December 8-10, 2018 Winter Storm

[SnowDawg]

54 minutes ago, mackerel_sky said:

I’m just looking for “ trends” the NAM has the strongest of any high pressures modeled! If we’re dependent on stronger high , to get colder wedge and temps , on a borderline airmass already, not much room for a weakening trend!

To be fair though that is an hour we had yet to get to in the NAM and the high was still 1041 in just the frame before, so to this point it still hasn’t wavered. We’re just getting further ahead into the event.

[BullCityWx]

2 minutes ago, griteater said:

I think the cold damming is going to lock in pretty well with this one.  Yeah, legit concerns for substantial ice...just a matter of how much sleet vs. frz rain, and where that shakes out

1000% agree there. I dont know where the freezing rain area sets up but where it does, ouch. 

[FallsLake]

3 minutes ago, rduwx said:

It'll be interesting to see if that change over is more of a zr vs a rn scenario.  Or if we get a lot more mixing period.  It is extremely close in my area.

As Grit just stated, if there is more ice then I think we get a big storm. If this is a miller a snow/rain storm we may only get that 1" (...then it will wash away). 

[beanskip]

Man, there was some terrible Euro analysis last night. If you're going to stay up that late, at least get it right. 

Couple observations:

1) EE rule is in effect. For newbies, the NAM used to be called the ETA. The EE rule is that if the Euro and the ETA are in agreement, take it to the bank

2) This also reminds me of the "Larry Cosgrove" storm from about 10 years ago (strongwx/QueenCityWx/Lookout/HKY and others will remember) when he came on the boards and pooh poohed those who argued that the models were underforecasting the CAD based on the position of the high. Needless to say, he hasn't been back to the board since and the entire southeast was crippled.

3) I'm trying to remember a system with such widespread QPF consistently forecasted from a week out -- heck, even in the short term I'm not sure I ever remember 3+" of QPF forecasted with a winter storm. Have to wonder if the models will accurately predict the interaction between that much water and the rest of the atmosphere.

4) Wish I was still up there to be in the thick of things!

[BullCityWx]

Just now, FallsLake said:

As Grit just stated, if there is more ice then I think we get a big storm. If this is a miller a snow/rain storm we may only get that 1" (...then it will wash away). 

I think maybe for the airport and south/east you're right. For me, you and sean who are on the NW fringes of the metro, I feel much better. 

[lilj4425]

As long as Brick Tamland gets three feet of snow, I really don’t care what happens. 

[SnowNiner]

13 minutes ago, griteater said:

I think though that we are headed in the direction of more of a Miller B or Miller B Hybrid as HkyWx calls it....where that was straight Miller A...so, I would expect much more mixed precip compared to that one, IMO

I'm surprised that even with a strong stj storm with confluence and some blocking we still get a Miller b. I dont know how in the world to get a miller a anymore. 

[franklin NCwx]

This looks more like a slider to me than Miller b

[rduwx]

2 minutes ago, FallsLake said:

As Grit just stated, if there is more ice then I think we get a big storm. If this is a miller a snow/rain storm we may only get that 1" (...then it will wash away). 

Yes, I agree.  At this point I feel confident we get the snow at the beginning.  Then it's a matter of how long we hold on to that.  After the transition starts it's going to be close to what that p-type is. Again this is talking from what I've seen lately.  This could easily change in the next 2 days...LOL!

[ozmaea]

http://coolwx.com/cgi-bin/getbufr.cgi?region=SC&stn=KCAE&model=gfs&time=current&field=prec
 
You can't have a lower "trace" than that...

Explain how to break that down, does that mean of the 2 inches of liquid what portion would be snow akd etc.??

Sent from my SM-N950U using Tapatalk

[griteater]

33 minutes ago, SnowNiner said:

I've seen 2 noticeable trends on the EPS.  First, the 50/50 low has trended stronger and SW, which I think is good.  That's why our high pressure is modeled great and our confluence is keeping the low suppressed in the gulf nicely.  However it seems like once the storm hits the coast, the northern stream energy is phasing and tugging it closer to the coast on the last several runs.  Therefore I still like the threat of a good first thump of snow/sleet, but once the storm is to our south, things may pull north and WAA will take over.  

That's right now.  Hopefully that 50/50 will get keep trending stronger and the northern energy will trend slower to keep this thing south.  

