Snowfall NYC subforum Jan 6 and OBS if needed

[RU848789]

SIAP (been playing at a disc golf tourney all day), but the NWS updated their regional snowmap (I love these as they show Mt. Holly and nearby adjacent areas).  Clearly backed off for snow north of 276/195 in EPA/CNJ, especially N of 78 which is <1" but beefed snowfall up a bit for Philly/SNJ and south of there.  Still lots of uncertainty and bust potential in both directions.  

[RU848789]

5 hours ago, donsutherland1 said:

FYI, regarding the National Blend of Models issue:

I emailed the development team this morning with screen shots. I used the text from the guidance rather than vendor maps to illustrate that the issue exists with the product itself. The three screenshots I included are below.

I will post any updates I receive from the development team.

 

Can you elaborate?  Is this related to the conversation Walt, Mike Gorse and I were having over precip/snowfall discrepancies and the time-lagged NBM issue?  I can't tell what you've highlighted.  Thanks. 

[donsutherland1]

As previously noted in this thread, I had pointed out that there were cases where NBE was showing snowfall amounts with 0 qpf and unrealistic snow-liquid ratios e.g., 95:1 for NYC, issues that did not occur with the prior version (4.1). I also saw that there were areas where qpf was present, but ratios were still unrealistic. That raises questions about not just the periphery of the storm where a degree of smoothing might have been involved, but all the storm totals. On account of concluding that all storm totals could be compromised, I decided to contact the development team.

I suspect that the issue is common to your discussion, Drag's discussion, and my discussion.

[Allsnow]

Gfs bumps north 

[MJO812]

3 minutes ago, Allsnow said:

Gfs bumps north 

 

[winterwx21]

Just now, Allsnow said:

Gfs bumps north 

And with how NAM and HRRR look, our area is still in the game. NE of NYC has no shot, but our area can get a couple inches out of this. I think people have been giving up too early since the mesoscale models will have a better idea on the northern extent of the precip. Let's hope the HRRR is onto something. This can end up more south with our area getting almost nothing, but we do have a shot. 

[RU848789]

14 minutes ago, Allsnow said:

Gfs bumps north 

Yes it does.  Nice to at least have the NAM/GFS and even the long range HRRR on the snowier side; maybe some of the others will want to join the party at 18Z.  

[RU848789]

Long range RAP anyone?  Hey, if we're going to grasp at straws, at least let them be good ones, like this and the long range HRRR, lol.  

 

[Tatamy]

23 minutes ago, RU848789 said:

Long range RAP anyone?  Hey, if we're going to grasp at straws, at least let them be good ones, like this and the long range HRRR, lol.  

 

I am waiting for the 0z runs where the models tighten the screws on the weenies regarding this event.  That seems to be the pattern for the past two nights…lol

[wdrag]

Watch the 18z EC and 00z/5 global models. Either the globals are too far south or you'll see a sudden shift north by 30-60 miles.

I am seeing too many members trying to hook northeast at 5H up into NYS-CT.  The 21z RAP continues its northward trend.  Bothersome.  Wouldn't take much for the confluence zone to shift north past I84.  

 

WPC and WFO's have all the guidance, more than what I'm seeing but something is going to eve to change south in the short term mesoscale models (ALA the oddly south Canadian) or the globals will be bleeding north in the next cycle or two. 

 

We'll know more by morning.  Globals suppressed vs mesoscale modeling now.  Compromise? I'll check the HSD and QPFPMD but I continue to think a little snow throughput NJ-LI til I see the mesoscale models move south from the 18z modeling. 

[Allsnow]

Euro will bump north at 18z 

[MJO812]

1 minute ago, Allsnow said:

Euro will bump north at 18z 

Yep just a smidge

[WestBabylonWeather]

2 minutes ago, MJO812 said:

Yep just a smidge

We need a total of three smidges for 1-3 

we will define a smidge as 25 miles 

[Allsnow]

1 minute ago, MJO812 said:

Yep just a smidge

Helps a phl a little 

1 inch line very close to me but I’ll consider a coating a win out of this system 

[donsutherland1]

6 hours ago, donsutherland1 said:

FYI, regarding the National Blend of Models issue:

I emailed the development team this morning with screen shots. I used the text from the guidance rather than vendor maps to illustrate that the issue exists with the product itself. The three screenshots I included are below.

I will post any updates I receive from the development team.

