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Wintry January 3rd-6th, 2018 Winter Storm The ARCC/Xtreme Weather Special

The GFS is clearly shifting the qpf NW with each run. It may be slow but we're still nearly 2 days away from the event. If this slow but steady NW qpf shift were to continue over the next 6-7 runs, it will increase substantially on land considering how much closer the 1"+ qpf is getting. The NW qpf shift has averaged, say 20 miles/run. If that were to continue, that could still be another 140 miles NW shift. With it now being only 50-100 miles to the SE, a 140 mile NW shift would bring it onshore.
 
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GaWx said:
The GFS is clearly shifting the qpf NW with each run. It may be slow but we're still nearly 2 days away from the event. If this slow but steady NW qpf shift were to continue over the next 6-7 runs, it will increase substantially on land considering how much closer the 1"+ qpf is getting. The NW qpf shift has averaged, say 20 miles/run. If that were to continue, that could still be another 140 miles NW shift. With it now being only 50-100 miles to the SE, a 140 mile NW shift would bring it onshore.
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I think a pro met on the other board said that the OPs don't make significant shifts in the short range.
 
Webberweather53 said:
The models usually do a piss poor job with handling the northwesterly extent and intensity of the precip shield in events like this so I'm not sure or very confident that we'll see a consistent shift SE over the next day or so, if anything more NW adjustments seem probable given everything at hand
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I definitely agree they make NW adjustments in the precip field, but I just think the NAM is truly 'best case scenario'. Perhaps I just find it insanely hard to believe this storm will produce 12+ inch amounts deep in GA/SC and 20+ inch amounts in NC. I just think the RGEM is a good compromise between the NAM and globals give or take another 50 mile or so shift. If the RGEM trends towards the super amped NAM, then I'd put all my chips on the NAM.
 
LovingGulfLows said:
I definitely agree they make NW adjustments in the precip field, but I just think the NAM is truly 'best case scenario'. Perhaps I just find it insanely hard to believe this storm will produce 12+ inch amounts deep in GA/SC and 20+ inch amounts in NC. I just think the RGEM is a good compromise between the NAM and globals give or take another 50 mile or so shift. If the RGEM trends towards the super amped NAM, then I'd put all my chips on the NAM.
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It would not be wise imo to bet on the wet biased NAM literally. In the past when it has been much wetter than model consensus, it has almost always busted way too wet. However, if one were to cut the NAM qpf in half (especially the biblical highest qpf areas), that would imo be a reasonable compromise. After cutting the last few NAM runs' qpf in half, many areas are still hit with a severe winter storm. Also, the NAM has been pretty consistent with its trending at H5 and the surface. Sometimes the NAM likes to jump around wildly from one run to the next and that's when I ignore it for guidance. But in the current case, that's clearly not happening making me think it really may be onto something. Thus I'm not throwing it out....just cutting in half the insanely high qpf and then considering it a a viable option.

I still think that a big key is how the surface low moves from Grand Bamaha Island.
 
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Meanwhile for the coastal sections, there is huge disagreement not only about qpf but also about the form that that qpf would take %wise. For SAV-CHS, I'm suspecting that a lot that is showing up as ZR will verify as sleet and snow. The ZR just doesn't look reasonable with 850s of only +1 to +2. Climo says that would usually be IP. Moreover, I'm not sure I believe the warmer models' +1 to +2 850s for the first part of the storm. Also, ZR this doesn't seem like a classical ZR setup, with shallow cold air/wedging. Are these models properly taking into account evaporative cooling at 850 and possible dynamic cooling from such a potent system?
 
packfan98 said:
-------------‏Verified account @wxbrad 3m3 minutes ago
Here are my 1st thoughts on the Coastal storm Wednesday into Thursday. Very tight gradients for the snow to nothing along I-95 with ice closer to the coast mixed in.
DSfUlKaUMAAdwup.jpg
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Looks like B rad, is riding the GFS , lol! But he's also the one that 2 days before the big December storm, said no one in NC would see accumulating snow outside the mtns! Whoops!
 
