Tennessee Valley Severe May22-27

[jaxjagman]

GFS is showing instability ramping up some what starting tomorrow through possibly into early next week

...Day 5/Sat - Southern Plains to the Ozarks vicinity...

   Low-amplitude west/southwest mid/upper flow is forecast across the
   southern Plains to the Mid-South vicinity for much of the diurnal
   period on Saturday. By 00z, forecast guidance suggests a shortwave
   trough will eject from the southern Rockies into the southern
   Plains, and eventually impinging on the Ozarks/Mid-South area by
   Sunday morning. A very moist and unstable airmass is forecast over
   the southern Plains vicinity ahead of this feature as a surface warm
   front lifts northward through the day. Increasing ascent may not
   arrive until after 00-03z, limiting convective initiation until the
   nighttime hours. If storms can develop during the day across
   portions of OK/TX, all hazards severe potential will exist.
   Otherwise, thunderstorm potential may be more likely during the
   evening/overnight from north TX into southeast OK and AR as
   large-scale ascent increases and a 65-75 kt 500 mb jet overspreads
   the region. The north and west bounds of severe potential are a bit
   uncertain, so this area may shift in subsequent outlooks. 

   ...Day 6/Sun - Ozarks to the Lower OH and TN Valleys...

   An upper shortwave trough will progress across the region on Sunday.
   Forecast guidance depicts a 50-60 kt southwesterly 700 mb jet
   overspreading the region during the day. Meanwhile, a surface low
   will intensify over MO/IL, shifting northeast along the OH River
   through the period. A very moist and unstable airmass is depicted
   ahead of the low and attendant south/southeastward-progressing cold
   front. Intense severe thunderstorms will likely accompany this
   system. Consistency among deterministic guidance, favorable synoptic
   pattern, as well as CSU/NSSL ML output, support introduction of 15
   percent probabilities for Sunday.

   ...Days 7-8/Mon-Tue...

   Spread among forecast guidance increases substantially by the end of
   the forecast period. However, a pattern shift by Day 8/Tue appears
   possible, with an amplified upper ridge potentially building over
   the western half of the CONUS. Overall, predictability is too low to
   delineate areas of severe potential across the eastern half of the
   CONUS.

[jaxjagman]

[nrgjeff]

I think we need dates on this thread do differentiate it from the general severe wx topic. @jaxjagman will it still let you edit?

Wednesday we have that boundary likely settling over the Mid-South. Upper flow is modest at best, but sometimes that's all it takes in late May.

Thursday needs that 15% into West Tenn. Probably depends too much on Wednesday. However what I see is a residual outflow under decent upper-level flow. 

Friday could be farther north; or, the boundary gets stuck in the Mid-South again. Moderate flow (more than Wed/Thu) ejects from the southern Plains. 

Saturday and Sunday switch back to synoptic pattern recognition. Saturday has the next Plains wave. By Sunday it's forecast over our direction. Yet another Monday is possible. 

All of this feels too late in the season, but a check back at the records indicates it's not. Guess that's one reason I'm not in the Plains this week.

[Matthew70]

Looks extremely wet for the area for the next week.  

[Matthew70]

2 hours ago, jaxjagman said:

The wx sure is not playing by the rules anymore.  Kinda like the cicadas!

[Matthew70]

Just now, Matthew70 said:

The wx sure is not playing by the rules anymore.  Kinda like the cicadas!

Derecho possibly tomorrow afternoon/evening for west/mid TN?

[nrgjeff]

I prefer the discrete cells shown by the RRFS and FV3. HRRR and ARW have red bows.

Edit: no reason to quote for continuity. Posts are only minutes apart. 

Looks like the Derecho checklist won't be met. We will have the west-east boundary and moderate theta-E. However the height falls are not met. Also 700 mb is more classic CAA than the WAA associated with derechos. 850 mb is neutral-ish and probably why CAMs can't make up their mind bow or sups. 

Why am I hoping for sups? I'm like the only storm chaser not in the Midwest or Plains this week, haha!

