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NEG NAO

March 13 - 15 Major Winter Storm Potential

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Excerpt from Upton's 5:43 AM forecast discussion

The closer to the coast track points to heavy qpf for the entire area...but now spells a high likelihood for mixing or changeover to sleet/rain across E LI/SE CT during the morning into afternoon. If westward trend continues a bit more...mixing/changeover could occur into much of western LI. Before any changeover though...6+ inches of snow are still likely across much of E LI and SE CT in intense snow banding in the morning. If western shift continues...snowfall across south and eastern coastal areas may have to reduced further. With high changeover likelihood and a wetter snow across E LI/SE CT...have converted Blizzard Watch to a Winter Storm Warning. 

Meanwhile...the threat for Blizzard conditions with 1 to 2 ft of snow is high for the NYC metro...NE NJ...Lower Hudson Valley and SW CT. Blizzard Warning has been issued for this area. Coupled jet structure...approaching phased mid level shortwave energy...and deep and strong frontogenetic forcing...interacting with inflow of gulf/sub-tropical moisture points towards intense snowfall rates late tonight and pivoting north through early Tuesday afternoon. Fairly good operational model agreement on 1 1/4 to 1 1/2 inches qpf...with locally up to 2 inches qpf. Most of this falling in a 9 hr period! Snowfall rates of 2 to 4 inches per hour look likely in this area based on SPC SREF strongly signaling potential for snowfall rates of 2 to 3 inches per hour and the 3km experimental NAM showing still showing potential for snowfall rates of 3-5 inches per hour. Intense comma head banding may linger over the western portions of the cwa into the afternoon.

 

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Yikes at that 0z Euro run as many have mentioned. :yikes: 

First off, I'm not sure how it prints out as much snow as it does around NYC given the mid level low tracks. 700mb is west of the city and 850mb looks to cross overhead or maybe just SE. It must be counting some as sleet. There would definitely be a zone of heavy sleet around where winds are still northerly and sub-32 air can stay in place and warm air is advecting aloft. The dryslot would also make it past NYC with that 700mb low track. If the 0z Euro ends up happening, I would find it hard to see more than 6-9" unless the snow comes in like a wall at 2-3"/hour and pounds for the few hours we have there before sleet. Inland over N NJ, Hudson Valley, etc are still fine regardless and on track for a huge event.

But that being said, other models are a little further east and allow for a real thump of snow before any mixing near NYC-the GFS run at 6z was great. The RGEM also looks like it ticked slightly east. So there's still time for a correction east 30-50 miles which is all that the city really needs to salvage a big event, but some of the 0z guidance was pretty scary in terms of how much midlevel warmth pushes in. Again, pay attention to where the mid level lows track before looking at snow or precip maps. If the 700mb low goes west of you, expect a dryslot and you'll likely mix because there's warm southerly winds coming in at this level. 

Hopefully at 12z we see this correction east. It was a little reassuring to see the EPS members a little bit east of the Euro OP run, maybe a sign the west trend is over. 

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11 minutes ago, F5TornadoF5 said:

Look at those sustain winds on the coast...impressive. 

IMG_1015.GIF

Definitely a substantial coastal flood threat here. That's 60mph onshore ENE winds near high tide. 

Jones Inlet's high tide tomorrow is at 9:31AM, right about when this map happens. :yikes:

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2 minutes ago, jm1220 said:

Yikes at that 0z Euro run as many have mentioned. :yikes: 

First off, I'm not sure how it prints out as much snow as it does around NYC given the mid level low tracks. 700mb is west of the city and 850mb looks to cross overhead or maybe just SE. It must be counting some as sleet. There would definitely be a zone of heavy sleet around where winds are still northerly and sub-32 air can stay in place and warm air is advecting aloft. The dryslot would also make it past NYC with that 700mb low track. If the 0z Euro ends up happening, I would find it hard to see more than 6-9" unless the snow comes in like a wall at 2-3"/hour and pounds for the few hours we have there before sleet. Inland over N NJ, Hudson Valley, etc are still fine regardless and on track for a huge event.

But that being said, other models are a little further east and allow for a real thump of snow before any mixing near NYC-the GFS run at 6z was great. The RGEM also looks like it ticked slightly east. So there's still time for a correction east 30-50 miles which is all that the city really needs to salvage a big event, but some of the 0z guidance was pretty scary in terms of how much midlevel warmth pushes in. Again, pay attention to where the mid level lows track before looking at snow or precip maps. If the 700mb low goes west of you, expect a dryslot and you'll likely mix because there's warm southerly winds coming in at this level. 

Hopefully at 12z we see this correction east. It was a little reassuring to see the EPS members a little bit east of the Euro OP run, maybe a sign the west trend is over. 

Thanks nice write up. Will be a long day!

