Tn Valley Severe Weather

[jaxjagman]

Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0100 AM CDT Sun Mar 18 2018

   Valid 191200Z - 201200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS MIDDLE
   TENNESSEE...NORTHERN ALABAMA...AND FAR NORTHWEST GEORGIA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM TENNESSEE
   SOUTHEASTWARD INTO GEORGIA AND NORTHERN FLORIDA...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
   THE SOUTHEAST...

   ...SUMMARY...
   Tornadoes, damaging wind and hail are expected across parts of
   Middle Tennessee, much of northern Alabama, and northwest Georgia. A
   strong tornado or two is possible during the late afternoon. Severe
   wind is also possible into northern Florida.

   ...Synopsis...
   A compact shortwave trough will move quickly from AR Monday morning
   to the TN Valley by 00Z Tuesday, with a slight deamplification. Wind
   profiles will increase throughout the day, with cooling aloft
   overspreading KY, TN, and northern AL/GA. At the surface, low
   pressure will move from OK across TN, with a cold front extending
   from Middle TN across central MS by 00Z Tuesday. Ahead of the front,
   dewpoints into the lower 60s F will reach as far north as TN, with
   mid 60s F over AL and GA. To the east, a warm front will lift across
   northern AL and GA during the day, allowing for destabilization.
   Severe thunderstorms are likely near the surface low and along the
   cold front, with the primary threat area from Middle TN into
   northern AL and northwest GA during the afternoon.

   ...Middle TN into northern AL and northwest GA...
   Scattered showers and a few thunderstorms may be ongoing Monday
   morning from TN into northern GA associated with warm advection near
   the warm front. This activity should lift north, allowing for
   heating farther upstream across western TN and MS. If early day
   storms are more widespread than expected, this could have an impact
   on the position of the main threat area later in the day.

   A minor capping inversion will be present around 850 mb according to
   forecast soundings. This will keep the warm sector free of
   additional precipitation contamination. Lapse rates aloft will
   steepen as the shortwave trough approaches, and wind profiles will
   strengthen creating a favorable setup for tornadic supercells. The
   area of strongest lift, shear and instability will exist over a
   relatively limited in area, but supercells that do occur will have
   significant tornado potential, along with large hail. The eastern
   extent will be limited by a wedge of cooler air from eastern TN
   across northern GA. Storm density will likely decrease across north
   central AL, farther away from the main area of lift, but a
   conditional threat of supercells capable of a tornado or two and
   large hail will exist. This threat may spread across eastern AL into
   western GA during the evening, as warmer air spreads east resulting
   in surface based instability.

   ...Fl Panhandle into southern GA...
   Although well removed from the shortwave trough to the north, a
   broad belt of strong flow aloft will encompass the Southeast, with
   deep-layer shear profiles favorable for severe storms. Mid to upper
   60s F dewpoints will result in favorable thermodynamics to support
   strong to severe storms. Storms are expected to form over the FL
   Panhandle into northern FL by early to mid afternoon, spreading into
   southern GA. Although low-level shear is not particularly strong, it
   may be sufficient to support a tornado or two, with the primary risk
   being damaging winds.

   ..Jewell.. 03/18/2018

[jaxjagman]

6 hours ago, Stovepipe said:

Nice storm rolled by just a tad south of me.




.

That's a cool pic Stove

[jaxjagman]

[Runman292]

I think they underestimated yesterday's system in regards to the Southern Valley. No watches were issued south of Loudon county and that part of TN seemed to get hit the worst. 

[TellicoWx]

MRX disco for Monday evening:

Per SPC discussion, there is a potential of long-lived tornado
supercells with the southern Plateau and southeast Tennessee
placed in an enhanced potential of severe storms.

[Windspeed]

Had a possible tornado touchdown just south of Tellico Plains in Coker Creek area. 1 structure damaged alot of trees/power poles snapped. Currently 1048 FLEC customers out of power. No injuries.

 

**Warning: Loud volume with explicit language**

 

I saw this video on another site that mentioned near Etowah. Save your ears and adjust volume down prior to viewing.

[jaxjagman]

SREF has a small 45% marker in N/Alabama,it backed down away from Nashville as well as the last NAM while the GFS  is now showing more instability to the Ky border

[McMinnWx]

2 hours ago, Windspeed said:

 

**Warning: Loud volume with explicit language**

 

I saw this video on another site that mentioned near Etowah. Save your ears and adjust volume down prior to viewing.

Says the URL has expired. 

[Jim Martin]

Latest tidbit from SPC on the afternoon Day 2 Outlook...

