TV Severe Weather2025-?

[PowellVolz]

3 minutes ago, nrgjeff said:

If the 12Z Tuesday forecast holds. Saturday is going to be a day. CSU model is probably keying in on outflow in Bama. Plus that surface low. Mass response (LLJ other levels) has trended up on Saturday due to the more obvious 2nd wave at the upper levels. Also the reason for the surface low. It's all connected. 

kinda of a catch 22. The potential lack of moisture for Friday that the mods are now showing could mean less convection Friday/Friday night which could potentially allow for more moisture return on Saturday. However the mods are also showing a little less zonal flow and more 500mb winds running parallel to the CF. More zonal flow, more discrete cells. More parallel winds, more of a QLCS or squall line. Something to watch. 

[Matthew70]

I could see the SPC expanding the 30% at this time.  I am afraid moisture return is going to be much more expansive. 

[*Flash*]

7 hours ago, PowellVolz said:

kinda of a catch 22. The potential lack of moisture for Friday that the mods are now showing could mean less convection Friday/Friday night which could potentially allow for more moisture return on Saturday. However the mods are also showing a little less zonal flow and more 500mb winds running parallel to the CF. More zonal flow, more discrete cells. More parallel winds, more of a QLCS or squall line. Something to watch. 

Wouldn't surprise me if middle TN comes out of this relatively unscathed, granted for west/southern middle/southeast TN...different story. Too many times in this scenario, I've seen some sort of stabilizing intrusion cap the severe criteria potential. Looking at the 18z guidance, the bulk of the greatest energy will be well south of BNA. Plenty of time for adjustments but frankly, I'm not worried or amped up about the threat. That said, I'm looking forward to a chase down 65. Could be a red letter day for our friends in MS/AL/GA. 

[Matthew70]

26 minutes ago, *Flash* said:

Wouldn't surprise me if middle TN comes out of this relatively unscathed, granted for west/southern middle/southeast TN...different story. Too many times in this scenario, I've seen some sort of stabilizing intrusion cap the severe criteria potential. Looking at the 18z guidance, the bulk of the greatest energy will be well south of BNA. Plenty of time for adjustments but frankly, I'm not worried or amped up about the threat. That said, I'm looking forward to a chase down 65. Could be a red letter day for our friends in MS/AL/GA. 

Agree.  I believe the mid state is going to see a lot of rain & thunderstorms but nothing more than that.  Seems Nashville has its every few years  long track tornado.  Other than that no red letter day.  The storm shield is stout. 

[Runman292]

Day 4 Outlook from the SPC:

...SEVERE WEATHER OUTBREAK POSSIBLE ON D4/SAT...

   ...DISCUSSION...
   ...Day 4/Sat - Central Gulf Coast States to the Ohio Valley...

   A strong large-scale upper trough is forecast to quickly move across
   the Plains to the MS Valley on Saturday. An intense jet streak will
   move across the Deep South into the OH Valley as this occurs. At the
   surface, a low secondary to the 980 mb low over the Upper Midwest is
   forecast to develop during the late morning/early afternoon across
   the mid-South. This will aid in further northward transport of rich
   Gulf moisture into portions of the Lower MS Valley and TN Valleys.
   Atop this moisture-primed boundary layer, cold 500 mb temperatures
   are forecast. This may support fairly steep lapse rates, which would
   foster moderate instability across portions of MS/AL amid supercell
   wind profiles. However, some uncertainty remains tied to the
   evolution of convection in the Day 3/Fri period into the morning
   hours of Saturday. Some forecast guidance suggests a relatively
   pristine warm sector will be maintained, or if only isolated
   convection develops overnight/early Saturday, recovery could occur.
   If this scenario unfolds, a concerning severe weather setup
   supporting all-hazard severe could unfold across portions of
   LA/MS/AL through the day and into evening, and eventually spreading
   east into GA overnight. Trends will be monitored closely over the
   coming days and further adjustments to the 30 percent/Enhanced risk
   area may be needed in future outlooks.