 

The head of the NBM development team has replied.  Several points:

1. The team is aware of the issue
2. NBM inputs for QPF and snow differ. It is implied that this may be resulting in the observed issue
3. The team will seek to align the QPF and snow inputs in v5.0, which will be released sometime next year

The exact reply is below:

"We are aware of this issue and are attempting to align the NBM qpf inputs with those used for snow for NBM v5.0 which is scheduled to come out sometime next year.   It is likely we will cut down on some of the qpf inputs in order to make this happen."

For those looking for a preview of v5.0, the last paragraph of this press release offers a short description: https://vlab.noaa.gov/web/mdl/-/nbm-upgraded-to-version-4-2?redirect=%2Fweb%2Fmdl%2Fevents

[MJO812]

[mikem81]

fwiw sREF about 25-30 miles north at 21Z from 15Z

[MJO812]

3 minutes ago, mikem81 said:

fwiw sREF about 25-30 miles north at 21Z from 15Z

 

[dseagull]

Ill take these bumps and halt them right here.   No whammy no whammy

[psv88]

Sticking with my dusting to an inch call out here. 

[MJO812]

Just now, psv88 said:

Sticking with my dusting to an inch call out here. 

That's a good call

[wdrag]

I think strong isentropic lift with sw jet at 7H/8H in the Virginia's with 8H trying to form a low in PA-NJ by 00z/7. The mesoscale models are holding onto the trough structure longer as we come toward T0 (Monday)...  so presuming it has the upper low right in the OV, it wont disappear as fast as modeled-mushed by the globals. 

There wont be much northerly BL flow into the system prior to its arrival on the 6th so dry air advection I dont think is a player. It has basically what is out there now, a 15-20 degree T/Td spread.  It will take awhile for snow aloft in any CSI Band to work down to the ground up here around I80.  There may be some small ocean effect contribution along the NJ coast?

I have to think the globals will drift north tomorrow... or I've interpreted wrong.

 First thing I have to see is there Canadian come way north. Just not what I expected from the Canadian (GDPS-RGEM).  For now I think it the southerly outlier.   

 

That's it for me tonight.  Thanks for the MDL NBM reply.

 

[hudsonvalley21]

8 minutes ago, wdrag said:

I think strong isentropic lift with sw jet at 7H/8H in the Virginia's with 8H trying to form a low in PA-NJ by 00z/7. The mesoscale models are holding onto the trough structure longer as we come toward T0 (Monday)...  so presuming it has the upper low right in the OV, it wont disappear as fast as modeled-mushed by the globals. 

There wont be much northerly BL flow into the system prior to its arrival on the 6th so dry air advection I dont think is a player. It has basically what is out there now, a 15-20 degree T/Td spread.  It will take awhile for snow aloft in any CSI Band to work down to the ground up here around I80.  There may be some small ocean effect contribution along the NJ coast?

I have to think the globals will drift north tomorrow... or I've interpreted wrong.

 First thing I have to see is there Canadian come way north. Just not what I expected from the Canadian (GDPS-RGEM).  For now I think it the southerly outlier.   

 

That's it for me tonight.  Thanks for the MDL NBM reply.

 

Nice write up Walt, it will be interesting too see what the next few model runs show. Have a good night.

[Franklin0529]

Hrr is more north an amped. The models are starting to see the confluence over the NE is weaker then modeled couple days ago. Still got 40 hrs till this thing gets here. 

[MJO812]

7 minutes ago, Franklin0529 said:

Hrr is more north an amped. The models are starting to see the confluence over the NE is weaker then modeled couple days ago. Still got 40 hrs till this thing gets here. 

Yep snow gets up just north of NYC

[jm1220]

1 hour ago, psv88 said:

Sticking with my dusting to an inch call out here. 

 Car topper/coating. The south shore may get 0.5-1”. I guess something is better than nothing but nothing is very possible too if the dry air is underestimated which happens frequently. 

[jm1220]

8 minutes ago, Franklin0529 said:

Hrr is more north an amped. The models are starting to see the confluence over the NE is weaker then modeled couple days ago. Still got 40 hrs till this thing gets here. 

HRRR can be too amped at long range. It’s not useful for probably another 18 hours. 

[MJO812]

Just now, jm1220 said:

 Car topper/coating. The south shore may get 0.5-1”. I guess something is better than nothing but nothing is very possible too if the dry air is underestimated which happens frequently. 

Sometimes the models overdo the confluence just to have it lift out quicker on the models as the storm is near.

[MJO812]

Rap

[Franklin0529]

1 minute ago, jm1220 said:

 Car topper/coating. The south shore may get 0.5-1”. I guess something is better than nothing but nothing is very possible too if the dry air is underestimated which happens frequently. 

It'll be more then that, look how strong the primary is. The confluence is lifting more an more every run. This thing is coming back north 2-4" from city south