OT: Major winter storm 3/20-21?

29PAS

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Snow lover here in Manhattan. I'm hoping this will be a good one here as the last three have left nothing on the ground around my part of town. And I say this knowing that what I want or wish for has no impact at all on what's going to happen. I do understand that it makes things difficult, can be dangerous and that a lot of people don't like it and/or get tired of it. Personally, I just like it.

I've lived in New Hampshire, both northern and southern Maine and eastern Canada (New Brunswick) and loved the winters there.

And keep up the good work #'s, bac and the others who contribute - I rely on the info you provide and pass it on to others and we're all grateful.
 
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RU848789

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Lee Goldberg finally upped his forecast to 10-14" for basically Philly to Sandy Hook and then central Nassau on the SE side and the SE Warren/Sussex county borders to about Danbury CT on the NW side, with 6-10" for points SE and NW of that swath.

Nick Gregory had a wider area of 9-14" from Belmar to Glassboro on the SE side to Allentown, PA to Newburgh, NY on the NW side and areas of 6-9" on the SE of that swath and the NW of that swath (less precip N/W and some mixing S/E). Both are pretty consistent with each other and a little lower than the NWS - I like their forecasts. Sticking with my 12" prediction for my house.
 

DJ Spanky

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Why, this afternoon, did the Philly office up their snow totals to the north, but bordering the same area the NYC office dropped theirs?



 

RU848789

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the 3K nam is wonky south of Trenton..interesting...really moves the axis of heaviest snows from central jersey on north...yet another evolution

'
earthlight explained that one pretty well. The NAM had over 1/2" of liquid equivalent fall by now in much of SNJ, but they probably only have 1-2" to show for it and that precip is now subtracted from the 6 hour later model, as it already fell. He can't explain why the RGEM shows less snow everywhere now, though - models do go through blips - other models are still showing a lot of snow...
 
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bac2therac

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'
earthlight explained that one pretty well. The NAM had over 1/2" of liquid equivalent fall by now in much of SNJ, but they probably only have 1-2" to show for it and that precip is now subtracted from the 6 hour later model, as it already fell. He can't explain why the RGEM shows less snow everywhere now, though - models do go through blips - other models are still showing a lot of snow...

I have a feeling that we are more in a 8-12 range than the 18 inches on that Mt Holly map, not sure why they are going there...thinking long duration snow that will not have the banding like last time...some heavy bands but probably more moderate, do we get compaction thats the issue....i heard the HRRR is warm for what its worth
 

kyk1827

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I have a feeling that we are more in a 8-12 range than the 18 inches on that Mt Holly map, not sure why they are going there...thinking long duration snow that will not have the banding like last time...some heavy bands but probably more moderate, do we get compaction thats the issue....i heard the HRRR is warm for what its worth
Any guess on what we might get in paramus?
 

RU848789

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I have a feeling that we are more in a 8-12 range than the 18 inches on that Mt Holly map, not sure why they are going there...thinking long duration snow that will not have the banding like last time...some heavy bands but probably more moderate, do we get compaction thats the issue....i heard the HRRR is warm for what its worth
Agree and as I said when they upped their totals this afternoon, " I think the NWS is being a little too aggressive with snowfall totals, by a few inches. I’m “only” predicting 12” for my house in Metuchen." I think what they had, around 10-14" was a better call - I would've waited to see 00Z models tonight before jumping to 12-18". But then again, the 12-18" call may still be right.
 

RUChoppin

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My wife's job in Edison still hasn't canceled, and they're expecting her in by 8am - and expecting patients to show up. I'm hoping that some snow hits a bit earlier and gets them to reconsider - because the last thing they need is people getting into work to then have to fight their way home at 10 am in heavy snow.

My wife's going to call out anyway - will just be a difference of an emergency day with no pay vs. a snow day with pay. But there are three other people who work in that office who are planning to go in.
 

RU848789

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Why, this afternoon, did the Philly office up their snow totals to the north, but bordering the same area the NYC office dropped theirs?



Send them a note and ask - I made the same comment when the maps came out. They're supposed to collaborate with neighboring offices to avoid major discontinuities, although to be fair, the swaths are the same (all in 12-18"), while the city numbers look pretty discontinuous.
 

RU848789

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Ok, off the soapbox and back to the weather (but thanks for the support, folks!). Let's do the 00Z model suite in this post. First up is the 00Z NAM. Yeah, there's some odd looking lesser amounts/almost discontinuities, but these are likely aberrations from convective feedback, as it just doesn't make sense for the output to not be a bit smoother.



