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January Medium-Long Range Discussion


Holston_River_Rambler
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2 hours ago, Carvers Gap said:

On a non-winter wx note.... @Math/Met , is this a high end event?  It looks like it may take a while to burn out....

Screen_Shot_2024-01-07_at_2.02.53_PM.png

 

Yes, this could be a very impressive event. I need to give credit to MRX for their great afternoon discussion regarding this. I completely agree with everything they wrote, and I actually agree that the mountain waves might extend a little further away from the mountains than usual. 

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That system on Tuesday looks to be real stout. Lots of rain and wind. Even noticed models have increased the backside flurries and snow showers. Does anyone think the models will get a better read of the 7+ day cold/snow chances after Tuesday? I know big storms usually lead to big changes. 

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From MRX and just adding to what @Math/Metmentioned:

The main hazard will be a strong mountain wave event that is set to
begin Monday night. The synoptic pattern favors a high-end mountain
wave event with the core of the 850mb wind maximum (nearly 70-80+
knots) west of the Appalachians. Additionally, cross-mountain flow,
a stable layer across the ridge tops, and a strong pressure gradient
aligned across the mountains only add to the confidence of a strong
mountain wave event likely to take place. Just as the previous
discussion from this morning mentioned, gusts up to 100 mph wouldn`t
be a surprise for the usual wind-prone areas such as Cove Mountain,
and Camp Creek. Additionally, in the very strong cases, its not
surprising to see the "waves" extend further into the foothills than
what is typical, although the magnitude of winds isn`t as strong as
those higher elevations. Downsloping from this event will lead to
adiabatic warming across the foothills and the forecast will reflect
some of this warmth Monday night and Tuesday.

Winds will still be strong outside of the mountains, albeit weaker.
There will be a delay between when the mountain wave winds start and
the winds in the lower elevations. Lower elevations probably won`t
see these winds pick up until daylight hours Tuesday. Gusty winds
will continue into Tuesday night before decreasing as the jet core
races off toward the northeast and the pressure gradient relaxes. As
the rain moves out, much colder temperatures will advect eastward
with 850mb temperatures falling to -6C to -8C leading a subsequent
increase in lapse rates. Scattered rain and snow showers will be
possible Tuesday night into early Wednesday morning within the base
of the trough. Moisture will be limited so not expecting any
significant accumulations from this or the weak orographically
induced snow across the Smokies. High pressure at the surface
settles across the northern Gulf coast and Florida peninsula through
Thursday bringing drier weather to the region.

 

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The 18z GFS is quite cold around the aforementioned time frame.  Wind chills are well below zero, even during daylight hours.  It reminds me quite a bit of the system from December '22.  Portions of middle TN reach -15F on the thermometer.  Real Feel is -20 to -30.  We are seeing this across modeling to varying degrees.  Does it happen?  No idea.

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Man that 18z would be rough to take. We get to watch a massive snow storm lurk just outside the area while it's 33 with heavy rain, out of an actually perfect track storm with record breaking cold very close by. For some reason the HP that feeds the cold moves SE that run then suddenly moves due south without further easterly movement. I'd guess 99.99 percent chance the whole storm that run is wrong but that would be one of the worst ways to be right.

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Just looking at the cutter or slider around the 16th.  The 18z operational was more of a middle/west TN system.  The ensemble for the same run is much further south and gets the entire state.  

This is the system which comes after the mid-state cutter on the 13th.  The one on the 13th might end-up needing a thread tomorrow or Tuesday for west TN, western KY, eastern Arkansa, and southwest Mizzou.  It starts Friday night.

IF the trend continues.  The GEFS supports the operational at 18z....

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Just now, John1122 said:

Man that 18z would be rough to take. We get to watch a massive snow storm lurk just outside the area while it's 33 with heavy rain, out of an actually perfect track storm with record breaking cold very close by. For some reason the HP that feeds the cold moves SE that run then suddenly moves due south without further easterly movement. I'm 99.99 percent chance the whole run is wrong but that would be one of the worst ways to be right.

Pretty par for the course the past few years. Lots of 30s and rain in the valley while the Plateau west cleans house. It's like we are stuck in that Nina pattern. 

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The 18z GEFS ensembles is south of 12z which was suppressed to begin with for the 16th system.  The ensemble does not agree with the operational for that timeframe.  Could the operational be leading the way?  Sure, but that is a long way out....almost 8 days.  At this range, the operational is just a member of the ensemble.  Now, this Friday's system is a different story....

 

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The 18z GEFS  ensemble runs the risk of suppressing the system below the TN/KY line completely...and maybe south of I-40.  It has snow and ice in Louisiana.  MUCH different than the operational.  Suppression is my concern.  The eastern 2/3 of the US was roughly 3-5 degrees colder on that run during the timeframe of the 16th.   The trend on the ensemble is suppression.