   With northward extent, instability will become more limited.
   Nevertheless, sufficient moisture amid intense deep-layer flow will
   support swaths of strong/damaging winds into the Ohio Valley and
   portions of the central Appalachians Saturday and Saturday night.
   Higher outlook probabilities may be needed in subsequent outlooks if
   confidence increases.

 

[nrgjeff]

A look at the 84 hr. NAM - not yet reliable for surface beyond 60 hr. - shows an upper level regime somewhere between that of the GFS and that of the Euro.

Note the globals are 06Z. GFS has robust instability, and still enough turning with height. Euro is not quite as unstable, but the turning with height is greater. 850 is about 10-20 deg. backed from straight south. Others are not. So two paths are offered to high overall parameters. All have a distinct Saturday short-wave. 

Surface is still TBD. Friday night into Saturday morning convection evolution is TBD. Without those pieces I don't consider siggy severe locked in. It's on the table though. 

[Runman292]

4 hours ago, nrgjeff said:

A look at the 84 hr. NAM - not yet reliable for surface beyond 60 hr. - shows an upper level regime somewhere between that of the GFS and that of the Euro.

Note the globals are 06Z. GFS has robust instability, and still enough turning with height. Euro is not quite as unstable, but the turning with height is greater. 850 is about 10-20 deg. backed from straight south. Others are not. So two paths are offered to high overall parameters. All have a distinct Saturday short-wave. 

Surface is still TBD. Friday night into Saturday morning convection evolution is TBD. Without those pieces I don't consider siggy severe locked in. It's on the table though. 

I know it's way too far to determine this with any sense of absolute certainty, but if the instability is sufficient, could we see something similar to April 27th?

[andyhb]

Saturday could be a bad day.

The overlap of cold mid level temperatures, upper 60s dewpoints, and a 55-70+ kt LLJ cannot be underestimated.

[Matthew70]

9 minutes ago, andyhb said:

Saturday could be a bad day.

The overlap of cold mid level temperatures, upper 60s dewpoints, and a 55-70+ kt LLJ cannot be underestimated.

Do you think this is a west TN threat Friday night & an East TN threat Saturday afternoon?  Skipping over middle?

[Matthew70]

24 minutes ago, Runman292 said:

I know it's way too far to determine this with any sense of absolute certainty, but if the instability is sufficient, could we see something similar to April 27th?

As Spann says.  “Nothing can compare to April 2011”.  That’s a once every 30-40 years outbreak. 

[andyhb]

33 minutes ago, Matthew70 said:

Do you think this is a west TN threat Friday night & an East TN threat Saturday afternoon?  Skipping over middle?

That's impossible to really say this far out, but yes I'd lean towards Middle TN being too far east on Friday and too far north on Saturday.

[vortexse93]

 

I am currently keeping my eyes out for Friday into Saturday. By glancing at the models over the last few days, I am personally not liking the timing nor the placement of this setup. This round I may end up sitting this one out. For me personally, it will be a stretch to make near Northeast AR/MO on Friday.

For Saturday, the threat will be to my east and chasing east of I-55 is nearly impossible. While there are some spots that are decent to chase in, I am not much on fighting trees and hills. Plus, have some concerns in how Saturday morning may play out with the morning storms ahead of the main show. Have seen time after time when morning storms tend to ruin events. Not saying that will happen, it is something to keep in the back of the mind when making these decisions. Will continue to watch and see what the higher res models are showing by this time tomorrow. 

[andyhb]

D3 moderate risk out from SPC.

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0229 AM CDT Thu Mar 13 2025

   Valid 151200Z - 161200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
   SOUTHEAST LOUISIANA INTO SOUTHERN AND CENTRAL MS/AL...

   ...SUMMARY...
   A severe weather outbreak is expected on Saturday from the central
   Gulf coast states/Deep South into the Ohio Valley. Significant
   tornadoes (focused across the South), swaths of damaging gusts, and
   hail are expected.

   ...Synopsis...

