2023 Mid-Atlantic Severe Wx Thread (General Discussion)

[Kmlwx]

4 minutes ago, yoda said:

A more cellular event could lead to a better chance of large hail over damaging winds 

I certainly find it hard to believe that there will be fewer than 5 severe reports in the LWX area tomorrow. But we'll see. 

[Stormfly]

39 minutes ago, Eskimo Joe said:

Big red flag for tomorrow.is how underwhelming the event has been today in the Midwest. Was expected to be a squall line, instead it's mostly clusters.

Have to butter up the pan to fry lots of nothinburgers.

I just hope they don't burn after all that smoke we had to endure two weeks ago!

[yoda]

Wouldn't mind the 18z NAM NEST sim radar around 5pm tomorrow 

[Eskimo Joe]

26 minutes ago, yoda said:

Wouldn't mind the 18z NAM NEST sim radar around 5pm tomorrow 

Got a screencap?

[Rhino16]

Do gaps like that in the storms usually happen? It’s been pretty consistent with it being where it is. Over me… I’ll know when it happens I guess.

[yoda]

9 minutes ago, Eskimo Joe said:

Got a screencap?

h/t @Bubbler86

[Kmlwx]

6 minutes ago, Rhino16 said:

Do gaps like that in the storms usually happen? It’s been pretty consistent with it being where it is. Over me… I’ll know when it happens I guess.

That's a micro/mesoscale occurrence. Anecdotally I think we all tend to think the gaps happen over us. In reality, it's probably terrain/orographic in nature. 

Gaps in storms are normal - consider in hurricanes when a major eyewall is in place - the area immediately surrounding can often have subsidence (particularly during an eyewall replacement cycle. 

The concept of "storms robbing energy" is sort of true. If you have a massive lone cell, and no cold pool or meteorological reason for it to grow upscale into a line segment/squall line, it may "use up" energy for other storms around it - often it will impact the inflow for another potential storm. 

There's also, of course, the outflow racing out ahead that can cause storms to die off and then "jump over" a given locale as the outflow triggers new storms. 

[Kmlwx]

0z HRRR continues with the lower dews for many of us. Has dews down as low as the upper 50s for some spots even pre-storms tomorrow. That will likely impact the rest of the run and subsequent storm chances for us. 

[Moosey2323]

Just now, Kmlwx said:

0z HRRR continues with the lower dews for many of us. Has dews down as low as the upper 50s for some spots even pre-storms tomorrow. That will likely impact the rest of the run and subsequent storm chances for us. 

71 F on NAM / 61 F on HRRR...that's a pretty large difference. Even if we land somewhere in the middle, that might be enough though. I also wonder if the bust over central Ohio will reduce the amount of cloud cover the region receives tomorrow.

[Kmlwx]

Just now, Moosey2323 said:

71 F on NAM / 61 F on HRRR...that's a pretty large difference. Even if we land somewhere in the middle, that might be enough though. I also wonder if the bust over central Ohio will reduce the amount of cloud cover the region receives tomorrow.

HRRR does have pretty substantial cloudiness for much of the morning for our region. 

If we are looking only at dews...would think that 70+ could net us an impressive day (verification of the ENH risk). Mid 60s perhaps would verify us in the slight risk, and if the HRRR is completely right - general thunderstorms with some gusty winds perhaps. 

In reality - more factors go into it (MLLR, shear etc) - but dews will be a big deal tomorrow. 

[yoda]

14 minutes ago, Kmlwx said:

0z HRRR continues with the lower dews for many of us. Has dews down as low as the upper 50s for some spots even pre-storms tomorrow. That will likely impact the rest of the run and subsequent storm chances for us. 

I'm not buying the big mixing out of the HRRR... southerly winds and flow should keep DPs 65+ 

[high risk]

4 hours ago, Eskimo Joe said:

Big red flag for tomorrow.is how underwhelming the event has been today in the Midwest. Was expected to be a squall line, instead it's mostly clusters.

   Is this really underwhelming?     Maybe for western OH, but......

[high risk]

not totally worthy of being mentioned in the severe thread, but for those of us who have been anxiously awaiting nocturnal convection, some of the CAMs say that at least several of us will be woken up later tonight by a round of storms.     Radar is trying to light up a bit to our west.

