2026 Mid-Atlantic Severe Storm General Discussion

[yoda]

Also, not saying we will get one here, but the derecho definition has changed

https://x.com/evan_bentley/status/2032572486982791628?s=20

 

[yoda]

Those who know better can correct me... but 18z RRFS sim radar looks ugly.  Looks like warm sector prefrontal sups appear in the afternoon with a QLCS right around sunset moving through the region

[Eskimo Joe]

Oh

 

[Nomz]

55 minutes ago, yoda said:

Those who know better can correct me... but 18z RRFS sim radar looks ugly.  Looks like warm sector prefrontal sups appear in the afternoon with a QLCS right around sunset moving through the region

Yeah it looks pretty bad, but its also the RRFS @ 84

[Eskimo Joe]

 

[Nomz]

10 minutes ago, Eskimo Joe said:

 

That's about a good of a definition of the two tornado alleys as you can get.

[wxmeddler]

46 minutes ago, Eskimo Joe said:

*snip*

I'm fairly well convinced that the recent SPC changes have fundamentally altered the way higher percentages are given out. So much so that most of the SPC climatology is going to have to be tossed / step-changed. Arguably for the better though!

SPC Forecasters have repeatedly said that the % were under-done due to the way the rubric was constructed. That's why things like NadoCast and PPF's were always markedly higher. New 30%D3 is the old 15%. And that's good! I think it better conveys the actual risk. It's just going to get some getting used to.

 

[SnowenOutThere]

To my relatively novice eyes the 0z NAM run looks primed. Lapse rates, decent enough cape, and ofc insane shear. 

[AmericanWxFreak]

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER MUCH OF
THE CAROLINAS...VIRGINIA...AND EXTENDING NORTHWARD INTO SOUTHERN
PENNSYLVANIA...

...SUMMARY...
Widespread damaging winds and several tornadoes are forecast on
Monday for parts of the Mid Atlantic and Southeast.

...Discussion...
A large and deepening upper trough will eject east/northeastward out
of the MS/OH/TN Valleys and across the Appalachians and into the Mid
Atlantic/Northeast on Monday, with an expansive area of strong wind
fields aloft. A surface low move from Lower MI into southern Quebec,
with a deep pre-frontal trough extending southward across eastern
PA, VA, and NC by around 21Z. Ahead of this trough/front, southerly
winds will bring 60s F dewpoints as far north as southeast PA.

Storms will likely be ongoing along the length of the cold front,
roughly from OH to the FL Panhandle Monday morning. Given the
uncapped air mass over the Carolinas, a few storms, possibly
supercells, may develop relatively early in the day as well, with
tornado potential. The greatest threat however will be during the
afternoon as cold front nears, and pressure falls are maximized
along with daytime heating. A few supercells ahead of the line will
be possible, along with embedded circulations and/significant
damaging winds within the squall line.

There are model differences regarding the speed/position of the cold
front, as well as the degree of instability. Regardless, damaging
winds over a large area appear likely, along with at least a few
tornadoes. Depending on the degree of destabilization, a strong
tornado or two may occur especially over parts of the Carolinas and
Virginia during the late afternoon. Many models forecast 300-500
m2/s2 SRH, along with pockets of SBCAPE over 1000 J/kg, which is
clearly favorable for tornadic supercells.

[Eskimo Joe]

 

[TSSN+]

9 minutes ago, Eskimo Joe said:

 

Not very impressive 

[09-10 analogy]

14 hours ago, Eskimo Joe said:

 

I'm sure I'm totally misreading this, but so often around here the gust front out ahead dampens down the severe potential. But Monday might be different? In that in a dominant shear environment -- if one is realized on Monday -- the gust front is attenuated? Or is my reasoning here too linear or just outright horribly wrong?

[Eskimo Joe]

2 hours ago, 09-10 analogy said:

I'm sure I'm totally misreading this, but so often around here the gust front out ahead dampens down the severe potential. But Monday might be different? In that in a dominant shear environment -- if one is realized on Monday -- the gust front is attenuated? Or is my reasoning here too linear or just outright horribly wrong?

70 - 125 kt shear on a neutral to negatively tilted trough in March is a recipe for a decent event.

[high risk]

1 minute ago, Eskimo Joe said:

70 - 125 kt shear on a neutral to negatively tilted trough in March is a recipe for a decent event.

But is that too much shear for the very modest cape?    

[Eskimo Joe]

1 minute ago, high risk said:

But is that too much shear for the very modest cape?    

We'll see. I would favor DC and points south for torandoes, maybe some rogue QLCS thingy in MD through Central PA.

[high risk]

The high end potential is definitely there, but two things stand out  1) a clear trend towards earlier timing    2) a lot of guidance showing clouds and showers well ahead of the main forcing.  With the right timing, the early convection could be supercells, but the trend towards an earlier event opens the door to insufficient time to recover after morning showers. 

[Rhino16]

It seems like some of the 12z guidance shifted everything earlier in the day. It could be noise this far out, but it’s something to watch.

[high risk]

4 minutes ago, Eskimo Joe said:

We'll see. I would favor DC and points south for torandoes, maybe some rogue QLCS thingy in MD through Central PA.

I think that’s reasonable, although climo says (and guidance agrees) that the best tornado threat will be even further south. 

[Rhino16]

2 minutes ago, high risk said:

but the trend towards an earlier event opens the door to insufficient time to recover after morning showers. 

Are there any notable events where recovery occurred from showers earlier in the day? Is it something we struggle to do around here?

[high risk]

21 minutes ago, Rhino16 said:

Are there any notable events where recovery occurred from showers earlier in the day? Is it something we struggle to do around here?

Yes and yes.      The failures are way too many to note, but a famous day when we successfully recovered is the La Plata event. 

[TSSN+]

12z Nam has nasty line in the afternoon 

 

[Eskimo Joe]

1 hour ago, Rhino16 said:

Are there any notable events where recovery occurred from showers earlier in the day? Is it something we struggle to do around here?

Feb 7, 2020. 

[Newman]

Latest 12z CSU-MLP forecast for Monday