CONCERNING THE SEVERE POTENTIAL, A CORRIDOR OF MODERATE INSTABILITY  
IS FORECAST TO DEVELOP BY AFTERNOON FROM EASTERN MISSISSIPPI INTO  
MUCH OF ALABAMA. NAM FORECAST SOUNDINGS AT 21Z IN EASTERN  
MISSISSIPPI AND NEAR BIRMINGHAM SHOW MLCAPE VALUES REACHING THE 2000  
TO 2500 J/KG RANGE. IN ADDITION, THE MID-LEVEL JET WILL CREATE  
STRONG DEEP-LAYER SHEAR PROFILES ACROSS MOST OF THE REGION. FORECAST  
SOUNDINGS ACROSS THE SLIGHT RISK AREA BY LATE AFTERNOON SHOW 0-6 KM  
SHEAR GENERALLY IN THE 60 TO 65 KT RANGE. THIS ENVIRONMENT WILL  
SUPPORT SEVERE THUNDERSTORM DEVELOPMENT FROM THE MID AFTERNOON  
THROUGH MUCH OF THE EVENING. THE SHEAR SHOULD BE FAVORABLE FOR  
SUPERCELL FORMATION ESPECIALLY FROM MIDDLE TENNESSEE SOUTHWARD INTO  
NORTH-CENTRAL ALABAMA WHERE HAILSTONES OF GREATER THAN 2 INCHES IN  
DIAMETER, WIND DAMAGE AND A TORNADO THREAT WILL BE POSSIBLE. A  
STRONG TORNADO MAY OCCUR WITH ANY SUPERCELL THAT CAN BECOME  
DOMINANT. THE POTENTIAL FOR VERY LARGE HAIL IS ALSO FORECAST  
SOUTHEASTWARD INTO PARTS OF WESTERN GEORGIA WHERE VIGOROUS  
CONVECTIVE DEVELOPMENT MAY TAKE PLACE DURING THE EARLY EVENING. THE  
WIND DAMAGE THREAT MAY INCREASE BY EARLY EVENING ESPECIALLY IF A  
MESOSCALE CONVECTIVE SYSTEM CAN ORGANIZE.  

[jaxjagman]

Looking around Mid Tn around 3 tomorrow afternoon the GFS shows the  the TT's around 58 and the Showalter -4 to -5 with steep lapse rates 8.0, bulk shear around 80kts

 

Edit:This would be just west of Nashville

[jaxjagman]

The latest SOI took a big rise and a big drop recently,have to keep watching the long range forecast into the1st week to the 2nd week of April

 

Date	Tahiti (hPa)	Darwin (hPa)	Daily Contribution	30 day Av. SOI	90 day Av. SOI
18 Mar 2018	1013.04	1006.25	12.83	7.15	1.58
17 Mar 2018	1012.51	1000.90	35.90	6.47	1.33
16 Mar 2018	1011.36	1006.15	5.26	4.81	0.71
15 Mar 2018	1011.20	1006.85	1.15	3.90	0.44
14 Mar 2018	1011.61	1007.00	2.39	3.15	0.29

[jaxjagman]

The latest NAM takes the low into north Alabama,i really can't believe the GFS or Euro would be this far off in the short range,but could be.The GFS 0z went further north into Kentucky,how insane is this

[Windspeed]

Good morning. I suspect we're in for a long evening and night. Good luck to everyone as far as hail or wind damage. And don't forget to unplug your sensitive electronics and hardware if you're going to be away from your home this afternoon-evening. Sometimes surge & ups fail and warranties can't replace everything.

[PowellVolz]

Gonna be a wild day south and west of 40/75.


.

[jaxjagman]

Mesoscale Discussion 0143
   NWS Storm Prediction Center Norman OK
   0952 AM CDT Mon Mar 19 2018

   Areas affected...north-central and northern AL...northwest GA...far
   southern middle TN

   Concerning...Outlook upgrade 

   Valid 191452Z - 191615Z

   SUMMARY...An upgrade to a Moderate Risk categorical outlook (driven
   by a 15% significant tornado risk) is planned for the 1630Z outlook.

   DISCUSSION...It appears increasingly probable the risk for several
   tornadic supercells will traverse across northern portions of AL
   late this afternoon and through the early evening.  Thunderstorm
   activity will be largely void across a large part of this area
   (north-central AL) prior to peak heating and a moderately unstable
   airmass is expected to develop by mid afternoon.  The arrival of a
   speed max in the mid-levels will correspondingly lead to a marked
   strengthening in low-level flow and increasing hodograph size, which
   will be more favorable for supercells and low-level mesocyclones. 
   Given these factors, confidence has increased such that a 15%
   significant tornado risk and the potential for longer lived
   supercells and damaging tornadoes will focus across north-central
   and northern AL, far southern middle TN beginning during the late
   afternoon/early evening, then moving east into northeast AL and far
   northwest GA later this evening.

[jaxjagman]

You going out Jeff?

[nrgjeff]

Here we go! I was a skeptic until seeing Saturday indeed produced the EF-0. Perhaps that Etowah Telilico Plains tornado was the atmosphere tipping its hand.

Local WFOs had noted a slower than forecast warm front; however, low clouds are breaking up on VIS. Apparently SPC is expects a robust warm sector in North Alabama. Kinematics, no question, yield SRH 300 J/kg+. Now appears the forecast CAPE values are within reach. Middle Tennessee has a tornado risk, but the low contrast sloppy variety. North Alabama is the clear chase target in the more established warm sector with better visibility.

