Snowfall NYC subforum Jan 6 and OBS if needed

[MGorse]

2 hours ago, RU848789 said:

Interesting that the NBM snowfall forecast bumped up for 07Z vs 01Z last night and yet the NWS-Philly is clearly downplaying the event potential north of Philly, as per the part I bolded below, when they often follow the NBM for snow events.  Maybe they're going by the WPC precip forecast and not the NBM snowfall forecast...

@MGorse- any comments on this apparent disconnect?  Just trying to figure out what you guys are thinking, thanks...

National Weather Service Mount Holly NJ

401 AM EST Thu Jan 2 2025

LONG TERM /SUNDAY THROUGH WEDNESDAY/...

Guidance from a synoptic standpoint is depicting a Miller B
nor`easter to develop with an upper level trough swinging a
surface low from west to east across the KY/TN area before
redeveloping as a low pressure system offshore Monday. Ensemble
guidance is split into 2 different clusters with the variance
generally explained by how strong the upper level ridge will be
over Quebec. This boils down into two scenarios, one with a more
northern track bringing snow towards the RDG/TTN/PHL, and one
with a more southern track keeping the snow more over the DC
area. The more northern stream track relies on a weaker high and
thus develops a bit more cyclogensis over our region thus
lifting the band of 2-4 inches of snow further north, whereas in
the southern track, the high is stronger and displaces the
surface low to the south more leading to most of the area seeing
little in the way of snow.

01Z/02 NBM generally is taking a blend of the two scenarios thus
leads to probabilities similar to the 13z/01 NBM with snowfall
greater than 1 inch is 60 to 80 percent across southern New
Jersey, the Delaware Valley including Philadelphia, and the
eastern shores of Maryland and Delaware while the probability of
snowfall greater than 3 inches is 40 to 50 percent. North of
Philadelphia, probabilities lower to 30 to 50 percent for
greater than 1 inch of snow and 20 to 30 percent for greater
than 3 inches of snow.

For the time behind will continue to show a blend of the two
tracks but anticipate that the gradient of snowfall will sharpen
quickly somewhere north of Philadelphia over the coming runs
depending on how guidance handles the upper level ridge. While
it is still too soon to tell how much snow will fall, the trend
looks to be for advisory level snowfall for Delmarva, sub-
advisory amounts for southeast New Jersey and the Delaware
Valley, and minimal amounts north of Philadelphia.

 The NBM is not the greatest guidance many times and I will leave it at that.

[RU848789]

1 minute ago, MGorse said:

 The NBM is not the greatest guidance many times and I will leave it at that.

Enough said, thanks.  My one comment for the author of that AFD would be to perhaps address the NBM/precip inconsistency, especially given how often the NBM is invoked by the NWS as a major aid in forecasts.  

[wdrag]

8 minutes ago, MGorse said:

You want to come back? We are still short staffed! 

Sure.  You can do all the Severe.  My fingers don’t work as quickly as yours and my severe detection is not up to snuff   Keep me posted 

[tristateweatherFB]

10 minutes ago, MGorse said:

You want to come back? We are still short staffed! 

You should hire taller people. 

[MGorse]

1 minute ago, RU848789 said:

Enough said, thanks.  My one comment for the author of that AFD would be to perhaps address the NBM/precip inconsistency, especially given how often the NBM is invoked by the NWS as a major aid in forecasts.  

That inconsistency has been noticed by some NWS field offices, but I am not aware of where that stands. In my opinion if something like this NBM stuff is referenced in things like AFDs then some added info should be included to provide more context of that data. The deterministic NBM is bias corrected (60 days I believe) which results in a lag especially during pattern changes. Still not all that sure why a blend of models has a bias correction applied. 

[MJO812]

Gfs ticking north

[MGorse]

3 minutes ago, wdrag said:

Sure.  You can do all the Severe.  My fingers don’t work as quickly as yours and my severe detection is not up to snuff   Keep me posted 

And you were not the only one at PHI to push the envelope on alerting. We have made some progress on that but still work to be done. Not an easy task either when staffing keeps changing. 

