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John1122

Feb 1st-2nd 2018 Potential Snow Event.

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The Euro and GFS are coming into a line with this being a .5-2 inch type event in the lower elevations along 40 and north in the Eastern forum. The GFS is more NE of Knoxville and Plateau and mountains with it's snow accumulations. Euro includes Knoxville. Euro map is actual snow depth too, so it probably shows a solid 1-3 inches of snow falling.

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SREF Plums for the storm still look pretty good actually, below are the mean and big dog member for area locations.  Some have seen large jumps in mean and big dogs over 24 hours.

TYS: Mean 1.47" - Big Dog - 5.44" 

TRI: Mean 1.89" - Big Dog - 5.12 

BNA: Mean .47" - Big Dog - 2.23"

CHA: Mean .22" - Big Dog - 1.60"

CSV: Mean .92" - Big Dog - 3.47"

LOZ: Mean 1.42" - Big Dog - 4.22" 

 

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MRX on the Thursday into Friday storm:

Quote
For Thusday night, frontal boundary will move across the region
during the evening with vertical temperature profile becoming cold
enough for rain change over to snow. There is some disagreement on
the amount of forcing and moisture left after change over to snow.
The GFS and ECMWF are more aggressive and the NAM the least. Will
follow the GFS solution for now which suggest 1 to 3 inches
possible Thursday night through Friday morning.

Winds will become strong and gusty behind frontal passage
producing upslope flow into the Mountains. Will have the 3 to 5
inches for the higher terrain. These amounts may warrant advisory
issuance over the next couple of days.

 

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1 hour ago, Carvers Gap said:

18z 12k NAM...comments?

Funny thing is watch this one over perform, and the next one be a dud for us... lol  Take it where we can get it.

Also plumes had all but died off, now they are at least for TYS the highest they have been for the event, Mean at 1.56" big dog over 6".

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7 minutes ago, ShawnEastTN said:

Funny thing is watch this one over perform, and the next one be a dud for us... lol  Take it where we can get it.

Also plumes had all but died off, now they are at least for TYS the highest they have been for the event, Mean at 1.56" big dog over 6".

18z NAM at TYS has that snow falling at 35-36 degrees.  I doubt anything ends up sticking.  Might be able to get up in the middle of the night and see flakes though.

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1 minute ago, Stovepipe said:

18z NAM at TYS has that snow falling at 35-36 degrees.  I doubt anything ends up sticking.  Might be able to get up in the middle of the night and see flakes though.

I'll take slush with big giant wet snowflakes if that is all I can get.

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MRX on Thursday into Friday system:

Quote
.SHORT TERM...(Tonight through Thursday night)...Moisture will
begin to increase tonight ahead of an approaching cold front. The
front will move through tomorrow afternoon and exit in the early
evening. Some rain will move in during the day, but the better
forcing will lag behind the front with the strengthening upper jet
and better frontogenetic forcing. The best lift will be northern
areas late Thursday into Thursday night. With the colder air
moving in, this will allow for some snow across the higher
elevations first, and likely ending as snow even in valley areas.
Best chances for accumulations will be higher elevations of SW VA
and the central/northern mountains of E TN, where 2 to 4 inches
looks likely and localized higher amounts cannot be ruled out. The
northern plateau higher peaks may also see an inch or two, while
northern into central TN valley areas look to be around an inch
or less. It is still early, so these amounts are likely to be
adjusted further. Since it will be primarily a period 3 event will
not issue the winter weather advisory yet, but likely to end up
needing one at least higher elevations. Will keep mention in HWO
for now.

 

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Robert Gamble (WxSouth) thoughts:

Tomorrow brings a rapid change in the weather for TN, KY and then into West Virginia and the NC mountains overnight, with rain turning to snow very quickly. A few inches pile up in southeast Kentucky, northeast Tennessee and West Virginia down to the mountains of NC north of Asheville mainly. The more important thing may be the fact that all of that fast falling moisture along and just west of the mountains will become a frozen brick by Friday morning, affecting your drive, as temps are in the teens or low 20s there. So snow , plus frozen rain (ICE) will create havoc on the ground.
Rain showers may end as brief snow in eastern VA and NC as well, but not amount to much there.
Then, the next system which is much bigger but is proving to be a major headache to forecast. I have both storms covered in my updates tonight for subscribers.

Sent from my XT1585 using Tapatalk

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11 minutes ago, Greyhound said:

Latest SREF plumes have 2.67 average for Knoxville and a 2.81 average for Tri-Cities. And .78 average for our Chattanooga friends.


Sent from my iPad using Tapatalk

I just noticed this. The last 4 runs for Knoxville has been kinda crazy.

03 - Average .43 Big dog 2.66

09 - Average .17 Big dog 1.19

15 - Average 1.53 Big dog 6.21

21 - Average 2.67 Big dog 2 @ 6.5

The 00z Nam looks to be about the same as the 18z. Good trends on this system and maybe folks Knoxville north can squeeze out something.

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14 minutes ago, Greyhound said:

Latest SREF plumes have 2.67 average for Knoxville and a 2.81 average for Tri-Cities. And .78 average for our Chattanooga friends.


