18Z Discussion

[jdt]

Often a band sets up rather far to the W or NW of these systems somewhere unexpectedly, sometimes it can even screw the areas further SE because it produces sinking motion over them...but this would be more typical to set up further northward up the coast in places like NW CT, interior SE NY, or NE PA.

That is an observation I have seen many times! Again, it will be fun to watch how this all sets up as the coastal starts to bomb tomorrow moring.

[psuhoffman]

Ji, instead of hanging your hat on false satements of model accuracy and wishcasting, why not just point out that the models might simply be wrong with the back edge. They were with the deform band that set up with the Feb 10th blizzard last year. Just about all the models the final 12 hours backed off for the DC area and pushed that wrap around snow further north and east but when the deform blew up it happened right over northern VA and central MD, a good 50 miles west of the progs. Same could happen here.

[weathercoins]

Right north of Balt City now, I really can see two equally likely scenarios of us getting 3-4" total from this, or getting a full foot. Heavy banding once this thing blows up is not out of the question at all here (or DC for that matter). I really don't think this is just wishful thinking after last year. Thoughts?

[Terpeast]

Right north of Balt City now, I really can see two equally likely scenarios of us getting 3-4" total from this, or getting a full foot. Heavy banding once this thing blows up is not out of the question at all here (or DC for that matter). I really don't think this is just wishful thinking after last year. Thoughts?

No it isn't wishful thinking, but it's just as likely that west of i-95 south of i-70 gets little or nothing.

We want to compare the model's sfc low progs at 0-6 hr with what's going on right now (actual sfc low pressures), and the 500mb progs with the vapor loop. That will give us clues as to whether the sfc low is deepening slower or faster than progged

[psuhoffman]

Look at the precip breaking out in TN right now. That is associated with the upper level energy starting to dive in. How that interacts in the next few hours will tell the tale. That look right now has the "this is about to explode" feel to it IMHO. Models are going to struggle mightily with this kind of system. Lets see what happens as that upper level energy phases in the next few hours. Where that cuts off and how quickly this can back the flow and amplify will determine where the back edge of the extremely heavy ccb snows set up. I doubt the models will be able to pin that until they see how exactly the process is taking place and what the exact timing is. Probably 0z runs will have a better idea, but even those might have issues resolving the exact location of the back edge.

[psuhoffman]

No it isn't wishful thinking, but it's just as likely that west of i-95 south of i-70 gets little or nothing.

We want to compare the model's sfc low progs at 0-6 hr with what's going on right now (actual sfc low pressures), and the 500mb progs with the vapor loop. That will give us clues as to whether the sfc low is deepening slower or faster than progged

true... looking at radar and wv loop right now...this has that "about to pop" look to it .

[psuhoffman]

I also like the speed at which the axis of the precip is rotating into a more negative tilt alignment. Again I am very interested to see how this reacts in the next few hours with the energy about to dive into the system. Now im off to Christmas dinner. Happy Holidays everyone

[Chase]

I am sure I was only dreaming it each time it has happened down here in a coastal.

Agreed. The band sets up down here every time there's a coastal... Because that's what they do. It's not exclusive to NY/NJ

[mdwx]

http://weather.unisys.com/surface/sfc_map.gif

[winterymix]

Nice squall line in the GOM

[winterymix]

something new:

http://www.erh.noaa.gov/lwx/onset/

http://www.erh.noaa.gov/er/lwx/winterstorm/

[packbacker]

Not like the latest RUC, has shifted east a bit.

22z RUC

19z RUC

[goldstar]

Are the models picking something up w/regards to a more easterly jog at this late hour? Or are we nowcasting at this point as far as intensity and loccation of the intense banding?

[winterymix]

Are the models picking something up w/regards to a more easterly jog at this late hour? Or are we nowcasting at this point as far as intensity and loccation of the intense banding?

wait until the 0Z NAM and 0Z GFS and most likely, a blend of the two will be good guidance.

I've been suggesting and thinking all a long that one of two scenarios is likely;

1. large area of precip but less qpf than what the most generous models are depicting

or

2. heavy, intense precip but jogging east 30 to 50 miles from the most west depictions.

bottom line; NE New Jersey to Harrison NY is the closest we have to a lock

[RUNNAWAYICEBERG]

Are the models picking something up w/regards to a more easterly jog at this late hour? Or are we nowcasting at this point as far as intensity and loccation of the intense banding?

nowcasting pretty much...but looking at mesoscale models to see where the bands set up.

everything looks on point at the moment. pressure drops in GOM might be a couple mb stronger than forecasted, but not much. also, recon says good lightning growth going on as the northern stream is phasing in.

water vapor loop looks sick.

[5speed6]

something new:

http://www.erh.noaa.gov/lwx/onset/

http://www.erh.noaa....wx/winterstorm/

These are updated. They've shifted it a hair west and moved the onset up a few hours across the Metro area.

[afvet89]

is it possible that the 850 freezing line is depicted too far south on the 18z runs when compared to what the winter radar is showing in NC . Just thought I'd throw it out there. Slow nite at work here.

[poleshiftnow]

Just for S&G 12z JMA