2022 Mid-Atlantic Severe Wx Thread (General Discussion Etc)

[TSG]

That large cell WSW of Richmond has been going since 4:45pm when it was coming off the Blue Ridge West of Charlottesville. Impressive echo tops, over 50k ft now. I got to watch it march into the Piedmont from the reservoir.

[CAPE]

Morning take from Mount Holly on the MCS-

We continue to monitor the chances for a decaying MCS that guidance has persistently been forecasting to transition from from the Midwest and across the Great Lakes towards the East Coast. With many environmental factors present to support such a system, it really comes down to where today`s cold front stalls. Should it stay further north and stall over our region to just north of our region, then the MCS would likely ride along the boundary around the expansive ridge to our southwest. If the deepening and closed 500 mb low over the Saint Lawrence River shifts further southwest, then the high over Ontario will push the continental airmass further south and take the front cleanly through our area. There is actually pretty decent spatial agreement as of this morning with the GFS, NAM, EC, and Canadian taking the MCS across Pennsylvania from northwest to southeast and into the Delmarva Peninsula. Best chances are probably across the northern Chesapeake Bay region around Baltimore to northeastern Maryland and norther Delaware. On the other hand, there remains poorer agreement temporally- speaking. Timing of this system remains difficult to iron out given that the thunderstorm complex is just now forming over portions of South Dakota. The GFS remains the fastest of the model spread, bringing the system through around 8 am tomorrow, whereas the others bring it in around noon to the very early afternoon. While all severe hazards can come into play with these systems, damaging straight-line winds is the greatest threat. Forecast sounding suggest dry air entrainment should support healthy cold pool maintenance, which should balance well with low-level shear. The more optimal the balance between these two, the greater the longevity of the system. With the forecast taking the system around the northeastern flank of a broad zone of 4000 to 5000 J/kg of MUCAPE, there shouldn`t be any problem in the way of lifting, it`s just how well it is maintained today across the Midwest. A quick look at the current cloud cover on satellite suggests the relatively clear conditions should foster a supportive future for the feature today.

[CAPE]

I am good with a decaying feature moving through. Eff damaging winds, but some solid rain with T&L would be cool.

[aldie 22]

So in other words I should stop paying attention? 

[midatlanticweather]

 

[Kmlwx]

5 minutes ago, leesburg 04 said:

So in other words I should stop paying attention? 

 Probably safe to ignore weather until tonight. I personally still think something rather significant is possible - higher odds the farther north and west you go...but these things can surprise. 

[aldie 22]

1 minute ago, Kmlwx said:

 Probably safe to ignore weather until tonight. I personally still think something rather significant is possible - higher odds the farther north and west you go...but these things can surprise. 

Nam basically whiffs my area.. going to be interesting to watch. Glad it's not snow and my water bill has been low so far

[mappy]

Noticeably more humid this morning 

[high risk]

I do love how the Day 2 Outlook discussed a "weakened carcass of an MCS".        That said, there is still a lot of uncertainty about how and where this MCS will evolve overnight.    I'm still not overly worried at this time about widespread wind potential into the metro areas, given the poor timing and lack of instability, but these systems can certainly surprise if they develop a sufficiently strong cold pool.

[George BM]

8 minutes ago, high risk said:

I do love how the Day 2 Outlook discussed a "weakened carcass of an MCS".        That said, there is still a lot of uncertainty about how and where this MCS will evolve overnight.    I'm still not overly worried at this time about widespread wind potential into the metro areas, given the poor timing and lack of instability, but these systems can certainly surprise if they develop a sufficiently strong cold pool.

Yeap. I remember the June 3, 2020 derecho to our north producing hurricane-force wind gusts despite only weak to modest CAPE available and early time of day owing to the MCSs cold pool/ rear-inflow jet. Granted there were a couple hours of solar heating before the storms got to New Jersey where the most extreme damage occurred. But it was still solidly before peak heating with relatively modest LLLRs.

Not that I expect that here, of course.  Just pointing that out.

[Eskimo Joe]

16 hours ago, Kmlwx said:

It's been a busy weekend...but I'm just now having a chance to come up for air and take a look at everything. 

We tend to get lines of storms ahead of schedule...not sure if this would apply to the D-word or large MCSs as well...but I'd assume so. Still, the current timing is well into the overnight period tomorrow night and even closer to 12z Tue AM on some of the models. That's not ideal as @high risk already said for true surface based activity. 

The 2012 derecho came through late into the evening - but it was also a ridiculously hot airmass area-wide and it was before midnight. 12z is like the worst time entirely for anything severe t'storm related (it's happened, yes...but it's rare). 

MCS activity (and particularly derechos) are insanely tough to model/predict...and when we are talking about sensible weather, a different of a hundred miles or two is going to mean a ton for your specific location. 

Few things that I'll be watching for - 1) how much instability is left if the line/complex comes through at that awful time in the diurnal cycle. 2) If the timing really is 12z Tue AM - I think even 6 hours earlier would increase the risk substantially - make it 8-12 hours earlier and even better for severe odds (I think 12 hours might be a tall task, though). 3) We'll need to see where the instability gradient sets up - it's a razor sharp margin on some of the models and if you're too far NE of that...game over. 

I think EVERYONE is in the game in this subforum for right now. That will obviously change as we get closer to (and into) the event. 

Doesn't mean anything - but that day 2 Outlook has "the look" of 2012...obviously not basing that on any other analog factor other than map drawings (which don't mean much). 

I think today will be a feast or famine - if a supercell or two form, somebody will get pummeled - but I'm punting. If something pops this evening, I'll track it of course. 

