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12/15 - 12/16 Coastal/Winter Storm & Observations


Northof78
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Increasing agreement for an impactful winter storm for some (or possibly most of the forum; especially NW) this Thursday and Friday. Strong Block and blocking low, entrenched arctic/cold air with low passing just to our SE or near our area. Should be a mixed bag storm for many with more accumulating snow likely. Below depictions from 12Z GFS. 12z CMC also shows a nice front end dump for many within forum. 

 

image.png.45a76f33cf87376430c1b369a1a0b252.pngimage.png.88ffad25d1d11dc36affb04c2e6f7a8e.png

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8 minutes ago, Northof78 said:

Increasing agreement for an impactful winter storm for some (or possibly most of the forum; especially NW) this Thursday and Friday. Strong Block and blocking low, entrenched arctic/cold air with low passing just to our SE or near our area. Should be a mixed bag storm for many with more accumulating snow likely. Below depictions from 12Z GFS. 12z CMC also shows a nice front end dump for many within forum. 

 

image.png.45a76f33cf87376430c1b369a1a0b252.pngimage.png.88ffad25d1d11dc36affb04c2e6f7a8e.png

Any early thoughts for Vernon, NJ?

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3 minutes ago, sussexcountyobs said:

Any early thoughts for Vernon, NJ?

Depends on your choice of model.  The GFS would be over 12” of snow.  The CMC would be 4-8” of snow going over to an extended period of sleet.  The Euro is still quite warm and would be mostly rain after some frozen/ freezing precip to start.  FWIW the NAM which usually leads the way with mid level warming was going cold with this one on the 12z run (at least initially).

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1 hour ago, Tatamy said:

Depends on your choice of model.  The GFS would be over 12” of snow.  The CMC would be 4-8” of snow going over to an extended period of sleet.  The Euro is still quite warm and would be mostly rain after some frozen/ freezing precip to start.  FWIW the NAM which usually leads the way with mid level warming was going cold with this one on the 12z run (at least initially).

The Euro is warm but I still think parts of the interior see a front end dump of snow that most other models show. There is a definite CAD signature to support frozen at the onset. How long and how much is still in question. The coast is basically toast on this one but still hope for others. 

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Looks like NAM is a blast of snow on front end (at least) for most on the forum...with cold air actually building SW during this period. frozen/freezing line from Sandy Hook due West after much precip already has fallen @ hour 84. Both graphics are from hour 84 on NAM (with 1st being precip that has already fallen)

image.png.7cf689f876f035d767f5b5fc3c3e302b.pngimage.png.182e85969f050c7a210fe31c0e5b1f10.png

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Hi... saw the 18z NAM.  First batch 1-5" east to west, and most of the accumulation, if not all, starts just west of I95. 

 

Here are 12z/12 ensembles through 360 hours (15 days). Again favors interior. Doesn't lock out the coast, but interior I think is best choice until we see a considerable eastward shift in the ensembles. Not impossible to shift east but for reliability considerations, I favor inland. 

NWS blend of models, also 12z/12, attached last (only through 10 days).  So it too allows a little on the coast, but favors interior. 

TOP yo bottom: EPS, CMC, GEFS through D15.  Bottom is the NWS blend of models through 10 days. 

Screen Shot 2022-12-12 at 4.07.25 PM.png

Screen Shot 2022-12-12 at 4.08.59 PM.png

Screen Shot 2022-12-12 at 4.09.44 PM.png

Screen Shot 2022-12-12 at 4.10.16 PM.png

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Few notes: Again I wouldn't go 10-1 ratio. Two reasons: split model ptype always adds snow 10 to 1. IP is treated as snow.  If you want,  at early stages, I'd merge positive snow depth change with 10 to 1.  For sure NWS just doesn't use a straight 10 to 1 in producing its snowfall, exception possibly for a short 6 hr period in the event.

In this case: I checked Sparta NJ thermal profile and it has temps near freezing ~750MB Thursday evening... and the 1000-500 thickness is above 540.  I think it helps to be a little cautious at early stages.  Main upper low at 500MB is west and northwest of us.  Anyway,  hope you're right about as much or more snow here in nw NJ than what we enjoyed yesterday.  Dendrite growth on the 18z/12 NAM is supportive of a 2-3 hour inch/hr, provided it doesn't get any warmer at 750MB here in Sussex County.  Fingers crossed.