[MGorse]

7 minutes ago, tristateweatherFB said:

You should hire taller people. 

I see what you did there. 

[Allsnow]

Nice bump North of the gfs 

[Allsnow]

Gfs lingers snow like the icon now 

[NEG NAO]

4 minutes ago, MJO812 said:

Gfs ticking north

notice the 540 line makes it up to North of Atlantic City - this is a good look with still 100 hours to go

[Allsnow]

22 minutes ago, jm1220 said:

Fingers crossed but we’ll see. If there’s the confluence brick wall it won’t matter how much moisture this storm brings. If the upper air flow over us is from the W or N, it will get shunted away. 2/6/10 also had a lot of moisture in a strong El Niño. NYC had flurries to 2”, PHL had 2 feet. These confluence setups always drop the immovable brick wall somewhere. We need to see it let up or the S/W notably strengthen and nudge the confluence N to have a chance. 

No high pressure to the north will help in this situation 

the swfe always come north 

[Stormlover74]

Just now, NEG NAO said:

notice the 540 line makes it up to North of Atlantic City - this is a good look with still 100 hours to go

we're only 30-50 miles from warning criteria snowfall

[MJO812]

Cmc 

[RU848789]

4 minutes ago, Allsnow said:

Nice bump North of the gfs 

Yessiree!  That along with the ICON getting much snowier for areas N of 276/195 are good signs...

[Allsnow]

Here comes the north trend 

[Stormlover74]

still pretty light on the cmc but did nudge north

[Allsnow]

2 minutes ago, Stormlover74 said:

still pretty light on the cmc

2 inch line is to the south shore and nyc 

 

6-10 for snj/phl 

[MJO812]

Just now, Allsnow said:

2 inch line is to the south shore and nyc 

 

6-10 for snj/phl 

Very close

[Stormlover74]

Just now, Allsnow said:

2 inch line is to the south shore and nyc 

 

6-10 for snj/phl 

yep still plenty of time to get heavier amounts up here...or go back south and give us flurries. but hopefully the north trend will continue

[forkyfork]

jumpy but a general wnw trend with that pv lobe

[mikem81]

This was a good start to the 12Z lineup keeping in mind the normal trend on SWFE events is a north bump inside of 72 hours. I would want to be around 50 miles north of the heaviest snow axis at this point. 

[RU848789]

A small uptick on the CMC and later precip too...warning snows south of 276/195 and advisory snows from there up to 78, i.e., all of CNJ.  

[Stormlover74]

1 minute ago, mikem81 said:

This was a good start to the 12Z lineup keeping in mind the normal trend on SWFE events is a north bump inside of 72 hours. I would want to be around 50 miles north of the heaviest snow axis at this point. 

yeah I wouldn't really want to be too far south of DC with this

[Allsnow]

1 minute ago, Stormlover74 said:

yeah I wouldn't really want to be too far south of DC with this

Going to be a nasty dry slot after a thump of snow around that area. 

[Stormlover74]

Just now, Allsnow said:

Going to be a nasty dry slot after a thump of snow around that area. 

or more mixing if the low keeps trending north

[forkyfork]

1 minute ago, Allsnow said:

Going to be a nasty dry slot after a thump of snow around that area. 

day 4 and we're on the northern fringe

[NEG NAO]

3 minutes ago, mikem81 said:

This was a good start to the 12Z lineup keeping in mind the normal trend on SWFE events is a north bump inside of 72 hours. I would want to be around 50 miles north of the heaviest snow axis at this point. 

 

3 minutes ago, Stormlover74 said:

yeah I wouldn't really want to be too far south of DC with this

Also wouldn't want to be near the South Jersey Coast mixing issues there

[NEG NAO]

1 minute ago, forkyfork said:

day 4 and we're on the northern fringe

do you think there is still a possibility of everything trending south again ?

[North and West]

Why don’t we just go with the model that gives us our own preferred selfish solution


.