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March 24-25 Winter Storm Threat


Mitchel Volk

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I'm sorry but location of the low in this event is not where he models are having spread. How the low gets there in addition to the interactions in the mid and upper levels is how they differ. That is how you get one model printing out 2.5 inches of precip and another showin 0.25 with low pressure being less than 100 miles apart

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I'm starting to get slighlty more excited about the setup as we move forward each model cycle. The guidance has abandoned the idea of turning this into a large cutoff low over the Central US/Plains states, which is important -- because that would likely mitigate our chances of seeing any type of significant snowfall. WIth the mid and upper level lows cutting off back to our west, the trough would slide eastward underneath the block with minimal dynamics and precipitation.

 

The guidance, now, is showing an amplifying shortwave in the Tennessee Valley. And although it eventually gets pushed underneath the confluent flow to the north from the upper level low north of New England, the dynamics are more impressive and we're starting to see more robust precipitation amounts on some guidance once the surface low transfers to the coast. It really is remarkable to see this type of cold air available this late in the season, but I guess a -5.6 AO will do that.

 

Using the NCEP model guidance as an example we can see the favorable setup at 78 hours, but there are a few improvements that we would want to see in order to start talking significant winter storm here. As it stands on the image below, the shortwave is well positioned and heading northeast towards the Mid-Atlantic coast. There is plenty of moisture and good dynamics. However in the position it is in here, given the confluent flow directly to the north and oriented  in a position moving south towards the system, the mid level centers are actually de-amplifying. We want to see the confluent flow give a little more breathing room so that the coastal system can develop farther north instead of being shunted eastward. 

 

post-6-0-27843100-1363885393_thumb.png

 

These are just some general things to watch over the next few days. The general model trends have been favorable...I think we'll eventually be dealing with a sharp cutoff on the north side of the system. Myself and a few others mentioned that a few days ago and it seems like the models are pushing towards showing that once again. These types of blocking episodes are notorious for producing very sharp cutoffs to precipitation amounts on the northern end. Hopefully this doesn't come back to bite us. 

 

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12z GGEM is an absolute bomb for the interior, rain for the coast..

It's very likely over done considering how much more suppressed the other models are. I agree though, verbatim a low over Delaware Bay is rain for the coast, guaranteed, and likely even a ways inland. That's where you would want the low for a huge event from well-interior PA northeast.

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I went through the whole loop, stays mostly rain for the immediate coast and interests south of I-78. The low tracks basically right over NYC. This run is an absolute dream for my backyard.

 

 

Meteograms are out and they have 16-18mm of precip as snow for NYC.

NYC switches to HEAVY snow when the precip matters.

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with an AO standing at near -6 today, it would argue the CMC is likely too amped up, but that does leave open the possibility of a compromise solution, something a little more amped than the EURO/GFS/UKMET but not as amped as the CMC

Hopefully today or tonight we get a north shift in the Euro. It's very hard to jump fully on board until that happens. I'm gradually becoming more confident in something happening here, but it's almost time to really start wanting a north shift on the Euro since it's getting into its more accurate range.

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Hopefully today or tonight we get a north shift in the Euro. It's very hard to jump fully on board until that happens. I'm gradually becoming more confident in something happening here, but it's almost time to really start wanting a north shift on the Euro since it's getting into its more accurate range.

This is my thought process; When we have blocking that initially isn't so intense, but is forecast overtime to become more widespread and strong, the tendency of the models is to shift things further south over time. We've seen this happen many times this year. Right now we have HISTORIC, anamolous high lattitude blocking, that basically has reached its peak negativity today. It is forecast to make a huge rebound towards neutral over the next wk. My thought process is that this is the situation where you would have a NW trend in the models, as they are incorrectly assessing the blocking stronger than what it is truly forecast to be. Now if the blocking were to slowly rebound towards neutral thats a different story. What do you guys think?

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This is my thought process; When we have blocking that initially isn't so intense, but is forecast overtime to become more widespread and strong, the tendency of the models is to shift things further south over time. We've seen this happen many times this year. Right now we have HISTORIC, anamolous high lattitude blocking, that basically has reached its peak negativity today. It is forecast to make a huge rebound towards neutral over the next wk. My thought process is that this is the situation where you would have a NW trend in the models, as they are incorrectly assessing the blocking stronger than what it is truly forecast to be. Now if the blocking were to slowly rebound towards neutral thats a different story. What do you guys think?

 

Excellent Analysis. I fully agree.

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This is my thought process; When we have blocking that initially isn't so intense, but is forecast overtime to become more widespread and strong, the tendency of the models is to shift things further south over time. We've seen this happen many times this year. Right now we have HISTORIC, anamolous high lattitude blocking, that basically has reached its peak negativity today. It is forecast to make a huge rebound towards neutral over the next wk. My thought process is that this is the situation where you would have a NW trend in the models, as they are incorrectly assessing the blocking stronger than what it is truly forecast to be. Now if the blocking were to slowly rebound towards neutral thats a different story. What do you guys think?

Honestly, I agree.  Haven't the models done this most of this winter, trying to keep the storms south, only for them to come further north?  I mean not every time, but most of the time. 

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This is my thought process; When we have blocking that initially isn't so intense, but is forecast overtime to become more widespread and strong, the tendency of the models is to shift things further south over time. We've seen this happen many times this year. Right now we have HISTORIC, anamolous high lattitude blocking, that basically has reached its peak negativity today. It is forecast to make a huge rebound towards neutral over the next wk. My thought process is that this is the situation where you would have a NW trend in the models, as they are incorrectly assessing the blocking stronger than what it is truly forecast to be. Now if the blocking were to slowly rebound towards neutral thats a different story. What do you guys think?

It's a possibility, but what we really want is for a piece coming around the PV to phase into the storm. That will force the block to relent just a little, and raise heights and allow the storm to gain some latitude. There's time for models to trend that way but hopefully it happens soon. An overall weakening of the block and confluence would also help. The sharp cutoff is definitely real though, weenies will likely go from thrilled to screaming lots of curse words within 75 miles of each other.

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Crazy that it would be 6-12" for Harlem/The Bronx while Southern BK & Queens would be mostly rain.

 

That will probably occur though, or something like it. Every bit of elevation counts this late in the season. 

It's snowed plenty down to the coast in late-season events, events significantly less dynamic than this one could be. When the low is over Delaware Bay, it's not even close to favorable for the coast.

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12z Euro, looks nothing like the 12z GFS but gets a weak coastal low pretty far NW. Light to moderate snow at hr 102. Primary holding over Ohio. End result is a track well offshore. Light snow continuing at hr 108. Moving out at 114.

 

More northwest on this run. Time for improvements.

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