Snow Potential Dec 26-27

[Volcanic Winter]

The city, immediate metro, LI, and SW/W CT deserve this one, enjoy it guys. Fairly narrow and overall small fun zone with this one and that’s fine -  hope you had an awesome Christmas for those that celebrate! Nice day after event here.

I’m good with a couple inches if we can squeak that out, brings me up to just about double digits already in Dec - can’t complain about that. 

[WeatherGeek2025]

1 minute ago, Snowlover11 said:

NAM did come south, still sucks from extreme northern nj, westchester, and down. This thing was extremely north before though.

i'll be paying attention to reggie from now on and rap

[eduggs]

I don't think there has been much model flip flopping over the past 48 hours. A few mesos were really suppressed at the end of their ranges initially and the 18z NAM jumped pretty far north. Other than that, most models, esp globals and ensembles, have been pretty consistent.

That should lend confidence. And in fact it does. The problem is there have been plenty of cases in the past where a late shift in a model (often the NAM) heralded a true shift in outcome despite model consensus. These cases being memorable probably biases the memory and skews perceptions of likelihood, but it has and can happen.

[jm1220]

4 minutes ago, TJW014 said:

I think all this flip flopping we're seeing with the models is them trying to simulate where the heaviest banding sets up, rather than how far the warm nose edges in.

Given all the trends today so far, there's little change in temps aloft. For nearly all of us that we stay below freezing up to 700mb until the wee hours of the storm when precip is winding down. 

All these jumps north/south are figuring out the heaviest bands. Lift vs subsidence. Someone's gonna be sitting under a weenie band, and someone 10 miles north or south is going to be screwed. 

The heavy banding would help keep the mid level warm air at bay. The 0z NAM 3k has kinda crappy QPF across the area which you can see in soundings-when precip is patchy/shredded you see the mid level warm air show up more. The major overrunning snow shield overshooting to the NE is always a possibility here. 

[donsutherland1]

4 minutes ago, eduggs said:

Don, I think you know that's not NAM output. That looks like Pivotal 10:1 "clown" map. NAM produces liquid precipitation output and a vertical temperature profile. I believe it also generates a ptype. I recall it did pretty well on all three. Just because you get 0.2" liquid with mostly snowflakes doesn't mean they will accumulate. That's not the NAM's fault. That's user error.

Max temp profile did ok using Bufkit. But these are the maps being posted to make claims about the snowfall (past storm and the upcoming one). Thus, my critique covers those maps. As noted previously, virtually none of the individual EPS and GEFS ensemble members supported the idea that NYC would see < 1” snow from the upcoming system. In fact, the quality guidance has consistently favored a 3”-6”/4”-8” event for the NYC area. 

[dseagull]

7 minutes ago, Volcanic Winter said:

The city, immediate metro, LI, and SW/W CT deserve this one, enjoy it guys. Fairly narrow and overall small fun zone with this one and that’s fine -  hope you had an awesome Christmas for those that celebrate! Nice day after event here.

I’m good with a couple inches if we can squeak that out, brings me up to just about double digits already in Dec - can’t complain about that. 

Ironically,  I think you're going to see the highest QPF, just on the edge of rhe sleetfest.  

 

You're sitting pretty, brother.  Trust me.  This setup is going to offer a surprise.   

[sussexcountyobs]

Clear. Windy. 21.9F

[SomeguyfromTakomaPark]

NAM still a little too bouncy, other models been steadier.  I like the HRRR + globals combo until the NAM settles in to something for 2 runs in a row. 

[eduggs]

1 minute ago, donsutherland1 said:

Max temp profile did ok using Bufkit. But these are the maps being posted to make claims about the snowfall (past storm and the upcoming one). Thus, my critique covers those maps. As noted previously, virtually none of the individual EPS and GEFS ensemble members supported the idea that NYC would see < 1” snow from the upcoming system. In fact, the quality guidance has consistently favored a 3”-6”/4”-8” event for the NYC area. 

You implied the NAM was wrong regarding snowfall last Tue... Not that posters who misinterpret its output were wrong. But you can't hold misinterpretation against the NAM.

I agree with you about this event. The 18z NAM was at or past the outer envelope of ensemble solutions. It also has a tendency to make larger run-to-run changes than other models. That makes its outlier depictions unlikely.

[BoulderWX]

NAM is the only model where I’d be frustrated were it to occur but the I can’t rule it out. NYC, north and east look best ATM as well as LHV

[jm1220]

We have a banter thread, please use it for non-storm related stuff. And the "storm cancel" stuff, I don't care if it's meant in jest, trolling or frustration but I'm removing those. You can go to banter or just not post it. 

