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JAN 4th Coastal

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Gefs moved west but I wouldnt have expected not to. Gefs moves lock step in the medium range most of the time and short range is a bunch of op clones. 

gfs-ens_apcpn24_eus_6.png

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Don't know if it matters at this point (someone asked about it a while ago so I'm posting), but the GEFS shifted West. 0.1" contour is very close to DC

gefs_qpf_mean_ma_10.thumb.png.7ce46e4d905ad9ca2ebdbee21c0011ea.png

Edit: Ninja'd!

 

 

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The really interesting part of this storm for me will be the convection over the ocean and how that will affect moisture transport. 

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7 minutes ago, Bob Chill said:

Gefs moved west but I wouldnt have expected not to. Gefs moves lock step in the medium range most of the time and short range is a bunch of op clones. 

gfs-ens_apcpn24_eus_6.png

I never understand why this game is so predictable for so long. definitely high odds further west precip. This is based on observing 17 years of winter storms. 

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There's actually more spread in the members than I thought. A few whiffs along the corridor but most push at least a trace in. Half get .1 to i95. A couple outliers push .3 to dca. One gets .1 all the way to HGR. Lower resolution and shorter leads don't give much weight to the members but the outliers are notable for the short lead time. 

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6 minutes ago, Bob Chill said:

There's actually more spread in the members than I thought. A few whiffs along the corridor but most push at least a trace in. Half get .1 to i95. A couple outliers push .3 to dca. One gets .1 all the way to HGR. Lower resolution and shorter leads don't give much weight to the members but the outliers are notable for the short lead time. 

part of me wonders if not having a strong H up in the NE, that it would argue for a little less tightening of the Western gradient, and if we continue to see it tuck in a little more, that the western side, could expand some (like back to i 81 corridor).

i also realize that the speed of the system would also argue against that, but something to watch IMO.

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1 minute ago, pasnownut said:

part of me wonders if not having a strong H up in the NE, that it would argue for a little less tightening of the Western gradient, and if we continue to see it tuck in a little more, that the western side, could expand some (like back to i 81 corridor).

 

Well, not having a high to the North has been the kiss of death for many events, especially when it moves out just as the storm arrives (such as presidents day 2016 storm). Not sure how much of an impact it'll make here.

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As we approach the models tonight, at this point does the NAM (I know I can’t believe I’m asking this) actually begin to be the one to focus on since we are 24 hours out or are we still all-innon the globals still?

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I think we are close to winter weather advisory territory.  If we do get .1-.2 qpf and it comes during the Thursday morning rush hour it could create some havoc.  Especially if there is little warning.  I suppose 0z will be a deciding factor for any advisories to be issued.

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1 minute ago, SnowGolfBro said:

I think we are close to winter weather advisory territory.  If we do get .1-.2 qpf and it comes during the Thursday morning rush hour it could create some havoc.  Especially if there is little warning.  I suppose 0z will be a deciding factor for any advisories to be issued.

With such a low confident storm and lack of moisture on the west they would hold off until at least the 12z run.  It is not like we are talking about 6 inches 

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Here’s the 18z GFS sounding when precip is overhead DC.  DP is 17 and temp is 22.  The column is saturated through 950.  Question for the experts here — with the DP at 17 but the column saturated down to 950, would this indicate snow reaching the ground?  I would think yes but wanted to throw it out here for discussion.  

D001C29F-E8FF-4E33-9243-FFCBB774FD5E.png

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11 minutes ago, Cobalt said:

Well, not having a high to the North has been the kiss of death for many events, especially when it moves out just as the storm arrives (such as presidents day 2016 storm). Not sure how much of an impact it'll make here.

Yeah I thought not having a high to the north often kept the precip field more compact and a high to the north usually helped to expand the precip field? Maybe I'm wrong. Either way, this is a wild storm. It's going to really bomb and be super intense but kinda funny how, despite all that, it's not really going to be a prolific snowstorm at all. Eastern NC gets a great storm and maybe Boston and parts of northern NE. But even those snow totals won't be outrageous. Having some kind of block to the north really would have helped change the game and make this truly epic for many.

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How come everyone always says the "next" run of models will be the deciding factor, for the last 3 days? Sorry, new here.

Sent from my SAMSUNG-SM-G891A using Tapatalk

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Just now, SlamSlam said:

How come everyone always says the "next" run of models will be the deciding factor, for the last 3 days? Sorry, new here.

Sent from my SAMSUNG-SM-G891A using Tapatalk
 

We've thought there would be consensus, but the setup is very complicated here. Many players on the field, and to even get 3", every player has to be on the right part of the field at the right time. Also, model consensus hasn't improved much over the past few days. 

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8 minutes ago, Cobalt said:

Well, not having a high to the North has been the kiss of death for many events, especially when it moves out just as the storm arrives (such as presidents day 2016 storm). Not sure how much of an impact it'll make here.

The kiss of death is usually temp problems and that's nonexistent no matter how you slice it. What a high to the north helps with (other than temps) is moisture transport. NE-E midlevel and surface flow bring in moisture off the Atlantic and transports it well inland (usually). When lift and dynamics approach there is much more moisture available to wring out and it doesn't take much to precipitate. That's one of the reasons we often have precip onset start well in advance of the approaching low center. Another import thing is a hp will slow a storm's forward progress. 

In this case we have none of that so what we are dealing with is a very fast moving storm with dynamics tight to the low pressure center. When the partial and full phase idea first showed up (and when I got a little excited), upper level help was going to make up for not having a good high to the north. Even just a partial phase could have helped moisture transport well west of us. All we have working for us is an unusually strong storm that passes close enough to *maybe* bully some precip into the dry air and drop a little snow on us. 

