2023 Mid-Atlantic Severe Wx Thread (General Discussion)

[Kmlwx]

Marginal risk for Friday. 

I'm also intrigued - the past two runs of the longer range GFS are hinting at some EML action for late next week. Euro is less enthusiastic - but it's at least something to keep an eye on. Some super long range (300hr+) runs in the past few days hinted at this as well (GFS) but it's kind of vanished and returned with model inconsistency. 

[Stormchaserchuck1]

I like the threat setting up around 7/17.. We have a Great Lake's trough cutting in, and there should be more of a SE ridge this time, ahead of it, with the PNA being negative. 

[stormy]

5 hours ago, Stormchaserchuck1 said:

I like the threat setting up around 7/17.. We have a Great Lake's trough cutting in, and there should be more of a SE ridge this time, ahead of it, with the PNA being negative. 

I would prefer the 1024 mb to be into Nassau instead of near Bermuda.

[Stormchaserchuck1]

1 hour ago, stormy said:

I would prefer the 1024 mb to be into Nassau instead of near Bermuda.

Yeah there is only a 0.2 correlation between -PNA and warmer temperatures but I bet we will trend warmer out ahead of it.

[Kmlwx]

Mesoanalysis actually has semi-decent mid-level lapse rates over the area

[Eskimo Joe]

3 hours ago, Kmlwx said:

Mesoanalysis actually has semi-decent mid-level lapse rates over the area

Yea, 1,500 SBCAPE, bit of a lee trough, good ll lapse rates, and okay mid level lapse rates. Also got a belt of 40kt shear. Maybe some sneaky storms in the NW suburbs today?

[yoda]

 

   Mesoscale Discussion 1521
   NWS Storm Prediction Center Norman OK
   0136 PM CDT Thu Jul 13 2023

   Areas affected...Portions of eastern WV...VA...DC...western/central
   MD...and central/eastern PA

   Concerning...Severe potential...Watch possible 

   Valid 131836Z - 132100Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Some threat for damaging winds and hail may exist as
   thunderstorms move eastward this afternoon. The need for a watch
   remains unclear, but trends will be monitored.

   DISCUSSION...Scattered thunderstorms have developed this afternoon
   across parts of the central Appalachians. More isolated activity is
   attempting to deepen across parts of north-central into northeastern
   PA, closer to the upper trough over NY and southern Quebec. A
   surface lee trough is present along/east of the Appalachians/Blue
   Ridge Mountains, with ample daytime heating acting to steepen
   low-level lapse rates. Latest mesoanalysis shows a relative minimum
   in instability along/east of the lee trough across parts of
   central/eastern VA into central MD and eastern PA. This area appears
   to have shallower low-level moisture based on area 12Z soundings,
   and some lingering MLCIN.

   Still, various RAP/NAM forecast soundings across this region suggest
   that a well mixed boundary layer will support at least an isolated
   damaging wind threat with any convection that can spread eastward
   off the higher terrain this afternoon and evening. Around 25-35 kt
   of deep-layer shear should also foster some thunderstorm
   organization, with multicells to marginal supercells possible. Some
   hail may occur with the strongest cores. With better large-scale
   ascent focused farther north across NY and New England, overall
   thunderstorm coverage remains uncertain. The need for a Severe
   Thunderstorm Watch this afternoon is also unclear, but observational
   trends will be closely monitored.

   ..Gleason/Bunting.. 07/13/2023

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...PHI...BGM...AKQ...CTP...LWX...RNK...

https://www.spc.noaa.gov/products/md/md1521.html

 

[aldie 22]

Weather underground starting its slow creep downward on rain for tonight in my backyard. Was over .71 and is now at .20

[Terpeast]

7 minutes ago, aldie 22 said:

Weather underground starting its slow creep downward on rain for tonight in my backyard. Was over .71 and is now at .20

I was never into today's chance. As soon as I saw a cell dissipate over WV/VA border earlier today, that confirmed it for me.

