December 2018 Pattern And Forecast Discussion

[John1122]

I do look at that snow map and it's extremely similar to December 2009 when Campbell County got 4-8 inches of dynamically cooled snow. Areas near me got 1-2 inches in Scott/Claiborne and Whitley Ky. Tri/SWVA also got heavy snow with that one. It nailed the mountains and western Carolinas too. I can't remember the exact set up for that one or how similar it might be to this one. The rest of the region was heavy cold rain.

[AMZ8990]

3 hours ago, *Flash* said:

12z CMC with my Christmas wish...

Yeah, yeah...CMC has a cold bias. We all know this.

12z GFS is more realistic with a mostly rain to maybe snow event. Doesn't appear to be your traditional cold chasing precip scenario given the slider look. Not to mention I think temps will have a decent starting point before they crash/wet bulb, whatever. Almost like reverse overrunning (i.e. CAA > WAA), but it's all speculation at D9.

 

Whatever the case, we got decent digging at our latitude which we'll take early December, though lack of phasing, dull troughing, and out of place ridging (too far east) could end up spelling cold rain before all is said and done. Still think someone on I-40 is going to be happy next weekend. 

Me and you both brother.  I’ve been dreaming of a an I-40 special for a while now.  If we could get the entire forum in on the action it would be epic.  Maybe this is the year it happens!!

[jaxjagman]

No one mentioned the controlthrough 240 hr

[AMZ8990]

13 minutes ago, jaxjagman said:

No one mentioned the controlthrough 240 hr

That’s what I’m talking about.  Nice find Jax.  

[John1122]

After looking at the PSU site, the 2009 event was a miller A. HP over Minnesota and another over New York funneling cold into the CAD regions. Low developed off Brownsville and tracked NE. Classic Miller A that followed the path of the OP GFS rather than the further north solutions. 

[John1122]

I'll have one of what the control is having and call it a December.

The frigid yesterday dropped most of the areas around the region .5-1 degree in the November anomaly dept. Notably Tri fell from -2 to -2.7. It should fall a bit more today but once again temps are oddly warm there vs the rest of the region.  Most of East Tennessee is between 35 and 37 right now, even Chattanooga is only at 41. Tri is at 45, not sure what the low was there this morning or if they got to the predicted 49 today.

[Carvers Gap]

6 minutes ago, John1122 said:

I'll have one of what the control is having and call it a December.

The frigid yesterday dropped most of the areas around the region .5-1 degree in the November anomaly dept. Notably Tri fell from -2 to -2.7. It should fall a bit more today but once again temps are oddly warm there vs the rest of the region.  Most of East Tennessee is between 35 and 37 right now, even Chattanooga is only at 41. Tri is at 45, not sure what the low was there this morning or if they got to the predicted 49 today.

I don't think it is the station.  I started to wonder about that after seeing the other sites.  But it fits with the overall NA departure map.  "Warm" is a relative term.  LOL.   I am in the 40s right now, so it seems legit.  I just think everyone to the west of us have been hit by cold air masses that have modified as they spread eastward.  The cold by itself(excluding the past two days) has not been remarkable in terms of extreme lows.  Our mins rarely approached record lows, if at all.  I don't think we even set a record low.   What has been impressive are the cold high temps.  We had one day where we only reached 32.  I would not be surprised if we approached some record low max temps.  For whatever reason, I though the month ended on Sunday! Those days will obviously not be factored into November.  Ha!  Our normal high tomorrow is 53 w the low 31.  The high is predicted to be 57 w a low of 40.  So today and tomorrow will likely just cancel each other out.  We should finish right around the current -2.6 that is shown on the NWS site.  

 

[John1122]

We had some low to mid 10s on the Plateau yesterday morning. The record is around 8. So within 5 degrees. 

[Carvers Gap]

TRI's lows are only .7 lower than last November which was +1.0 overall for the month(Nov 17).  However, the high temps are 5.9 lower than last year.  That is the difference.

[Holston_River_Rambler]

Really interesting evolution of our potential wave over the next few days in the Pacific: https://imgur.com/a/f4h4twn 

It is now N. of Hawaii and as it rolls east, it stalls slightly because of the ridging being backbuilt through Alberta, long enough to phase with a piece dropping down from the Aleutians. Then it cuts off with ridging into AK above it, and rolls on into CA and across the US. Obviously this is just one model's depiction in one run of a fluid process, but I wonder if the relative steadiness of the wave as it has been depicted at such a long lead has something to do with the fact that other than the potential phase above it just seems to be on its own for a long time. 