[jaxjagman]

1 hour ago, nrgjeff said:

I think we need dates on this thread do differentiate it from the general severe wx topic. @jaxjagman will it still let you edit?

Wednesday we have that boundary likely settling over the Mid-South. Upper flow is modest at best, but sometimes that's all it takes in late May.

Thursday needs that 15% into West Tenn. Probably depends too much on Wednesday. However what I see is a residual outflow under decent upper-level flow. 

Friday could be farther north; or, the boundary gets stuck in the Mid-South again. Moderate flow (more than Wed/Thu) ejects from the southern Plains. 

Saturday and Sunday switch back to synoptic pattern recognition. Saturday has the next Plains wave. By Sunday it's forecast over our direction. Yet another Monday is possible. 

All of this feels too late in the season, but a check back at the records indicates it's not. Guess that's one reason I'm not in the Plains this week.

I was just starting another thread in general,the old one is over 3 years old,but i changed it,can make a new severe thread later on.I'll adjust times if needed.

[nrgjeff]

Wednesday through Friday we have that meandering boundary across our region with modest flow aloft. Mid-South to West Tenn have Slight risks Wed/Thu. Marginal covers much of our region. Timing short-waves and some low-level winds will determine whether storms are garden variety or something more. 

Then on Saturday a new system develops in the Plains and ejects east for Sunday funday. Mid-South is the focus with some through much of our region. SPC looks at concentration. Low pressure may be up in IL/IN along with the warm front and triple point. Depends on previous days precip. We'll see. 

 

[John1122]

Lost power yesterday evening with some big time winds that sent trees toppling. Not sure if the juice is there today or not, but we are under a severe t-storm watch.

[nrgjeff]

Oh yeah the Wednesday evening storms looked nasty up that way. Thursday not as bad?

Same boundary is hanging around Friday but lacks robust upper-level support East Tenn. I think West Tenn atmo is too overturned but there's modest upper flow that way. 

Attention shifts to Sunday. Outflow could get all the way into our region, though SPC has lifted that north with the models. I figure the tornado risk is north of the Ohio River on the warm front Sunday. I'll visit the Oho Valley region to discuss Sunday in more detail. 

Sunday night the cold front should provide a chance of linear storms here in the Mid-South and Tennessee Valley.

[Matthew70]

In today’s wx it’s expect the unexpected.  Seems forecast are busting a lot these days.  It was supposed to be a stormy rainy week.  Instead some rain & storms but not nearly what was expected.  Even with the technology today we still have a long long way to go.  

[jaxjagman]

On 5/24/2024 at 2:32 PM, Matthew70 said:

In today’s wx it’s expect the unexpected.  Seems forecast are busting a lot these days.  It was supposed to be a stormy rainy week.  Instead some rain & storms but not nearly what was expected.  Even with the technology today we still have a long long way to go.  

Not sure i'd call it a bust.The models never did show much of any low level shear until it starts to ramp up later on into Sunday,there never seemed to be a tornado threat until Sunday,yeah you could maybe say that yesterday  as there was a pretty decent cap from MO Valley into the Mid South but even that the models showed this,just wasnt as strong,plus the models showed the cap breaking up into the early morning hours today and was a great light show before dawn here,we lost power for a little bit at my house

[nrgjeff]

Weather went about as I expected for three Marginal risk days. We had thunderstorms. Not many were severe. Some were strong. Chattanooga got a good light show or two also.

Sunday is a true Slight Risk with Enhanced north. Most of us will probably see morning and then overnight storms and straight wind. Enhanced area might be more interesting Sunday afternoon but rotation is conditional on how the outflow behaves. It's a good Enhanced for wind in my opinion.

Monday things depart. How about a mid-Atlantic Slight? Watch the best storm of the week be east of the Appalachians, lol!

