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12/7-12/8 Potential Event Discussion Part II


earthlight

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This run may be better for Northern New Jersey and Southeast New York..just glancing at the 30 hour panel compared to the 36 hour panel on the 18z run. It's shifted the 850mb low and 0c line east by 25 or more miles. The deformation band is also farther east. Looking back..this trend has been ongoing for the last three to four model cycles on the NAM. Notice how the deformation band is now actually located over Northeast New Jersey at 30 hours.

The mid-levels have been improving - and thus a tighter wrapped surface low. That should pull deform bands in tighter to the low center. And if the banding is an intense as that chart indicates, some places within the heaviest reflectivity could flip to snow even with 850mb through surface above freezing by as much as 1.5C. I've seen rain columns go isothermal in intense bandings. But that's grasping at straws I think.

What killed us was the "cold front" never sagging south on Wednesday as originally modeled. That leaves the lowest levels so warm I don't think we'll ever recover. A narrow warm layer between 800mb and 900mb can be mixed out dynamically. The very highest elevations - say over 2000ft - could really cash in as the vertical profile and adjusted (for elevation) thicknesses are much more favorable.

Side note - I think some of the shift between 0z and 18z on the NAM is once again due to a slightly faster speed.

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Great pic! Interesting how there is that eastern snow wedge into Monmouth. Slight elevation perhaps and inland off the bay? There is also a bright snow lolly if you zoom in that appears right over my town. I did measure 3" for that. Hope it's not our biggest snow fall this season.

Great sat pic. Amazing how MBY in Monmouth is just barely inside that eastern boundary. Sharp cut off. Also interesting to note how northern Holmdel received less than Colts Neck, due to warm influence from the bay

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The mid-levels have been improving - and thus a tighter wrapped surface low. That should pull deform bands in tighter to the low center. And if the banding is an intense as that chart indicates, some places within the heaviest reflectivity could flip to snow even with 850mb through surface above freezing by as much as 1.5C. I've seen rain columns go isothermal in intense bandings. But that's grasping at straws I think.

What killed us was the "cold front" never sagging south on Wednesday as originally modeled. That leaves the lowest levels so warm I don't think we'll ever recover. A narrow warm layer between 800mb and 900mb can be mixed out dynamically. The very highest elevations - say over 2000ft - could really cash in as the vertical profile and adjusted (for elevation) thicknesses are much more favorable.

Side note - I think some of the shift between 0z and 18z on the NAM is once again due to a slightly faster speed.

Looks like from extreme NW NJ into Western Orange County are in for a nice solid 5"+ event as per 0z NAM..

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Looks like from extreme NW NJ into Western Orange County are in for a nice solid 5"+ event as per 0z NAM..

Yeah, I'd say it's really borderline right now along that geographical line considering the 0z NAM, RGEM and the 18z GFS. I really like the current modeled location of the most consistently intense precipitation. That's the wild card and it has to happen in the absence of significant CAA. I could see a 3-4 hour period of 2" per hour or a slushy 1-2" on the hilltops. My money's on 1-2" until something turns in favor.

My target zone is Mt. Pocono to Monticello to Slide Mt.

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On the raleigh maps they're east at 30 compared to their location at 36hr on the 18z run.

That's only true for a small bump in the 0c line that the 18z GFS had in western NJ. Otherwise, the system is more amplified, with the 850mb temps and surface low more west. You can clearly see the differences in Long Island as the 850mb temps are warmer.

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GFS doesn't help things at all from what I can see. Not a lot of snow anywhere and no discernible positive trend for snow lovers. It's disappointing because the model is really developing it into a strong gale now. And there aren't any obvious threats out in the mid-range.

Still a low but existing probability of a parachute bomb scenario in the far NW suburbs (definitely warrants watching) and a coating to a few inches is likely from S to N and W from NYC.

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That's only true for a small bump in the 0c line that the 18z GFS had in western NJ. Otherwise, the system is more amplified, with the 850mb temps and surface low more west. You can clearly see the differences in Long Island as the 850mb temps are warmer.

Yeah, it definitely looks warmer and further west. It also looks to be moving a little faster than 18z. So it makes sense for 850mb 0C line to be a little farther east.

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I think in general the NW trend has plateaued, with minor wobbles left and right with heights and temps and SLP placement the past couple cycles. With a good 24 hours before the storm commits to a track up the coast, I'd like to see it trend a couple hours slower on its NE haul... otherwise I don't think even I can expect anything significant.

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Joe B on GFS moments ago:

Likes the Nam as its in line to his ideas.

There aren't really enough :rolleyes: 's for when a professional meteorologist just spouts off stuff like this. What evidence is there that the GFS is completely mishandling the storm? Is every model mishandling it? It is easy to make a claim like that but if it were just so obvious, I'm sure the modelers at NCEP would fix it...

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I think in general the NW trend has plateaued, with minor wobbles left and right with heights and temps and SLP placement the past couple cycles. With a good 24 hours before the storm commits to a track up the coast, I'd like to see it trend a couple hours slower on its NE haul... otherwise I don't think even I can expect anything significant.

The problem is precipitation is already streaming into the Ohio Valley and the thermal boundary is way to the west of our area. That boundary was modeled to sag far southwest as of a few days ago, allowing the wave behind it to send some moisture up over the fresh cold air. That didn't happen and now a stronger low center is forming along the baroclinic boundary that is too far west for most of us. It could still wrap up really tightly, jog east, and send heights and temps crashing at the last moment... but we probably won't know that until it happens. The antecedent warmth is locked in, making a major track change very unlikely and rain the dominant ptype.

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There aren't really enough :rolleyes: 's for when a professional meteorologist just spouts off stuff like this. What evidence is there that the GFS is completely mishandling the storm? Is every model mishandling it? It is easy to make a claim like that but if it were just so obvious, I'm sure the modelers at NCEP would fix it...

You would have to go on his twitter page. He explains it more and provides some maps. Hes been saying this for a long time now.

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Just thought i would pass this on from David Cox in reference to down south in reference to soundings :

We have an unfavorable sounding in Shreveport and its snowing there lol..Not much moisture in the snow growth region of -12 to -18 degrees Celsius so normally w/ sfc temps low u would think freezing drizzle as no ice crystals would form but an atypical snow was falling in Shreveport and Ruston, LA. We may have some shot in Jackson, MS area and here in Starkville, look to saturate up in the snow growth region and get a little snow here
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Just thought i would pass this on from David Cox in reference to down south in reference to soundings :

Just saw that actually and responded (assuming its from that Facebook page).

Some of the soundings even here have poor snow growth & poor saturation. Could be crappy flake production w/ 700 low closed off to the N.

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