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John1122

December 2020 Medium/Long Term Pattern Discussion.

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0z GFS is most eastward of the last four runs with a slight eastward jog of the slp center since 0z last night.  The 0z. GFS now sends a portion of the energy east of the Apps.  The 0z run from last night too the center through middle TN.  This run is splits the app with the designated low along the spine or just a hair west of it.

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Hey all.  Interesting storm. Tons of small variables can really enhance or suppress our backside moisture.  Hoping to squeeze out an inch or two here! 
 

Waiting to see what high res models show over the next day. Very fascinating storm evolution.

 

3km has a legit line of broken cells and then snow a few hrs later.. going to be a wild few days.

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Snow amounts did tick up in the 00z suite so far.  If I were guessing I'd say an inch or two may fall in some non elevated areas of Middle Tennessee especially, but it'll be hard to have more than a heavy dusting to 1/2 inch on the grass the further west you are due to time of day and warm ground temps. 

 

Right now I'm just hoping to see something and hopefully it's not the best event of winter. 

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Marginal differences towards the 72 timeframe vs 84 at 12z.  Low is in western New York, 992 vs 990 at 12z. Overall snow showers across the eastern 2/3rds of the state. The low moves slower this run and the change to frozen happens later across our area. The low does a loop in New York this run instead of moving into SW Ontario like it did at 12z. This keeps the upslope more towards SW Virginia a little longer than 12z did. 

Looks like it's going to be Plateau and mountains getting 1+ inch accumulations with less in most lower elevations. Overall it backed off a little in both areas vs 12z. 

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What an odd run of the Euro. 138 there's a southern system running along the Gulf coast. The primary goes from the Texas coast to the Florida coast then seems to jump from Panama City to Arkansas where it sits for 18 hours pounding Oklahoma. 

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The 12z WRF-ARW is southeast of its 0z run.  Not a ton of difference in track, but if the storm consolidates on either side of the Apps(not as confident as yesterday that happens west of the Apps), this storm may be stronger.  Right now, it may well be missing the phase until later - just guessing as I have not seen the vort maps.  Just seems like there is less of a mechanism to pull it Northwest which is why some modeling is sliding it further eastward before turning it.   Just giving the ARW one last look, it is now basically a Miller A.

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There are actually two lows present at 51z on the 3K NAM for TT (national view).  Either energy handoff or a lee side low develops.  Not sure the slp placement changes the solution(outside chance it might) much, but really watching this for future reference.  I have thought the Euro was over-amped...just wanting to see if that hypothesis is correct for this circumstance.  

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Seems like the differences go back to when the storm comes north from Louisiana.  Recent solutions get the storm further East before turning.  The 12z RGEM pivots the bottom of the total precip shield eastward and the precip shield in Indiana and Illinois westward.  Was a bit later with the turn but sharper turn north once it turned.  As Holston notes, once the northern stream energy grabs it, it goes almost due northward.  It is worth noting that the RGEM shifted eastward in regards to when it arrived in the TN Valley.  May well be that the trend is a later phase.

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Just now, Carvers Gap said:

Some decent differences in the RGEM in SLP placement and strengthening immediately after hour 40.  

It gets really close to jumping it up the eastern slope of the Apps. 

The surface front has made it to around 100 miles (maybe) off the Gulf Coast, it will be interesting to see exactly where the SLP forms on that front

giphy.gif

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12z GFS is way eastward with the slp....phase is just later.  There are two lobes of precip with the southern system - one over northern MS and the other sliding along the GOM.  When the lobe over norther MS is weaker, the primary low/energy shifts to the GOM.  I am guessing that is due to a later phase.  Pretty much can see that on all modeling.  When the lobe over MS is stronger, system and slp are west which indicates an earlier phase.  Finesse stuff.

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The 12z GFS is just weaker by a few mb.  One can go to TT and toggle back about 5 runs from that point.  You can see the system slide eastward every so slightly.  Could it be a more progressive bias from the GFS?  Maybe.   That weaker solution is likely due to a later phase.  This could still trend into a stronger system east of the Apps or it could just run the Apps.  Lots of moving parts and interesting to watch.

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1 minute ago, Holston_River_Rambler said:

Not looking at any other aspect of what the GFS is showing for now, that is some upslope heaven at 60 hours:

giphy.gif 

a fetch at 850 right off of lakes Superior and Michigan 

Pretty much a great angle in terms of winds.

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15 minutes ago, Holston_River_Rambler said:

It gets really close to jumping it up the eastern slope of the Apps. 

The surface front has made it to around 100 miles (maybe) off the Gulf Coast, it will be interesting to see exactly where the SLP forms on that front

giphy.gif

Which model has that modeled the best?

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