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2021 Mid-Atlantic Severe Weather - General Discussion


Kmlwx
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SPC has adjusted/expanded the slight risk area further south..

OH to Mid Atlantic Region... Overnight convection has resulted in a large canopy of mid/high clouds across portions of eastern OH and western/central PA. This will significantly limit daytime heating and destabilization later today. Therefore, have adjusted the SLGT risk area farther south into parts of OH/WV/MD where stronger heating is expected, and where CAM guidance in is better agreement regarding thunderstorm development. A shortwave trough currently over Lower MI will help to initiate storms across northern OH by mid-afternoon, with storms tracking southeastward through the evening.

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2 minutes ago, CAPE said:

Time to move discussion to the other thread. Maybe a few garden variety storms later as the front drops in. A quarter inch or so of rain would be nice.

On to Tuesday I guess. As it looks now, timing might not be ideal.

I'm actually lowkey watching Monday. Some CAMs are hinting that MLLRs may steepen during the day with moisture from Claudette in the lower levels leading to higher CAPE. At the same time shear looks to strengthen to modest/moderate levels. If storms can form along the surface trough near the mountains on Monday and/or organized storm activity from further west can propagate eastward into the region, the ingredients may be there for a few decent storms.

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20 minutes ago, Kmlwx said:

Extended range CIPS has a pretty good signature (especially by this year's standards) out at 168 hours. 

PRALLC01_gefsF168.png

Yes. I've noticed that some models have looked a bit more 'sheary' than usual for the time of year in the long range. Fingers, toes, arms, legs and anything you can cross crossed.

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7 minutes ago, George BM said:

Yes. I've noticed that some models have looked a bit more 'sheary' than usual for the time of year in the long range. Fingers, toes, arms, legs and anything you can cross crossed.

We should of course expect it to fade out with time - or if not that, the timing will suck when game time arrives. There's some signature way out at 312hr too. I feel like I've become the king of over using CIPS - but I mean...it's the "quickest" way to get a sense of what the GFS is showing out in range without doing the analysis yourself ;)

That's one of the more robust signatures I think we've seen this year. And having it honk that hard at 168 is pretty eye opening. 

I think tomorrow afternoon could have some decent storms - Tuesday looks dead right now. 

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51 minutes ago, Kmlwx said:

I think tomorrow afternoon could have some decent storms - Tuesday looks dead right now. 

            I have to agree that we're now in the "Monday or bust" realm, as the timing for Tuesday shows no indication now of slowing down enough for us.   There is certainly an increasing signal here for scattered storms later Monday into Monday evening, and there may be enough dry air in the low levels for a few downbursts, but the much better deep layer shear will remain to our west and likely preclude a more organized SVR threat.    At this point, I just want to be sure avoid missing out entirely on rain by the time we get to Tuesday evening.

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Another note on the CIPS stuff for those who aren't familiar with it. The severe stuff on there usually has a tier for "Percent of analogs with at least 1 severe report within X number of km" and then a tier for the same thing but for 5 or more reports. 

It makes it a quick way to see 1) Are the analogs hinting at severe potential and then 2) Our garden variety severe or something a bit more substantial. If you notice the percentages for 1+ report are lighting up like a Christmas tree, but the 5 or more is pretty lackluster...can be a good indication that the analogs are suggesting a decent shot at a window of severe potential but not anything on the higher end. 

And of course...the range and such all come into play - we've seen things fizzle from way closer in than 168 hours. 

I also like to poke around to look at the different domains they have available. Sometimes the analogs from one domain will show a big swath of potential for us, while the domain over the Mid-Atlantic will show nada or very limited potential.

And of course...analogs are just that. Rough guides on what happened when certain aspects of the pattern/atmosphere were in a similar state. Doesn't mean it will match up on a subsequent "match" in conditions. 

AND FURTHER - CIPS uses the NAM for the shorter range stuff, and then GFS for the longer range stuff. There's not (to my knowledge) any factoring in of the Euro, CMC, ICON etc. So you'll get the American models - but if they are vastly wrong it won't mean s**t. 

During severe season (I guess during winter too) - I usually do a quick glance at CIPS to decide if I want to do a more indepth look at any of the modeling from overnight. If it's pretty dead on CIPS, I'll usually peak on the forums in case there's something that the mets here are watching - and if not...usually safe to go mow the lawn or enjoy the day. :lol: 

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And yet another thing to add to my "wall of text" above. A factor I didn't even think about when writing that post...

You'd have to assume that more densely populated areas will report larger numbers of severe reports in a comparable event versus a more rural area. Thus...that could bias those percentage maps to show a more "honking" kind of look when it might look much more toned down in less densely populated areas. I'm not aware (but I haven't checked) to see if there's any population adjustment to those maps. 

So you'd wonder if a "corrected" map of what I posted earlier might look a lot less impressive. 

 

ETA: Just look at the relative minimum in the percentages on that map in WV. 

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After the miserable bust of Saturday, it looks like we've got a somewhat better chance today. Issues include a cap and some deep mixing potential. We're also going to probably be a bit dependent on LEWPs or bows surging well out ahead of the front to get the job done, since forcing locally will be pretty weak.

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I certainly don't hate the storm cluster that the HRRR has been advertising moving through the region late this afternoon. Other 0z CAMs to a slightly lesser extent showed a similar thing. Much like what csnavywx hinted at above. I don't hate the large DCAPE and 30-40kt mid-level flow showing up on CAMs either (Wind potential).

Fingers crossed.

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