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Jan. 12-13, 2018 winter storm Nowcast and Forecast

nrgjeff

By nrgjeff,
in Tennessee Valley

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nrgjeff

nrgjeff

Posted
Posted

Time for a thread! Looks like possible heavy snow inside our Region. Some areas could get ice under the snow. Dynamic system with strong push of low level cold air is forecast..

First the ice consideration is due to rapid low level CAA into West Tenn. and West Ky. Mid levels still warm at onset, part of the TROWAL, so it could be ice. Hopefully not but...

More interesting is the TROWAL forecast from the Mid-South to Kentucky. Could go as far north as Indiana. Could slide right across our region. Wouldn't that be great? Euro seems too far north; yes, it's still my favorite model. In this seasonably cold winter GFS needs more respect. NAM follows it more east/south. So, I'm confident enough to start a thread for our Region.

TROWALs are great in the South, because they let us kind of cheat and get snow without cold air solidly in place. This time, confidence is added by robust low level CAA too. Upstairs WAA goes into a core that is cold enough for snow, convenient. Dynamic cooling plays a role. Snowfall rates can approach/match those in other robust WAA conveyor belts (in contrast to meh comma heads). Big challenge is that a TROWAL is basically a mesoscale feature. It will be tough to pin down the big winners early. 

Rest of us can hope for that low level CAA to change over other parts of the rain shield, but it will be difficult. Mid-levels (700 mb) will not be ideal for snow production outside the TROWAL. However thickness crashes farther upstairs and that low level CAA...

Did we get slammed about this time in Jan. 2011, a similar analog year?

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AMZ8990

AMZ8990

Posted
Posted
20 minutes ago, nrgjeff said:

Time for a thread! Looks like possible heavy snow inside our Region. Some areas could get ice under the snow. Dynamic system with strong push of low level cold air is forecast..

First the ice consideration is due to rapid low level CAA into West Tenn. and West Ky. Mid levels still warm at onset, part of the TROWAL, so it could be ice. Hopefully not but...

More interesting is the TROWAL forecast from the Mid-South to Kentucky. Could go as far north as Indiana. Could slide right across our region. Wouldn't that be great? Euro seems too far north; yes, it's still my favorite model. In this seasonably cold winter GFS needs more respect. NAM follows it more east/south. So, I'm confident enough to start a thread for our Region.

TROWALs are great in the South, because they let us kind of cheat and get snow without cold air solidly in place. This time, confidence is added by robust low level CAA too. Upstairs WAA goes into a core that is cold enough for snow, convenient. Dynamic cooling plays a role. Snowfall rates can approach/match those in other robust WAA conveyor belts (in contrast to meh comma heads). Big challenge is that a TROWAL is basically a mesoscale feature. It will be tough to pin down the big winners early. 

Rest of us can hope for that low level CAA to change over other parts of the rain shield, but it will be difficult. Mid-levels (700 mb) will not be ideal for snow production outside the TROWAL. However thickness crashes farther upstairs and that low level CAA...

Did we get slammed about this time in Jan. 2011, a similar analog year

28 minutes ago, nrgjeff said:

Time for a thread! Looks like possible heavy snow inside our Region. Some areas could get ice under the snow. Dynamic system with strong push of low level cold air is forecast..

First the ice consideration is due to rapid low level CAA into West Tenn. and West Ky. Mid levels still warm at onset, part of the TROWAL, so it could be ice. Hopefully not but...

More interesting is the TROWAL forecast from the Mid-South to Kentucky. Could go as far north as Indiana. Could slide right across our region. Wouldn't that be great? Euro seems too far north; yes, it's still my favorite model. In this seasonably cold winter GFS needs more respect. NAM follows it more east/south. So, I'm confident enough to start a thread for our Region.

TROWALs are great in the South, because they let us kind of cheat and get snow without cold air solidly in place. This time, confidence is added by robust low level CAA too. Upstairs WAA goes into a core that is cold enough for snow, convenient. Dynamic cooling plays a role. Snowfall rates can approach/match those in other robust WAA conveyor belts (in contrast to meh comma heads). Big challenge is that a TROWAL is basically a mesoscale feature. It will be tough to pin down the big winners early. 

Rest of us can hope for that low level CAA to change over other parts of the rain shield, but it will be difficult. Mid-levels (700 mb) will not be ideal for snow production outside the TROWAL. However thickness crashes farther upstairs and that low level CAA...

Did we get slammed about this time in Jan. 2011, a similar analog year?

I'm glad you started this thread  Jeff!  I'm sure it makes us all feel a little more confident having you on board.  

