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2020 Mid-Atlantic Severe Weather - General Thread


Kmlwx
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     Very active period coming up for the mid-Atlantic and northeast, as noted in the previous posts.      The soundings for today certainly do look great (per CAPE's post), but as noted by SPC, storm coverage is a question.     All of that westerly low-level flow and low-level dry air due to the downsloping makes for amazing DCAPE but also makes storm maintenance tougher.   A few recent HRRR runs actually have a convective MIN in the DC-Baltimore corridor, for what that's worth.

       Tomorrow looks like poor timing for us.   I wouldn't rule out Thursday, as even though the bigger show will be well to our north, there is really good flow and hard-to-time shortwaves.   Was a bit surprised to see a Saturday outlook - the upper trough looks sweet, but I've been under the impression that clouds and rain from the remnants of Laura will keep our instability low. Fun tracking for sure!

 

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5 minutes ago, high risk said:

     Very active period coming up for the mid-Atlantic and northeast, as noted in the previous posts.      The soundings for today certainly do look great (per CAPE's post), but as noted by SPC, storm coverage is a question.     All of that westerly low-level flow and low-level dry air due to the downsloping makes for amazing DCAPE but also makes storm maintenance tougher.   A few recent HRRR runs actually have a convective MIN in the DC-Baltimore corridor, for what that's worth.

       Tomorrow looks like poor timing for us.   I wouldn't rule out Thursday, as even though the bigger show will be well to our north, there is really good flow and hard-to-time shortwaves.   Was a bit surprised to see a Saturday outlook - the upper trough looks sweet, but I've been under the impression that clouds and rain from the remnants of Laura will keep our instability low. Fun tracking for sure!

 

After seeing outlooks like 6/29/12 I tend not to rule *anything* out completely until we are right up on the event. We've seen several/many times when we are barely in a 5% and end up in a higher end SLGT or even moderate. Not saying the setup is at all similar to that - just comparing how things can shift/evolve with severe. 

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Just now, WxUSAF said:

12z NAM and latest hrrr both have a fairly coherent line moving south out of PA and through the metro area between 5-9pm.

this morning's nam was empty. like nothing.... glad 12z shows some action

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1 minute ago, mappy said:

this morning's nam was empty. like nothing.... glad 12z shows some action

    The CAMs tend to not produce a lot of storms here in downsloping.... they're often underdone but on the general right track.    The 12z NAM nest solution is kinda scary verbatim for the DC-Baltimore corridor.      If a line can really get organized, the potential for widespread damaging winds is very real.    But it's a definite "IF".

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2 minutes ago, high risk said:

    The CAMs tend to not produce a lot of storms here in downsloping.... they're often underdone but on the general right track.    The 12z NAM nest solution is kinda scary verbatim for the DC-Baltimore corridor.      If a line can really get organized, the potential for widespread damaging winds is very real.    But it's a definite "IF".

Latest HRRR would at least water everyone's grass.

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Just now, Kmlwx said:

NAM nest and HRRR actually look pretty decent - especially the NAM nest - even some UD helicity tracks lol

They would certainly produce some rain for everyone's yards. It seems the HRRR has handled the morning batch of convection the "best". We are going to have to see what things look like around 5:00 pm or so. The action doesn't really appear to develop until it sinks south of the PA Turnpike. The latest HRRR, for example, has the line coming through the DC area around 23z to 01z. Not the greatest timing, but NW flow events usually jackpot someone.

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11 minutes ago, high risk said:

    The CAMs tend to not produce a lot of storms here in downsloping.... they're often underdone but on the general right track.    The 12z NAM nest solution is kinda scary verbatim for the DC-Baltimore corridor.      If a line can really get organized, the potential for widespread damaging winds is very real.    But it's a definite "IF".

oh my. i have not been paying enough attention it seems. thanks, keep us updated if you think thats a real possibility. ive got plenty around the yard to batten down if so.

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10 minutes ago, Eskimo Joe said:

They would certainly produce some rain for everyone's yards. It seems the HRRR has handled the morning batch of convection the "best". We are going to have to see what things look like around 5:00 pm or so. The action doesn't really appear to develop until it sinks south of the PA Turnpike. The latest HRRR, for example, has the line coming through the DC area around 23z to 01z. Not the greatest timing, but NW flow events usually jackpot someone.

23-1z seems fine to me. It's not overnight - and it's still summer so there should still be enough instability around that time. Plus, these things do tend to come in just a touch ahead of schedule. 

Also that cluster in NoVA right now could lay down some additional boundaries to enhance later convection. 

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9 minutes ago, mappy said:

oh my. i have not been paying enough attention it seems. thanks, keep us updated if you think thats a real possibility. ive got plenty around the yard to batten down if so.

        Yeah, those soundings really support strong downdraft potential IF storms can organize, consistent with the SPC outlook.

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1 minute ago, Kmlwx said:

23-1z seems fine to me. It's not overnight - and it's still summer so there should still be enough instability around that time. Plus, these things do tend to come in just a touch ahead of schedule. 

Also that cluster in NoVA right now could lay down some additional boundaries to enhance later convection. 

         Yeah, that's an interesting ongoing event for sure.     I was wondering if that might help or screw things up later, but the 14z HRRR has a modest handle on the ongoing activity and still cranks up the later show.

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Just now, high risk said:

         Yeah, that's an interesting ongoing event for sure.     I was wondering if that might help or screw things up later, but the 14z HRRR has a modest handle on the ongoing activity and still cranks up the later show.

I would think if they hang around too long they might reduce the risk over in NoVA. But Central Maryland and other areas still seem like a decent risk area (as evidenced by SPC area). 

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8 minutes ago, Kmlwx said:

15z HRRR rolling in now is pretty robust for the metro area. 

Eh, it's okay. Mappy get a couple of 55dbz pixels over her. The rest is pretty typical summer storms. Nothing that would warrant an ENH. In fact, the 15z HRRR is mostly dry for the DY1 ENH area. The best activity is west of Westminster.

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1 hour ago, Eskimo Joe said:

Eh, it's okay. Mappy get a couple of 55dbz pixels over her. The rest is pretty typical summer storms. Nothing that would warrant an ENH. In fact, the 15z HRRR is mostly dry for the DY1 ENH area. The best activity is west of Westminster.

      C'mon now, you know that SPC's forecasts aren't just made on model simulated forecasts.     Yeah, verbatim the reflectivity signals aren't massive, as I would expect the model updrafts to struggle a bit with the lower level dry air.    But with the models showing an organized line segment moving into an environment with ample instability and large downdraft cape, I would say that the ENH is absolutely warranted.    

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