Buckle up...let's see what tomorrow holds as we get closer to the potential.

Folks, the 2012 Derecho was the example of the high end potential in these parts. The AFD written just before the event showed the 860 temps were +24 on the 00z IAD RAOB, an event that only occurred 6 times in the 52 years of IAD sounding history. There is absolutely no way we even come close to that potential tomorrow. Best case scenario is a solid MCS with elevated convection and very vivid lightning. 

[George BM]

Completely unrelated to any thoughts about tonight/tomorrow... today marks nine years since the last time the immediate area was under a MOD risk of severe weather from the SPC.

[Kmlwx]

14 minutes ago, George BM said:

Completely unrelated to any thoughts about tonight/tomorrow... today marks nine years since the last time the immediate area was under a MOD risk of severe weather from the SPC.

WD index summer edition lol

[Kmlwx]

15 minutes ago, Eskimo Joe said:

Folks, the 2012 Derecho was the example of the high end potential in these parts. The AFD written just before the event showed the 860 temps were +24 on the 00z IAD RAOB, an event that only occurred 6 times in the 52 years of IAD sounding history. There is absolutely no way we even come close to that potential tomorrow. Best case scenario is a solid MCS with elevated convection and very vivid lightning. 

Yep. Not even close to having the same fuel available. 

[Eskimo Joe]

2 minutes ago, Kmlwx said:

Yep. Not even close to having the same fuel available. 

Depending on the storm motion, this could turn into a flash flood event if the book ends of the vortex setup a training event. Similar to the July, 2019 event.

17 minutes ago, George BM said:

Completely unrelated to any thoughts about tonight/tomorrow... today marks nine years since the last time the immediate area was under a MOD risk of severe weather from the SPC.

That was an interesting day. Early morning MCS blew through then left a boundary for an afternoon long track EF-0 tornado. Was my first damage assessment for a tornado.

[RDM]

1 hour ago, mappy said:

Noticeably more humid this morning 

Yup - just came in from watering some transplanted azaleas.  DP is 74 here.  The air has that thick/yucky feel to it.   

[Maestrobjwa]

37 minutes ago, Kmlwx said:

WD index summer edition lol

You rang?  (even in summer that phrase teleports me in)

[midatlanticweather]

NAM looked interesting

 

[Eskimo Joe]

NAM is an elevated convection snoozefest.

[Kmlwx]

Biggest thing I'm watching for now is timing. It's entirely possible we start to see the arrival time moved up as the storms unfold 

[MN Transplant]

If you continue the loop on the NAM Nest it has a westward moving squall line through SC/GA.  That would be wild.

[high risk]

   The HREF products reflect the idea among the CAMs that the chances for what's left of the MCS to bring strong winds down to the surface is fairly low (but not zero).

 

[Hoosier]

1 hour ago, Kmlwx said:

Biggest thing I'm watching for now is timing. It's entirely possible we start to see the arrival time moved up as the storms unfold 

Fwiw, leaning on the later timing for organization into a forward propagating MCS out here in the Midwest.  But this has been a tricky setup from the get-go.

[batmanbrad]

the SPC day 1 outlook scheduled to be released at 12:30PM is delayed (by 1/2 hour so far), wonder if that means they are waiting on more model data.

[Kmlwx]

Really no sig changes. 

[WxWatcher007]

Honest to God part of me wants to pack up and head to Ohio to chase…

[Hoosier]

7 minutes ago, WxWatcher007 said:

Honest to God part of me wants to pack up and head to Ohio to chase…

It's a MDT risk caliber setup if things play out right, but there are lingering uncertainties on details.  The environment near/just south of the front is, well, ridiculous.

You'd be better off trying to get to southern MI/northern IN if possible, given probable arrival prior to sunset.  That area is chaseable. 

[yoda]

Hmmm from the new Day 2 OTLK at 1730z

Central Appalachians/Mid Atlantic/Carolina Piedmont...
   A cluster(s) of thunderstorms, potentially in the form of an
   organized MCS, may be underway across the central Appalachians at
   the start of the period. Regardless of early storm mode, the
   manifestation of Day 1 convection will be embedded in the modest
   mid-level flow (along with 20-30 kts of deep-layer shear) while
   progressing southeast into a diurnally heated, destabilizing
   airmass. 70+ F surface dewpoints beneath 7+ C/km mid-level lapse
   rates will support 2000-3000 J/kg MLCAPE ahead of the ongoing
   storms. In addition, a mixing boundary-layer will also support
   efficient cold pool production should a more substantial MCS
   materialize, with damaging gusts a concern. A Category 2/Slight Risk
   has been maintained across portions of the Mid Atlantic into the
   Carolinas. Should confidence increase in a more organized, sustained
   MCS becoming established in the morning hours upstream of the
   aforementioned buoyancy, a Category 3/Enhanced risk may be needed.
   Also, some CAM guidance hints at considerable southwestward
   propagation of MCS convection into SC and a southwestward expansion
   of the Slight Risk is also possible in future Day 1 Outlooks.

[yoda]

SLGT risk on the afternoon OTLK was yanked a good 100 to 200 miles to the NW compared to the morning OTLK for the Day 2

[WxWatcher007]

16 minutes ago, Hoosier said:

It's a MDT risk caliber setup if things play out right, but there are lingering uncertainties on details.  The environment near/just south of the front is, well, ridiculous.

You'd be better off trying to get to southern MI/northern IN if possible, given probable arrival prior to sunset.  That area is chaseable. 

Ugh, missed opportunity for me. I wouldn’t be able to make it there in time due to work.