[Daniel Boone]

2 hours ago, Carvers Gap said:

I don't think it is the station.  I started to wonder about that after seeing the other sites.  But it fits with the overall NA departure map.  "Warm" is a relative term.  LOL.   I am in the 40s right now, so it seems legit.  I just think everyone to the west of us have been hit by cold air masses that have modified as they spread eastward.  The cold by itself(excluding the past two days) has not been remarkable in terms of extreme lows.  Our mins rarely approached record lows, if at all.  I don't think we even set a record low.   What has been impressive are the cold high temps.  We had one day where we only reached 32.  I would not be surprised if we approached some record low max temps.  For whatever reason, I though the month ended on Sunday! Those days will obviously not be factored into November.  Ha!  Our normal high tomorrow is 53 w the low 31.  The high is predicted to be 57 w a low of 40.  So today and tomorrow will likely just cancel each other out.  We should finish right around the current -2.6 that is shown on the NWS site.  

 

The high at my home in Jonesville today was 40. Yesterday was 31. Tuesday, 28. 

[Daniel Boone]

4 hours ago, John1122 said:

I do look at that snow map and it's extremely similar to December 2009 when Campbell County got 4-8 inches of dynamically cooled snow. Areas near me got 1-2 inches in Scott/Claiborne and Whitley Ky. Tri/SWVA also got heavy snow with that one. It nailed the mountains and western Carolinas too. I can't remember the exact set up for that one or how similar it might be to this one. The rest of the region was heavy cold rain.

Oh yeah, that was the one that broke down alot of trees and power lines. Electric was out for about 2 days at my home. 9 inches officially in Jonesville.  It started and stayed mixed here until late afternoon the 18th b4 going to heavy snow. Upper Lee County , wise and Russell absolutely got pulverized.  All snow with 28 inches reported in the Wise area. Electric was out for a week or more in places. 

[Daniel Boone]

Here's an article describing the Dec. 18-19 2009 event. https://www.highknoblandform.com/2010/01/mega-disaster-storm-of-december-2009.html?m=1

[Holston_River_Rambler]

Love that blog. Had forgotten about it. Whoever writes that really loves High Knob. 

[TellicoWx]

Just starting to follow the event since it's within the Euro Ens time frame, but if you need a fix of snow porn lol, some of the individual members go crazy with the depth. It seems on the 12z there is 3 camps, each to a varying degree. 1 takes everything over KY, 2 is the slider solution which focuses on TN and hammers NC, and 3 is nothing to see here. The lean on the 12z was slightly in favor of the 1 camp. Should be fun to watch the trends over the next several days as the individual members should start coming together.

[John1122]

The 18z was epic. 00z is showing some snow on Wednesday now as well. 

[John1122]

18z had a big 1044 high in the Midwest. 1036 further north on the 00z at 198. Probably going to be a rainy solution on there for our region. The most important take away will be it hopefully staying Miller A instead of cutting.  

[John1122]

I had to laugh at the 198 to 204 panels on the GFS. Shows the storm off the Louisiana coast and seems to move it 300 miles due N into West Central Arkansas over the next 6 hours.  Straight towards the 1036mb high in the Plains.  It's an hilarious path. It drops Southeast from West Texas to off Louisiana,  moves straight north 300 miles, then starts moving due east just south of the Tennessee border and it moves due east and off the coast.  I don't know what path/solution we will see, but I'll bet my house it's not that.  

[John1122]

The Canadian is a cutter, I can understand that path, even though it's not good for anyone here. 

[John1122]

Euro no longer cuts and now goes from Eastern Texas to near Columbus Georgia then up the coast rapidly. It's heavy snow axis is about 150 miles south of the GFS heavy snow axis now.  The FV3 GFS is very close to the Euro on track/snow axis. We need the track 100-150 miles further south an we'd have a 40 special. It spits out a snow map sort of similar but not as extreme as it's 12z run, with temps being very borderline and near 32 at 850/925/surface for north of 40 in parts of our forum. So very very close to rain/snow. 

