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.