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21 minutes ago, HeadInTheClouds said:

That same map using kuchera is considerably less which makes sense. 

 

 

 

snku_acc.us_ne.png

Thanks. Unfortunately GFS.  I hope GFS locks on at 60-72 hours.  Next several cycles should indicate something steady. I did see the 18z RDPS is well southeast of its prior inland heavier snowband.  !8Z EC slightly colder but with sleet to HP arriving 00z/16 which makes sense to me at a 546 thickness. 

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and.  the 18z EC has about 1" in western NJ by 06z/16.  I can live with an inch or 2 as a start in nw NJ with the heavier snowfall in the Pocs. I just don't yet buy the further se GFS/RDPS.  Also with these warm thicknesses,  unless the short wave can burrow beneath us,  I think the future NAM cycles will warm mid levels and more ice faster northwest.  Fingers crossed that I'm real wrong but I would not brief an EM on the heavier scenario of the GFS/NAM...only note in passing but preparation for the lesser still slippery onset is I think best at this time. 

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32 minutes ago, winterwx21 said:

0z NAM just came in very warm. You have to go to extreme NW Jersey to see snow on this run. NW Jersey gets its accumulation at the end of the event with the rain changing over to snow on this run.  Looks similar to 12z Euro with the warm solution.  

Maybe it's the 84hr NAM doing 84hr NAM things. But the way wrapped up primary low is bringing mid level warm air with it unless the coastal low can take over early. The 700/850 lows around the coastal aren't developing until very late which could help lock cold air in. In that sense this really will be more like a SWFE where you want the front end thump.

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Not so much a concern for this subforum but there could be some nasty icing in central PA down into VA if the mid level cold is scoured early and surface cold can hang on with the heavy onset of precip. There's a pretty strong high over Quebec that will be leaving but enough to have surface CAD in time for the precip.

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46 minutes ago, winterwx21 said:

0z NAM just came in very warm. You have to go to extreme NW Jersey to see snow on this run. NW Jersey gets its accumulation at the end of the event with the rain changing over to snow on this run.  Looks similar to 12z Euro with the warm solution.  

It didn't look that different to me and it gives snow to places N and W. 

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15 minutes ago, HeadInTheClouds said:

It didn't look that different to me and it gives snow to places N and W. 

It was different because it was rain for most of the event, even for NW New Jersey. It comes in much warmer and NW New Jersey gets its accumulation only due to a changeover near the end. As Jm1220 said you want a front end thump from this event, and 0z NAM doesn't hava a front end thump at all. Of course it's just 1 run and could be wrong. 0z RGEM does have a nice front end thump for NW areas. 

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9 minutes ago, winterwx21 said:

It was different because it was rain for most of the event, even for NW New Jersey. It comes in much warmer and NW New Jersey gets its accumulation only due to a changeover near the end. As Jm1220 said you want a front end thump from this event, and 0z NAM doesn't hava a front end thump at all. Of course it's just 1 run and could be wrong. 0z RGEM does have a nice front end thump for NW areas. 

Nam is a tad warmer but does have a front end dump N and W. 

 

ref1km_ptype.us_ne.png

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40 minutes ago, HeadInTheClouds said:

Nam is a tad warmer but does have a front end dump N and W. 

 

ref1km_ptype.us_ne.png

Depends on how far NW we're talking. I was talking about NW New Jersey in my post. You can see on the map that you posted that Warren and Sussex counties are mostly rain or mixed precip at hour 75. It's a few hours later that they change to snow. It's that last minute change that gives Warren and Sussex counties the several inches of snow on 0z NAM, not a front end dump.

But again it's only 1 model run. Other model runs do give NW Jersey a front end dump. It's not looking good for NYC and nearby NW suburbs though. The 0z model runs tonight have all rain for these areas. Unless there are changes, it appears you'll have to go well to the NW to see snow from this event. 

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Quick note: am playing this one for the I84 corridor as LESS snowfall than that of this past Sunday.  Impact may be similar due to occurrence mostly between 4P and 4A Friday but so far, can't get excited about snowfall above that of Sunday. nw NJ Sussex County: am thinking 1-2" snow will suffice for now with some sleet and probably a touch of ice.

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