TellicoWx

Winds picked back up to 30mph, with moderate snow coming down...almost looks like a mini blizzard outside. If only the temp wasn't 36....

Finally switched over to sloppy flakes here.

For those new to the hobby, and not quite familiar with the topo and how it greatly impacts the Great Valley hopefully this will help...(and yes there is some truth to the Cattanooga Snowdome lol).

This generally applies to anafrontal and Northwest Snow Flow Events. Surface LP has a ton of other variables. 

Think of the atmosphere as a liquid with differing viscosity. Warm is less dense and rises, cold undercuts the warm as if it has a thicker viscosity.

The Plateau acts like a dam for the denser cold air (Blue Arrows over Middle TN). Just west of Knoxville near Kingston, the Plateau has a natural spillway/funnel that allows as small area for the cold to funnel into the valley (if you watch fronts pass over, you can actually see this occur live on PWS's in the area). There is a much smaller spillway west of Chattanooga, but due to the nature/design of the Plateau, cold must slowly fill the Sequatchie Valley first before trying to continue advancing toward Chattanooga (leaving that area to primarily rely on the Kingston "spillway" to supply it with the cold. As lift generally pulls away from the valley from SW to NE, the column dries the quickest at Chatt. Add in the distance from Kingston to Chatt the slow moving cold air arrives almost too late...hence the Chattanooga Snowdome.

Other areas of interest due to topo..

1) Green Box Areas - as the cold naturally pushes SE, it sometimes can force moisture to pool up in these areas, enhancing snowfall output. This is what occurs 9/10x when East of Hwy 411 ends up with greater totals than west side.

2) Red Boxe Area - The downsloping winds of the Plateau speeds up the drying process further...making the Dome that much stronger.

1 hour ago, PowellVolz said:

In a anafrontal system, is their elements that can enhance qpf that the mods don’t pickup on? NW flow, steep lapse rates, low level moisture, etc….? I’m assuming it could be rationed higher from cold 850’s?


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In an anafrontal setup some things that models will not have a grasp of at this ramge:

1) the depth of the shallow low level moisture. This range they have a tendency to sometimes dry the DGZ out to quickly, not picking up on where the moisture banks up against micro climate areas (such as the plateau/foothills etc).

2) Under estimate how far ahead the shallow arctic air has actually advanced during very powerful cold fronts.

3) The exact placement of Vertical Velocities. Becomes more important with anafrontal due to having to rely on the UVVs more for the lift, than have the traditional SLP aided lift.

5 minutes ago, Knoxtron said:

Heavy sleet storm just passed Waldens Ridge and put a dusting (?) down really quick. Just east of Dunlap

 

Edit: Melted quickly, currently 40 and dropping 

I'm in Madisonville in Monroe Co.. just had quick burst sleet here as well, Temps about same as there

Long story short...think suppressed is the ultimate outcome currently

1 hour ago, Carvers Gap said:

It is also very important to look at ensembles.   The means for the 6z GEFS and 0z EPS actually suppress the system like the CMC does, rotate the energy below the forum, and bring it up the coast.  Maybe that is where we want it?  Maybe not.  But I will say, I do think the operationals are driving the bus and catching trends that the ensembles are likely washing out.  Operational trends matter at this point.

To me there is 2 possible outcomes still being figured out and 1 joker card.

A) the Hudson Low and 1050+ High dropping down are too far south currently modeled (there placement is what pushes the front thru). Which would mean the Ops are too suppressed. I give that about 40% weight based on this winter of the SE trend, plus climate.

B. Those features are too north and Ops too slow with the front = cold rain, which some ensembles show. Think that is more likely currently on most modeling. 

And Joker Card...whether or not the wave can generate cyclogenisis along the Gulf. Joker can reck havoc on both A) and B...think that will be an issue foe the next several days.

2" mean on 6z GEFS now basically extends down to I-40 between Memphis and Nashville now for Fri system

Hr 90 on 6z GEFs....0z only had about 1/3 of members bringing the backside into the state.

West and Middle TN folks may not wanna sleep on this Fri system..6z GEFS continues trend of inching the mean LP eastward. 

5 minutes ago, weathertree4u2 said:

Placement will likely change but when this gets in forecast window for local Mets lookout at the store 

Yeah, would love to see a sleet map for LA/MS/AL...FZ Rain accum goes all way to Mobile

Rain/snow line enters state around hr 135, and exits around 180...

If you wanna see how the whole state can get smoked, 6z GFS is how. This thing just crawls across the entire state, overrunning from the Gulf.

Starting to get power outages across Southern end of the county. Highest gust so far 56.4 mph on Skyway below Indian Boundary (highest elev weather station in area, 1700')

2 minutes ago, Matthew70 said:

Curious what is the Icon model for?  Also do they still use the NBM any?  Think it was called National Blend Model. 

Most weather offices tend to lean on it 

10:1

00z Euro with a big hitter on 15th-16th timeframe

Individual members to tag along with @John1122 post

2 minutes ago, John1122 said:

The GEFS mean keeps rising. 

 

 

Yeah was just looking at that, as far as individual members it's definitely monsters or nothing. Wherever these tracks setup, looks like will be a winter to remember.

2 minutes ago, Holston_River_Rambler said:

Euro was pretty close to a storm on the 12th. 

Jumped the storm SE again, as you guys have said over the past couple days or so, seems to be something this winter to that. With those lofty numbers shown just across the MS river last few days of runs, it will be interesting to see if west TN starts getting into the game for anything within 150 hrs.

6 hours ago, Holston_River_Rambler said:

There are those creamsicle colors I like again. The end of the 6z GFS was tasty. 

Creamsicle is back on the 12z GEFS lol

12z GEFS looks alot better thru the ext (run not complete quite yet), especially for the central and west TN folks. Instead of one storm skewing the mean and the rest kinda of blah, almost each member has some for of storm/s. One member even pushes 2"-4" right to the gulf/FL panhandle area. When ensembles start getting into the 4"-5" means (west/central TN), usually something is coming

Probably should be in banter, but noticed a large jump in the 00z GEFS overall run mean..so piqued my interest. And there it was, Member 8 aka The TN Mauler. One member jumped the entire mean 2+ inches (pegs out COD's accum chart)

12z GEFS screams model chaos after the first system...will be very hard for it to determine where/how to interact with this many lows parading across the country.

Have to get the 1st system out of the way, but if the GFS can consolidate the energy with the southern piece of energy like the CMC, then the 2nd system could get very interesting.