[stormy]

1 hour ago, Terpeast said:

I was never into today's chance. As soon as I saw a cell dissipate over WV/VA border earlier today, that confirmed it for me.

The greatest threat tonight and Friday contrary to models seems to be over southwest and west central Virginia.

[Eskimo Joe]

Pretty robust DCAPE western zones and already a warned cell with CG in West Virginia. 

[Kmlwx]

2 minutes ago, Eskimo Joe said:

Pretty robust DCAPE western zones and already a warned cell with CG in West Virginia. 

Derecho incoming. That cell will grow upscale and make a biblical cold pool. 

[Kmlwx]

Just like in prior days - there is a relative min of instability over the area. Hoping that DCAPE and other parameters can increase locally - otherwise this is going to be cells dying as they approach. 

[Eskimo Joe]

Latest HRRR tries to bring a few beefy cells into the northwest suburbs this afternoon.

[Kmlwx]

I know it's like my favorite word on here - but ANECDOTALLY - I've found that in many "significant severe" events locally - at least for MBY - if we can get a really good wind core or line to go through roughly Winchester - the odds are pretty good for MBY. I like the current radar trends but the threat for stuff dying on approach is still high in my mind. 

July 25, 2010 comes to mind very readily - that was a big time power outage producer in the area. 

[George BM]

1 hour ago, Kmlwx said:

I know it's like my favorite word on here - but ANECDOTALLY - I've found that in many "significant severe" events locally - at least for MBY - if we can get a really good wind core or line to go through roughly Winchester - the odds are pretty good for MBY. I like the current radar trends but the threat for stuff dying on approach is still high in my mind. 

July 25, 2010 comes to mind very readily - that was a big time power outage producer in the area. 

Just about my favorite event experienced pre-derecho. Lots of 80-90+mph gusts in Montgomery county and northside/north of the DC beltway IIRC.

[Kmlwx]

Just now, George BM said:

Just about my favorite event experienced pre-derecho. Lots of 80-90+mph gusts in Montgomery county and northside/north of the DC beltway IIRC.

So many in the public were screaming about "we had no warning" on that one. AFD had "big tstms" mentioned that morning, SPC had added a 30% wind area for us, and we had a severe watch and warnings as the wind core came through. Sometimes the average Joe can be really ridiculous. 

[Eskimo Joe]

26 minutes ago, Kmlwx said:

So many in the public were screaming about "we had no warning" on that one. AFD had "big tstms" mentioned that morning, SPC had added a 30% wind area for us, and we had a severe watch and warnings as the wind core came through. Sometimes the average Joe can be really ridiculous. 

Events like that are why I'm in favor of the Enhanced Risk category from SPC. Helps with those rando events where there's decent upside potential but it's not one of those "uh oh" events.

[Kmlwx]

8 minutes ago, Eskimo Joe said:

Events like that are why I'm in favor of the Enhanced Risk category from SPC. Helps with those rando events where there's decent upside potential but it's not one of those "uh oh" events.

Agreed. Though I think one could argue that in some of those "random" events - it may not even be clear until there's actively a storm spewing out high-end wind damage in a relatively narrow swath. 

That one happened to be REALLY well-centered for a high population area - and I think it was fairly well forecasted by SPC. 

[Kmlwx]

Side note - I love the DC area split you can already see setting up on radar. 

[Eskimo Joe]

18 minutes ago, Kmlwx said:

Side note - I love the DC area split you can already see setting up on radar. 

Looks like 2 distinct clusters. Southern end that already had a warning on it and appears to have a verified LSR coming out. Second cluster near Cumberland. So far, that one looks decent.

[Kmlwx]

1 minute ago, Eskimo Joe said:

Looks like 2 distinct clusters. Southern end that already had a warning on it and appears to have a verified LSR coming out. Second cluster near Cumberland. So far, that one looks decent.

Still is a bit north for my liking, but the cell at the tail end of the northern cluster (near Keyser) seems like an okay trajectory for taking it into the DC area. Needs more of a southernly component to that east motion, though. I'd feel better if that area between the Keyser cell and the cells near Petersburg, WV filled in. Wishful thinking! 