Cheat sheet:

Pros: no temp worries, strong storm, close enough 

Cons: no phase, limited upper level support from northern stream, no hp where we normally want it, close but still too far east, very fast moving 

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5 minutes ago, nj2va said:

Here’s the 18z GFS sounding when precip is overhead DC.  DP is 17 and temp is 22.  The column is saturated through 950.  Question for the experts here — with the DP at 17 but the column saturated down to 950, would this indicate snow reaching the ground?  I would think yes but wanted to throw it out here for discussion.  

 

Yeah, snow is easily reaching the ground.  More disappointing aspect is the sh-tty dendrite growth it looks like.  Kiss the 20:1 fantasies goodbye.  

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It never ceases to amaze me how often the models tell us we are going to get a certain amount which we believe and wish for right up until we don't get it yet when the models tells we won't get something we all freak out on how close of a miss we are going to have.  If there was one thing that I learned as a snow nut of a kid living in Maryland and into my adulthood it is that storms coming from the south are unpredictable no matter what the models say and when the models are wrong in these cases we often get hammered!  Just putting this up for posterity!

 

image.thumb.png.c52a439b665ef223cba2ce138b2da99c.png

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Per Boston AFD, looks like they are doing recon flights for the models tonight.

Not that it might matter here, but interesting nonetheless 

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20 minutes ago, SnowGolfBro said:

I think we are close to winter weather advisory territory.  If we do get .1-.2 qpf and it comes during the Thursday morning rush hour it could create some havoc.  Especially if there is little warning.  I suppose 0z will be a deciding factor for any advisories to be issued.

I really don't think we are close to anything advisory wise D.C. West and NW.  Dry air we discussed.  Then there is the dominant low pressure issue which could steal it from everyone.  They could wait until the Wed afternoon package.  Or evening.  There is plenty of warning.  This is not an ULL that sneaks up on us. All eyes are on this. Just my 2 cents.

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2 minutes ago, BristowWx said:

I really don't think we are close to anything advisory wise D.C. West and NW.  Dry air we discussed.  Then there is the dominant low pressure issue which could steal it from everyone.  They could wait until the Wed afternoon package.  Or evening.  There is plenty of warning.  This is not an ULL that sneaks up on us. All eyes are on this. Just my 2 cents.

Yeah, dry air has cut snow totals in half many times. Not saying it will this time, but this isn't an overrunning event where precip has nowhere to go. 

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4 minutes ago, yoda said:

Per Boston AFD, looks like they are doing recon flights for the models tonight.

Not that it might matter here, but interesting nonetheless 

When they do that, do they feed that data into the models?  Just curious.

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1 minute ago, BristowWx said:

I really don't think we are close to anything advisory wise D.C. West and NW.  Dry air we discussed.  Then there is the dominant low pressure issue which could steal it from everyone.  They could wait until the Wed afternoon package.  Or evening.  There is plenty of warning.  This is not an ULL that sneaks up on us. All eyes are on this. Just my 2 cents.

I guess I was just thinking if we see another jump west at 0z the forecasters might get a little antsy.  Of course if we see a shift east they can just put up cold and windy as hell for their forecast.

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5 minutes ago, WxUSAF said:

Yeah, snow is easily reaching the ground.  More disappointing aspect is the sh-tty dendrite growth it looks like.  Kiss the 20:1 fantasies goodbye.  

Thanks...and yeah pixie dust flakes with that sounding. Snow growth zone is non existent. 

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8 minutes ago, WxUSAF said:

Yeah, snow is easily reaching the ground.  More disappointing aspect is the sh-tty dendrite growth it looks like.  Kiss the 20:1 fantasies goodbye.  

Far better than the crappy snow growth we had at the beginning of the Dec 8 storm though, which was dominated by stunted and heavily rimed needles and columns. At least there's a big chunk of the column at or in the -10 to -20C range, which is good enough for plates or stellar plates and less riming.

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Just now, SnowGolfBro said:

I guess I was just thinking if we see another jump west at 0z the forecasters might get a little antsy.  Of course if we see a shift east they can just put up cold and windy as hell for their forecast.

Right. Obviously they, LWX are not sold on this yet.  But still a little time and it's weather so it can do what it wants. The wild card factor.  Always present and rarely predictable 

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1 minute ago, BristowWx said:

Right. Obviously they, LWX are not sold on this yet.  But still a little time and it's weather so it can do what it wants. The wild card factor.  Always present and rarely predictable 

This pretty much sums up why I'm here.  Weather is always present and rarely predictable.  And this one is even more fun to track because I'm assuming 0.0 inches of snow so anything more than that is gravy.

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1 hour ago, ryanconway63 said:

I thought DT said this storm couldnt happen.....

If you saw his podcast last night, he explained why we were not going to get a snowstorm because of the low pressure was forming in the Bahamas. he was adamant that we needed to low pressure to form near the coast but I don't remember him making an exact forecast on the podcast I think he was just giving us the possibilities.

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8 minutes ago, Cobalt said:

Yeah, dry air has cut snow totals in half many times. Not saying it will this time, but this isn't an overrunning event where precip has nowhere to go. 

At least models account for it so the qpf output is an accurate depiction of what happens on the ground with each run. I've seen it work both ways but agree that it's more common to see less than more QPF at verification. One thing that could potentially bump things on the edge is banding. Outer bands can often outproduce model qpf output. This storm has the potential to throw back a decent band somewhere in MD. Could be one of the times where the outer band outproduces with an under performing zone in between. Something like i95 or ROCKVILLE for instance get's 2-3" while Mitch only gets 1". Yea, something like that.  

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