00Z 3 km NAM (high resolution); both NAMs show the axis of heaviest snow moving a bit NW, but the NAM has been bouncing around, so unless other models show it, I'd ignore that part of it. Still a huge snowstorm.



The 00Z RDPS/RGEM, showing noticeably less precip for almost everywhere - not sure why and neither are the pros, as far as I can tell.



00Z GFS - also with a bit less snow for most...could be a real trend or could be something the models are "seeing" that isn't represented accurately (like maybe flawed data inputs), but affects the output (it happens). We're almost at radar watching/nowcasting anyway...



00Z GDPS/CMC is less than it was earlier, but is still pretty substantial for most.



The 00Z HRDPS (high res version of the RDPS) was pretty healthy still, although a fair amount less for CNJ vs. 18Z. Wondering if we're seeing real trend, possibly related to the best precip now being modeled further north.



00Z UK still a good hit of over a foot for most, but less than 12Z..

Bumping since the quoted post has all the 12Z model runs and...

Well, it's pretty clear to me that we've seen a small to modest downward trend in almost all of the models runs tonight, especially for CNJ/SNJ/Philly (not as much for NNJ/NYC). While the pros always say not to look at snowfall maps too much, I'm not expert enough to analyze upper air maps and trends and figure out what's going on, but I am pretty good at pattern recognition and nearly every 00Z model - Euro GFS, UK, CMC, RDPS (RGEM), and HRPDS (high res RPDS) - showed a modest to occasionally significant decrease in snowfall vs. 18Z or 12Z. Only the NAM 12 km and 3 km looked similar, at least for CNJ/NNJ/NYC. In fact the Euro showed a 30-40% reduction in snowfall for most; from 10-16" to 6-10". Ouch. But earthlight a brilliant pro on 33andrain said its solution made no sense and to toss it.

On 33andrain I posted about this and asked if it's truly meaningful. I think it is and others have been saying it is, but nobody has really addressed my question yet. I mostly am wondering if this will be the extent of the reduction or might we be facing more. At some point, if we don't get near the 1-2" per hour rates being advertised for 2 days now, we're going to see some white rain, even with better surface temps than the previous nor-easters and that will reduce accumulations even more (and if we don't get as good a level of crystal growth, we also might not reach 10:1 as I was hoping, given good column thermal profiles). Don't get me wrong - getting 6-10" in March would still be pretty impactful - but not nearly as impactful as the 12-18" NWS forecast.

So, what happens now? Even if we discount the Euro, the other model reductions are at least modest, so I expect forecast reductions to come from the NWS in a couple of hours. I'm guessing they'll drop back to 10-15" for CNJ, NNJ, NYC and LI, but drop further for E PA, Philly/SNJ (maybe to 6-10"), if they don't lean too heavily on the Euro, as 10-14" is defensible from the other models. The funny thing is that would be in line with what I said earlier today, when they upped their totals to 12-18" this afternoon: "I think the NWS is being a little too aggressive with snowfall totals, by a few inches. I’m “only” predicting 12” for my house in Metuchen." I think what they had, around 10-15" was a better call - I would've waited to see 00Z models tonight before jumping to 12-18". Well, we'll see pretty soon what happens. Also, 10-14" is in line with what Lee Goldberg and Nick Gregory, two of the most respected NYC mets were predicting for most of the CNJ/NNJ/NYC/LI area (with less towards Philly and the Shore).

Edit - forgot to post last night's 00Z Euro...

 
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RU848789

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Bumping since the quoted post has all the 12Z model runs and...

Well, it's pretty clear to me that we've seen a small to modest downward trend in almost all of the models runs tonight, especially for CNJ/SNJ/Philly (not as much for NNJ/NYC). While the pros always say not to look at snowfall maps too much, I'm not expert enough to analyze upper air maps and trends and figure out what's going on, but I am pretty good at pattern recognition and nearly every 00Z model - Euro GFS, UK, CMC, RDPS (RGEM), and HRPDS (high res RPDS) - showed a modest to occasionally significant decrease in snowfall vs. 18Z or 12Z. Only the NAM 12 km and 3 km looked similar, at least for CNJ/NNJ/NYC. In fact the Euro showed a 30-40% reduction in snowfall for most; from 10-16" to 6-10". Ouch. But earthlight a brilliant pro on 33andrain said its solution made no sense and to toss it.

