Winter Speculation 17/18 -December Thread

[John1122]

After 240 a major warm surge comes north and switches everything to rain. Doesn't feel particularly correct with a 1040 hp sliding along the Great Lakes north of the system. With that high strength and placement we stay frozen 90 percent of the time. Odd run again as the LP decides to cut inbetween a 1040 high over the eastern lakes and a 1040 high over the planes. I guess this particular storm would be where a -NAO would help a lot.

Still a long way out but it's becoming more and more likely that weather will be an issue around Christmas, either in the form of ice or heavy rain.

[Wurbus]

Looks like the CMC brings the cold right before Christmas. No storm like the GFS has, although looks to be spinning up something in Texas at the end of the run.

[Carvers Gap]

When you look at that 12z GFS run at 500...I just cannot explain it.  From about day 8....At one point there is a -EPO, -NAO, SER, and cutoff low in the southwest.  We need the meme of the lady w no teeth saying, "Wat?"

[tnweathernut]

Not going to allow 12z GFS modeling to zap my optimism, lol.  All I will say is through day 10 improving trends were shown. 

After day 10, a lot of things were modeled that are not very likely to actually happen.   Carry on.......

[Carvers Gap]

However, one thing I can take away from that run...and there is not much.  Each system that rides the boundary pushes the boundary further SE.  I do suspect the GEFS will hold serve to its earlier solution.  One other point, sometimes the 500 maps looked awful, but there was cold under the ridge.  The models are struggling w the placement of the surface boundary.  The pattern really looks icy for someone in the forum area.

[Carvers Gap]

I will say that since 0z, each successive run of the operational has pushed the SER southward.  Great disco, everyone.

[Carvers Gap]

2 hours ago, AMZ8990 said:

Yeah it was, it's a good thing it will flip flop in a few hours though! Lol.  

Prophetic statement was prophetic.  Ha!

[Carvers Gap]

26 minutes ago, John1122 said:

After 240 a major warm surge comes north and switches everything to rain. Doesn't feel particularly correct with a 1040 hp sliding along the Great Lakes north of the system. With that high strength and placement we stay frozen 90 percent of the time. Odd run again as the LP decides to cut inbetween a 1040 high over the eastern lakes and a 1040 high over the planes. I guess this particular storm would be where a -NAO would help a lot.

Still a long way out but it's becoming more and more likely that weather will be an issue around Christmas, either in the form of ice or heavy rain.

Good point and I agree.  Even though that run is probably not going to happen...it is a good point that a 1040 hp would be expansive and would likely not get out of the way fast enough.  I think we may see a similar set-up in actuality but under realistic circumstances.  Big, cold, expansive highs that moisture rides up and over.  Each wave will successively push the cold boundary southward.  I still think there are model problems with that cutoff.  The smaller it is, the weaker the SER.  At 18z, it was not there.  Since 0z, it has been progressively lessened.

[AMZ8990]

17 minutes ago, Carvers Gap said:

Prophetic statement was prophetic.  Ha!

Haha, that's right!  Get your popcorn ready folks, cause things are gonna get interesting the next few days!!

[Carvers Gap]

I keep forgetting my rule...when cold air with big hp is in play, the models will struggle.  The 12z GEFS is a massive improvement.

[ShawnEastTN]

I think the NAM at 84 has a better handle than the GFS at 84, and its the NAM at 84...  

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[Carvers Gap]

The 12z GEM is a nice run...not my find.

[ShawnEastTN]

2 minutes ago, Carvers Gap said:

The 12z GEM is a nice run...not my find.

Yeah it definitely looks better!

[John1122]

GEFS temps after a warm few days next week.

Dec 20th - 25th

 

23rd-28th

 

25th-30th

[nrgjeff]

12Z Ensembles are less of a SER train wreck, but I'd rather be sunny and 70 than dealing with ice. I really want to see the Euro weeklies in a few hours.

Forecaster note: When HP is settling in with precip falling undercut MOS temps. Once the center of HP is east of the Apps (like Penn.) the Great Valley will warm as forecast by MOS. Knoxville freezing is usually a 50/50 bet. CHA/HSV will go above freezing. Since I can't stand ice, that scenario is one of the few times I like the CHA stubborn warm bias.

Ice in the region is miserable at work, but I can tolerate it when CHA is 34 and my home has heat and power.

Bottom line: The cold is likely coming but timing is elusive. Worst chase would be cold splits to Southwest USA and Great Lakes/New England, with the western part modifying before arriving here. However that's an unlikely scenario. 

[John1122]

And I know I posted this yesterday, but look at the -EPO forecast. Look at the GEFS temp maps and compare them to this typical -EPO pattern. Looking at those GEFS panels a front stalls well on the other side of the Apps and into the deep south with re-enforcing shots of cold working into our area as the EPO ridge over Alaska forces NW flow into the lower 48 east of the Rockies.

 

[Carvers Gap]

Really, this pattern seems to hinge on the cutoff over the four courners area.  The 12z GEM just kicks it out and places a trough over the East.  The 12z GEFS places it there(maybe a bit too long), and then kicks it out.  The Euro I think will be up to its usual bias and leave it there to long like it did at 0z.   I mentioned the Butterfly effect earlier.  Crazy how one feature, at least on the surface, is creating problems downstream on numerical modeling. The weaker the cutoff out West, the deeper the trough here. If the boundary is anywhere close to this area, I think the cold will be SE of that line.  The stronger the HP, the more displaced SE the cold.  Like John posted, GEFS is much cooler.  Jeff, I missed the only ice storm in E TN in my lifetime.  It was during the early 80s.  Though Knoxville, had some snow on ice during the early 90s.  

