Two Mdt to high impact events NYC subforum; wknd Jan 6-7 Incl OBS, and mid week Jan 9-10 (incl OBS). Total water equiv by 00z/11 general 2", possibly 6" includes snow-ice mainly interior. RVR flood potential increases Jan 10 and beyond. Damaging wind.

[Allsnow]

North trend has stopped for now. wouldn’t mine it sinking a south a little more being 6 days out 

[Allsnow]

Eps Snow mean for next weekend is 5 inches for NYC. That’s probably the highest it’s been at this lead time since January 22 

[bluewave]

20 minutes ago, Allsnow said:

Eps Snow mean for next weekend is 5 inches for NYC. That’s probably the highest it’s been at this lead time since January 22 

The last time NYC scored a 6” snowstorm with a deep trough digging into the West was 2-3-14. It’s rare for that set up to actually work for us. As we have seen numerous potentials beyond 5 days since then with a deep trough in the West fall apart once we got to within 72 hrs. That storm in 2014 was much weaker and strung out and was a true thread the needle. More like a SWFE. Just weak enough not to run too far north. But most of the models are really amped with this system. Which leads to concern about a too far north 0z CMC outcome. But if the system were to become weaker in future runs, then suppression would become a concern with the waves so close together in the fast flow. 
 

[wdrag]

Always concerned about how good it looks for snow this far out.  The GEFS in the past 24 hours is showing a slightly sharpening of the causative short wave -- that still is troublingly far south.  The EPS however (as opposed to the 00z/1 op we saw) is showing a negative tilt short wave and strengthening trend since 12 hours ago. It validates the ensemble chance of 3+ by the NWS shown in.darker green, and 4+ by the EPS, and note the blend of models (07z/1 version) for both storms.

Things will change... I dont know how but there is little doubt in my mind that a 6+ axis will occur probably from the Virginias somewhere across PA. After that... I dont know.

So the GEFS overall is the weakest in its ensembles.  

I think the 12z/2 modeling will be important, since by then global models will be pretty accurate on the upper air pattern with probably no major change in the 500MB after that. 

I95 eastward to the coast is my greatest area of uncertainty (ptype) as well as just north of I84  (northern fringe-suppression). 

Of interest is the likelihood that whatever wet snow occurs PA/NJ this c coming weekend, it gets washed away by next Wednesday the 10th. The rapid snowmelt and storm two qpf have me concerned about renewed flooding, all dependent on qpf at this stage. You dont want to see the BOM total qpf by 00z/11. It seems overall high but if occurred even 1" less, would mean river flooding compared to the more vigorous first event of a couple weeks. I just can't post it... it surprised me.  Lets get storm one up here first. 

Also...coastal wind damage-power outage unknown risk for storm one DE/NJ/LI?  and then storm two fairly extensive northeast USA around the 9th-10th? Power outages as well documented here is not an easy predictor but knowing of potential can be helpful. 

If interested, please click the image below for clarity. 

[Allsnow]

14 minutes ago, bluewave said:

The last time NYC scored a 6” snowstorm with a deep trough digging into the West was 2-3-14. It’s rare for that set up to actually work for us. As we have seen numerous potentials beyond 5 days since then with a deep trough in the West fall apart once we got to within 72 hrs. That storm in 2014 was much weaker and strung out and was a true thread the needle. More like a SWFE. Just weak enough not to run too far north. But most of the models are really amped with this system. Which leads to concern about a too far north 0z CMC outcome. But if the system were to become weaker in future runs, then suppression would become a concern with the waves so close together in the fast flow. 
 

I think if the high and 50/50 continue to be a permanent feature there is a good chance NYC breaks the snowless streak. 
 

if you had a huge ridge out west suppression would be a concern in this set up as well. The trough out west could also help move a stronger system east quicker 

[Volcanic Winter]

It would make sense that even with a janky pattern we finally score with some luck on our side. We’ve been the antithesis of luck for too long. 

With that said, cautious optimism until we get closer. Really hoping this is a nice metro hit, and I’ll gladly take a sloppy 2-3 inches down here (hi @North and West) if we get NYC rockin’. 