Tarheel1 said:
Looks like B rad, is riding the GFS , lol! But he's also the one that 2 days before the big December storm, said no one in NC would see accumulating snow outside the mtns! Whoops!
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He always does the same thing. Says no no no then dumps it on everyone
 
I am not quite sure what to believe. Something just tells me that the NAM is off it's rocker, to an extent. You really mean to tell me that the majority of the Global operational and ensemble members are all missing what the NAM sees?

The NAM is a very big deal, and still, even with the RGEM "hinting", is a giant difference versus everything.
 
Tarheel1 said:
Looks like B rad, is riding the GFS , lol! But he's also the one that 2 days before the big December storm, said no one in NC would see accumulating snow outside the mtns! Whoops!
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And the UKMET, and the Euro, and the CMC, and the, . . . shall I go on? Rule for snowfall in the SE: go with the warmest model and the one showing the least amount of snow.
 
Sorry if it's already been mentioned but tropical tidbits now has a 2.5km hd rgem... unfortunately it cuts off majority of the southeast so no idea what it is doing downstream for those in NC. Also only goes out to 48hours.
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StoneMtnWx said:
Sorry if it's already been mentioned but tropical tidbits now has a 2.5km hd rgem... unfortunately it cuts off majority of the southeast so no idea what it is doing downstream for those in NC. Also only goes out to 48hours.
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I just did research into the 2.5KM. The only grib files, which are experimental, is that view. Sadly. We can't even make the maps our selves for the SE. :(
 
Don't y'all just love the weather. Lol.
***Ok kind of a longer post***
I for one don't think the trends are over yet at all, good or bad** it does concern me that the NAM (both 12km and 3km) virually has no support on how strong of a solution it's showing. Does it meannits wrong, no not all, but we know NAM loves to over do things as well. In fact it's usually awful at it. With that being said do I think it could be on to something absolutely. rgem will be a big help as well, but remember it still runs with a parent global, the CMC and can have a progressive bias as well. I really wish the euro had more support toward a NAM type solution to feel more comfortable about it. I will say the doc did trend toward the NAM a bit with more tilt and a slightly sooner phase there are 2 massive wild cards, IMHO here, 1. Where and when the phase happens (clearly the NAM is further west with that process then any other model) and 2. All the vorticity bombs/spikes/whatever in the western Atlantic. Those are going to force the SFC low out from the coast. So I expect them to trend less with time, yes. And I think that's been apparent with all models showing the SFC low closer to the coast.
In the end tonight's runs will be HUGE!! President Trump's HUGE voice. Lol will the NAM continue it's massive solution? (Both 12 and 3km) if it does then we might*** have a trendsetter OR if it starts to buckle and go toward the other models, well then I think we are in trouble for most outside coastal areas.
Map coming soon, no amounts yet to be honest.
 
deltadog03 said:
Don't y'all just love the weather. Lol.
***Ok kind of a longer post***
I for one don't think the trends are over yet at all, good or bad** it does concern me that the NAM (both 12km and 3km) virually has no support on how strong of a solution it's showing. Does it meannits wrong, no not all, but we know NAM loves to over do things as well. In fact it's usually awful at it. With that being said do I think it could be on to something absolutely. rgem will be a big help as well, but remember it still runs with a parent global, the CMC and can have a progressive bias as well. I really wish the euro had more support toward a NAM type solution to feel more comfortable about it. I will say the doc did trend toward the NAM a bit with more tilt and a slightly sooner phase there are 2 massive wild cards, IMHO here, 1. Where and when the phase happens (clearly the NAM is further west with that process then any other model) and 2. All the vorticity bombs/spikes/whatever in the western Atlantic. Those are going to force the SFC low out from the coast. So I expect them to trend less with time, yes. And I think that's been apparent with all models showing the SFC low closer to the coast.
In the end tonight's runs will be HUGE!! President Trump's HUGE voice. Lol will the NAM continue it's massive solution? (Both 12 and 3km) if it does then we might*** have a trendsetter OR if it starts to buckle and go toward the other models, well then I think we are in trouble for most outside coastal areas.
Map coming soon, no amounts yet to be honest.
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The waves should both be sampled just fine. With an ingest of new data for 00z, if the NAM holds on, or amplifies even more; I'll feel more confident. Something has to give in this situation. My gut says NAM will start to back down.
 
