Snowfall NYC subforum Jan 6 and OBS if needed

[wdrag]

We're lucky we have this modeling.  I've made no Dr appt decisions for my life next Monday, but I think Philly-BWI need to be planning alternate Monday morning options. 

[wdrag]

Just now, Snowlover11 said:

meh euro and gfs shifting back south. Us northern folk will be sniffing flurries.

Maybe so,  but you haven't been sniffing much the past couple of years...  at least there is an option on the table just ahead.  Very little thereafter Jan 7-13. I'm counting on 1/4-2" CP until I see a decided ensemble shift south. 

[RU848789]

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.

[Allsnow]

There was an event last January around this time of the month. I believe I got 2 here in Metuchen while NYC got around an inch. Phl and snj did the best with 3-6. Wouldn’t be shocked if thats how this plays out Monday 

[donsutherland1]

There appears to be a significant disconnect between the snowfall forecast and QPF forecast on the National Blend of Models. Even where zero QPF is forecast, snow is forecast. I'm not aware of this issue having occurred with the prior version (4.1).

I suspect that there is an adjustment algorithm concerning the edge of the snow shield that is leading to this disconnect. Taken literally, NYC would see 95:1 snow-liquid ratios. More than likely, either the QPF will prove to be higher or the snowfall will prove to be lower. Perhaps the disconnect will also disappear as the event grows nearer.

[RU848789]

4 minutes ago, donsutherland1 said:

There appears to be a significant disconnect between the snowfall forecast and QPF forecast on the National Blend of Models. Even where zero QPF is forecast, snow is forecast. I'm not aware of this issue having occurred with the prior version (4.1).

I suspect that there is an adjustment algorithm concerning the edge of the snow shield that is leading to this disconnect. Taken literally, NYC would see 95:1 snow-liquid ratios. More than likely, either the QPF will prove to be higher or the snowfall will prove to be lower. Perhaps the disconnect will also disappear as the event grows nearer.

Look at the two maps I just posted above - significant disconnect, clearly, especially since it's the National Weather Service Blend of Models.  I'm glad I'm not the one having to make this forecast, lol.  

[wdrag]

8 minutes 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.  

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.

Regarding this AFD quote.  Go back to 316PM yesterday... similar.  Continuity.  Conservative approach.  2" in rush hour Phill Monday morning is advisory imo despite criteria, even the conservative view.  Doesn't snow much in Philly these days... big return to work day and GFS GGEM ECMWF all subfreezing. 

 

Using clusters: gotta make the right cluster call.  For now,  I wouldn't be downplaying PA-NJ and even NYC on the edge. Folks should be planning Philly south, maybe even up to I80.  Right now, no change in my I80 Dr appt but monitoring, 

[RU848789]

9 minutes ago, Allsnow said:

There was an event last January around this time of the month. I believe I got 2 here in Metuchen while NYC got around an inch. Phl and snj did the best with 3-6. Wouldn’t be shocked if thats how this plays out Monday 

Well, CPK got 2.3" last Jan, while we got 7.3" (2.0" on 1/2, 2.4" on 1/15 and 2.9" on 1/19) and they only got 7.5" all winter while we got 24.6" in Metuchen, which was an insane difference.  

[RU848789]

2 minutes ago, wdrag said:

Regarding this AFD quote.  Go back to 316PM yesterday... similar.  Continuity.  Conservative approach.  2" in rush hour Phill Monday morning is advisory imo despite criteria, even the conservative view.  Doesn't snow much in Philly these days... big return to work day and GFS GGEM ECMWF all subfreezing. 

 

Using clusters: gotta make the right cluster call.  For now,  I wouldn't be downplaying PA-NJ and even NYC on the edge. Folks should be planning Philly south, maybe even up to I80.  Right now, no change in my I80 Dr appt but monitoring, 

Yes, I noticed that - they actually upgraded their probabilities of snow from yesterday at 4 pm to today at 4 am in the AFD, but they're still "conservative" from a prediction perspective wanting to maintain continuity with previous forecasts, but the problem is that they're not being "conservative" at all with regard to alerting the public - a conservative approach there would be to play up the threat at least a bit so people aren't surprised on Monday if there's 1-2" in NNJ/NYC and 2-3" in CNJ.  