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Carvers Gap

Carvers Gap

Posted
Posted

Just took a quick glance at the GFS/CMC 12z suite w/ the NAM included(beware of the NAM past 84...it can be a mess).  The CMC/NAM combo digs into the south much more so than the GFS.  And for an amped tendency model, the NAM is further east?  By doing so, their angle of entry into the Valley is much different.  The GFS just runs the southern border of TN before eventually cutting NE.  It washes out the temp profile by doing so.  All three models above eventually take the eastern Valley north or almost over the Apps.  The runner immediately over the Apps is a rare deal.  The EPS did support the 0z run of the operational Euro, which as Jeff pointed out, seemed to be a bit too amped.  I think a sip track from the Plateau to spine of the Apps is what makes sense to me...I certainly will be rooting for a slider, but the 12z CMC, 0z Euro, and 12z NAM certainly look like they dig more to the south.  All eyes on the Euro and UKMET.  Anyone have any UKMET info for 12z?  Overall, still looks like decent chances for the western grand division of Tennessee.   

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Carvers Gap

Carvers Gap

Posted
Posted

Looks like the 12z UKMET tracks the slp through middle TN in a very similar pattern as at the 0z Euro.  Not sure if it would wash-out temps though.  That would suggest to me that the Euro is about to hold its ground as typically the UKMET is a precursor to the Euro run.  Still a ton of details to iron out w this.  The models that are usually amped at this stage are left of middle TN.  The ones(excluding the NAM) that are less amped as a bias are east of middle TN.  The GFS still cuts up the eastern valley, but has less snow due to being further norther.   The CMC and NAM cut up the eastern Valley.  Seems to me that the progressive models(excluding the NAM) are east and the amped bias models are west.  

 

Looks more and more that snow in E TN is going to be tough to come by this season in the eastern Valley.  I do hold out some hope for the energy behind this weekend's.  But I don't trust the model depiction on that one until the track of this one is ironed out.

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jaxjagman

jaxjagman

Posted
Posted

Snows ratios in Mid Tn would be pretty decent with that 2nd system on the Euro,if it's right of course 