   An upper cyclone over the Upper Midwest will lift northeast into
   Ontario through Saturday evening. Meanwhile, a large-scale upper
   trough over the Plains will eject east toward the MS Valley. Strong
   southwesterly mid/upper flow (with a 500 mb jet streak near 100 kt)
   will overspread the Lower MS Valley/Mid-South vicinity by 00z, and
   continue east/northeast overnight into the Ohio Valley and central
   Appalachians. An intense south/southwesterly low level jet greater
   than 60 kt is forecast to overspread the central Gulf coast/Deep
   South into the TN/OH Valley during the late afternoon and nighttime
   hours. Rich Gulf moisture with dewpoints in the mid/upper 60s is
   expected to be focused over LA/MS/AL and the FL Panhandle, and
   possibly as far north as Middle TN and far western GA. 50s to low
   60s F dewpoints will extend north into the Ohio Valley. This should
   support a widespread risk for severe storms across much of the
   central into the southeastern U.S. Saturday into early Sunday.

   ...Deep South/TN Valley vicinity...

   Forecast guidance has generally trended toward less widespread
   precipitation coverage Saturday morning as stronger height falls are
   not expected until late morning/early afternoon as the Plains trough
   ejects and a surface low begins to develop over the Mid-South.
   Persistent strong southerly low-level flow will allow for a
   moisture-rich boundary layer that should remain relatively pristine
   across southeast LA into southern/central MS/AL before convection
   develops by midday. Forecast soundings show cooling aloft will
   support steep midlevel lapse rates atop this moist boundary layer,
   leading to MLCAPE values perhaps approaching 2000 J/kg (decreasing
   with northward extent in Middle TN). Vertically veering wind
   profiles with strong anvil-level divergence amid moderate
   instability should support robust updrafts and intense supercells.
   Significant tornadoes, damaging gusts and large hail will be
   possible through the afternoon and spreading into AL during the
   evening/nighttime hours.

   Additional convection is expected to develop along an
   eastward-advancing cold front during the afternoon and into the
   overnight. An organized line of storms will pose a risk for damaging
   wind swaths and tornadoes across northern MS/AL into TN, eastward
   into GA and the western Carolinas overnight. 

   ...Ohio Valley...

   Very strong deep-layer flow will be in place across the Ohio Valley
   on Saturday with some convection possibly ongoing from southeast
   Lower MI into western/central KY. The extent of severe potential is
   uncertain and dependent on how much precipitation occurs early in
   the forecast period. Too much convection early in the day could
   largely limit destabilization and temper the overall risk. However,
   if less convective contamination occurs, greater destabilization
   could occur ahead of a deepening surface low lifting northeast from
   the Mid-South to OH during the evening. Given the strength of
   deep-layer flow at least some risk of strong/damaging gusts within
   bands of thunderstorms should occur through Saturday night.

   ..Leitman.. 03/13/2025

[Runman292]

Here's the AFD from MRX:

2. Severe Weather

The original surface low is expected to track into Canada with another area of low pressure developing west of the Mississippi River Valley. During this time, focus will also turn towards impressive upper divergence due to a coupled jet structure Saturday afternoon. At the time of this update, the latest HREF data ends Friday evening with the FV3 and high-res NAM only reaching until 12Z Saturday. There are indications of decaying convection moving into the area Saturday morning but likely with only elevated instability. The main focus will be anytime from Saturday afternoon through Saturday night. The timing and some details will still need to be resolved with higher resolution model data, but the latest indications raise significant concerns for what will unfold. Very curved hodographs and MLCAPE over 500 J/kg are indicated during the day on Saturday with effective shear of well above 50 kts and low-level SRH of 300 to 500 m2/s2. The latest models indicate convection to be in the area Saturday afternoon, which would likely be in the form of robust supercells. This is noted even more notably to our south and west with this convection likely forming into a line and moving towards the area by the evening hours. With the environment being indicated from the NAM and other models, a severe weather outbreak with all hazards is likely in store across the region. There are still questions as to how the local environment will evolve in our area, in addition to the initiation, evolution, and coverage of convection. These details will be better resolved once more high-res model guidance is available through the event. Ahead of this potential line, most sources increase 850mb winds to in excess of 70 kts, which would present a significant damaging wind risk if these winds are brought to the surface.