[wdrag]

8 minutes ago, RU848789 said:

Yes, I noticed that - they actually upgraded their probabilities of snow from yesterday at 4 pm to today at 4 am in the AFD, but they're still "conservative" from a prediction perspective wanting to maintain continuity with previous forecasts, but the problem is that they're not being "conservative" at all with regard to alerting the public - a conservative approach there would be to play up the threat at least a bit so people aren't surprised on Monday if there's 1-2" in NNJ/NYC and 2-3" in CNJ.  

Agree 100%.  NWS general field office approach differs from NHC.  It's definitely not my approach to well advertised multi modeling.  

NWS was pretty happy to see me go, at least at field level where I was generally pushing the envelope to get alerting going. I thought LWX was advanced in leading these winter situations as NHC in tropical. 

Automation will end this personal - institution conservative approach...  it has to be coming as progress is made.  These AMWX discussions will become moot I think in a few years, at least inside 7 days...  presuming the monies are available for research, platform improvement and processing.  Then I can sleep later.

Right now, reliably accurate interpreting voices are needed to get planning considerations on the table, sooner than saying nothing. I

[Allsnow]

27 minutes ago, RU848789 said:

Well, CPK got 2.3" last Jan, while we got 7.3" (2.0" on 1/2, 2.4" on 1/15 and 2.9" on 1/19) and they only got 7.5" all winter while we got 24.6" in Metuchen, which was an insane difference.  

It was the 1/19 event that had a sharp cutoff just to our north 

[RU848789]

3 minutes ago, wdrag said:

Agree 100%.  NWS general field office approach differs from NHC.  It's definitely not my approach to well advertised multi modeling.  

NWS was pretty happy to see me go, at least at field level where I was generally pushing the envelope to get alerting going. I thought LWX was advanced in leading these winter situations as NHC in tropical. 

Automation will end this personal - institution conservative approach...  it has to be coming as progress is made.  These AMWX discussions will become moot I think in a few years, at least inside 7 days...  presuming the monies are available for research, platform improvement and processing.  Then I can sleep later.

Right now, reliably accurate interpreting voices are needed to get planning considerations on the table, sooner than saying nothing. I

Thanks for the insights. 

Unfortunately, if certain folks in the incoming administration have their way, we might not have a NWS any more or at least not one that makes forecasts - perhaps they'll only be the collector/provider of data for private firms to use for their paid forecasts.  I hope it doesn't come to that as I've always liked having professional mets at the NWS offices with great general meteorological knowledge paired with strong local knowledge of the area's weather.  

[Allsnow]

 

[wdrag]

5 minutes ago, RU848789 said:

Thanks for the insights. 

Unfortunately, if certain folks in the incoming administration have their way, we might not have a NWS any more or at least not one that makes forecasts - perhaps they'll only be the collector/provider of data for private firms to use for their paid forecasts.  I hope it doesn't come to that as I've always liked having professional mets at the NWS offices with great general meteorological knowledge paired with strong local knowledge of the area's weather.  

I like that too....  if its shared with the public outside of an AFD.  It needs to be in print-graphics.  Not happening as well as it could be.  

 

I just think we do not help the public prepare as much as could with all the tools available as added here.  We're behind. 

Tomorrow afternoon event also an example.  

My last on this as I need get back to the basics of what will happen or not up here next Monday. 

[mikem81]

NAM can start to be used out to 60 hours or so for trends. Looks like tronger vort in the central US and less confluence than 6Z in SE canada

[RU848789]

29 minutes ago, Allsnow said:

It was the 1/19 event that had a sharp cutoff just to our north 

A bit off topic, but below was my recap for the 1/19 event (for my email lists/FB/other non-weather forums - I post a lot more in those places than here, since most posters here are pretty knowledgeable), discussing that sharp cutoff and the graphic that showed it pretty clearly.  We got very lucky in Metuchen for this one.  