ECMWF Deterministic FORECAST FOR: BNA    LAT=  36.12 LON=  -86.68 ELE=   591

                                            12Z JAN09
                 2 M     2 M     2 M     SFC     SFC    6 HR    FROZN   TOTAL
                 MXT     MNT     TMP     DEW     WIND    QPF     PCP    CLOUD
                 (F)     (F)     (F)     (F)    (KTS)   (IN)    (IN)    (PCT)
TUE 12Z 09-JAN                  38.0    37.8    03002   0.00    0.00     100    
TUE 18Z 09-JAN  45.1    38.0    45.2    43.4    08003   0.00    0.00     100    
WED 00Z 10-JAN  51.3    44.4    44.7    43.8    06003   0.00    0.00      98    
WED 06Z 10-JAN  46.2    43.4    45.6    44.8    17007   0.00    0.00      76    
WED 12Z 10-JAN  45.9    43.8    45.0    44.5    17006   0.00    0.00      44    
WED 18Z 10-JAN  56.9    45.0    56.9    54.3    17009   0.00    0.00     100    
THU 00Z 11-JAN  59.1    56.3    56.3    53.4    16009   0.00    0.00     100    
THU 06Z 11-JAN  57.9    56.1    57.4    54.5    16011   0.00    0.00      99    
THU 12Z 11-JAN  57.6    56.4    56.5    54.1    16009   0.01    0.00     100    
THU 18Z 11-JAN  61.3    55.5    61.5    56.5    16013   0.04    0.00      99    
FRI 00Z 12-JAN  63.3    58.4    58.2    56.1    16008   0.01    0.00      94    
FRI 06Z 12-JAN  58.3    56.8    57.1    56.9    15008   0.39    0.00      98    
FRI 12Z 12-JAN  58.1    53.0    52.9    52.7    34002   0.36    0.00     100    
FRI 18Z 12-JAN  53.3    39.0    39.0    38.7    35010   0.24    0.00     100    
SAT 00Z 13-JAN  39.1    35.6    35.5    35.3    32010   0.84    0.01     100    
SAT 06Z 13-JAN  35.5    29.8    29.7    27.0    30013   0.38    0.31     100    
SAT 12Z 13-JAN  29.8    24.6    24.5    18.8    31012   0.13    0.13     100    
SAT 18Z 13-JAN  24.6    22.2    24.3    14.3    32010   0.00    0.00     100    
SUN 00Z 14-JAN  25.3    22.8    22.7    13.6    33006   0.00    0.00      97    
SUN 06Z 14-JAN  22.7    13.8    13.6     9.0    32004   0.00    0.00       0    
SUN 12Z 14-JAN  13.5     4.6     4.5     0.0    31005   0.00    0.00       0    
SUN 18Z 14-JAN  19.5     2.8    19.6     0.5    30003   0.00    0.00      82    
MON 00Z 15-JAN  21.9    15.4    18.0     2.8    31001   0.00    0.00       0    
MON 06Z 15-JAN  18.7    11.2    15.0     4.0    17004   0.00    0.00      98    
MON 12Z 15-JAN  19.4    13.4    18.4     7.5    18005   0.00    0.00      88    
MON 18Z 15-JAN  35.6    18.1    35.9    17.1    20007   0.00    0.00      56    
TUE 00Z 16-JAN  38.9    32.4    32.3    24.7    21005   0.00    0.00      96    
TUE 06Z 16-JAN  32.3    28.2    30.2    25.0    24003   0.00    0.00     100    
TUE 12Z 16-JAN  31.1    26.7    26.7    24.5    00006   0.08    0.08     100    
TUE 18Z 16-JAN  26.7    19.7    19.7    14.5    35007   0.23    0.23     100    
WED 00Z 17-JAN  19.7    15.8    15.7    11.2    35006   0.15    0.15     100    
WED 06Z 17-JAN  15.7     9.6     9.5     3.4    36007   0.06    0.06      93    
WED 12Z 17-JAN   9.5    -0.8    -0.9    -5.0    02005   0.00    0.00       0    
WED 18Z 17-JAN  12.6    -2.9    12.9    -2.5    01003   0.00    0.00       0    
THU 00Z 18-JAN  16.2     6.9     6.7    -1.1    00005   0.00    0.00       0    
THU 06Z 18-JAN   6.9    -1.5    -0.5    -5.6    10004   0.00    0.00       0    
THU 12Z 18-JAN   4.7    -3.5    -2.4    -6.2    08003   0.00    0.00      47    
THU 18Z 18-JAN  25.6    -4.0    26.1     3.0    12001   0.00    0.00       0    
FRI 00Z 19-JAN  33.5    24.1    25.5    10.3    12003   0.00    0.00      94    
FRI 06Z 19-JAN  28.5    16.2    26.7    15.5    16007   0.00    0.00     100    
FRI 12Z 19-JAN  34.1    26.6    34.0    26.5    18005   0.01    0.00     100
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tnweathernut

tnweathernut

Posted
Posted
10 minutes ago, Queencitywx said:

Paris, TN was the winner that run with over 20" of snow. Doesnt seem to be much, if any, agreement with EPS on that OP run though. 

That was definitely a west TN nuke job.  As they say, y'all got NAM'd.....  At 54 the trough looked a little more positive, but quickly went negative from there....  Long ways to go, but anyone in west TN and middle TN need to keep an eye on this one.

Carver's mentioned to me a bit ago, the EPS was east of the OP and well east of the 0z suite...  In general, a good snow is becoming more likely.........but where?

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AMZ8990

AMZ8990

Posted
Posted
3 minutes ago, *Flash* said:

18z NAM is on PED's. Obviously, won't happen...but still :blink: FWIW.

2sa0b28.thumb.png.82eb7fe8680e6751b69647a9ed9d17e9.png

Goodness Gracious.  It's gonna be Hard to temper expectations if maps like that continue to come out.  I know it won't pan out but it's cool to see that this close to our possible wintry event.  Thanks for sharing flash.

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Vol4Life

Vol4Life

Posted
Posted
42 minutes ago, John1122 said:

The Euro control almost matches the opp exactly.  Track shifted a good 200 miles east from 00z, which had kept things basically west of the Mississippi. 

In the game, Little Rock to Crossville imo. Fading fast, anywhere east of Crossville. 

Not sure how anywhere East is fading fast.  Another 100 mile shift East and nearly the entire state comes into play. If anything, this thing is trending towards getting East TN in play.

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Chattownsnow

Chattownsnow

Posted
Posted
23 minutes ago, Vol4Life said:

Not sure how anywhere East is fading fast.  Another 100 mile shift East and nearly the entire state comes into play. If anything, this thing is trending towards getting East TN in play.

The EPS trended fairly significantly east from 0Z to 12Z. However no individual member on 12Z had the low further east than Chattanooga, where as the 0Z had a couple. The mean seemed to shift east, but the spread shrank for sure. 

edit - actually 12z did have a couple lows into NW South Carolina. Just not at the time stamp I was looking at. 

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