When's the next NAM ing begin?
 
Yeh as much as I want the NAM to keep NAMing. I got a gut feeling the NAM is gonna hurt a lot of feelings for us inland folks on the 00z runs
 
This is the likely scenario, tbh.

gefs_qpf_mean_nc_15.png


gefs_snow_ens_nc_15.png
 
To show you how far off the NAM is from the GEFS & EPS for the CAE area:

GEFS:
KCAE_2018010112_gefs_snow_384.png


EPS:
KCAE_2018010112_eps24_snow_360.png


If the NAM were to verify with it's 12/18z runs, it would be embarrassing to those two.
 
12k NAM is out in left field guys, if anything the 3km version looks plausible based on the surface reflections. I still can’t figure why the globals are not slinging more QPF inland given a bombing low off the Carolina’s. End result is the NAM will likely meet the GFS / ECMWF in the middle. If anything I feel less confident how this will play out than 24hrs ago. Moderate snow event for Florence to Norfolk, possiblility for a foot in NE NC and SE VA. Still expect to see a slight NW correction now that we are inside 48hrs, FAY to RWI should do very well.
 
Shawn said:
To show you how far off the NAM is from the GEFS & EPS for the CAE area:

GEFS:
KCAE_2018010112_gefs_snow_384.png


EPS:
KCAE_2018010112_eps24_snow_360.png


If the NAM were to verify with it's 12/18z runs, it would be embarrassing to those two.
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Dang...what a difference. I'm with you as well, not buying into the NAM's solution yet either. That'd be quite a coup for it to pull that off, esp. with no other support really.
 
The 18Z RGEM is a huge hit SAV-CHS with qpf of 0.80-0.60" through the end of the run at hour 48. It starts as IP/ZR initially changing to snow for most of it based on 850s going back below 0C. And this is before this storm is over, especially for CHS. So, the implication of this would be qpf likely approaching 0.90"-1.00" for wintry qpf. for the entire storm for SAV-CHS, an amount that SAV hasn't even come close to seeing since the severe 1/1922 icestorm! Yes, I know not to bet on this much qpf at this stage with the main global models having way less and a storm like this being extremely rare but at least it isn't insane like what the last couple of NAMs showed. Also, that seems plausible with this setup and considering the GFS is slowly but steadily trending NW with the qpf.

Three things worth noting about this run:
- NNE move of the sfc low from Grand Bahama Island associated with a big SE coast hit
- This run suggests about a 12 hour long storm
- This is another recent model run suggesting an earlier start (as early as 3 AM Wed) than some models have been showing.
 
Don't think this comes much if any west of 95 and maybe even closer to the coast than that. In storms like the one in 1989 and the Crusher, cut off of snow line was very sharp and distinct.
 
WeatherNC said:
12k NAM is out in left field guys, if anything the 3km version looks plausible based on the surface reflections. I still can’t figure why the globals are not slinging more QPF inland given a bombing low off the Carolina’s. End result is the NAM will likely meet the GFS / ECMWF in the middle. If anything I feel less confident how this will play out than 24hrs ago. Moderate snow event for Florence to Norfolk, possiblility for a foot in NE NC and SE VA. Still expect to see a slight NW correction now that we are inside 48hrs, FAY to RWI should do very well.
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It's plain and simple.... It's too dry in the lower levels. There will be some snow in the Piedmont, but none of it will ever reach the ground unless those lower levels moisten up a lot. That's the problem.
 
For Phil:

That same 18Z RGEM has about 13 straight hours of ZR in Gainesville, FL, (~midnight - 1 PM Wednesday) adding up to a whopping 0.60" of ZR! I suspect that would be an all-time icestorm record for there if that were to verify as I'm not even aware of a single major icestorm on record there! Phil are you aware of any?
Unlike further north in the SAV-CHS corridor, I can more readily buy a lot of ZR because 850s are +4 to +5, which is a common 850 range for major ZR.

So, Phil could conceivably be the member hit the hardest in a sense. Is that unreal?

Edit: I wouldn't be surprised if a 0.60" ZR icestorm would be a multi-hundred year long record at Gainseville!
 
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