Fingers crossed. Good analyses so far guys, thanks. 

[wdrag]

10 minutes ago, Volcanic Winter said:

 

 

10 minutes ago, Volcanic Winter said:

It would make sense that even with a janky pattern we finally score with some luck on our side. We’ve been the antithesis of luck for too long. 

With that said, cautious optimism until we get closer. Really hoping this is a nice metro hit, and I’ll gladly take a sloppy 2-3 inches down here (hi @North and West) if we get NYC rockin’. 

Fingers crossed. Good analyses so far guys, thanks. 

I like the sloppy 1-3"LI/NYC... that definitely appears more likely to me since the 06Z/EPS while slightly less amplified, is faster and certainly permits qpf up here... Here's the EPS 850MB at 144 hours and the EPS snow depth change.  

Provided the EPS does not flatten out much from the 06z/1 cycle as we go into the event, then we'll do well. The 06z GEFS looks sharper...all modeling faster.  My guess this is a Sat night-Sunday event.

Click images for clarity. The 850 low is over Ches Bay at this 144 hr image. 

 

[bluewave]

1 hour ago, Allsnow said:

I think if the high and 50/50 continue to be a permanent feature there is a good chance NYC breaks the snowless streak. 
 

if you had a huge ridge out west suppression would be a concern in this set up as well. The trough out west could also help move a stronger system east quicker 

There are plenty of things that need to go just right for a location like NYC which has a long term snowfall average around 25” and is so close to the ocean. It’s much easier to get it to snow in Northern Maine which averages over 110”. So this is why snowfall forecasting is so challenging around NYC. It’s no surprise that sometimes even model forecasts issued the day before the event can be significantly off. 

[jbenedet]

I’m def more in the camp that this is a mid Atlantic—>south snow storm at the moment. However there will be a significant longitudinal gradient. 

Where H5 closes off, in and away from the coast, sees the jack. 

The GFS track/evolution was near perfect for a significant mid Atlantic storm but look at the east surface winds ripping. And they never orient N/Northeast, instead to ENE. The surface high in reality extends from eastern Canada to Bermuda, and therefore maintains the surface wind direction off the Atlantic. This is being flagged on the ensembles, with +surface temp anomalies.

Model guidance has consistently been too cold with very short lead times this season. It’s ridiculous that GFS has LI in low mid 30’s with this wind and SST’s in upper 40’s. It’s a major issue for NYC metro. Hell even BOS will be 40F with this look.

[Allsnow]

25 minutes ago, bluewave said:

There are plenty of things that need to go just right for a location like NYC which has a long term snowfall average around 25” and is so close to the ocean. It’s much easier to get it to snow in Northern Maine which averages over 110”. So this is why snowfall forecasting is so challenging around NYC. It’s no surprise that sometimes even model forecasts issued the day before the event can be significantly off. 

Absolutely 

[TJW014]

Well, it seems to just be my fantastic luck that I will be out of state for 10 days, so of course it'll snow at home. I spent winter 2021-22 in Florida and Jan/Feb 2022 was a great time for snow on the Jersey Shore.

[RCNYILWX]

I’m def more in the camp that this is a mid Atlantic—>south snow storm at the moment. However there will be a significant longitudinal gradient. 
Where H5 closes off, in and away from the coast, sees the jack. 
The GFS track/evolution was near perfect for a significant mid Atlantic storm but look at the east surface winds ripping. And they never orient N/Northeast, instead to ENE. The surface high in reality extends from eastern Canada to Bermuda, and therefore maintains the surface wind direction off the Atlantic. This is being flagged on the ensembles, with +surface temp anomalies.
Model guidance has consistently been too cold with very short lead times this season. It’s ridiculous that GFS has LI in low mid 30’s with this wind and SST’s in upper 40’s. It’s a major issue for NYC metro. Hell even BOS will be 40F with this look.

You're not wrong that in the GFS depiction, it would start out mild due to the easterly fetch off the mild ocean. Except the flow does turn northeasterly enough to cool things off. It doesn't have to go due north to funnel colder and drier air southward. Look at the lower dew points to the north of NYC/LI during the day.