You got it Niner.  Trend loop here on the EPS, including the most recent 06z run.  So the 3 key players are the SE Canada trough (50/50 low), the southern stream wave, and the new shortwave dropping down from the northern stream (in S Dakota on the last image of the loop).  Over time: 1) the 50/50 low has nudged southwest, 2) the model is seeing increased amplitude with the southern wave, and 3) the new northern stream shortwave is now getting more involved, and earlier.  Note the trend of the height rises from Georgia up thru Kentucky.  Height rises = warmer, and a more north solution (warmer aloft that is, not really at the surface where the damming high will do its dirty work).  So, for a more south solution, we'd want to see the SE Canada trough to nudge more to the southwest, the southern stream wave to not be as amped, and to lessen the early involvement of the northern stream shortwave.  The SW VA group would want to see it stay the same as it is now

[NCSNOW]

Ripping fatties up in Boone, one of those squall moments just happened. Amazing not just how historic this storm could be for mtn region, but how historic this winter can be for them especially as well as some others in foothills, piedmont.

[BullCityWx]

Looking at the 6z NAM, we're clouded over here before Saturday even begins. The more we can limit sunlight that day, the better. With CAD already starting from the high, that could mean temperatures are cooler on Saturday and thus you get a lower wet bulb that evening or night. 

 

and yes, this is a time where I think this could absolutely matter. 

[Cold Rain]

2 minutes ago, Queencitywx said:

Looking at the 6z NAM, we're clouded over here before Saturday even begins. The more we can limit sunlight that day, the better. With CAD already starting from the high, that could mean temperatures are cooler on Saturday and thus you get a lower wet bulb that evening or night. 

Yep, that is definitely going to be key here.  Every little bit will help.

[Orangeburgwx]

5 minutes ago, ozmaea said:

Explain how to break that down, does that mean of the 2 inches of liquid what portion would be snow akd etc.??

Sent from my SM-N950U using Tapatalk
 

Yep... Rain, Snow, Ice, and ZR

[NCSNOW]

Of all 3 things Grit and Niner alluded to, to me the elephant in the room is holding off the NS  sw as long as we can. Earlier this thing gets wound up back to our west the more its gonna waa up at 5,000ft above our heads. Now when its off the SE coast , it can go to town all it wants and deepen and suck in the cold air up above us on the NW side

[Cold Rain]

4 minutes ago, griteater said:

You got it Niner.  Trend loop here on the EPS, including the most recent 06z run.  So the 3 key players are the SE Canada trough (50/50 low), the southern stream wave, and the new shortwave dropping down from the northern stream (in S Dakota on the last image of the loop).  Over time: 1) the 50/50 low has nudged southwest, 2) the model is seeing increased amplitude with the southern wave, and 3) the new northern stream shortwave is now getting more involved, and earlier.  Note the trend of the height rises from Georgia up thru Kentucky.  Height rises = warmer, and a more north solution (warmer aloft that is, not really at the surface where the damming high will do its dirty work).  So, for a more south solution, we'd want to see the SE Canada trough to nudge more to the southwest, the southern stream wave to not be as amped, and to lessen the early involvement of the northern stream shortwave.  The SW VA group would want to see it stay the same as it is now

I said this on the other board, but I've seen these waves coming in off the Pacific show up in the mid-range weak, many times, only to end up verifying stronger when they come ashore.  I think it has to do with sampling.  We'll know pretty soon, but that is going to make a difference, IMO.  Also, I'm wondering if the waves dropping in from up north (strengthening the HP and interacting with the southern stream) are not well sampled yet either?  All of that should be resolved soon, if they are even issues currently.

[Buddy1987]

11 minutes ago, franklin NCwx said:

This looks more like a slider to me than Miller b

Yea the models have been going back and forth on this, most notably the FV3 and the Canadian. They are more so the hybrids of a bonafide miller b however. I think in the end we see the slider but I do believe once the n/s energy gets better sampled the end result will be more phasing and interaction between the two streams. 

[griteater]

10 minutes ago, SnowNiner said:

I'm surprised that even with a strong stj storm with confluence and some blocking we still get a Miller b. I dont know how in the world to get a miller a anymore. 

Get the northern stream to leave the southern wave alone, move the 50/50 low a little southwest (-NAO would help), and have better pre-storm cold...hang in there, it's early in the El Nino winter

[Brick Tamland]

The ensembles have been pretty consistent. Mean keeps showing 3 to 6 for Wake, and the control 5 to 8. I think we get too caught up in the totals sometimes. They don't ever get the totals exactly right. The good thing is they are still showing the potential for a good storm here. Just have to see what actually happens. It's like having a good basketball team that shows potential to get a big win, but it doesn't guarantee they are going to do it.