We have seen the operational grow weaker and southeast during the past few weeks in regards to trends.   The ensemble makes more sense at this range.

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The system on the 16th is 198 hours from potential reaching E TN -> just 198 hours to go.   That is a long, long way to reality.  Ensembles are my choice at this range, and they look good for much of the state.  Still, we are so far out from that storm....details will almost certainly change.  The entire system could change at this range.  The operational was just about a Miller A.  My main concern is that operational modeling is not sensing the Atlantic block(result is spinning up into the block), and ensembles are trending south.  It is a good, big-storm look.  I wouldn't swing one way or the other at this range.

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Here are 18z to 12z GEFS side-by-side comparison slides.  I use that comparison a lot.    The 18z is on the left of each slide.  Notice the entry point into the region is much further south.  Look at the rain/snow line in the second slide.  First side-by-side comparison is 189 and the second is 207.....

This storm is so far out there, I am bordering on posting a 240 operational map and discussing details about it.  But here it is....

 

Screen_Shot_2024-01-07_at_6.48.20_PM.png

 

Screen_Shot_2024-01-07_at_6.48.04_PM.png

 

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1 hour ago, Daniel Boone said:

All good except for one. 2004.

I don't like the '59 analog, even though it fits nearly perfectly w/ this past anomalous dry Sept/Oc.   During future winters, I may start looking at a correlation between precip during Sept/Oct and winter.

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5 minutes ago, tnweathernut said:

Just looking at the operational 18z vs the ensemble at 500 at hour 180 (truncation).  See if you can spot the differences.

18z GFS 500 Anomaly Map 01072024 valid 01152024.png

18z GEFS 500 Anomaly Map 01072024 valid 01152024.png

Good comparison.  The good thing(or bad thing) is that likely will change at this range.

Feedback over the Southwest in the operational and more blocking on the ensemble (slight orange above MI)????  The feedback in the operational pops the SER?   The SER maybe(?) shouldn't be there w/ that NAO configuration?  The ensemble is much colder and has a deeper air mass(cold).

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2 minutes ago, Carvers Gap said:

Good comparison.  The good thing(or bad thing) is that likely will change at this range.

Feedback over the Southwest in the operational and more blocking on the ensemble (slight orange above MI)????  The feedback in the operational pops the SER?   The SER maybe(?) shouldn't be there w/ that NAO configuration?  The ensemble is much colder and has a deeper air mass(cold).

Biggest things I noticed were:

1.  The OP has the ridge off the west coast tipping to the northeast.  This invites the northern stream to roll downhill further southwest, interacting with the southern branch feature and pumping the heights in the east just enough to screw up something possibly great. 

2. The ensemble is smoothed (I get that), but if it has any energy in the southern branch it is suppressed.  Since the ridge off the west coast doesn't tip northeast, the cold shot progresses to the SE.

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10 minutes ago, tnweathernut said:

Just looking at the operational 18z vs the ensemble at 500 at hour 180 (truncation).  See if you can spot the differences.

18z GFS 500 Anomaly Map 01072024 valid 01152024.png

18z GEFS 500 Anomaly Map 01072024 valid 01152024.png

Doesn’t look like the EPS has that energy diving into the southwest.  The GEPS looks like it was TRYING to do the same as the GEFS but doesn’t get there.  Like Carvers said, we’re still over 7 days out and who knows exactly how this storm plays out.  Fun to watch though…

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5 minutes ago, Carvers Gap said:

With any of those looks (on the bright side), somebody in the forum is getting ice/snow.

And if you like dynamic systems, these next couple of weeks will be your jam.

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3 minutes ago, BNAwx said:

And if you like dynamic systems, these next couple of weeks will be your jam.

Yeah, gonna be wild.  But at least we are tracking legit systems.  Great points by all involved.  Now, we just have 28 more runs to hammer out!  LOL. 

I am not sleeping on next weekend though.  Could be interesting for western areas.  

Get a couple of looks before this cold shot slides past, and then reload for Feb?

The MJO is possibly going to pass into phase 4 around the 16th.  That is a double edged sword.  There should be a SER, but there could also be a big storm as the MJO rotates out of possible phases.  Phase 3 has produced big storms before.  

Fun stuff for sure.....

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42 minutes ago, Carvers Gap said:

I don't like the '59 analog, even though it fits nearly perfectly w/ this past anomalous dry Sept/Oc.   During future winters, I may start looking at a correlation between precip during Sept/Oct and winter.

My mistake. Somehow mixed up with 58. 2 duds that way, 59 and 04.

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