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2/13 Significant/Major Winter Storm Discussion & Observations


Northof78
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2 hours ago, jm1220 said:

Happened last 2/28. The south shore had white rain, I had 5” because it was 2-3 degrees colder where I live. The airmass coming into this is quite marginal, that shouldn’t be forgotten either. Maybe this will work out for all of us, who knows, but there are definitely obstacles to be overcome. The odds are still better north of the city. We want it to track a good 100 miles south of the city and for it to be quick developing-not sheared crap like the GGEM so dynamically it can get cold enough. 

If the 6Z GFS is correct for Trenton to NYC along 95, for example (and we have no clue), it's showing 7-8" of 10:1 snow falling from the sky from 10 am to 4 pm with good looking DGZ snow crystal formation/growth, column temps well below 32F until very close to the surface and surface temps around 33F.  Verbatim, that snow is ;likely going to accumulate easily at over 1" per hour rates and will likely do better than the Kuchera algorithm, which treats a 1500 foot deep 33F layer aloft the same as it does a shallow 300 foot 33F layer right at the surface (it only takes max column temp into consideration, not depth=time at that max temp) and those aren't the same, as less partial melting will occur in the latter case, meaning less compaction and loss of good ratios.  If the GFS is correct.

Interestingly, the GEFS shows warmer surface temps of 35-37F during the event, but since it's showing a smoothed mean of many members, the ~6" of snow it shows falls over 9-12 hours, so at maybe 0.5" per hour, which is not nearly as dynamic and that could be why there is less cooling at the surface; at those temps during the day and at lower intensity, though, one would expect a fair amount less snow to accumulate.  One would think the Op is more likely to show dynamics better than the ensemble mean, though.  

Intensity is going to be so important for this storm if the GFS is close to right, especially during the day...

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1 hour ago, donsutherland1 said:

I think the focus on a light event is warranted until there is more support for something bigger. The GFS is too aggressive. Apparently, a social media account compared the upcoming event to the February 1969 Lindsay Storm (15.3” in NYC and 20.2” at JFK). But that account didn’t tell a key part of the story: the temperature for that storm fell from 34 into the middle 20s. Most of the precipitation fell with readings that were below freezing. That’s not the case this time around. Were there a similar air mass, then we’d be looking at a significant snowfall. One other omission, the 1969 storm was much wetter than what is likely this time: NYC: 1.82” and JFK: 2.49”.

I read your post and how to go check to see if it was who I thought it was.  It was.  This person has really gone off the deep end last several years. 

Shame. 

Lindsey Storm :lol:

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5 minutes ago, RU848789 said:

If the 6Z GFS is correct for Trenton to NYC along 95, for example (and we have no clue), it's showing 7-8" of 10:1 snow falling from the sky from 10 am to 4 pm with good looking DGZ snow crystal formation/growth, column temps well below 32F until very close to the surface and surface temps around 33F.  Verbatim, that snow is ;likely going to accumulate easily at over 1" per hour rates and will likely do better than the Kuchera algorithm, which treats a 1500 foot deep 33F layer aloft the same as it does a shallow 300 foot 33F layer right at the surface (it only takes max column temp into consideration, not depth=time at that max temp) and those aren't the same, as less partial melting will occur in the latter case, meaning less compaction and loss of good ratios.  If the GFS is correct.

Interestingly, the GEFS shows warmer surface temps of 35-37F during the event, but since it's showing a smoothed mean of many members, the ~6" of snow it shows falls over 9-12 hours, so at maybe 0.5" per hour, which is not nearly as dynamic and that could be why there is less cooling at the surface; at those temps during the day and at lower intensity, though, one would expect a fair amount less snow to accumulate.  One would think the Op is more likely to show dynamics better than the ensemble mean, though.  

Intensity is going to be so important for this storm if the GFS is close to right, especially during the day...

Nice write up.  It will be interesting when the short range models such as the HRRR and HRDPS are in range. 

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24 minutes ago, RU848789 said:

If the 6Z GFS is correct for Trenton to NYC along 95, for example (and we have no clue), it's showing 7-8" of 10:1 snow falling from the sky from 10 am to 4 pm with good looking DGZ snow crystal formation/growth, column temps well below 32F until very close to the surface and surface temps around 33F.  Verbatim, that snow is ;likely going to accumulate easily at over 1" per hour rates and will likely do better than the Kuchera algorithm, which treats a 1500 foot deep 33F layer aloft the same as it does a shallow 300 foot 33F layer right at the surface (it only takes max column temp into consideration, not depth=time at that max temp) and those aren't the same, as less partial melting will occur in the latter case, meaning less compaction and loss of good ratios.  If the GFS is correct.