On 33andrain I posted about this and asked if it's truly meaningful. I think it is and others have been saying it is, but nobody has really addressed my question yet. I mostly am wondering if this will be the extent of the reduction or might we be facing more. At some point, if we don't get near the 1-2" per hour rates being advertised for 2 days now, we're going to see some white rain, even with better surface temps than the previous nor-easters and that will reduce accumulations even more (and if we don't get as good a level of crystal growth, we also might not reach 10:1 as I was hoping, given good column thermal profiles). Don't get me wrong - getting 6-10" in March would still be pretty impactful - but not nearly as impactful as the 12-18" NWS forecast.

So, what happens now? Even if we discount the Euro, the other model reductions are at least modest, so I expect forecast reductions to come from the NWS in a couple of hours. I'm guessing they'll drop back to 10-15" for CNJ, NNJ, NYC and LI, but drop further for E PA, Philly/SNJ (maybe to 6-10"), if they don't lean too heavily on the Euro, as 10-14" is defensible from the other models. The funny thing is that would be in line with what I said earlier today, when they upped their totals to 12-18" this afternoon: "I think the NWS is being a little too aggressive with snowfall totals, by a few inches. I’m “only” predicting 12” for my house in Metuchen." I think what they had, around 10-15" was a better call - I would've waited to see 00Z models tonight before jumping to 12-18". Well, we'll see pretty soon what happens. Also, 10-14" is in line with what Lee Goldberg and Nick Gregory, two of the most respected NYC mets were predicting for most of the CNJ/NNJ/NYC/LI area (with less towards Philly and the Shore).

Edit - forgot to post last night's 00Z Euro...

NWS reduced snowfall to where I thought they would, i..e., to about 10-14" for most of the 95 corridor and areas within 30-40 miles of there, while they reduced far NWNJ and the Poconos/Lehigh Valley to 6-10", due to less precip and the coast to 6-10", due to mixing (and to only a few inches along extreme SNJ. Still waiting for the NWS NYC map.




Well, no map yet, but surprisingly, NWS NYC still says 12-18" still for most of their area, as per below...

National Weather Service New York NY
446 AM EDT Wed Mar 21 2018

NEAR TERM /UNTIL 6 PM THIS EVENING/...
Upper low continues to march toward the east coast, with
coastal low development noted just east of the Delmarva.

With an expected track of the sfc low near the 40N/70W
benchmark along with strong deep lift and banded precip, the
stage is set or a major winter storm for the area. Colder and
drier air is in place when compared to previous events. Nam, and
lesser extent GFS along with various ensemble members indicate
slight warming aloft for a possible wintry mix over SE LI, and
perhaps SE CT through the morning. The storm has slowed a bit,
and heavier precip will allow for ample cooling to result in a
changeover by afternoon over these eastern locales. Colder air
will be pulled down from the north as the storm deepens.

Elsewhere, NYC metro including NE NJ, the lower Hudson Valley
and into SW CT, would typically be in the bulls eye of heavier
snow conceptually. Always hard to pinpoint any potential bands,
but generally expect 12 to 18 inches across these locations if
everything pans out as expected (track, thermal profiles, etc).

Temps in the 30s remain steady or fall as the heavier snow
commences. Snow ratios look to be at least 10 to 1, and even 13
to 1 or 15 to 1 is possible interior.

The western extent of the precip shield should keep amounts well
NW down slightly, but a foot or more is possible even up across
those locations.

Winds will be quite gusty, with 40+ mph at times possible.
Blizzard conditions are possible at times, just not quite enough
confidence for that upgrade to the hazard.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
As the slow moving storm begins to pull away, heavier snow will
taper from west to east tonight. Once again, 7-12 inches

possible well NW, 12-18 around NYC metro and into SW CT, and
slightly lower totals are expected east due to mixing
initially, and lower snow ratios.


Upton map finally...



The 6Z 12 km and 3 km NAMs are still pretty big hits, so maybe the Euro was an aberration earlier tonight.



 
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jerzey devil

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Oh wait nevermind... I was looking at a San Diego..... But seriously...everyone be safe..Many thanks to RU#'s and Bac for the constant updates... We'll hope for the best..But thanks to these guys, we're prepared for the worst...
 
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Machiavelli23

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#s... quick question.

I am guessing you might have explained it earlier but what is the 10:1, 13:1, 15:1 ratios mean and how do they come about?

Also, what causes the ratios to increase?
 

MadRU

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Started snowing here in Linden. See dusting on car windows and roofs.
 

RU848789

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NWS reduced snowfall to where I thought they would, i..e., to about 10-14" for most of the 95 corridor and areas within 30-40 miles of there, while they reduced far NWNJ and the Poconos/Lehigh Valley to 6-10", due to less precip and the coast to 6-10", due to mixing (and to only a few inches along extreme SNJ. Still waiting for the NWS NYC map.




