18z Model Guidance 12/8

[TUweathermanDD]

I would have to argue the potential for frozen precipitation in some areas away from the immediate coast...especially given the regression of the upper level low and the potential for secondary development similar to that of the 12z UKMET or 06z DGEX (can't believe I am referencing the DGEX, but it's a similar solution with the NAM probably a bit more inland).

Earthlight, did you see the 18z DGEX? Its not looking good at all for around the DC/BAL/PHI/NYC corridor as the storm lacks any backend moisture and the storm takes a somewhat lousy track. Unfortunate but it is the DGEX.

[earthlight]

Earthlight, did you see the 18z DGEX? Its not looking good at all for around the DC/BAL/PHI/NYC corridor as the storm lacks any backend moisture and the storm takes a somewhat lousy track. Unfortunate but it is the DGEX.

Wasn't even sure it was completed yet, so no I haven't seen it. But thanks for the update--and I am not totally surprised by the solution.

[ag3]

Earthlight, did you see the 18z DGEX? Its not looking good at all for around the DC/BAL/PHI/NYC corridor as the storm lacks any backend moisture and the storm takes a somewhat lousy track. Unfortunate but it is the DGEX.

Where is 18z DGEX out? What site?

[benfica356]

through 36, our shortwave is weaker than 18z NAM, clipper a hair stronger

[TUweathermanDD]

Where is 18z DGEX out? What site?

Over on Allan's Raleigh site

Here ya go, 18z DGEX

[ag3]

Where is 18z DGEX out? What site?

Just starting coming out on ewall.

[tombo82685]

just comparing things so far, it looks like the pv is a little further south on this run, also the hgts over the northeast are a little higher. West coast ridge though does seem a little flatter.

[ag3]

18z DGEX...Still going with the CCB snows.

[benfica356]

i'd take the DGEX right now then lol

[earthlight]

Over on Allan's Raleigh site

Here ya go, 18z DGEX

Apparently the DGEX thinks we're going to see a 955mb low develop low near Rhode Island.

Seriously though, I am surprised with what I see on the DGEX. That's a completely offshore solution, actually, and the furthest thing from inland with the secondary. It is trying to redevelop the secondary along the frontal boundary--which offers hope for the suburban areas trying to see frozen precipitation.

http://www.meteo.psu.edu/~gadomski/DGEXEAST_18z/f120.gif

[earthlight]

18z DGEX...Still going with the CCB snows.

It's been several years since I have seen temperatures in the teens with heavy snow, and I am going to put my eggs in the basket that this will not be the setup to deliver it.

[Kaner587]

It's been several years since I have seen temperatures in the teens with heavy snow, and I am going to put my eggs in the basket that this will not be the setup to deliver it.

955mb low sitting on block island...may be a little breezy

[eduggs]

I would have to argue the potential for frozen precipitation in some areas away from the immediate coast...especially given the regression of the upper level low and the potential for secondary development similar to that of the 12z UKMET or 06z DGEX (can't believe I am referencing the DGEX, but it's a similar solution with the NAM probably a bit more inland).

Fair points and you could be right. But I don't see it that way. The latest NAM is just too sharp at h5 with a huge jet max on the western flank about to sharpen the whole structure even further. The UKMET is on its own and would still bring mostly rain for most. The 06z DGEX was based on an initially much more progressive s/w that allowed the surface low to slide further SE before bombing. And I believe it is doubtful a solution like the GFS would actually produce much snow for the cities.

Over the next 2 runs, I expect the GFS to back off on the wraparound snow while maintaining a roughly similar track and the UK to trend westward. There's just too much data to suggest an inland track. Only with entrenched cold air and a northerly flow could be win with this track (or maybe a well placed bomb and late CAA).

Praying I'm wrong about everything.

[LVblizzard]

Earthlight, did you see the 18z DGEX? Its not looking good at all for around the DC/BAL/PHI/NYC corridor as the storm lacks any backend moisture and the storm takes a somewhat lousy track. Unfortunate but it is the DGEX.

Huh? The 18z DGEX is out on Ewall and it shows a backend blizzard for Philly north with about 1" of QPF as snow for some places. Not sure what you're looking at.

[benfica356]

at 54, GFS has storm a little bit south than 18z NAM and 850 line running on I-95, while 18z NAM had it north of it

[tombo82685]

through 66 hrs gfs is weaker with the s/w coming out of the plains, looks like the ridge out west is a little flatter. Also, the hgts from the pv pushing down up north arent arashing towards the low yet....