[mclean02]

33 minutes ago, jjwxman said:

Not sure how accurate this output is from coolwx.com, but if no sleet were to mix in, in GSO like this image depicts below, this could be the outcome.  But I'm pretty sure sleet will be factor in GSO.

As long as I have lived in Greensboro sleet has always found away !

[BullCityWx]

UKMET had an increase at 0z over 12z yesterday, fwiw. 

[BullCityWx]

[jjwxman]

7 minutes ago, Queencitywx said:

Looking at the 6z NAM, we're clouded over here before Saturday even begins. The more we can limit sunlight that day, the better. With CAD already starting from the high, that could mean temperatures are cooler on Saturday and thus you get a lower wet bulb that evening or night. 

Per the 6z NAM the wet bulb temps were generally in the low to mid 20's across a big portion of NC, with low 20's in the North and West Piedmont and Foothills, upper teens in the far NW Mountains.

[Buddy1987]

This is gold guys! ORH Wxman is amazing with this stuff when I lived up in the northeast still. Compliments to @North Balti Zen for posting in mid atl forum as well. Here’s the discussion:

This makes so much sense - see below, I guess all options are open.

Maybe at long leads we expect too much from the models, even in this day and age IMHO. 

I brought this over from the New England forum, thanks @ORH_wxman .   

 < 

The primary northern stream shortwave that phases on the euro doesn't come onshore near Juneau AK until 00z Friday. 

The kicker behind it doesn't come onshore until 12z Saturday in the PAC NW. 

The Arctic shortwave from the PV lobe that contributes to Quebec confluence is still over the central Arctic Ocean. It reaches Hudson Bay on Saturday...prob doesn't get decent sampling until it is near there since northern NW territories and the Canadian archipelago isn't exactly a poster child for a dense obs network...and satellite isn't going to be great there either with the extreme cold. 

Bottom line is that we have a lot of northern stream and Arctic jet shortwaves that will matter to this system that are more prone to large changes than usual due to their position. So don't be surprised to see large changes on some model guidance between now and Saturday. It doesn't mean the changes will always be good for us, but obviously we will want to see changes for a hit here. 

[Brick Tamland]

4 minutes ago, Queencitywx said:

Gotta love that tight gradient between 5 and 12 inches. 

[Cold Rain]

2 minutes ago, Buddy1987 said:

This is gold guys! ORH Wxman is amazing with this stuff when I lived up in the northeast still. Here’s the discussion:

This makes so much sense - see below, I guess all options are open.

Maybe at long leads we expect too much from the models, even in this day and age IMHO. 

I brought this over from the New England forum, thanks @ORH_wxman .   

 < 

The primary northern stream shortwave that phases on the euro doesn't come onshore near Juneau AK until 00z Friday. 

The kicker behind it doesn't come onshore until 12z Saturday in the PAC NW. 

The Arctic shortwave from the PV lobe that contributes to Quebec confluence is still over the central Arctic Ocean. It reaches Hudson Bay on Saturday...prob doesn't get decent sampling until it is near there since northern NW territories and the Canadian archipelago isn't exactly a poster child for a dense obs network...and satellite isn't going to be great there either with the extreme cold. 

Bottom line is that we have a lot of northern stream and Arctic jet shortwaves that will matter to this system that are more prone to large changes than usual due to their position. So don't be surprised to see large changes on some model guidance between now and Saturday. It doesn't mean the changes will always be good for us, but obviously we will want to see changes for a hit here. 

Thanks for posting this. I'm I wasn't out in left field with thinking that.  I still think the Pac wave comes onshore a bit stronger than modeled.  We'll see.

[Cheeznado]

Since here in ATL we will just get a nasty cold rain, I plan to travel up to the AVL area, the ensembles have been incredibly consistent with some very hefty totals, check out the 06Z ensembles- 14 members with 20" or more.

[Buddy1987]

Just glancing at the nam at 57 here. LP placement looks to be the same when comparing it to 6z although HP up in Iowa is 2mb weaker. See if that has an effect on where the low goes toward the end of the run. 

[jjwxman]

1 minute ago, Cheeznado said:

Since here in ATL we will just get a nasty cold rain, I plan to travel up to the AVL area, the ensembles have been incredibly consistent with some very hefty totals, check out the 06Z ensembles- 14 members with 20" or more.

That is just insane, I don't know if I've ever seen an Ensemble Mean like that anywhere in NC. Be careful up there.