2.0 139  43 294.5 295.3 284.3 307.3  4.36
  7  700  2951  -4.1  -4.1 100  0.0  -4.1 155  35 298.0 298.7 285.4 310.1  4.04

[jm1220]

2 minutes ago, SnowGoose69 said:

The prior 06Z run was close as early as 23-00Z from 800-850.  It would not take much to push that layer over 0C

I think it’s really how long we can hold off the warming aloft in the heavy snow push. If that surges through the NYC area early obviously totals will be low but if it can be held off maybe we can make it to 10”. 

[jm1220]

3 minutes ago, SnowGoose69 said:

The 3km NAM has sleet to JFK and EWR at 23-00 but then miraculously holds it off and even pushes it south until 05Z.  Not sure I believe a push like that gets held off

It must think the lift/precip rate can overcome it for a time? I can see it happen if it really comes in like a wall. 

[SACRUS]

 

 

[MJO812]

3k Nam tonight 

[NJwx85]

I'm going with 5-8" at Central Park. Totals will increase dramatically North of the GWB. I'm expecting a quick thump of 1-2" per hour rates from about 4PM to midnight and then a flip to sleet and dry slot for the coastal plain. The dry slot probably makes it about as far inland as the Rockland/Orange County border would be my guess. NW of that line will see the 12"+ amounts although the Hudson Valley could also get into that range if the track ends up slightly further South. I'm not so much worried about the sleet as I am the dry tongue above 700mb.

[ForestHillWx]

35 minutes ago, crossbowftw3 said:

Narrowsburg, ~800 feet. Pretty close to them though 

Countless river trips at Landers. Going back this summer; covid can’t stop me. 

[LongBeachSurfFreak]

I doubt the warm push makes it north of the park. I have seen this multiple times in the past. That seems to be where it likes to stop

[MJO812]

12 -18 inches for the city 

[LongBeachSurfFreak]

31 minutes ago, weathermedic said:

Sun already disappeared (at least for now) behind the clouds here in lower Manhattan. Hopefully temps won't rise too  much from the morning lows.

It’s all about the dew point. Temps will plummet once the precip starts 

[Rittenhouse]

The initial band is impressive. All of that should fall as snow even at the coast. The mixing showed on the NAM occurs after the initial band, during the dry slotting.

[bch2014]

Feeling cautiously optimistic here in the E 80’s.. Wouldn’t surprise me if I get a bit of taint mid-storm but I think 8-12” is the responsible call here.

[SleetStormNJ]

12 minutes ago, SnowGoose69 said:

The 3km NAM has sleet to JFK and EWR at 23-00 but then miraculously holds it off and even pushes it south until 05Z.  Not sure I believe a push like that gets held off

SG - How does the NAM usually do on thermals in these set ups?  I recall it being hit or miss some events (some it nailed, others it came in too fast/warm).

 

[NJwx85]

3 minutes ago, MJO812 said:

12 -18 inches for the city 

I'm gong with a third of that. It's too short of a duration for snow. You would need 3-4" per hour rates to achieve 18".

[MJO812]

3 minutes ago, NJwx85 said:

I'm gong with a third of that. It's too short of a duration for snow. You would need 3-4" per hour rates to achieve 18".

Agree

3-6 for my area and more towards Manhattan 

[MJO812]

HRRR

[jm1220]

That being said it's a step back on the NAM-more amped with the 700 low track for sure. Tracks from around Allentown through CT. Hopefully it's wrong. I'd think warm air aloft would come in stronger and risk a good chunk of the front end being sleet (for near the city and LI). 

Just checked sounding for around Farmingdale-very marginal for most of the front end. Sleet gets into much of NJ at some point and even the Allentown area. The model thinks the precip rate can overcome the warming aloft but just barely. It's a little too cold and much of the front end can be sleet.

[SleetStormNJ]

4 minutes ago, jm1220 said:

That being said it's a step back on the NAM-more amped with the 700 low track for sure. Tracks from around Allentown through CT. Hopefully it's wrong. I'd think warm air aloft would come in stronger and risk a good chunk of the front end being sleet (for near the city and LI). 

It seems to be a bit more extreme with the track/mid level warmth push than the other models.  Worth watching for sure though.

[tdp146]

On the wind side of things, I received my new Weatherflow Tempest last week and hustled to get it up above roofline yesterday. I’m still in a pretty bad spot locally for wind measurements but I got it up at a height of 23.5 feet.

https://tempestwx.com/station/34338

 

[nflwxman]

Final Call:

KTTN 3-6"

KNYC 6-9"

KJFK 4-7"

KMMU 8-12"

KHPN 10-14"

This track historically does not give coastal sections high ratio snows. It's hard to see how mixing does not make it to the lower HV with a 700mb low track this north. The 3km NAM has a fairly significant warm layer at 700-800mb that, at this stage, is more often correct.

 

 

[Sn0waddict]

For what it’s worth the HRRR seems pretty cold, holding off most of the sleet for NYC until 07z

[wdrag]

Agree with everyone on north of GFS/EC cold snowy solutions.  

Added some 12z HRRR guidance.  Near blizzard possible around 03z LGA, but short duration, could be some around 12z in the CAA but again short.

The HRRR is very strong on wind and I can see it.  NAM 10M has 50kt 10 miles east of Toms River late tonight. 

I'll add the graphics... from th 12z HRRR  they look good to me.  Also someone asked about Thunder.  As you're probably aware SPC added T to a part of forum. And...the HRRR has a pretty strong signal for such this evening in those high snowfall rates.

Snow depth: I like as my answer to what is coming. Use w your own best judgement.  Added HRRR MAX gusts. and the 1am projected HRRR simulated radar...note sleet up here.

 

[MJO812]

The sleet is actually heavy snow on the Nam 

[donsutherland1]

At 9:45, snow was advancing through West Virginia, western Virginia and western Maryland. Snow was reported in the Washington, DC suburbs including Gaithersburg, MD, Fair Oaks, VA, and Vienna, VA.

While we wait for the snow to commence here, it's worth noting that if both New York City and Boston pick up 10" or more snow while both Baltimore and Washington, DC pick up less than 4" snow, that would be a rare outcome. Since 1892, there have been just 4 storms that produced such snowfall amounts. The sample size is 402 storms. The most recent such storm occurred on February 8-9, 2013.

[NYC10023]

what time does this party get started here in the city?

[kat5hurricane]

I think 4-8 is a reasonable call for the NYC area from south to north, been sticking with this call for a few days. The low track is less than ideal and those warm layers almost always overperform in these marginal situations, I expect a lot of sleet. These 12-18 inch forecasts is ridiculously bold IMO.

[psv88]

2 hours ago, uofmiami said:

OKX has Huntington with a range of 7-14” with 13” forecasted. Has me in Syosset also with a range of 7-14” with 14” forecasted. OKX definitely going with the higher end along the N Shore, let’s hope that’s correct in the end.

Western Suffolk upgraded to 8-14”, matches all guidance. We’re gonna rock

[Tatamy]

18 minutes ago, tdp146 said:

On the wind side of things, I received my new Weatherflow Tempest last week and hustled to get it up above roofline yesterday. I’m still in a pretty bad spot locally for wind measurements but I got it up at a height of 23.5 feet.

https://tempestwx.com/station/34338

 

Enjoy.  I have had mine for a few months.  It's a nice station.