[Carvers Gap]

9 minutes ago, John1122 said:

And I know I posted this yesterday, but look at the -EPO forecast. Look at the GEFS temp maps and compare them to this typical -EPO pattern. Looking at those GEFS panels a front stalls well on the other side of the Apps and into the deep south with re-enforcing shots of cold working into our area as the EPO ridge over Alaska forces NW flow into the lower 48 east of the Rockies.

Great post.  Teleconnections are in our favor in the Pacific including the low/trough near HI.

[PowellVolz]

Great post.  Teleconnections are in our favor in the Pacific including the low/trough near HI.

It’s why the cold filtering west doesn’t make sense


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[Carvers Gap]

4 minutes ago, PowellVolz said:

It’s why the cold filtering west doesn’t make sense


.

Check out the 12z Euro correction at day 8.5 .  LOL.  Man, what a swing.

[Carvers Gap]

The 12z Euro is almost perfect to d9.  Then, inexplicably reverts in a 12 hour period to the trough in the Southwest.  That said, the trough that was here leaves plenty of cold.  Like a Star Wars movie it ends w a cliffhanger.  1044 high over western Nebraska and a 1040 high over Wisconsin and western KY w a gathering storm moving north out of the western GOM along the TX coast.  D10 map below.

[nrgjeff]

East Valley can get light frozen events but fortunately devastating ice storms are rare. Mid South and Carolinas both get crushed more often. I concede the light/mdt events are pretty next day esp. with sun.

54 minutes ago, Carvers Gap said:

Jeff, I missed the only ice storm in E TN in my lifetime.  It was during the early 80s.  Though Knoxville, had some snow on ice during the early 90s.  

12Z Euro verbatim is nice. Surface ridge still working in with 850 temps cooling. Too bad it's hour 240.

[Carvers Gap]

4 minutes ago, nrgjeff said:

We can get light frozen events but fortunately devastating ice storms are rare. Mid South gets crushed relative to us. I concede the light/mdt events are pretty next day esp. with sun.

12Z Euro verbatim is nice. Surface ridge still working in with 850 temps cooling. Too bad it's hour 240.

No doubt on both counts.   Though d10 for the storm, some nice changes are seen just after d7 with the trough dropping southeastward out of the Rockies.  Really, give me the changes from days 7-9, and I will take those....seems to be the trend at 12z.  But the way the models are swinging....definitely need to keep the powder dry.

[Carvers Gap]

It is pretty wild how expansive the cold is from days 7-10 on the 12z Euro.

[John1122]

Bad ice storms occur on the plateau fairly often. Usually every 2-3 years we get a moderate event. Seems especially common around Crossville as they are in the I-40 battle zone. A couple years ago they were just devastated with freezing rain. I got the sleet storm of a lifetime and 20 miles up the road in Corbin, they got 12 inches of snow. I believe the entire Central Valley of East Tennessee got 1/2-3/4ths inch of ice from that one. 

Christmas 1998 will be the ice storm of record here, probably for my entire life. 3 inches of ice and a no power Christmas wasn't fun.

[John1122]

This is what's budding for our SW forum members Christmas  Eve Morning under what Carvers showed. Perfect set up for a Valley wide slider with that sprawling 1040 high across the Ohio Valley.

[tnweathernut]

John, I love the simplicity of that graphic.  Very clean and "old school" look....  

Such small changes in the 3-6 are yielding huge changes down the line.  Going to have to get through the next 7 days to really know where this is going or how it will play out, but overall I am feeling encouraged by the 12z model suite.  The Canadian looked like I thought it should in the extended, just based on such a strong EPO and also a little transient help from the NAO region.

Would be fun if it plays out like the Euro OP, as someone in the mid-south region would have a sizable winter storm on their doorstep by Christmas.

[PowellVolz]

I still think we will see a strong push SE with the arctic air. IDK if it will be enough for all of us to get in the game but I just don’t see the SER holding on that long.


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[nrgjeff]

That one two years ago crushed Volunteer Electric. Plateau does get it too. Meanwhile Chattanooga was mostly just rain - good.

5 hours ago, John1122 said:

Bad ice storms occur on the plateau fairly often. Usually every 2-3 years we get a moderate event. Seems especially common around Crossville as they are in the I-40 battle zone. A couple years ago they were just devastated with freezing rain. I got the sleet storm of a lifetime and 20 miles up the road in Corbin, they got 12 inches of snow. I believe the entire Central Valley of East Tennessee got 1/2-3/4ths inch of ice from that one. 

Christmas 1998 will be the ice storm of record here, probably for my entire life. 3 inches of ice and a no power Christmas wasn't fun.

Christmas 1998 is a great memory. It started in Texas. I'm quoted in the Christmas Day Dallas Morning News(paper) saying, it's going to be a Black Ice Christmas. Reporter had asked me about White Christmas, and that came out of my early career mouth. Fun times in Wichita, KS I think we scored a dusting of snow Christmas Day while Texas (to Tennessee) got iced.

Finally the Euro weeklies kind of say what the ensembles say: Hurry up and wait. Cold is coming. Verbatim it has the 16-20 day cold. Could be a little faster.

[Carvers Gap]

Weeklies.  Not even worth an in-depth analysis.  Minus the western third getting a token week, the forum area is AN wall-to-wall after this week.  Those are the Weeklies we know and love.  The morning run was warm...the Weeklies (that are based off that run) just continued a really ugly run.  No surprise.