[Kmlwx]

I'm surprised there is no pity meso discussion out yet. Seems some days we get them while it's still clear as day on radar - others we go straight into a severe thunderstorm watch. Would think there'd at least be one out saying "sporadic nature will probably preclude the need for a watch. Nonetheless trends will be monitored"

[Eskimo Joe]

7 minutes ago, Kmlwx said:

I'm surprised there is no pity meso discussion out yet. Seems some days we get them while it's still clear as day on radar - others we go straight into a severe thunderstorm watch. Would think there'd at least be one out saying "sporadic nature will probably preclude the need for a watch. Nonetheless trends will be monitored"

Tend to agree. Even if it's a 20% watch issuance meso. Seems like there's an overall lack of deep layer shear to really congeal the activity, so it's probably just going to be decent pulsers with some wet microbursts.

[Kmlwx]

Lots of lightning on the Harrisonburg area cell(s)

[Kmlwx]

MESOSCALE DISCUSSION 1545  
NWS STORM PREDICTION CENTER NORMAN OK  
0102 PM CDT FRI JUL 14 2023  
  
AREAS AFFECTED...PARTS OF THE MID-ATLANTIC  
  
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY   
  
VALID 141802Z - 142030Z  
  
PROBABILITY OF WATCH ISSUANCE...20 PERCENT  
  
SUMMARY...A FEW INSTANCES OF MARGINALLY SEVERE HAIL AND DAMAGING  
GUSTS ARE POSSIBLE ACROSS PARTS OF THE MID-ATLANTIC THROUGH THE  
AFTERNOON. A WATCH IS NOT EXPECTED.  
  
DISCUSSION...ISOLATED TO WIDELY SCATTERED THUNDERSTORMS ARE EVOLVING  
EASTWARD ACROSS PARTS OF SOUTHERN PA INTO EASTERN WV AND WESTERN VA  
THIS AFTERNOON -- WHERE A 1-INCH HAIL REPORT OCCURRED EARLIER.  
DURING THE NEXT FEW HOURS, THIS ACTIVITY WILL GENERALLY  
SPREAD/DEVELOP EASTWARD ACROSS THE MID-ATLANTIC REGION, WHERE A  
PLUME OF DIURNALLY STEEPENING LOW-LEVEL LAPSE RATES IS DEVELOPING.  
GIVEN AROUND 30 KT OF EFFECTIVE SHEAR AND THE INCREASINGLY UNSTABLE  
PRE-CONVECTIVE ENVIRONMENT, MARGINALLY SEVERE HAIL AND LOCALLY  
DAMAGING GUSTS ARE POSSIBLE WITH ANY STRONGER MULTICELL CLUSTERS OR  
TRANSIENT SUPERCELLS THAT DEVELOP. THE OVERALL SEVERE THREAT SHOULD  
REMAIN TOO ISOLATED/SPORADIC FOR A WATCH.  
  
..WEINMAN/BUNTING.. 07/14/2023  
   
..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT  
  
ATTN...WFO...OKX...PHI...BGM...AKQ...CTP...LWX...RNK...

They said "sporadic"  

[yoda]

Transient supercells, but too isolated is a new one for me

[yoda]

10 minutes ago, Kmlwx said:

Lots of lightning on the Harrisonburg area cell(s)

Just got severe warned

[Kmlwx]

Keyser cell from earlier is now nearing Romney. I'm not mad at that trajectory thus far. Further, it seems like the stuff down near Petersburg/Lost City etc has storm tracks a little north of east. Meet in the middle for a biblical severe event in the metro area?!

[high risk]

I haven't been a big fan of today's potential, because while there is some decent flow in the upper levels, the shear through the majority of the cloud layer sucks.   That said, as others have pointed out, there is modest CAPE and decent downdraft CAPE, so there is *some* potential.     IF the HRRR idea of an organized line with a coldpool is correct, the threat might be a bit higher than thought: