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December 2018 Pattern And Forecast Discussion

AMZ8990

By AMZ8990,
in Tennessee Valley

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Blue Ridge

Blue Ridge

Posted
Posted
4 minutes ago, John1122 said:

Neighboring WFO in Kentucky, NC and VA have issued winter weather advisories for snow overnight and into tomorrow. Waiting to see if MRX follows suit. Fairly robust wave working through the area over the next 24 hours. Just had a burst pass through that was blinding for about 10 minutes. Hopefully they increase in frequency overnight.

GSP has followed suit with a WWA for border counties >3500 ft. 

MRX has not yet issued the afternoon disco/forecast package, so we should soon know one way or another.

 

EDIT: There she is.  

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...None.
TN...Winter Weather Advisory from 8 PM this evening to 1 PM EST
     Wednesday for Blount Smoky Mountains-Cocke Smoky Mountains-
     Johnson-Sevier Smoky Mountains-Southeast Carter-Southeast
     Greene-Unicoi.

VA...Winter Weather Advisory from 8 PM this evening to 1 PM EST
     Wednesday for Russell-Wise.
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Math/Met

Math/Met

Posted
Posted
11 minutes ago, John1122 said:

Neighboring WFO in Kentucky, NC and VA have issued winter weather advisories for snow overnight and into tomorrow. Waiting to see if MRX follows suit. Fairly robust wave working through the area over the next 24 hours. Just had a burst pass through that was blinding for about 10 minutes. Hopefully they increase in frequency overnight.

Model soundings show fairly steep low level lapse rates and saturation extending into the snow growth zone tonight. I would expect there to be some decent snow shower activity. Just need to get lucky and be under the right band. 

 

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John1122

John1122

Posted
Posted
Just now, Math/Met said:

Model soundings show fairly steep low level lapse rates and saturation extending into the snow growth zone tonight. I would expect there to be some decent snow shower activity. Just need to get lucky and be under the right band. 

 

The ones that have drifted across my area today are almost convective in nature. Very heavy snow and windy but for short times.

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BlunderStorm

BlunderStorm

Posted
Posted

Today's flurries are only adding to my excitement. It's like the appetizer before the main course. I'm trying to keep my expectations down but significant snow is starting to become expected. I say that cautiously of course! :lol: EDIT: Sorry wrong thread... my mind was still running on yesterday! :arrowhead:

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BlunderStorm

BlunderStorm

Posted
Posted
8 hours ago, John1122 said:

The Euro has the second system again tonight. Looks like it drops 3-5+ on the Plateau and Mountains.

It would be fun to have this storm come through and segue to another storm the weekend after next. If it's still there in a couple of days we might as well transition our focus to that as soon as the snow or lack thereof is done.

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Carvers Gap

Carvers Gap

Posted
Posted

Seems almost a certainty that the mountains at the very least are going to get hammered w snow.  Looking at the last three runs of the Euro around d8-9, it has strong slp moving through the upper South.  Looks like a likely rain event(outside shot as snow).  Seems like a good recipe for mountain stream and foothill rivers having some flooding issues.

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Carvers Gap

Carvers Gap

Posted
Posted
7 hours ago, nrgjeff said:

ECMWF has the second storm around Dec 14. No high press north; but, Euro dynamically cools the column. Euro shows a more vigorous 500 mb trough and deeper surface low. I would not trust any of that past day 7; but, FWIW the GFS concurs. 

I may have to work out some sort of George Costanza mid-day napping plan if this continues...

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nrgjeff

nrgjeff

Posted
Posted

Overnight NWP wants to kick the Dec 14 system north. Yup it does wrap around a comma head west half to 2/3 of sub-forum region, plus higher elevations (Plateau and Mountains). Easy all rain forecast for Chattanooga though. Still a week out, but verbatim looks like the Midwest/OV benefits from some sort of phase. Again this is the December 14th event.