[earthlight]

Fair points and you could be right. But I don't see it that way. The latest NAM is just too sharp at h5 with a huge jet max on the western flank about to sharpen the whole structure even further. The UKMET is on its own and would still bring mostly rain for most. The 06z DGEX was based on an initially much more progressive s/w that allowed the surface low to slide further SE before bombing. And I believe it is doubtful a solution like the GFS would actually produce much snow for the cities.

Over the next 2 runs, I expect the GFS to back off on the wraparound snow while maintaining a roughly similar track and the UK to trend westward. There's just too much data to suggest an inland track. Only with entrenched cold air and a northerly flow could be win with this track (or maybe a well placed bomb and late CAA).

Praying I'm wrong about everything.

You have fair points as well---all is fair in good argument. That's what these forums are for, right?

Back to the discussion..I would agree with your points but I think the real game changer is how the NAM has the jet stream oriented at H250-H300. Notice the jet stream screaming east in the Northeast at the end of the run. This feature is well to the north on the GFS and especially the ECMWF and GGEM. The NAM extrapolation as a result shows that the primary goes north and then east, and by the time the Polar Vortex phase occurs, the secondary surface low develops on the offshore baroclinic zone and tugs northward. The potential exists for some snows with this feature anywhere from South-Central to Northeast PA, far Northwest NJ and into Upstate New York, if you ask me. That being said, the entire thing is still 114+hours away, so we are probably being overly analytical.

[eduggs]

Im not so sure it would be all that inland if the southern low is the one that takes over...I certainly dont think it would be to the extent of the 12Z Euro.

It can't take over because the mid/upper levels support a low center near the lakes. When air converges near the surface or diverges high in the atmosphere, air pressure at the surface is low. And when it does both in the same spot, pressure drops or deepens. And the NAM depiction charts indicate this will happen too far NW to sustain a coastal snowstorm (barring wraparound of course).

But you're right, not quite like the 12z Euro.

[earthlight]

The 18z GFS seems a bit more de-amplified with the heights across the Southeast United States...which opens the window for a slight slip southeast. We shall see.

[benfica356]

60, clipper is a lil stronger and well north of how 18z NAM had it while the storm down south is still more south and colder up here

[TUweathermanDD]

Huh? The 18z DGEX is out on Ewall and it shows a backend blizzard for Philly north with about 1" of QPF as snow for some places. Not sure what you're looking at.

Well yes this is true, however bad for DC. I was looking at something else. It certainly isn't too bad for Baltimore north on the backend. If we are looking for a good coastal and actual snows not including backend this isn't our set up. My apologies once again, in the meanwhile liking the 18z GFS. Hopefully for us the DGEX is right on with the backlash though, I'd take 2'' in Baltimore, Philly gets around 9". Good stuff, lets keep it up.

[earthlight]

At 72 hours the GFS is ready to amplify with the upper level jet streak expanding southeast over the top of the West Coast ridge, this should be wrapped up..but it's still slightly encouraging to see the de-amplified heights in the east initially. Wondering where this run will go at the surface..

[tombo82685]

this may slide off the southeast coast...im out to hr 75 and there is hardly a surface pressure reflection yet, just a broad area of 1012 hgts from the lakes to mexico

[Alpha5]

Wow GFS is really disorganized with the energy, troughs stays postiive for a while

Hmmm, im out to hr 81

[EasternUSWX]

this may slide off the southeast coast...im out to hr 75 and there is hardly a surface pressure reflection yet, just a broad area of 1012 hgts from the lakes to mexico

[earthlight]

We have a rouge shortwave de-amplifying the upper level trough axis over the Northeast in PA--but the upper level shortwave still can't seem to get to the base of the trough, and it's already east of Arkansas.

[Alpha5]

vort might break into 2?

[LVblizzard]

This looks great through 78. Way weaker and flatter than 12z.

[earthlight]

The Polar Vortex is ready to tug this entire thing north, and it's closing in fast. It's a race against time here, but the GFS is doing it's best to slide this east and keep it disorganized this run.

[tombo82685]

lol at this 18z run...hr 87 has broad area of low pressure over ohio valley 1008, another popping off the delmarva 850s and frz line just north west of cities