Brief Recap of 1/19 Event: The NWS forecast was excellent for everyone about 5-10 miles south of 78 and south of there, with 2-4” from there down to about 276/195 and a general 4-6” from along 276/195 down through the rest of SEPA, SNJ, DE, MD, etc., as that’s where the Norlun Trough set up.  As I feared from just south of 78 northward, the NWS forecast busted, as snowfall was 1-2” near 78 and generally <1.5” N of 78, including <1” for almost all of NENJ, NYC, SENY and LI; the exception was Sussex/Poconos where 2-3” fell.  We got very lucky in Metuchen, where we got 2.9” vs. my forecast of 3.3” at my house, as the radar showed the moderate to heavy echoes including us, but slammed shut just a few miles north of me (too much dry air to the north), which is why Clark, just 6 miles north of me only got about 1”.  So, NYC continues its snow futility, but Trenton, Philly, Wilmington, Baltimore and DC all got 4” or more, breaking their snow futility streaks, as per the 2nd graphic below. 

[Allsnow]

3 minutes ago, Stormlover74 said:

Icon looks slightly south

Further north on weather bell maps 

 

2-3 into nyc 

[Stormlover74]

Icon looks really good. Much more expansive precip shield

[Stormlover74]

Just now, Allsnow said:

Further north on weather bell maps 

 

2-3 into nyc 

Yeah it was initially south but came further north and looks much better

[MJO812]

Just now, Stormlover74 said:

Icon looks really good. Much more expansive precip shield

 

[Allsnow]

4 minutes ago, Stormlover74 said:

Icon looks really good. Much more expansive precip shield

Close to .50+ of qpf for us 

[Stormlover74]

3" line up to 78 using 10:1

[BoulderWX]

I’m not currently on board with ICON depiction but it begins to show us our envelope. Icon probably the best case scenario for this sub forum. Worst case is obviously being completely dry. verbatim, icon is a nice 3-6 event for most 

[mikem81]

1 minute ago, BoulderWX said:

I’m not currently on board with ICON depiction but it begins to show us our envelope. Icon probably the best case scenario for this sub forum. Worst case is obviously being completely dry. verbatim, icon is a nice 3-6 event for most 

I have no idea how this will play out but the ICON actually makes perfect sense. There is an area of Warm air advection precip that thumps the northern precip shield while a coastal takes over. There is a dry slot in between. Classis SWFE precip shield. Its just a matter of where the WAA makes it up to and where and when the coastal moves the energy to the coast.

[Big Jims Videos]

Icon with a much slower exit as some Atlantic moisture lingers over Jersey. Interesting solution. 

[Stormlover74]

10 minutes ago, BoulderWX said:

I’m not currently on board with ICON depiction but it begins to show us our envelope. Icon probably the best case scenario for this sub forum. Worst case is obviously being completely dry. verbatim, icon is a nice 3-6 event for most 

Yeah it is the icon after all. I don't expect the gfs to follow suit

[Allsnow]

 

[MGorse]

1 hour ago, wdrag said:

Agree 100%.  NWS general field office approach differs from NHC.  It's definitely not my approach to well advertised multi modeling.  

NWS was pretty happy to see me go, at least at field level where I was generally pushing the envelope to get alerting going. I thought LWX was advanced in leading these winter situations as NHC in tropical. 

Automation will end this personal - institution conservative approach...  it has to be coming as progress is made.  These AMWX discussions will become moot I think in a few years, at least inside 7 days...  presuming the monies are available for research, platform improvement and processing.  Then I can sleep later.

Right now, reliably accurate interpreting voices are needed to get planning considerations on the table, sooner than saying nothing. I

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

[ForestHillWx]

The Icon depiction would argue for a decent storm; Miller B with a decent coastal starting up. 

[jm1220]

2 minutes ago, Allsnow 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.