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AMZ8990

AMZ8990

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13 hours ago, John1122 said:

FV3 system at 186 has some major wrap around snow over the western 2/3rds of the forum. Not sure if that had been showing up out west or not.

 

5 hours ago, nrgjeff said:

Overnight NWP wants to kick the Dec 14 system north. Yup it does wrap around a comma head west half to 2/3 of sub-forum region, plus higher elevations (Plateau and Mountains). Easy all rain forecast for Chattanooga though. Still a week out, but verbatim looks like the Midwest/OV benefits from some sort of phase. Again this is the December 14th event.

Hadn’t noticed that, I’ve been to wrapped up with the current system we’ve all been tracking to even look out hat far. Ha.  It is surprising that you guys bring this up though.  The small November snow storm we just had last month wasn’t showing up long range for a while but another storm had been for a week or so.  We all tracked it and then about 3 days out things changed and we lost out on the storm.  But no sooner did we lose out on the first storm then the second (November snow system) started to show up on models.  By Wednesday night I had an inch of snow on the ground.  I say this just to point out how it’s funny how these systems have come in waves lately, it’s kinda similar to the setup we had with our Trowal snowstorm this past January as it was preceded by another system 3 days later that dropped more snow for a lot of the forum.  Seems like there has been a trend with these systems this year!

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Carvers Gap

Carvers Gap

Posted
Posted
2 hours ago, Wurbus said:

That looks awesome.....too bad its not the FV3 & Euro with that look.

Interestingly, the 12z Euro and FV3 now have a similar look as the ICON/GFS run, but is warmer.  That is a wild look.  (@nrgjeff, what is that look called w the big, arching look of that low? It takes at a steep rate out of the GOM.  I am always a bit suspicious of models that show a "storm after the storm."  Always seems like a common feedback problem to have a second storm. That said, that system has been popping up on models for some time.  Now, I am not saying it is going to snow...as it has little cold to work with.  Jeff has a great description of that scenario above about how it "could" snow.  Interesting and unusual setup.  Just something to watch.

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nrgjeff

nrgjeff

Posted
Posted

Yes that Dec. 14-15 storm looks quite elevation dependent now. Probably too warm Valleys, maybe warmer than this weekend. 

1 hour ago, Carvers Gap said:

Interestingly, the 12z Euro and FV3 now have a similar look as the ICON/GFS run, but is warmer.  That is a wild look.  (@nrgjeff, what is that look called w the big, arching look of that low? It takes at a steep rate out of the GOM.  I am always a bit suspicious of models that show a "storm after the storm."  Always seems like a common feedback problem to have a second storm. That said, that system has been popping up on models for some time.  Now, I am not saying it is going to snow...as it has little cold to work with.  Jeff has a great description of that scenario above about how it "could" snow.  Interesting and unusual setup.  Just something to watch.

Are you looking for TROWAL, comma head, or another one? I got plenty of names for it in Chattanooga, but I should not write them on the forum, lol! 

Seriously, about the path to higher elevation snow, yes dynamic cooling method works better Plateau/Mountains. Fails Valleys if surface temps mid-30s. Anyway the current event looked better a week out than the 14/15 event looks now. Current event still looks better (north of course) so good luck to all!

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Carvers Gap

Carvers Gap

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Posted
9 minutes ago, nrgjeff said:

Yes that Dec. 14-15 storm looks quite elevation dependent now. Probably too warm Valleys, maybe warmer than this weekend. 

Are you looking for TROWAL, comma head, or another one? I got plenty of names for it in Chattanooga, but I should not write them on the forum, lol! 

Seriously, about the path to higher elevation snow, yes dynamic cooling method works better Plateau/Mountains. Fails Valleys if surface temps mid-30s. Anyway the current event looked better a week out than the 14/15 event looks now. Current event still looks better (north of course) so good luck to all!