[MJO812]

13 minutes ago, BoulderWX said:

NAM is the only model where I’d be frustrated were it to occur but the I can’t rule it out. NYC, north and east look best ATM as well as LHV

Nam caving 

[eduggs]

For what it's worth, the RRFS gets sleet the NJ-NY border, including NYC, after a really good thump. QPF is higher this run, however, and there's likely a little more snow to end. 

[Nibor]

2 minutes ago, MJO812 said:

Nam caving 

It's still showing a substantial warm nose leading to sleet. Everyone should keep that in mind.

[mob1]

Just now, Nibor said:

It's still showing a substantial warm nose leading to sleet. Everyone should keep that in mind.

It's the most likely outcome IMO. Snow to sleet and then maybe back to some light snow. 

These very sharp cutoffs on snow maps juuuuust south of us rarely (if ever) work out in our favor. 

2-4" is what I'm going with now

[jm1220]

4 minutes ago, eduggs said:

For what it's worth, the RRFS gets sleet the NJ-NY border, including NYC, after a really good thump. QPF is higher this run, however, and there's likely a little more snow to end. 

Yep-the thump happens then the snow turns to shredded, and the sleet line advances in. I can't see soundings but verbatim from the sim radar that's what looks like happens. There does seem to be a good shot at hangback snow after the low begins to depart and the cold air returns in the mid levels that could add another inch or two around dawn on Sat. 

Again it's one model's interpretation but IMO it can't just be dismissed. 

[BoulderWX]

Always throw out a guess for each storm - thinking 3.7” and a decent amount of sleet. (Morristown)

27 degrees

[MJO812]

6 minutes ago, mob1 said:

It's the most likely outcome IMO. Snow to sleet and then maybe back to some light snow. 

These very sharp cutoffs on snow maps juuuuust south of us rarely (if ever) work out in our favor. 

2-4" is what I'm going with now

Nam has been horrendous 

Other models have several inches 

[mob1]

RGEM is solid

[BxEngine]

6 minutes ago, mob1 said:

It's the most likely outcome IMO. Snow to sleet and then maybe back to some light snow. 

These very sharp cutoffs on snow maps juuuuust south of us rarely (if ever) work out in our favor. 

2-4" is what I'm going with now

At the risk of causing issues…who is “us”? This is a large geographical forum. 

[North and West]

Always throw out a guess for each storm - thinking 3.7” and a decent amount of sleet. (Morristown)
27 degrees

Fun to see a sleet storm, if that’s what we’re facing. Out of our control.


.

[mob1]

Just now, BxEngine said:

At the risk of causing issues…who is “us”? This is a large geographical forum. 

Sorry, I meant Ant and myself. We live in southern Brooklyn and SI respectively. 

 

[MJO812]

Rgem

[MJO812]

Just now, mob1 said:

Sorry, I meant Ant and myself. We live in southern Brooklyn and SI respectively. 

 

Why are you worried?

[eduggs]

The 0z HRRR and NAM had pretty well defined 700mb lows NORTH of Lake Ontario. They keep the circulation alive almost to Ottawa. That's why they push sleet past Binghamton and briefly to Monticello, NY.

The GFS has a weaker 700mb low that dissipates more quickly. Hence warm air near 700mb doesn't surge as far northeast, keeping the mixing line much further southwest. We can't know for sure what will happen, but the NAM has a track record with mid-level lows.

[mob1]

Just now, MJO812 said:

Why are you worried?

Not worried, just discussing weather. I have no control over what happens, just have lived here long enough to know how this usually goes. 

I'm rooting for us harder than you can imagine, it's normal to be a bit pessimistic given overall trends. 

[sussexcountyobs]

Clear. Breezy. 20.9F

[MANDA]

Company has gone, dishwasher is running and fireplace is still going.  Just getting caught up.

Nothing over the last 6-8 hours has led me to change my forecast for my area.  Still going 3-6".

The 3" covers if NAM has a clue and we get mixing out here and the 6" covers .50" liquid at a little over a 10:1 ratio.  

Feel confident in .40" - .60"qpf.  do with those numbers as you wish.  

Don't see widespread over 6" amounts with the possible exception of the extreme northern fringes of this forum, even there 6" with a few isolated 7 or 8" amounts would be the upper limit, I think.

We'll see how it goes.

Good luck to all.

 

 

 

 

[eduggs]

Those are some hellacious snowfall rates just after 0z on the RGEM. Looks like 2"+ per hour for an hour or two. That would cause some serious problems on the roadways for holiday travelers.

[BoulderWX]

ICON bumps north a bit - not a huge jump but noticeable