Interestingly, the GEFS shows warmer surface temps of 35-37F during the event, but since it's showing a smoothed mean of many members, the ~6" of snow it shows falls over 9-12 hours, so at maybe 0.5" per hour, which is not nearly as dynamic and that could be why there is less cooling at the surface; at those temps during the day and at lower intensity, though, one would expect a fair amount less snow to accumulate.  One would think the Op is more likely to show dynamics better than the ensemble mean, though.  

Intensity is going to be so important for this storm if the GFS is close to right, especially during the day...

is this all your idea ?

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1 hour ago, RU848789 said:

If the 6Z GFS is correct for Trenton to NYC along 95, for example (and we have no clue), it's showing 7-8" of 10:1 snow falling from the sky from 10 am to 4 pm with good looking DGZ snow crystal formation/growth, column temps well below 32F until very close to the surface and surface temps around 33F.  Verbatim, that snow is ;likely going to accumulate easily at over 1" per hour rates and will likely do better than the Kuchera algorithm, which treats a 1500 foot deep 33F layer aloft the same as it does a shallow 300 foot 33F layer right at the surface (it only takes max column temp into consideration, not depth=time at that max temp) and those aren't the same, as less partial melting will occur in the latter case, meaning less compaction and loss of good ratios.  If the GFS is correct.

Interestingly, the GEFS shows warmer surface temps of 35-37F during the event, but since it's showing a smoothed mean of many members, the ~6" of snow it shows falls over 9-12 hours, so at maybe 0.5" per hour, which is not nearly as dynamic and that could be why there is less cooling at the surface; at those temps during the day and at lower intensity, though, one would expect a fair amount less snow to accumulate.  One would think the Op is more likely to show dynamics better than the ensemble mean, though.  

Intensity is going to be so important for this storm if the GFS is close to right, especially during the day...

If it snows heavily it will crash down to 32-33, I’ve never seen heavy snow before with 35-36. It’s really a question of the storm track along with intensity. If it’s sheared out like GGEM/UKMET very few will be happy anywhere. The ensemble members with lower resolution would probably show a less intense system in general. But they’re good in terms of showing overall trends and probabilities. 

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Just now, Allsnow said:

It’s not done…congrats NNE. 
 

The Good news is that the dry nonsense was oversold for after this week and the north trend isn’t going anywhere 

How do you know it's not done ? There is so much north this can go.

Why are people dismissing this on this forum ?

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2 minutes ago, Allsnow said:

Icon way north and gfs jumping on to that idea at 12z. 

For now, that's not a bad place to have it, but ideally, we'd like to see some more confluence pushing down, as we know these storms tend to have a north and west trend leading up to impact. I'd expect this trend to continue.

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I DONT like where the GFS has gone the last few runs with the northern interaction pulling the LP into PA before transferring to the coast. That never ever works for NYC. The current CMC track however gives me some comfort...The EURO at 12Z will be big. If it goes north again, we are in trouble in the metro area

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3 minutes ago, Allsnow said:

Because is phasing with a lobe off the tpv now 

Absolutely. Even if all the changes haven't been reflected in the surface yet, looking at the upper levels, when there is more phasing, there will be further north movement. 

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Its totally anecdotal but I swear anytime we have confluence issues the CMC seems to nail the idea in the medium range...could be due to some type of added sampling in Canada perhaps but I seem to recall so many cases where we had squashing/meat grinder concerns on the table and the CMC was pounding the idea over the Euo/GFS it tended to have some merit in the end result.

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Well, the GFS has moved the southern extent of 6"+ snow (at 10:1 ratios - maybe not a good assumption) north about 75 miles since 0Z, such that the 95 corridor from Trenton to NYC is now much closer to the "it gonna rain" line vs. 6Z and 0Z last night.  However, If folks want to know what a trend looks like, I give you the CMC, lol, as it's come hundreds of miles south over the last 36 hours.  But at the end of the day both the 12Z GFS and CMC are at least much closer to each other than they've been, so there's that.  

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