Once the surface low tracks far enough east, the subtle shift to more NE from E and ENE to start the day plus the air mass being cold enough aloft and higher precip rates amidst lower dew point air being advected southwest helps cool the boundary layer via dynamical and evaporative cooling.

It might take longer in reality than the model shows to cool off because of how warm the marine layer is over the well above normal SSTs, but the process the 06z GFS shows is still physically valid with the track it depicts.

Sent from my SM-G998U using Tapatalk

[donsutherland1]

Latest EPS ensemble and NBE depictions of the January 7-8, 2024 storm:

[EastonSN+]

8 hours ago, Wxoutlooksblog said:

Don't agree. Risk is either suppression or rain. We are in a phase where most of the models will trend south and east. We most likely will be in a trending north/west trend again as the event nears. It all depends on how far these trends go in each phase.

WX/PT

Wouldn't the storm on the west coast act to to push this storm east before it can gain much latitude? Understand if this storm absolutely bombs out and overwhelms the entire flow, but it does not look like that's the case.

[donsutherland1]

Nice jump on the 15z NBE for NYC (3.8"). Let's see where things are in a few days. There may be some basis to increase confidence in a 1"-3"/2"-4" snowfall (a "great storm" by winter 2022-23 standards). Interior sections appear most likely to see a significant (6"+) snowfall.

[wdrag]

For the 2m temps this far in advance suggest staying ensembles, which are all available in Trop Tidbits.

All suggest above freezing to I80 in NJ and up to coastal CT.  That mans the fringe temp transition near 33F is wet snow, provided cold enough above the BL.  Just too far in advance except as pre prev ensemble posts and NBE. I would not count on much accum NYC... I can live with 1-3 for now.

 

[Allsnow]

While we wait for the gfs, icon definitely digging more out west with higher hgts out east. It will definitely come north from the overnight run 

[Allsnow]

6 minutes ago, Allsnow said:

While we wait for the gfs, icon definitely digging more out west with higher hgts out east. It will definitely come north from the overnight run 

High is stronger this run so should be a cold run 

[Allsnow]

12z gfs going to be south of 06z 

the southwest energy is weaker 

[kingbaus]

southern mid Atlantic getting rocked

[Allsnow]

Gfs rocks the mid Atlantic while the cmc crushes the interior 

[Allsnow]

19 minutes ago, Allsnow said:

While we wait for the gfs, icon definitely digging more out west with higher hgts out east. It will definitely come north from the overnight run 

Icon as expected further north then 00z. 6-12 for dca to nyc 

[MJO812]

Just now, Allsnow said:

Icon as expected further north then 00z. 6-12 for dca to nyc 

Gfs miss to the south and cmc is a hugger

[Allsnow]

Just now, MJO812 said:

Gfs miss to the south and cmc is a hugger

Would like to see the euro come south this afternoon 

[MJO812]

Just now, Allsnow said:

Would like to see the euro come south this afternoon 

It already did at 0z but I agree.

[NittanyWx]

12z GFS is a good example of the suppression risk that occurs with heights crashing out west.

 

Still a very delicate act here to make it work.

[Allsnow]

Nice cad signature on the cmc with the strong high to the north 

[NEG NAO]

Total confusion so far CMC OP and GFS OP totally different - BUT ICON came north which was suppressed up till now - no one can make an accurate forecast for this weekend YET IMO and waiting out west is the Jan 10-11 system with strong HP to the north

 

[Stormlover74]

Just now, NEG NAO said:

Total confusion so far CMC OP and GFS OP totally different - BUT ICON came north which was suppressed up till now - no one can make an accurate forecast for this weekend YET IMO

6 days out is an eternity. 

[jbenedet]

9 minutes ago, NittanyWx said:

12z GFS is a good example of the suppression risk that occurs with heights crashing out west.

 

Still a very delicate act here to make it work.

Yea, this looks a lot more like a latitude capped storm—>early occlusion, with UL heights building over top of it due to trough in the pacific and then slide ENE. 
 

The 12z CMC does not make any sense to me; 12z GFS much closer to the actual evolution imo.