Cells should track from west to east, which is convenient for a chaser on US-72 or Alt-72. However one needs to be mindful of the Tennessee River and limited crossings. A forecast of the outflow boundary position will be more crucial than usual due to the River. One chases either south or north of the River, except for those limited crossings. 

All that said, my chase status is still TBD. Prefer new cells over that one in Mississippi trying to root. New would have better contrast.

[Quincy]

10 minutes ago, nrgjeff said:

Here we go! I was a skeptic until seeing Saturday indeed produced the EF-0. Perhaps that Etowah Telilico Plains tornado was the atmosphere tipping its hand.

Local WFOs had noted a slower than forecast warm front; however, low clouds are breaking up on VIS. Apparently SPC is expects a robust warm sector in North Alabama. Kinematics, no question, yield SRH 300 J/kg+. Now appears the forecast CAPE values are within reach. Middle Tennessee has a tornado risk, but the low contrast sloppy variety. North Alabama is the clear chase target in the more established warm sector with better visibility.

Cells should track from west to east, which is convenient for a chaser on US-72 or Alt-72. However one needs to be mindful of the Tennessee River and limited crossings. A forecast of the outflow boundary position will be more crucial than usual due to the River. One chases either south or north of the River, except for those limited crossings. 

All that said, my chase status is still TBD. Prefer new cells over that one in Mississippi trying to root. New would have better contrast.

Not sure if it's accurate, but M40 just shot up to 70/70 on the latest ob. Seems suspect. Tupelo was 58/57 at the top of the hour, so that cluster is likely on a track just north of the warm front based on the current storm motion, at least in the short term. 

[jaxjagman]

Didn't take long

[jaxjagman]

   Mesoscale Discussion 0144
   NWS Storm Prediction Center Norman OK
   1118 AM CDT Mon Mar 19 2018

   Areas affected...Northeast MS and Northwest AL

   Concerning...Severe potential...Watch unlikely 

   Valid 191618Z - 191745Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Large hail may accompany small thunderstorm cluster as it
   tracks across northeast MS into northwest AL over the next few
   hours. At this time do not anticipate issuing a short-term severe
   thunderstorm watch.

   DISCUSSION...Long-lived cluster of convection has tracked from
   southwest AR into northeast MS. Over the last hour or so it appears
   updraft strength with this activity has intensified along nose of
   low-level warm/moist advection. Hail algorithm supports this with
   MRMS data exhibiting sizes possibly in excess of 1.5". Given the
   overall air mass destabilization expected into northern AL over the
   next few hours it appears this activity could maintain its intensity
   along with primarily a hail threat.

   More intense supercells are expected to develop along the
   western/southern flank of this early-day convection. At that time
   more significant severe threat, including the possibility for
   tornadoes, should evolve.

   ..Darrow/Grams.. 03/19/2018

[PowellVolz]

.

[Windspeed]

Yikes...

[Freshgeek]

8 minutes ago, Windspeed said:

Yikes...

That sounding is super contaminated by ongoing convection and not representative of the actual atmosphere.

[Windspeed]

That sounding is super contaminated by ongoing convection and not representative of the actual atmosphere.

Good to know. Thanks!

[Indystorm]

 Mesoscale Discussion 0146
   NWS Storm Prediction Center Norman OK
   0206 PM CDT Mon Mar 19 2018

   Areas affected...Northeast MS...Northern AL...Southern TN

   Concerning...Severe potential...Tornado Watch likely 

   Valid 191906Z - 192030Z

   Probability of Watch Issuance...95 percent

   SUMMARY...Tornado watch will be issued by 21z across portions of the
   Mid-South. A few strong tornadoes are possible in addition to large
   hail.

   DISCUSSION...Leading edge of mid-level drying/cooling is progressing
   across the MS Delta region at roughly 35kt. Over the next few hours
   lapse rates should adjust across western TN/northeast MS and deep
   convection is expected to expand in response to this feature.
   Conditions are becoming increasingly favorable for strong supercell
   development as boundary-layer moisture is advancing into northern
   MS/AL with mid 60s surface dew points now evident at TUP into
   Winston county AL.

   Early-day thunderstorm cluster that spread across northern MS is now
   into northern AL and this convection may impede deeper moisture
   surge into the Middle TN region. However, a well-defined and
   increasingly buoyant east-west boundary draped across northern MS/AL
   should provide a focus for potentially tornadic supercells. Shear
   profiles are becoming quite strong across this region and it appears
   discrete storms will evolve over the next few hours in response to
   approaching short-wave trough. Environmental parameters appear
   supportive of potentially long-track tornadoes and this will be
   addressed within the next few hours with a tornado watch.
 

[Indystorm]

[kayman]

The storm over Madison County is rotating with large hail...

[pbrussell]

Well, I do suppose it's time for me to come out of winter hibernation. Afternoon folks. Looking forward to tracking these storms with you all. 

[kayman]

PDS Tornado Watch issued until 11:00PM Central

[Witness Protection Program]

PDS south of I-840.