LOL.  100% agree it is not a high percentage look.  Thanks for the response!  Obviously that is a big low.  I did not know if that type of sprawling low had a particular name.  Seems like we see some with that look(huge low) over the Plains, but not so much over the East.  The backside of that low goes from the GL to north Georgia.  I kind of dismissed it as a wonky look until the Euro decided to play along, albeit warmer.  Is that a set up where we get a squall line of rain and then the TROWAL on the backside. of the system.  Just a wild look.  Sorry, I picked the snowiest one.  LOL. Probably should have picked one that is a bit more realistic.  

Screen Shot 2018-12-08 at 4.06.20 PM.png

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Math/Met

Math/Met

Posted
Posted
22 minutes ago, tnweathernut said:

I’d bet a dollar to a donut, @Math/Met   is searching for a mountain wave event with the look of the system on the 14th and 15th......

I've been too focused on the current system,  but you are right. The 12z GFS would have potential for a major mountain wave event with that system. 

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TellicoWx

TellicoWx

Posted
Posted

The system around the 15 may squeeze a few snow showers out for the mountains. The trailing 850 vort captures some neg 850s with it, 18z GFS came in further south while 12z Euro came north. With no cold air supply to the north, it's elevation driven. Looking at the teleconnections, around and after the 21st is where I'm interested to see if anything can begin to show up for anything in our forum. PNA is kinda blah.

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John1122

John1122

Posted
Posted

As we get towards Christmas the teleconnections look favorable. The AO is also forecast to tank towards late month. Tough to beat a strong +PNA, a -AO, -NAO, and the EPO falling rapidly towards negative and the WPO going towards negative helps too. When it's negative or neutral it doesn't effect our weather much. But when it's positive in January we tend to be slightly AN. 

4indices.png

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Holston_River_Rambler

Holston_River_Rambler

Posted
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If this big upper this weekend keeps looking like it will produce some nice elevation snow, I might take a little hike up above 5000 feet to see what happens. 

Yeah, as y'all pointed out, seeing different people saying that around Christmas time will be when a better pattern will start to set up. GFS starting to spit out big old highs in western Canada and dropping them down in it's fantasy range. I've seen those totally disappear as we get closer and I've seen them verify, but at maybe 10 to 15 mb smaller than the fantasy depictions. Case in point, Fv3 has one just 13 mb lower. Decent signal on EPS, GEFS, and GEPS for a storm (maybe a cutter for us) around the 20-22, so if a cutter verifies, it could bring down some cold and set up for something afterwards.  MJO op. forecast looks like it just wants to basically do exactly what it did last month, at exactly the same time, so if it works out that way Christmas would put us on the cusp of phase 8.  I think we might get another cutter, but further south around Christmas and then the next storm or so might be better for us, maybe around the New Year if this works out (NWS meteorologist for Louisville, KY: 

Of course all this assumes the MJO has a major impact on us and unfolds how I speculated above. The EPS MJO chart shows a lot of uncertainty. Everything from twisting back into phase 2, to jumping ahead to phase 6, to a high amplitude phase 4 are on the table on the EPS by the 23 Dec, even though the mean looks similar to it's progression last month.  

Wondering how the stratosphere will develop as well. Not been paying much attention over the past week, but man, even the ensembles (no access to EPS though) are honking that there will be a warming, but not a split. As I think Carver's has said (if I'm misrepresenting this I apologize) these can be wild cards and have effects that are felt at different times and different intensities across the N Hemisphere, so just something to watch at this time. I will throw this image out though. It is a composite of 60 days before and 60 days 500mb height anomalies after a SSW in 13 El Nino years (as far as I could tell no distinction made for SSWs that caused splits and those that caused displacements of the Stratospheric Polar Vortex, for new folk that is the large circulation at the very top of the troposphere over the N pole.) Looks like they tend to cause blocking at 500mb, but again that image is the average of 60 days over 13 events, so plenty could be different in this case and that's even if it happens. Link to paper I took the image from: https://www.earth-syst-sci-data.net/9/63/2017/essd-9-63-2017.pdf 

ssw butler paper.png

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