Well, no map yet, but surprisingly, NWS NYC still says 12-18" still for most of their area, as per below...

National Weather Service New York NY
446 AM EDT Wed Mar 21 2018

NEAR TERM /UNTIL 6 PM THIS EVENING/...
Upper low continues to march toward the east coast, with
coastal low development noted just east of the Delmarva.

With an expected track of the sfc low near the 40N/70W
benchmark along with strong deep lift and banded precip, the
stage is set or a major winter storm for the area. Colder and
drier air is in place when compared to previous events. Nam, and
lesser extent GFS along with various ensemble members indicate
slight warming aloft for a possible wintry mix over SE LI, and
perhaps SE CT through the morning. The storm has slowed a bit,
and heavier precip will allow for ample cooling to result in a
changeover by afternoon over these eastern locales. Colder air
will be pulled down from the north as the storm deepens.

Elsewhere, NYC metro including NE NJ, the lower Hudson Valley
and into SW CT, would typically be in the bulls eye of heavier
snow conceptually. Always hard to pinpoint any potential bands,
but generally expect 12 to 18 inches across these locations if
everything pans out as expected (track, thermal profiles, etc).

Temps in the 30s remain steady or fall as the heavier snow
commences. Snow ratios look to be at least 10 to 1, and even 13
to 1 or 15 to 1 is possible interior.

The western extent of the precip shield should keep amounts well
NW down slightly, but a foot or more is possible even up across
those locations.

Winds will be quite gusty, with 40+ mph at times possible.
Blizzard conditions are possible at times, just not quite enough
confidence for that upgrade to the hazard.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
As the slow moving storm begins to pull away, heavier snow will
taper from west to east tonight. Once again, 7-12 inches

possible well NW, 12-18 around NYC metro and into SW CT, and
slightly lower totals are expected east due to mixing
initially, and lower snow ratios.


Upton map finally...



The 6Z 12 km and 3 km NAMs are still pretty big hits, so maybe the Euro was an aberration earlier tonight.



Some of this is in the quoted thread, but that's a tough one to navigate (even for me and I wrote it, lol). Anyway, I think the probability of a modest to significant bust has increased with the models being less consistent in high snowfall amounts last night and this morning. Could still verify, especially for the lower amounts the NWS-Philly has on their map - the NWS-NYC general 12-18" amounts are just overdone IMHO.

And spring storms are notoriously hard to forecast, especially during the day with the high sun angle, which will melt up to 1/2” per hour snowfall rates during the day and most of this snow will fall during the day – need pretty good snowfall rates to ensure accumulation, especially on paved surfaces and if we don't get the rates we thought we were going to get, it's going to be hard to reach the forecasted targets. We'll see.

TWC just downgraded snowfall forecasts for the big cities; still has 8-12" for NNJ/NYC, but was 12-18" before. Cantore said the inland low closed off and will rob the ocean low of moisture reducing precip (seen on almost every model last night including the Euro).
Here's the fundamental problem in spring. if you get fairly heavy 1" per hour rates for 10 hours, you'll likely get 8-9" of snow, since you'll overcome the melting rate quickly and accumulate rather easily with minimal melting, especially if air temps are below 32F. But if you get moderate 1/2" per hour rates for 10 hours, you probably end up a slushy inch on the ground, since the melting rate is so close to the snowfall rate the entire time.
 
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kyk1827

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Snowing here in Hoboken with gusts of winds. Going to head to work in paramus now. Hope this is a dud!
 

RocktheRac

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Starting snowing in Hillsborough at 7am. Sticking to cars and grass. Not on the roads yet. Went out a 5am for some presalting and looked like less cars on roads than usual.
 

RocktheRac

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I put down some salt on my driveway last night. Was it a waste of time?

Not really. It will hold the snow accumulations down a bit but don't expect it to stay totally clear once the snow rates come down more than the melting rate.
 

bac2therac

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Bust potential for some...but too early to declare. Its definitely more of a possibility but for now err on the side of caution and everyone stay in today..just slight shifts in the track can make a difference. With the storm barely starting we are still hours away to know whats going to happen
 

CodyRU

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Went to work in camden county. Nothing but light rain so far. Fingers crossed for a bust
 

RocktheRac

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Zarrow said new model came out and cut totals but he still looking at snow bands so he still sticking to his 6 to 10.
 

RUChoppin

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Did u use table salt? My driveway is clear and the road by my house in development is clear and they didn't salt yet.
Remember, I'm at a slightly higher elevation than you are. Was already going steadily by 6:45 when we woke up. Put down calcium chloride late last night, and I've got accumulation on about 40-50% of the driveway right now.