[Matthew70]

4 hours ago, jaxjagman said:

Not sure i'd call it a bust.The models never did show much of any low level shear until it starts to ramp up later on into Sunday,there never seemed to be a tornado threat until Sunday,yeah you could maybe say that yesterday  as there was a pretty decent cap from MO Valley into the Mid South but even that the models showed this,just wasnt as strong,plus the models showed the cap breaking up into the early morning hours today and was a great light show before dawn here,we lost power for a little bit at my house

I was referring to the rain amounts.  Sorry for the confusion.  The light show was awesome last night.  Only thing that surprised me was it did not seem to be as loud as one would expect with that much lighting. 

[mob1]

That is an impressive morning line 

[mob1]

PDS tornado warning for the couplet south of Hokinsville. Even if it's staightline winds' those are some big boy velocity scans. 

 

[Runman292]

With the initial storms missing the eastern valley and staying in the northern plateau and Kentucky, will that lead to increased chances for worse storms later in the valley?

[jaxjagman]

6 minutes ago, Runman292 said:

With the initial storms missing the eastern valley and staying in the northern plateau and Kentucky, will that lead to increased chances for worse storms later in the valley?

yes

[jaxjagman]

Could be some rotation starting east of Fairview

[jaxjagman]

1 minute ago, jaxjagman said:

Could be some rotation starting east of Fairview

Should have said west of Fairview

[Met1985]

11 minutes ago, jaxjagman said:

Should have said west of Fairview

That line blowing through Nashville looks mean.

[Carvers Gap]

Southwest Virginia is lit up like the 4th of July.

[jaxjagman]

27 minutes ago, Met1985 said:

That line blowing through Nashville looks mean.

Been some rotation with that hook towards Frankin right now,just isnt tighten up right now

[Reb]

That cell between oak ridge and farragut looking interesting to me. Missing the Central Valley earlier may have set us up for a show 

[Runman292]

15 minutes ago, Reb said:

That cell between oak ridge and farragut looking interesting to me. Missing the Central Valley earlier may have set us up for a show 

The rotation stayed just to the south of my house.  

[Reb]

Looks to be hooking

[jaxjagman]

Moderate risk for tonight now

 

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0320 PM CDT Sun May 26 2024

   Valid 262000Z - 271200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS
   SOUTH-CENTRAL AND SOUTHEAST MISSOURI...FAR NORTHEAST
   ARKANSAS...SOUTHERN ILLINOIS...FAR SOUTHWEST INDIANA...WESTERN
   KENTUCKY...AND NORTHWEST TENNESSEE....

   ...SUMMARY...
   Severe storms are expected from the Ozarks this afternoon and
   evening to the Ohio and Tennessee Valley tonight. Tornadoes, some
   strong to intense, and large to very large hail are the primary
   threats this afternoon and evening with an evolving overnight severe
   wind/embedded tornado threat tonight.

   Primary focus of this outlook update was a moderate risk upgrade
   from south-central Missouri into western Kentucky and northwest
   Tennessee. An EML has advected across this region in the wake of
   morning convection which has permitted strong heating and
   destabilization. The outflow boundary and the destabilized region
   north of this boundary provide a vorticity rich low-level airmass
   favorable for tornadoes. Supercells are already starting to develop
   in the hot and unstable airmass across southwest Missouri and will
   move toward this vorticity rich airmass this evening. Additionally,
   a strengthening low-level jet is expected across this area tonight
   which will elongate low-level hodographs. Most members of the 18Z
   and 19Z WoFS show several intense, long track supercells through
   this region later this evening with increased 0-2km UH
   probabilities, giving more supporting evidence for the rapidly
   evolving tornado threat. Given the aforementioned factors, several
   strong to intense tornadoes are possible this evening. See MCD #980
   for additional information about the evolving threat in this region.


   Eventually, these supercells will likely congeal into an MCS which
   amid extreme instability, strong shear, and steep lapse rates, will
   likely have a significant wind threat into the late evening and
   early overnight hours. 

   In addition, added a small marginal risk across southwest South
   Dakota and northern North Dakota where a few stronger storms have
   developed amid weak instability and moderate shear. See MCD 982 for
   additional information about this threat.

[Runman292]

In addition, the 10% hatched tornado risk has expanded as far east as Knox County. 

[jaxjagman]

Tornado warn Rockwood