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February 20 - 21 Winter Storm Threat


NEG NAO

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4 minutes ago, RU848789 said:

Nice improvements on the 12Z Euro: 4-6" for most of CNJ/E PA and 3-4" for NYC/NE NJ (in Upton's CWA).   4" line runs from the NW Warren/Sussex border down to midtown Manhattan and then to JFK, roughly; a 2nd 4" line runs from about Baltimore to Wilmington and then over to about LBI, with everything in between those lines in the 4-6" swath in NJ and PA all the way out to Central PA (where it eventually gets to 6-8").  Like it.  3" line runs from about Middletown, NY to Stamford, CT and down to about Brookhaven, LI.  As modeled.  

Is that assuming 10:1 snow? 

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10 minutes ago, CarLover014 said:

Is that assuming 10:1 snow? 

Weather.us output just says "accumulated snow" but doesn't say it's 10:1 basis or if it includes sleet; however, the amount of "snow water equivalent" of 10-14 mm for the general area that's in the 4-6" swath is pretty consistent with 4-6" of 10:1 ratio snow.   

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19 minutes ago, RU848789 said:

Nice improvements on the 12Z Euro: 4-6" for most of CNJ/E PA and 3-4" for NYC/NE NJ (in Upton's CWA).   4" line runs from the NW Warren/Sussex border down to midtown Manhattan and then to JFK, roughly; a 2nd 4" line runs from about Baltimore to Wilmington and then over to about LBI, with everything in between those lines in the 4-6" swath in NJ and PA all the way out to Central PA (where it eventually gets to 6-8").  Like it.  3" line runs from about Middletown, NY to Stamford, CT and down to about Brookhaven, LI.  As modeled.  

Lets hope the north trend continues. Won't take much to get those heavier snows up into NYC metro.

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20 minutes ago, CarLover014 said:

Is that assuming 10:1 snow? 

Based on soundings and these sort of events it’s generally 10:1.  You might be 12:1 for a time when it first begins and snow is very light but the 2-3 hours before you transition it’s generally 10:1 or even 9:1 maybe at the very end.  The 700-850 temps are always fairly warm so even if you’re 25-28 at the surface ratios aren’t great.  NAM soundings if you assume WAA is underdone suggest we could start mixing at 22Z though many models say it doesn’t happen til 00-01

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Should be mostly frozen/snow through 0z for the city, NEPA, western Jersey (except south).  Thinking 2-4" as a guess, you're on the higher side of that in PA.  Warm nose probably a bit further north, same with main frontogen forcing as we tend to see in these types of setups.

 

OKX not having a single WWA seems weird to me.  Figure the overnight crew will have to do the lifting.

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Despite most of the models showing an increase in snowfall vs. last night (including the Euro, which is now showing 3-6" for all of the Philly-NYC corridor and CNJ/NNJ/NYC), the NWS-Philly actually decreased snowfall amounts for most of SE PA, SNJ, CNJ and NNJ and issued advisories for most locations for 1-3"/2-4" amounts (2-4" for Philly/SE PA; 1-3" for Trenton to Woodbridge, including all of CNJ to the coast). Some sleet is possible, as is a light glaze of freezing rain for most locations. 

A little surprised they didn't at least go with 2-4" to maybe 3-5" area wide, which is still just advisory level snow (warnings are for 6" or more N of 195/276 and for 5" or more for S of 195/276). NWS-NYC hasn't updated their area yet and no snowfall maps are up yet. Soon - more to come. Below and link is to advisories. 

https://forecast.weather.gov/wwamap/wwatxtget.php?cwa=okx&wwa=winter weather advisory

Map of Forecast Area

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2 minutes ago, RU848789 said:

Despite most of the models showing an increase in snowfall vs. last night (including the Euro, which is now showing 3-6" for all of the Philly-NYC corridor and CNJ/NNJ/NYC), the NWS-Philly actually decreased snowfall amounts for most of SE PA, SNJ, CNJ and NNJ and issued advisories for most locations for 1-3"/2-4" amounts (2-4" for Philly/SE PA; 1-3" for Trenton to Woodbridge, including all of CNJ to the coast). Some sleet is possible, as is a light glaze of freezing rain for most locations. 


https://forecast.weather.gov/wwamap/wwatxtget.php?cwa=okx&wwa=winter weather advisory

Map of Forecast Area

They're seeing the warm nose further north, which I think is the prudent call given what has been going on down south.  If main frontogen band is further north, likelihood of warm nose being further north than progged too.  There's a much higher risk of a quicker mix in PHL and SEPA into SWNJ.

Not an easy forecast at all down there.

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4 minutes ago, NittanyWx said:

They're seeing the warm nose further north, which I think is the prudent call given what has been going on down south.  If main frontogen band is further north, likelihood of warm nose being further north than progged too.  There's a much higher risk of a quicker mix in PHL and SEPA into SWNJ.

Not an easy forecast at all down there.

But why then have more for Philly/SE PA (2-4") than for Upper Bucks/Hunterdon/Somerset/Middlesex (1-3")?  

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24 minutes ago, SnowGoose69 said:

My hunch is there’s too much GFS weighting going into these forecasts.  I wouldn’t go under 2-4 right now.  1-3 is opening the door for trouble.  Especially in the Trenton to Staten Island corridor 

NAM pretty much held.

Where is the NE trend when we need it!

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The Upton call this time is a good one. 1-3 inches for the entire metro, I’d even go 1-2 inches, I think 3 would be the limit and isolated. The new 3K NAM illustrates my thinking exactly. There’s going to be a mid-level warm nose. The models always underdue the warm nose. Here’s the 3K NAM: https://www.tropicaltidbits.com/analysis/models/?model=nam3km&region=neus&pkg=asnowd&runtime=2019021918&fh=41

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5 minutes ago, snowman19 said:

The Upton call this time is a good one. 1-3 inches for the entire metro, I’d even go 1-2 inches, I think 3 would be the limit and isolated. The new 3K NAM illustrates my thinking exactly. There’s going to be a mid-level warm nose. The models always underdue the warm nose. Here’s the 3K NAM: https://www.tropicaltidbits.com/analysis/models/?model=nam3km&region=neus&pkg=asnowd&runtime=2019021918&fh=41

If the warm nose is pronounced this will be another mostly sleet to rain event right? Can't catch a break.

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16 minutes ago, SnowGoose69 said:

It’s been happening for the last 2 days.  It may happen in real time tomorrow.  The last couple of events ended up more north than even the recent cycle or two of models before it showed 

What do you think of the warm nose in terms of that TTN to SI line...wouldn't that argue for more sleet to rain? 

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