The last days runs have shown it moving with the GFS but always being further south than it. The 12z GFS was too far north for us, the FV3 nailed north of 40. The 18z GFS was a big hitter for our forum, the FV3 had North Georgia getting a big hit. Now the GFS is back north and the FV3 is south of it, but still back north. 

[TellicoWx]

Looking at the Euro Ens individual members, at very noticeable shift into the Northern camp (I40 north into KY). Southern solution members dropped from roughly 35% to around 20% for areas south of 40.

[AMZ8990]

Looks like we continue to have a good signal for a storm around the 8th of December.  Hopefully that trend continues through the weekend.  Plenty of options being spit out by the models, I still think we have another day or 2 of options being rotated through the models.  By Monday or Tuesday we should be able to start seeing which options the models are revisiting and hopefully that gives us somewhat of an idea of what this system is gonna want to do. 

[Holston_River_Rambler]

One thing I noticed was that the EPS average on TT was a little bit slower with it in the southwest. I'm interested in this extra energy the GFS and FV3 have as the initial storm is moving out. If I remember correctly sometimes these storms coming from the SW get delayed by a day or two as we get closer.  I wonder if there ends up being more interaction between the two if the first slows down enough. 

I'm also flabbergasted that the interaction between the 2 energies in the Pacific hasn't changed that much from 18z to 6z.  But then again it's only 72 hours out, so I guess there may not be much change in that. 

[Holston_River_Rambler]

Also just found this (link from Anthony Masiello) for SPV and SSW analysis: https://stratobserve.com/misc_vort3d 

[John1122]

The 06z is back to a slower and more miller A track. Still spits rain out but temps are 4 or 5 degrees colder vs 0z. The fv3 continues to have snow output or ptype output issues. Not sure which. But it dumps heavy snowfall totals while showing the rain/snow line at the ohio river. 

[Carvers Gap]

Euro Weeklies look much improved.  The four week warm spell has been contracted to about 10-14 days w a strong cold signal for January. The hindcast product has less of a warmup than that.  Very reasonable and well with in the parameters of a weak El Nino winter.  The ridge lifts out.  Seasonal temps slide underneath for late December and then January looks cold.  To sum up...The warmth will be there, but should be slowly transient. The cold returns with a nice signal for snow in early January.  Being suspicious of the previous runs appears to have been the proper course.  The timeline by @nrgjeffis on the money.  

 

[Carvers Gap]

As for the trends overnight w the seven day storm, just first glance....appears that we are lacking those cold highs that were trailing or north of the slp that we had on yesterday's runs.  Still plenty of time for everything to change.  The ensembles have backed-off slightly from their snowfall output.  Overall, still not a bad look and plenty of room for things to change for better or worse.  Also, there is a minor event right before it that probably deserves watching.

[Holston_River_Rambler]

I think Flash's warning about the thermal profiles is a good one. But I will say if there was an overall set up that at least has a shot at trending colder, this is it. Clipper blazes by to the north and reinforces the High, but like you said I wish the High was a little further west. 

I not totally sure just yet, but it just seems like the southern stream feature is not going anywhere. It may wobble and change strength and size, but a lot of how this unfolds looks like it depends on the northern part of the split flow and how those fast waves come in/ angle/ timing.

FV3 H5 energy is rounder as it hits CA (GFS had it more oblong) and the northern stream is quite a bit different at hour 138, let's see where it goes. 

[Carvers Gap]

As with the overnight suite, there is just no mechanism to hold the cold air in place.  Now, one thing to be watch is this....that is a very cold air mass in place prior to its arrival.  The parent high slides off.  If the WAA is too slow, some of the cold air could get trapped from I-40 north.  If it slides across and is weak w no warm nose, that is how one gets ice in the eastern Valley.  During the mid 90s I was working Knoxville.  Temp was in the mid to upper 30s.  It started raining, the temp dropped, the cold air got trapped, and it was a skating rink.  I think it happened on a Friday.  People just got out of their cars in the middle of Kingston Pike and walked to the nearest store.  Went on all day.  But plenty of time for this to change and it surely will.  

[Carvers Gap]

Also, take a look at the LR GEFS....it breaks down that ridge fairly quickly now(the pig, amirite?).   One can easily see that the area over AK is not the big blue blob.  There have been some pretty good things that have happened during the overnight and midday runs so far.