[high risk]

Monday obviously has the higher end potential, but it looks like all of the CAMs have widespread afternoon convection on Tuesday.     If you toss the NAM Nest low 70s dew points, the CAPE is modest in most solutions, and shear is weak, but there is a healthy amount of downdraft CAPE.      I would think that the outlook for Tuesday will expand the MRGL back to the west over more of the area.

[yoda]

00z NAM Nest has a large UD Helicity Swath just north of DC metro around 19z-21z (basically IAD to BWI)

[high risk]

8 minutes ago, yoda said:

00z NAM Nest has a large UD Helicity Swath just north of DC metro around 19z-21z (basically IAD to BWI)

     Very impressive signal.     It forms a discrete cell out ahead of the main line in the early-mid afternoon when surface winds will be somewhat more backed, leading to a shear profile that would actually support some healthy rotation.    But this is somewhat of an outlier solution.

 

[yoda]

7 minutes ago, high risk said:

     Very impressive signal.     It forms a discrete cell out ahead of the main line in the early-mid afternoon when surface winds will be somewhat more backed, leading to a shear profile that would actually support some healthy rotation.    But this is somewhat of an outlier solution.

 

02z HRRR has some explosive development in the i81 corridor at teh end of its run that looks like it matches the 00z NAM Nest a bit

[high risk]

3 minutes ago, yoda said:

02z HRRR has some explosive development in the i81 corridor at teh end of its run that looks like it matches the 00z NAM Nest a bit

    If you look at the forecasts valid at 20Z, they align with the line forming out to the west, but the HRRR doesn't have the lead storms that the NAM Nest has.   Probably not surprising, given the mixing out of the HRRR moisture.

 

[Kmlwx]

Some of the CAMs are uninspiring for a chunk of us. In fact, the latest NAM nest (6z) - largely missed DC proper with anything substantial and focuses most north and east of the city. Anne Arundel and Baltimore and north look good still on that run. 

[mappy]

No problem with dews this morning, 70/69. But its cloudy lol

[Eskimo Joe]

9 hours ago, Kmlwx said:

0z HRRR continues with the lower dews for many of us. Has dews down as low as the upper 50s for some spots even pre-storms tomorrow. That will likely impact the rest of the run and subsequent storm chances for us. 

That's gotta be the HRRR mix out bias. No other meso model gets our dews that low. 

[Eskimo Joe]

Socked in with clouds. Don't see how realize any potential today north of I-66.

[Kmlwx]

1 minute ago, Eskimo Joe said:

Socked in with clouds. Don't see how realize any potential today north of I-66.

Matches what the HRRR runs last night were showing. Band of clouds in the morning but potential clearing by later morning/afternoon. Question is will it be soon enough. Visible satellite shows promise with a nose of clearing in Virginia - it appears (unless it's a shadow) extends up all the way into the Panhandle of WV and Maryland and even into a sliver of S PA. It's still early enough for clouds to resolve. If it was 10am and we are still socked in - sure. 

[H2O]

Can confirm dews and humidity. Muggy sitting here at swim practice

[LeesburgWx]

Sun starting to poke out here

[Kmlwx]

[MN Transplant]

9 minutes ago, Eskimo Joe said:

Socked in with clouds. Don't see how realize any potential today north of I-66.

There is a realistic fail mode here that has been hinted at by some models where there are good storms up in PA where the dynamics are solid and down in southern VA and NC where the instability is better.  

[Kmlwx]

The dewpoint here is 71 at this time. If we can avoid that dropping too much, and can manage some sunshine we should be set for something semi-decent. All a balance...we can probably deal with less of one thing if there is enough of another factor present. I can see @Eskimo Joe's concern - and certainly does seem that best sunshine will be S of I-66 but the threat is not greatly reduced as of yet. At least IMO. 

[Kmlwx]

Just now, MN Transplant said:

There is a realistic fail mode here that has been hinted at by some models where there are good storms up in PA where the dynamics are solid and down in southern VA and NC where the instability is better.  

The good old fashioned DC screwjob essentially. Have seen it on more than one CAM overnight...I'd almost say that's becoming semi-likely with some crapvection/junk in between. 

[vastateofmind]

74/71 at Fort Belvoir right now...sun starting to break through, too.