Sent from my iPad using Tapatalk

It's interesting if you pull up two windows and look at the Total-SNO and 3hrly-TMP together.  It's all about how fast those temps crash and there is a decent amount of spread.  It's good to see the mean is up significantly.

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The RGEM and NAM12k and 3k once again bring the 1-3 inch range across the area from 40 north in Eastern Tennessee. It's going to be very close between heavy rain and heavy wet snow. I wish we all had an extra 1000 feet in elevation.

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MRX reminding us that travelling might be a bit dicey this time tomorrow in parts of eastern TN:

Special Weather Statement
National Weather Service Morristown TN
313 AM EST Thu Feb 1 2018

313 AM EST Thu Feb 1 2018 /213 AM CST Thu Feb 1 2018/

...AREAS OF SNOW TONIGHT...

Rain will spread across the Southern Appalachian Region today as a
cold front moves into the area. With cooler air moving in behind
the front...the rain will transition to snow this evening. The
Chattanooga area could see a dusting to a few tenths of an inch of
snow overnight. The Cumberland Plateau, Knoxville and Tri-Cities
and surrounding areas as well as extreme Southwest North Carolina
can expect a half inch to around an inch and a half of snow
accumulation. With the daytime rainfall, temperatures falling
below freezing tonight and accumulating snow...area roads may
become slick, especially during the morning commute. If you will
be traveling on area roads tonight or Friday morning, be prepared
for icy or snow covered roads.

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SREF Plumes have jumped even higher this morning.  TYS up to 3.09" mean, TRI 3.11", BNA 1.89", LOZ, 3.12"  CHA .87", all with Big Dogs around and above 7", with the exception of Chatt with a big dog around 4".  

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Still having a difficult time buying this setup...cold chasing rain is usually heartbreak city.  But, here is the TRI SREF plume.
5a730c355b3c7_ScreenShot2018-02-01at7_42_33AM.thumb.png.d764d278cd66d83db5710860bfa9d0cc.png
 


Look like a tight cluster around 2” with a big outlier at 7 inches that is skewing the mean a little bit. I have always thought the SREF means were always a little beefy. MRX has a WWA out for me for 2-4” but I would reserve the 4” for places like High Knob.

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1 hour ago, 1234snow said:

Look like a tight cluster around 2” with a big outlier at 7 inches that is skewing the mean a little bit. I have always thought the SREF means were always a little beefy. MRX has a WWA out for me for 2-4” but I would reserve the 4” for places like High Knob.

 

MRX has expanded the WWA into TRI now. Calling for 1-2" for us. 

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MRX mid morning update referencing what KVSkelton mentions, and also pointing to how tricky this is they are still uncertain on change over pace.  Interesting mid morning update, don't get these that often from MRX.  I have a feeling by afternoon updates we may see some WWA further down the valley, at least central valley locations by this evening.

Quote
.DISCUSSION...Strong southwesterly winds this morning is pulling
warmer air into the region. Temperatures are already climbing
through the 40s. Have upped high temperature for most of the
location.

Very strong 300mb jet of nearly a 170kts will move across the Ohio
Valley later today and tonight. This is an abnormally strong upper
jet with the upper forcing associated with the right entrance
region quite strong. This jet forcing will quickly strengthen the
frontal-genetic along a boundary moving southeast into Kentucky.

Models continue to show strengthening fronto-genetic forcing
rapidly developing precipitation over kentucky this afternoon,
then moving into the area by late afternoon and evening. The
precipitation type is the tricky part as initially the boundary
layer temperatures will be relatively warm, but strong diabatic
cooling due to the strong forcing will quickly cool the vertical
column.

A fairly quick change over from rain to snow will occur this
evening. The questions are the following:

1) How fast will the change over occur?
2) How fast will snow accumulate after transition?
3) How long will accumulating snowfall last?
4) Snow will initially accumulate on the grassy areas, but
how soon on the roadways?

After looking at new NAM/RAP runs and SPC SREF snowfall plumes
have decided to extend the advisory to the Plateau and northeast
Tennessee for now.

 

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So, it we do end up with a couple of inches from the first event, and we stay in low 30s tomorrow and get a good frozen base over night, how will that actually affect the snow to rain to snow sequence on Sunday? I'm guessing the models would not have the capability to pick up on any effect from that?

Also....agree with Carvers, Nut, KV and others...great to see more posters here...seems like this maybe the most I've seen active. A little snow brings out the kid in all of us! :-)

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11 hours ago, John1122 said:

The Canadian joins the NAM suite and RGEM and even gives Nashville a little love.

sn10_acc.us_ov.png

Thanks for the map,unfortunate tho the surface temps will steal a big chunk of that,plus looking at the short range it might last 1-2 hours depending on how fast the cold gets in.If we get a dusting i'd consider it a win,right now.

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29 minutes ago, Vol Man said:

So, it we do end up with a couple of inches from the first event, and we stay in low 30s tomorrow and get a good frozen base over night, how will that actually affect the snow to rain to snow sequence on Sunday? I'm guessing the models would not have the capability to pick up on any effect from that?

Also....agree with Carvers, Nut, KV and others...great to see more posters here...seems like this maybe the most I've seen active. A little snow brings out the kid in all of us! :-)

If the low pressure ends up in northern Ohio, I don't think it matters. Looks like it's going to be too warm on Sunday for most of us at this point.

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