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6z GFS shows how the city and most coastal areas can still have a big snow event. On the map, the 700mb low looks to go about over NYC, and the 850 low stays SE of Long Island. Dynamics delay the advance north of warm air, and it generally looks to be all snow away from the twin forks. But the GFS is still correcting west towards other models, so future runs might end up west too. But verbatim that would be a crusher in NYC, 12-18".  

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The big difference between the 06Z NAM and the RGEM/Euro now is that the NAM does not front end dump like the latter two, so as a result it does not have more than 5-6 inches of snow before the sleet changeover if you dig in really deep. 

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Just now, bluewave said:

The Euro continues to be really impressive on the high wind threat for Tuesday.

 

ecmwf_uv10g_mph_nyc_8.thumb.png.41af709f81f55fc93bc8a792137571c1.png

 

I lose power on that Euro run. Period. Heavy thump of snow, followed by mix and rain to add weight to the snow.With winds gusting to 80 (!?!) @ KFOK

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3 minutes ago, EasternLI said:

I lose power on that Euro run. Period. Heavy thump of snow, followed by mix and rain to add weight to the snow.With winds gusting to 80 (!?!) @ KFOK

Seriously, expect your power to be out if that verifies. 

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6 minutes ago, EasternLI said:

I lose power on that Euro run. Period. Heavy thump of snow, followed by mix and rain to add weight to the snow.With winds gusting to 80 (!?!) @ KFOK

The timing of the peak surge will be important in determining how high the tides get. The surge model now has 4 ft surges peaking around 1- 2 hrs after the morning high tide on the South Shore. It now has a 5 foot surge on Long Island Sound in the afternoon close to the high tide which is later there. The 12 and 0z runs will be important.

 

image040.thumb.gif.7acbab345873e0065d56803cfc36cba6.gif

image043.thumb.gif.26b7410b2bef78189c986657dd8e135e.gif

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22 minutes ago, jm1220 said:

6z GFS shows how the city and most coastal areas can still have a big snow event. On the map, the 700mb low looks to go about over NYC, and the 850 low stays SE of Long Island. Dynamics delay the advance north of warm air, and it generally looks to be all snow away from the twin forks. But the GFS is still correcting west towards other models, so future runs might end up west too. But verbatim that would be a crusher in NYC, 12-18".  

WPC has 70% of 12+ inches at NYC and 50% of 12+ inches at JFK

WPC has 30% of 18+ inches at NYC and 20% of 18+ inches at JFK

https://t.co/yKguvtCAlW

https://t.co/yKguvtCAlW

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2 minutes ago, bluewave said:

Hi res NAM still indicating that some spots could peak out near 5" per hour rates.

 

hiresp_snow_1h_nyc_35.png.bd9e4831055c2362b40bd57e6fd5cf90.png

What exactly is that little hole there in western NJ

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43 minutes ago, jm1220 said:

Yikes at that 0z Euro run as many have mentioned. :yikes: 

First off, I'm not sure how it prints out as much snow as it does around NYC given the mid level low tracks. 700mb is west of the city and 850mb looks to cross overhead or maybe just SE. It must be counting some as sleet. There would definitely be a zone of heavy sleet around where winds are still northerly and sub-32 air can stay in place and warm air is advecting aloft. The dryslot would also make it past NYC with that 700mb low track. If the 0z Euro ends up happening, I would find it hard to see more than 6-9" unless the snow comes in like a wall at 2-3"/hour and pounds for the few hours we have there before sleet. Inland over N NJ, Hudson Valley, etc are still fine regardless and on track for a huge event.

But that being said, other models are a little further east and allow for a real thump of snow before any mixing near NYC-the GFS run at 6z was great. The RGEM also looks like it ticked slightly east. So there's still time for a correction east 30-50 miles which is all that the city really needs to salvage a big event, but some of the 0z guidance was pretty scary in terms of how much midlevel warmth pushes in. Again, pay attention to where the mid level lows track before looking at snow or precip maps. If the 700mb low goes west of you, expect a dryslot and you'll likely mix because there's warm southerly winds coming in at this level. 

Hopefully at 12z we see this correction east. It was a little reassuring to see the EPS members a little bit east of the Euro OP run, maybe a sign the west trend is over. 

06z NAM soundings do indicate sleet on Long Island. I do agree though if the 700 mb low passes west of your area mixing will be definite, but not immediate because of the placement of the 850 low.

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1 minute ago, Zelocita Weather said:

Every model has a monster band/CCB develop at some over the area, but in different ways. As Goose says, NAM/GFS lacks an overrunning thump, but goes to town as coastal bombs, RGEM and other foreigns have a big overrunning thump

The NAM has generally been hitting on slow starts to systems this winter too.  If it ends up correct assuming 12Z guidance does not go back east again this could bust severely in some spots

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