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

[yoda]

Afternoon AFD from LWX... @high risk i know you mentioned instability... LWX seems to be suggesting around 1K SBCAPE in the disco (bold mine)

DISCUSSION...

KEY MESSAGE 1...A strong cold front pushes across the forecast area
 Monday, bringing gusty winds and potential for severe
 thunderstorms capable of producing significant damaging winds
 and tornadoes.

Precipitation chances begin increasing Sunday as a potent low
pressure system traverses across the Great Lakes into Canada,
pushing the associated fronts across the Mid-Atlantic. The
associated warm front lifts through the area Sunday night with the
cold front tracking across the region during the day Monday. Aloft,
a robust trough digs across the central CONUS, becoming slightly
negatively tilted as it approaches and pivots across the east coast
Monday. This will push the aforementioned cold front across the
forecast area, bringing impactful weather throughout the day.

In the wake of the warm front lifting through Sunday night, high
temperatures on Monday will be in the mid 60s to mid 70s.
Additionally, with southerly flow, dewpoints rise into the upper
50s to low 60s across much of the forecast area ahead of the
cold front. Storms may initiate Monday morning with any
shower/storm capable of producing gusty winds due to a strong
wind field aloft. Later Monday morning and into the afternoon,
storms develop along the cold front as it moves through from
west to east. Damaging winds are likely with severe storms
capable of producing significant damaging wind and tornadoes.
With such a strong wind field aloft, there is the potential for
wind gusts of 70 to 80 mph within severe storms.

Current model guidance shows 300-400 m2/s2 SRH and up to 1400
J/kg SBCAPE which is compatible with a tornado risk across the
area. SPC has the forecast area along and east of the I-81
corridor in an enhanced risk for severe weather with the rest of
the forecast area in a slight risk. PWATS will be seasonably
high, although a fast storm motion limits the flooding risk.

[yoda]

Afternoon day 3 from SPC 

 

[yoda]

Oh snap @Kmlwx @wxmeddler @high risk @Eskimo Joe

 

 

[Kmlwx]

Discussion leads with mentioning potential future upgrade to MOD risk for SC to MD

[yoda]

Oh my

Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0238 PM CDT Sat Mar 14 2026

   Valid 161200Z - 171200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM SC TO
   SOUTHERN PA...

   ...SUMMARY...
   Scattered to widespread severe storms are likely on Monday for parts
   of the Mid-Atlantic States and Southeast. The greatest potential for
   strong tornadoes and significant damaging winds appears centered on
   parts of South Carolina to Maryland during the late morning to
   afternoon.

   ...Mid-Atlantic and Southeast...
   Primary changes this outlook are to add a 45 total severe
   probability along with minor northeast and southeast expansion to
   the categorical risk areas. Portions of the region, centered on SC
   to MD, may warrant an upgrade to a level 4/Moderate Risk in later
   outlooks.

   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 to
   intense wind fields aloft. A deep cyclone will move from Lower MI
   into QC, with an occluding cold front arcing southeast across the
   northern Appalachians, then south-southwest into the northern Gulf.
   This front will clear all but the FL Peninsula by Monday evening.

   Ahead of the front, seasonably rich low-level moisture characterized
   by 60s surface dew points will spread northward from the eastern
   Gulf/western Atlantic. Convection will likely be ongoing at 12Z
   Monday, low-topped along the Upper OH Valley to central Appalachian
   portion of the front to deep convection in the lee of the southern
   Appalachians to eastern FL Panhandle. A diurnal uptick in storm
   intensity, including potential for semi-discrete supercells ahead of
   the front, should occur from north FL to the Carolina Piedmont.
   Further intensification is anticipated midday into the afternoon as
   a confined corridor of moderate buoyancy likely develops just ahead
   of morning storms.

   Enlarged low-level hodograph curvature, in conjunction with
   favorable elongation of the mid/upper hodograph, should foster a mix
   of broken supercells south with line-embedded supercells in the
   reinvigorated QLCS north. With such intense 700-mb flow aptly timed
   with the diurnal heating cycle overlying rich low-level moisture,
   setup could yield an expansive severe weather day, including strong
   tornadoes and significant damaging winds. The degree of
   boundary-layer heating, as well as timing of convection that may
   outpace the front late D2 into early D3, will play key roles in how
   intense severe magnitudes may become. At present, the most likely
   corridor for significant/widespread severe appears centered on the
   eastern Piedmont to coastal plain from SC to MD around midday into
   the afternoon.

   ..Grams.. 03/14/2026

[yoda]

Up close look (h/t @canderson)

 

[canderson]

SPC basically said C MD on south to the piedmonts will be upgraded a level 4 risk.